add(renderer/direct): write newline function to align view if necessary

Introduce `.cancel` event that is fired when the user sends EOF
in *non raw mode* renderings. The event `.line` now sends the
entire line (even if larger than the internal buffer) but requires
now an `Allocator`.

.gitea/workflows/release.yaml

@@ -15,9 +15,15 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
       - name: Setup zig installation
-        uses: mlugg/setup-zig@v1
+        uses: https://codeberg.org/mlugg/setup-zig@v2
         with:
-          version: master
+          version: latest
+      - name: Lint check
+        run: zig fmt --check .
+      - name: Spell checking
+        uses: crate-ci/typos@v1.39.0
+        with:
+          config: ./.typos-config
       - name: Run tests
         run: zig build --release=fast
       - name: Release build artifacts

.gitea/workflows/test.yaml

@@ -14,13 +14,13 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
       - name: Setup zig installation
-        uses: mlugg/setup-zig@v1
+        uses: https://codeberg.org/mlugg/setup-zig@v2
         with:
-          version: master
+          version: latest
       - name: Lint check
-        run: zig fmt --check .
+        run: zig fmt --check --exclude src/test .
       - name: Spell checking
-        uses: crate-ci/typos@v1.25.0
+        uses: crate-ci/typos@v1.39.0
         with:
           config: ./.typos-config
       - name: Run tests

README.md

@@ -1,9 +1,19 @@
-# zterm Terminal User Interface Library
+# zterm TUI Library
 
-`zterm` is a terminal user interface library to implement terminal (fullscreen or inline) applications.
+`zterm` is a terminal user interface library (*tui*) to implement terminal (fullscreen or inline) applications.
 
-> [!NOTE]
-> Only builds using the master version are tested to work.
+## Demo
+
+Clone this repository and run `zig build --help` to see the available examples. Run a given example as follows:
+
+```sh
+zig build --release=safe -Dexample=demo run
+```
+
+> [!tip]
+> Every example application can be quit using `ctrl+c`.
+
+See the [wiki](https://gitea.yves-biener.de/yves-biener/zterm/wiki) for a showcase of the examples and the further details.
 
 ## Usage
 
@@ -13,117 +23,19 @@ To add or update `zterm` as a dependency in your project run the following comma
 zig fetch --save git+https://gitea.yves-biener.de/yves-biener/zterm
 ```
 
-Add the dependency to your module as follows in your _build.zig_:
+Add the dependency to your module as follows in your *build.zig*:
 
 ```zig
 const zterm: *Dependency = b.dependency("zterm", .{
     .target = target,
     .optimize = optimize,
 });
-// ...
-exe.root_module.addImport("zterm", zterm.module("zterm"));
 ```
 
-For an example you can take a look at [build.zig](build.zig) for an example.
+### Documentation
 
----
-## Design Goals
-
-This project draws heavy inspiration from
-[clay](https://github.com/nicbarker/clay) in the way the layout is declared by
-the user. As terminal applications usually are rendered in intermediate mode,
-the rendering is also part of the event loop. Such that every time an event
-happens a render call will usually be done as well. However this is not strickly
-necessary and can be separated to have a fixed rendering of every 16ms (i.e. for
-60 fps), etc.
-
-There is only one generic container which contains properties and elements (or
-children) which can also be containers, such that each layout in the end is
-a tree.
-
-The library is designed to be very basic and not to provide any more complex
-elements such as input fields, drop-down menu's, buttons, etc. Some of them are
-either easy to implement yourself, specific for you needs or a too complex to
-be provided by the library effectively. For these use-cases there may be other
-libraries that build on top of this one to provide the complex elements as some
-sort of pre-built elements for you to use in your application (or you create
-them yourself).
-
-There are only very few system events, that are used by the built-in containers
-and properties accordingly. For you own widgets (i.e. a collection of elements)
-you can extend the events to include your own events to communicate between
-elements, effect the control flow and the corresponding generated layouts and
-much more.
-
-As this is a terminal based layout library it also provides a rendering pipeline
-alongside the event loop implementation. Usually the event loop is waiting
-blocking and will only cause a re-draw (**intermediate mode**) after each event.
-Even though the each frame is regenerated from scratch each render loop, the
-corresponding application is still pretty performant as the renderer uses a
-double buffered intermediate mode implementation to only apply the changes from
-each frame to the next to the terminal.
-
-This library is also designed to work accordingly in ssh hosted environments,
-such that an application created using this library can be accessed directly
-via ssh. This provides security through the ssh protocol and can defer the
-synchronization process, as users may access the same running instance. Which is
-the primary use-case for myself to create this library in the first place.
-
----
-## Roadmap
-
-- [ ] Container rendering
-  - [ ] Layout
-    - [x] direction
-      - [x] vertical
-      - [x] horizontal
-    - [x] padding
-    - [x] gap
-    - [ ] alignment
-      - [ ] center
-      - [ ] left
-      - [ ] right
-    - [ ] sizing
-      - [ ] width
-      - [ ] height
-      - [ ] options
-        - [ ] fit
-        - [ ] grow
-        - [x] fixed
-        - [x] percent
-  - [ ] Border
-    - [x] sides
-    - [x] corners
-    - [ ] separators
-  - [x] Rectangle
-  - [ ] Scroll
-    - [ ] vertical
-    - [ ] horizontal
-    - [ ] scroll bar(s)
-
-Decorations should respect the layout and the viewport accordingly. This means
-that scrollbars are always visible (except there is no need to have a scrollbar)
-irrelevant depending on the size of the content. The rectangle apply to all
-cells of the content (and may be overwritten by child elements contents).
-The border of an element should be around independent of the scrolling of the
-contents, just like padding.
-
-- *fit*:   adjust virtual space of container by the size of its children (i.e. a
-           container needs to be able to get the necessary size of its children)
-- *grow*:  use as much space as available (what exactly would be the difference
-           between this option and *fit*?)
-- *fixed*: use exactly as much cells (in the specified direction)
-
-- *center*: elements should have their anchor be placed accordingly to their
-            size and the viewport size.
-- *left*:   the anchor remains at zero (relative to the location of the
-            container on the screen) -> similar to the current implementation!
-- *right*:  the anchor is fixed to the right side (i.e. size of the contents -
-            size of the viewport)
-
-### Input
-
-How is the user input handled in the containers? Should there be active
-containers? Some input may happen for a specific container (i.e. when using
-mouse input). How would I handle scrolling for outer and inner elements of
-a container?
+A wiki should be created containing a bright overview of the structure and usage
+of the library. For details it should refer to the examples. The documentation
+should be minimal in terms of updateability in case the library changes. Maybe
+some documentation could be derived from the code documentation (there is a tool
+for this if I recall correctly).

build.zig

@@ -1,41 +1,111 @@
-const std = @import("std");
-
 pub fn build(b: *std.Build) void {
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
 
-    const zg = b.dependency("zg", .{
-        .target = target,
-        .optimize = optimize,
-    });
+    const Examples = enum {
+        all,
+        demo,
+        continuous,
+        // elements:
+        alignment,
+        button,
+        input,
+        progress,
+        radio_button,
+        scrollable,
+        selection,
+        // layouts:
+        vertical,
+        horizontal,
+        grid,
+        mixed,
+        // styles:
+        text,
+        palette,
+        // error handling
+        errors,
+        // non alternate screen applications
+        direct,
+    };
+
+    const example = b.option(Examples, "example", "Example to build and/or run. (default: all)") orelse .all;
+    const debug_rendering = b.option(bool, "debug", "Enable debug rendering. Highlight origin's, size's, padding's, gap's, etc. (default: false)") orelse false;
+    // NOTE do not support debug rendering in release builds
+    if (debug_rendering == true and optimize != .Debug) @panic("Cannot enable debug rendering in non-debug builds.");
+
+    const options = b.addOptions();
+    options.addOption(bool, "debug", debug_rendering);
+    const options_module = options.createModule();
 
     // library
     const lib = b.addModule("zterm", .{
-        .root_source_file = b.path("src/zterm.zig"),
+        .root_source_file = b.path("src/root.zig"),
         .target = target,
         .optimize = optimize,
+        .imports = &.{
+            .{ .name = "build_options", .module = options_module },
+        },
     });
-    lib.addImport("code_point", zg.module("code_point"));
 
-    const container = b.addExecutable(.{
-        .name = "container",
-        .root_source_file = b.path("examples/container.zig"),
-        .target = target,
-        .optimize = optimize,
-    });
-    container.root_module.addImport("zterm", lib);
-    b.installArtifact(container);
+    //--- Examples ---
+    const examples = std.meta.fields(Examples);
+    inline for (examples) |e| {
+        if (@as(Examples, @enumFromInt(e.value)) == .all) continue; // skip `.all` entry
+        const demo = b.addExecutable(.{
+            .name = e.name,
+            .root_module = b.createModule(.{
+                .root_source_file = b.path(switch (@as(Examples, @enumFromInt(e.value))) {
+                    .demo => "examples/demo.zig",
+                    .continuous => "examples/continuous.zig",
+                    // elements:
+                    .alignment => "examples/elements/alignment.zig",
+                    .button => "examples/elements/button.zig",
+                    .input => "examples/elements/input.zig",
+                    .progress => "examples/elements/progress.zig",
+                    .radio_button => "examples/elements/radio-button.zig",
+                    .scrollable => "examples/elements/scrollable.zig",
+                    .selection => "examples/elements/selection.zig",
+                    // layouts:
+                    .vertical => "examples/layouts/vertical.zig",
+                    .horizontal => "examples/layouts/horizontal.zig",
+                    .grid => "examples/layouts/grid.zig",
+                    .mixed => "examples/layouts/mixed.zig",
+                    // styles:
+                    .text => "examples/styles/text.zig",
+                    .palette => "examples/styles/palette.zig",
+                    // error handling
+                    .errors => "examples/errors.zig",
+                    // non-alternate screen
+                    .direct => "examples/direct.zig",
+                    .all => unreachable, // should never happen
+                }),
+                .target = target,
+                .optimize = optimize,
+                .imports = &.{
+                    .{ .name = "zterm", .module = lib },
+                },
+            }),
+        });
+        // mapping of user selected example to compile step
+        if (@intFromEnum(example) == e.value or example == .all) b.installArtifact(demo);
+    }
 
-    // testing
+    // zig build test
     const lib_unit_tests = b.addTest(.{
-        .root_source_file = b.path("src/zterm.zig"),
-        .target = target,
-        .optimize = optimize,
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/root.zig"),
+            .target = target,
+            .optimize = optimize,
+            .imports = &.{
+                .{ .name = "build_options", .module = options_module },
+            },
+        }),
     });
-    lib_unit_tests.root_module.addImport("code_point", zg.module("code_point"));
 
     const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
 
     const test_step = b.step("test", "Run unit tests");
     test_step.dependOn(&run_lib_unit_tests.step);
 }
+
+const std = @import("std");

build.zig.zon

@@ -6,34 +6,40 @@
     //
     // It is redundant to include "zig" in this name because it is already
     // within the Zig package namespace.
-    .name = "zterm",
+    .name = .zterm,
+
+    // Together with name, this represents a globally unique package
+    // identifier. This field is generated by the Zig toolchain when the
+    // package is first created, and then *never changes*. This allows
+    // unambiguous detection of one package being an updated version of
+    // another.
+    //
+    // When forking a Zig project, this id should be regenerated (delete the
+    // field and run `zig build`) if the upstream project is still maintained.
+    // Otherwise, the fork is *hostile*, attempting to take control over the
+    // original project's identity. Thus it is recommended to leave the comment
+    // on the following line intact, so that it shows up in code reviews that
+    // modify the field.
+    .fingerprint = 0xf10b37e210a619d7, // Changing this has security and trust implications.
 
     // This is a [Semantic Version](https://semver.org/).
     // In a future version of Zig it will be used for package deduplication.
-    .version = "0.0.0",
+    .version = "0.3.0",
 
-    // This field is optional.
-    // This is currently advisory only; Zig does not yet do anything
-    // with this value.
-    //.minimum_zig_version = "0.11.0",
+    // Tracks the earliest Zig version that the package considers to be a
+    // supported use case.
+    .minimum_zig_version = "0.15.0-dev.56+d0911786c",
 
     // This field is optional.
     // Each dependency must either provide a `url` and `hash`, or a `path`.
     // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
     // Once all dependencies are fetched, `zig build` no longer requires
     // internet connectivity.
-    .dependencies = .{
-        .zg = .{
-            .url = "git+https://codeberg.org/atman/zg#a363f507fc39b96fc48d693665a823a358345326",
-            .hash = "1220fe42e39fd141c84fd7d5cf69945309bb47253033e68788f99bdfe5585fbc711a",
-        },
-    },
+    .dependencies = .{},
     .paths = .{
+        "LICENSE",
         "build.zig",
         "build.zig.zon",
         "src",
-        // For example...
-        //"LICENSE",
-        //"README.md",
     },
 }

examples/container.zig

@@ -1,97 +0,0 @@
-const std = @import("std");
-const zterm = @import("zterm");
-
-const App = zterm.App(union(enum) {});
-const Key = zterm.Key;
-
-const log = std.log.scoped(.example);
-
-pub fn main() !void {
-    errdefer |err| log.err("Application Error: {any}", .{err});
-
-    // TODO: maybe create own allocator as some sort of arena allocator to have consistent memory usage
-    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
-    defer {
-        const deinit_status = gpa.deinit();
-        if (deinit_status == .leak) {
-            log.err("memory lead", .{});
-        }
-    }
-    const allocator = gpa.allocator();
-
-    var app: App = .{};
-    var renderer = zterm.Renderer.Buffered.init(allocator);
-    defer renderer.deinit();
-
-    var container = try App.Container.init(allocator, .{
-        .border = .{
-            .color = .blue,
-            .corners = .rounded,
-            .sides = .all(),
-            .separator = .{ .enabled = false },
-        },
-        .layout = .{
-            .gap = 1,
-            .padding = .all(5),
-            .direction = .horizontal,
-        },
-    });
-    try container.append(try App.Container.init(allocator, .{
-        .rectangle = .{ .fill = .blue },
-        .layout = .{
-            .sizing = .{
-                .width = .{ .fixed = 70 },
-                .height = .{ .fixed = 18 },
-            },
-        },
-    }));
-    try container.append(try App.Container.init(allocator, .{
-        .border = .{ .color = .light_blue, .corners = .squared },
-    }));
-    try container.append(try App.Container.init(allocator, .{
-        .rectangle = .{ .fill = .blue },
-    }));
-    defer container.deinit();
-
-    // NOTE: should the min-size here be required?
-    try app.start();
-    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
-
-    // event loop
-    while (true) {
-        const event = app.nextEvent();
-        log.debug("received event: {s}", .{@tagName(event)});
-
-        switch (event) {
-            .init => {
-                try container.handle(event);
-                continue; // do not render
-            },
-            .quit => break,
-            .resize => |size| try renderer.resize(size),
-            .key => |key| {
-                if (key.matches(.{ .cp = 'q' })) app.quit();
-
-                if (key.matches(.{ .cp = 'n', .mod = .{ .ctrl = true } })) {
-                    try app.interrupt();
-                    defer app.start() catch @panic("could not start app event loop");
-                    var child = std.process.Child.init(&.{"hx"}, allocator);
-                    _ = child.spawnAndWait() catch |err| app.postEvent(.{
-                        .err = .{
-                            .err = err,
-                            .msg = "Spawning $EDITOR failed",
-                        },
-                    });
-                }
-            },
-            .err => |err| {
-                log.err("Received {any} with message: {s}", .{ @errorName(err.err), err.msg });
-            },
-            else => {},
-        }
-
-        try container.handle(event);
-        try renderer.render(@TypeOf(container), &container);
-        try renderer.flush();
-    }
-}

examples/continuous.zig

@@ -0,0 +1,247 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+/// Spinner element implementation that runs a simple animation that requires
+/// the continuous draw loop.
+const Spinner = struct {
+    counter: u8 = 0,
+    index: u8 = 0,
+
+    const map: [6]u21 = .{ '𜺎', '𜺍', '𜺇', '𜹯', '𜹿', '𜺋' };
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                .content = content,
+            },
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        cells[size.x + 1].cp = map[this.index];
+
+        this.counter += 1;
+        if (this.counter >= 20) {
+            this.index += 1;
+            this.index %= 6;
+            this.counter = 0;
+        }
+    }
+};
+
+const InputField = struct {
+    allocator: std.mem.Allocator,
+    input: std.ArrayList(u21),
+    queue: *App.Queue,
+
+    pub fn init(allocator: std.mem.Allocator, queue: *App.Queue) @This() {
+        return .{
+            .allocator = allocator,
+            .input = std.ArrayList(u21).initCapacity(allocator, 8) catch unreachable,
+            .queue = queue,
+        };
+    }
+
+    pub fn deinit(this: *@This()) void {
+        this.input.deinit(this.allocator);
+    }
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                .handle = handle,
+                .content = content,
+            },
+        };
+    }
+
+    fn handle(ctx: *anyopaque, _: *App.Model, event: App.Event) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        switch (event) {
+            .key => |key| {
+                if (key.isUnicode()) try this.input.append(this.allocator, key.cp);
+
+                if (key.eql(.{ .cp = zterm.input.Enter }) or key.eql(.{ .cp = zterm.input.KpEnter }))
+                    this.queue.push(.{ .accept = try this.input.toOwnedSlice(this.allocator) });
+
+                if (key.eql(.{ .cp = zterm.input.Backspace }))
+                    _ = this.input.pop();
+
+                if (key.eql(.{ .cp = zterm.input.Delete }) or key.eql(.{ .cp = zterm.input.KpDelete }))
+                    _ = this.input.pop();
+            },
+            else => {},
+        }
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        if (this.input.items.len == 0) return;
+
+        const row = 1;
+        const col = 1;
+        const anchor = (row * size.x) + col;
+
+        for (this.input.items, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .black;
+            cells[anchor + idx].style.cursor = false;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+
+            if (idx == this.input.items.len - 1) cells[anchor + idx + 1].style.cursor = true;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var input_field: InputField = .init(allocator, &app.queue);
+    defer input_field.deinit();
+
+    var quit_text: QuitText = .{};
+    var spinner: Spinner = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+        .layout = .{
+            .direction = .vertical,
+            .padding = .all(5),
+        },
+    }, quit_text.element());
+    defer container.deinit();
+
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgrey },
+        .size = .{
+            .grow = .horizontal,
+            .dim = .{ .y = 10 },
+        },
+    }, input_field.element()));
+
+    const nested_container: App.Container = try .init(allocator, .{
+        .rectangle = .{ .fill = .lightgrey },
+    }, spinner.element());
+    try container.append(nested_container);
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    var framerate: u64 = 60;
+    var tick_ms: u64 = @divFloor(time.ms_per_s, framerate);
+    var next_frame_ms: u64 = 0;
+
+    // draw loop
+    draw: while (true) {
+        const now_ms: u64 = @intCast(time.milliTimestamp());
+        if (now_ms >= next_frame_ms) {
+            next_frame_ms = now_ms + tick_ms;
+        } else {
+            std.Thread.sleep((next_frame_ms - now_ms) * time.ns_per_ms);
+            next_frame_ms += tick_ms;
+        }
+
+        const len = blk: {
+            app.queue.lock();
+            defer app.queue.unlock();
+            break :blk app.queue.len();
+        };
+
+        // handle events
+        for (0..len) |_| {
+            const event = app.queue.drain() orelse break;
+            log.debug("handling event: {s}", .{@tagName(event)});
+            // pre event handling
+            switch (event) {
+                .key => |key| {
+                    log.debug("key {any}", .{key});
+                    if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit();
+                },
+                .accept => |input| {
+                    defer allocator.free(input);
+                    var string = try allocator.alloc(u8, input.len);
+                    defer allocator.free(string);
+                    for (0.., input) |i, char| string[i] = @intCast(char);
+                    log.debug("Accepted input '{s}'", .{string});
+                },
+                .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+                .focus => |b| {
+                    // NOTE reduce framerate in case the window is not focused and restore again when focused
+                    framerate = if (b) 60 else 15;
+                    tick_ms = @divFloor(time.ms_per_s, framerate);
+                },
+                else => {},
+            }
+
+            container.handle(&app.model, event) catch |err| app.postEvent(.{
+                .err = .{
+                    .err = err,
+                    .msg = "Container Event handling failed",
+                },
+            });
+
+            // post event handling
+            switch (event) {
+                .quit => break :draw,
+                else => {},
+            }
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const time = std.time;
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {
+    accept: []u21,
+});

examples/demo.zig

@@ -0,0 +1,196 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit. Press ctrl+n to launch `vim`.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    pub fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const y = 2;
+        const x = size.x / 2 -| (text.len / 2);
+        const anchor = (y * size.x) + x;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+
+    // TODO what should the demo application do?
+    // - some sort of chat? -> write messages and have them displayed in a scrollable array at the right hand side?
+    // - on the left some buttons?
+    var box = try App.Container.init(allocator, .{
+        .border = .{
+            .color = .blue,
+            .sides = .all,
+        },
+        .layout = .{
+            .gap = 1,
+            .padding = .vertical(2),
+            .direction = .vertical,
+        },
+        .size = .{
+            .dim = .{ .y = 90 },
+        },
+    }, .{});
+    try box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgreen },
+    }, .{}));
+    try box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgreen },
+    }, .{}));
+    try box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgreen },
+    }, .{}));
+
+    var scrollable: App.Scrollable = .init(box, .disabled);
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            .gap = 2,
+            .separator = .{ .enabled = true },
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+            .direction = .horizontal,
+        },
+    }, quit_text.element());
+    try container.append(try App.Container.init(allocator, .{}, scrollable.element()));
+
+    var nested_container: App.Container = try .init(allocator, .{
+        .layout = .{
+            .direction = .vertical,
+            .separator = .{
+                .enabled = true,
+            },
+        },
+    }, .{});
+    var inner_container: App.Container = try .init(allocator, .{
+        .layout = .{
+            .direction = .vertical,
+        },
+        .border = .{
+            .color = .lightblue,
+            .sides = .all,
+        },
+    }, .{});
+    try inner_container.append(try .init(allocator, .{
+        .rectangle = .{
+            .fill = .blue,
+        },
+        .size = .{
+            .grow = .horizontal,
+            .dim = .{ .y = 5 },
+        },
+    }, .{}));
+    try inner_container.append(try .init(allocator, .{
+        .rectangle = .{
+            .fill = .red,
+        },
+        .size = .{
+            .grow = .horizontal,
+            .dim = .{ .y = 5 },
+        },
+    }, .{}));
+    try inner_container.append(try .init(allocator, .{
+        .rectangle = .{
+            .fill = .green,
+        },
+    }, .{}));
+    try nested_container.append(inner_container);
+    try nested_container.append(try .init(allocator, .{
+        .size = .{
+            .grow = .horizontal,
+            .dim = .{ .y = 1 },
+        },
+    }, .{}));
+    try container.append(nested_container);
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+        .size = .{
+            .dim = .{ .x = 30 },
+        },
+    }, .{}));
+    defer container.deinit(); // also de-initializes the children
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| {
+                if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit();
+
+                if (key.eql(.{ .cp = 'n', .mod = .{ .ctrl = true } })) {
+                    try app.interrupt();
+                    renderer.size = .{}; // reset size, such that next resize will cause a full re-draw!
+                    defer app.start(.full) catch @panic("could not start app event loop");
+                    var child = std.process.Child.init(&.{"vim"}, allocator);
+                    _ = child.spawnAndWait() catch |err| app.postEvent(.{
+                        .err = .{
+                            .err = err,
+                            .msg = "Spawning $EDITOR failed",
+                        },
+                    });
+                    continue;
+                }
+            },
+            // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        // NOTE returned errors should be propagated back to the application
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const input = zterm.input;
+const App = zterm.App(struct {}, union(enum) {});

examples/direct.zig

@@ -0,0 +1,192 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                .minSize = minSize,
+                .content = content,
+            },
+        };
+    }
+
+    fn minSize(_: *anyopaque, _: *const App.Model, size: zterm.Point) zterm.Point {
+        return .{ .x = size.x, .y = 10 }; // this includes the border
+    }
+
+    pub fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const y = 0;
+        const x = 2;
+        const anchor = (y * size.x) + x;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.emphasis = &.{ .bold, .underline };
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+const Prompt = struct {
+    len: u16 = 3,
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                // .minSize = minSize,
+                .content = content,
+            },
+        };
+    }
+
+    // NOTE size hint is not required as the `.size = .{ .dim = .{..} }` property is set accordingly which denotes the minimal size
+    // fn minSize(ctx: *anyopaque, _: *const App.Model, _: zterm.Point) zterm.Point {
+    //     const this: *@This() = @ptrCast(@alignCast(ctx));
+    //     return .{ .x = this.len, .y = 1 };
+    // }
+
+    pub fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        assert(cells.len > 2); // expect at least two cells
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        for (0..this.len) |idx| {
+            cells[idx].style.bg = .blue;
+            cells[idx].style.fg = .black;
+            cells[idx].style.emphasis = &.{.bold};
+        }
+        cells[1].cp = '>';
+        // leave one clear whitespace after the prompt
+        cells[this.len].style.bg = .default;
+        cells[this.len].style.cursor = true; // marks the actual end of the rendering!
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var allocator: std.heap.DebugAllocator(.{}) = .init;
+    defer if (allocator.deinit() == .leak) log.err("memory leak", .{});
+
+    const gpa = allocator.allocator();
+
+    var app: App = .init(gpa, .{}, .{});
+    var renderer = zterm.Renderer.Direct.init(gpa);
+    defer renderer.deinit();
+
+    var container: App.Container = try .init(gpa, .{
+        .layout = .{
+            .direction = .vertical,
+            .gap = 1, // show empty line between elements to allow navigation through paragraph jumping
+        },
+        .size = .{
+            .grow = .horizontal_only,
+        },
+    }, .{});
+    defer container.deinit();
+
+    var quit_text: QuitText = .{};
+    var intermediate: App.Container = try .init(gpa, .{
+        .border = .{
+            .sides = .{ .left = true },
+            .color = .grey,
+        },
+        .layout = .{
+            .direction = .horizontal,
+            .padding = .{ .left = 1, .top = 1 },
+        },
+    }, quit_text.element());
+    try intermediate.append(try .init(gpa, .{
+        .rectangle = .{ .fill = .blue },
+    }, .{}));
+
+    try intermediate.append(try .init(gpa, .{
+        .rectangle = .{ .fill = .green },
+    }, .{}));
+
+    var padding_container: App.Container = try .init(gpa, .{
+        .layout = .{
+            .padding = .horizontal(1),
+        },
+    }, .{});
+    try padding_container.append(intermediate);
+    try container.append(padding_container);
+
+    var prompt: Prompt = .{};
+    try container.append(try .init(gpa, .{
+        .rectangle = .{ .fill = .grey },
+        .size = .{
+            .dim = .{ .y = 1 },
+        },
+    }, prompt.element()));
+
+    try app.start(.direct); // needs to become configurable, as what should be enabled / disabled (i.e. show cursor, hide cursor, use alternate screen, etc.)
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    event: while (true) {
+        // batch events since last iteration
+        const len = blk: {
+            app.queue.poll();
+            app.queue.lock();
+            defer app.queue.unlock();
+            break :blk app.queue.len();
+        };
+
+        // handle events
+        for (0..len) |_| {
+            const event = app.queue.pop();
+            log.debug("received event: {s}", .{@tagName(event)});
+
+            // pre event handling
+            switch (event) {
+                // NOTE draw the character with the ctrl indication and a newline to make sure the rendering stays consistent
+                .cancel => try renderer.writeCtrlDWithNewline(),
+                .line => |line| {
+                    defer gpa.free(line);
+                    log.debug("{s}", .{line});
+                },
+                // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback
+                .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+                else => {},
+            }
+
+            // NOTE returned errors should be propagated back to the application
+            container.handle(&app.model, event) catch |err| app.postEvent(.{
+                .err = .{
+                    .err = err,
+                    .msg = "Container Event handling failed",
+                },
+            });
+
+            // post event handling
+            switch (event) {
+                .quit => break :event,
+                else => {},
+            }
+        }
+        // if there are more events to process continue handling them otherwise I can render the next frame
+        if (app.queue.len() > 0) continue :event;
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const input = zterm.input;
+const App = zterm.App(struct {}, union(enum) {});

examples/elements/alignment.zig

@@ -0,0 +1,99 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var container: App.Container = try .init(allocator, .{}, .{});
+    defer container.deinit();
+
+    var quit_text: QuitText = .{};
+    const quit_container = try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+        .layout = .{
+            .direction = .vertical,
+            .padding = .all(5),
+        },
+        .size = .{
+            .dim = .{ .x = 25, .y = 5 },
+            .grow = .fixed,
+        },
+    }, quit_text.element());
+
+    var alignment: App.Alignment = .init(quit_container, .center);
+    try container.append(try .init(allocator, .{}, alignment.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {});

examples/elements/button.zig

@@ -0,0 +1,154 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+const Clickable = struct {
+    const text = "Press me";
+
+    queue: *App.Queue,
+    color: zterm.Color = .black,
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                .handle = handle,
+                .content = content,
+            },
+        };
+    }
+
+    fn handle(ctx: *anyopaque, _: *App.Model, event: App.Event) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        switch (event) {
+            .mouse => |mouse| if (mouse.button == .left and mouse.kind == .release) {
+                var value = @intFromEnum(this.color);
+                value += 1;
+                value %= 17;
+                if (value == 0) value = 1;
+                this.color = @enumFromInt(value);
+                this.queue.push(.{ .click = @tagName(mouse.button) });
+            },
+            else => {},
+        }
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = size.y / 2 -| (text.len / 2);
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = this.color;
+            cells[anchor + idx].style.emphasis = &.{.bold};
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var clickable: Clickable = .{ .queue = &app.queue };
+    const element = clickable.element();
+
+    var button: App.Button(.accept) = .init(&app.queue, .init(.default, "Button"));
+
+    var quit_text: QuitText = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+        .layout = .{ .padding = .all(5) },
+    }, quit_text.element());
+    defer container.deinit();
+
+    try container.append(try App.Container.init(allocator, .{ .rectangle = .{ .fill = .lightgrey } }, element));
+    try container.append(try App.Container.init(allocator, .{ .rectangle = .{ .fill = .black } }, button.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .click => |b| log.info("Clicked with mouse using Button: {s}", .{b}),
+            .accept => log.info("Clicked built-in button using the mouse", .{}),
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(
+    struct {},
+    union(enum) {
+        click: [:0]const u8,
+        accept,
+    },
+);

examples/elements/input.zig

@@ -0,0 +1,167 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+const MouseDraw = struct {
+    position: ?zterm.Point = null,
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                .handle = handle,
+                .content = content,
+            },
+        };
+    }
+
+    fn handle(ctx: *anyopaque, _: *App.Model, event: App.Event) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        switch (event) {
+            .mouse => |mouse| this.position = .{ .x = mouse.x, .y = mouse.y },
+            else => this.position = null,
+        }
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+
+        if (this.position) |pos| {
+            const idx = @as(usize, size.x) * @as(usize, pos.y) + @as(usize, pos.x);
+            cells[idx].cp = 'x';
+            cells[idx].style.fg = .red;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var input_field: App.Input(.accept) = .init(allocator, &app.queue, .init(.black, .blue));
+    var mouse_draw: MouseDraw = .{};
+    var second_mouse_draw: MouseDraw = .{};
+    var quit_text: QuitText = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+        .layout = .{
+            .direction = .vertical,
+            .padding = .all(5),
+        },
+    }, quit_text.element());
+    defer container.deinit();
+
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgrey },
+        .size = .{
+            .grow = .horizontal,
+            .dim = .{ .y = 1 },
+        },
+    }, input_field.element()));
+
+    var nested_container: App.Container = try .init(allocator, .{
+        .border = .{
+            .sides = .all,
+            .color = .black,
+        },
+        .rectangle = .{ .fill = .lightgrey },
+        .layout = .{
+            .separator = .{
+                .enabled = true,
+                .color = .black,
+            },
+        },
+    }, .{});
+    try nested_container.append(try .init(allocator, .{
+        .rectangle = .{ .fill = .lightgrey },
+    }, mouse_draw.element()));
+    try nested_container.append(try .init(allocator, .{
+        .rectangle = .{ .fill = .lightgrey },
+    }, second_mouse_draw.element()));
+    try container.append(nested_container);
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .accept => |input| {
+                defer allocator.free(input);
+                log.debug("Accepted input '{s}'", .{input});
+            },
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const Color = zterm.Color;
+
+const App = zterm.App(
+    struct {},
+    union(enum) {
+        accept: []u8,
+    },
+);

examples/elements/progress.zig

@@ -0,0 +1,174 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var progress_percent: u8 = 0;
+    var quit_text: QuitText = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{ .padding = .all(5), .direction = .vertical },
+    }, quit_text.element());
+    defer container.deinit();
+
+    {
+        var progress: App.Progress(.progress) = .init(&app.queue, .{
+            .percent = .{
+                .enabled = true,
+                .alignment = .left,
+            },
+            .fg = .blue,
+            .bg = .grey,
+        });
+        try container.append(try App.Container.init(allocator, .{}, progress.element()));
+    }
+    {
+        var progress: App.Progress(.progress) = .init(&app.queue, .{
+            .percent = .{
+                .enabled = true,
+                .alignment = .middle, // default
+            },
+            .fg = .red,
+            .bg = .grey,
+        });
+        try container.append(try App.Container.init(allocator, .{}, progress.element()));
+    }
+    {
+        var progress: App.Progress(.progress) = .init(&app.queue, .{
+            .percent = .{
+                .enabled = true,
+                .alignment = .right,
+            },
+            .fg = .green,
+            .bg = .grey,
+        });
+        try container.append(try App.Container.init(allocator, .{}, progress.element()));
+    }
+    {
+        var progress: App.Progress(.progress) = .init(&app.queue, .{
+            .percent = .{ .enabled = false },
+            .fg = .default,
+            .bg = .grey,
+        });
+        try container.append(try App.Container.init(allocator, .{}, progress.element()));
+    }
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    var framerate: u64 = 60;
+    var tick_ms: u64 = @divFloor(time.ms_per_s, framerate);
+    var next_frame_ms: u64 = 0;
+
+    var increase_progress: u64 = 10;
+
+    // Continuous drawing
+    // draw loop
+    draw: while (true) {
+        const now_ms: u64 = @intCast(time.milliTimestamp());
+        if (now_ms >= next_frame_ms) {
+            next_frame_ms = now_ms + tick_ms;
+        } else {
+            std.Thread.sleep((next_frame_ms - now_ms) * time.ns_per_ms);
+            next_frame_ms += tick_ms;
+        }
+
+        // NOTE time based progress increasion
+        increase_progress -= 1;
+        if (increase_progress == 0) {
+            increase_progress = 10;
+            progress_percent += 1;
+            if (progress_percent > 100) progress_percent = 0;
+            app.postEvent(.{ .progress = progress_percent });
+        }
+
+        const len = blk: {
+            app.queue.lock();
+            defer app.queue.unlock();
+            break :blk app.queue.len();
+        };
+
+        // handle events
+        for (0..len) |_| {
+            const event = app.queue.drain() orelse break;
+            log.debug("handling event: {s}", .{@tagName(event)});
+            // pre event handling
+            switch (event) {
+                .key => |key| {
+                    if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit();
+                },
+                .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+                .focus => |b| {
+                    // NOTE reduce framerate in case the window is not focused and restore again when focused
+                    framerate = if (b) 60 else 15;
+                    tick_ms = @divFloor(time.ms_per_s, framerate);
+                },
+                else => {},
+            }
+
+            container.handle(&app.model, event) catch |err| app.postEvent(.{
+                .err = .{
+                    .err = err,
+                    .msg = "Container Event handling failed",
+                },
+            });
+
+            // post event handling
+            switch (event) {
+                .quit => break :draw,
+                else => {},
+            }
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const time = std.time;
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(
+    struct {},
+    union(enum) {
+        progress: u8,
+    },
+);

examples/elements/radio-button.zig

@@ -0,0 +1,98 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var radiobutton: App.RadioButton = .init(false, .{
+        .label = "Test Radio Button",
+        .style = .squared,
+    });
+    var button: App.Button(.accept) = .init(&app.queue, .init(.default, "Button"));
+    var quit_text: QuitText = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+        .layout = .{ .padding = .all(5) },
+    }, quit_text.element());
+    defer container.deinit();
+    try container.append(try .init(allocator, .{}, radiobutton.element()));
+    try container.append(try App.Container.init(allocator, .{ .rectangle = .{ .fill = .black } }, button.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .accept => log.info("Clicked built-in button using the mouse", .{}),
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {
+    accept,
+});

examples/elements/scrollable.zig

@@ -0,0 +1,196 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+const HelloWorldText = packed struct {
+    const text = "Hello World";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{ .content = content },
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = size.y / 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer {
+        const deinit_status = gpa.deinit();
+        if (deinit_status == .leak) {
+            log.err("memory leak", .{});
+        }
+    }
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var element_wrapper: HelloWorldText = .{};
+    const element = element_wrapper.element();
+
+    var quit_text: QuitText = .{};
+
+    var top_box = try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+        .layout = .{
+            .gap = 2,
+            .separator = .{
+                .enabled = true,
+            },
+            .direction = .vertical,
+            .padding = .vertical(1),
+        },
+    }, .{});
+    try top_box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgreen },
+        .size = .{
+            .dim = .{ .y = 30 },
+        },
+    }, .{}));
+    try top_box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgreen },
+        .size = .{
+            .dim = .{ .y = 5 },
+        },
+    }, element));
+    try top_box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .lightgreen },
+        .size = .{
+            .dim = .{ .y = 2 },
+        },
+    }, .{}));
+
+    var bottom_box = try App.Container.init(allocator, .{
+        .border = .{
+            .sides = .all,
+            .color = .blue,
+        },
+        .layout = .{
+            .separator = .{
+                .enabled = true,
+                .color = .red,
+            },
+            .direction = .vertical,
+            .padding = .vertical(1),
+        },
+        .size = .{
+            .dim = .{ .y = 30 },
+        },
+    }, .{});
+    try bottom_box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+    }, .{}));
+    try bottom_box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+    }, element));
+    try bottom_box.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+    }, .{}));
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            .gap = 2,
+            .separator = .{
+                .enabled = true,
+                .line = .double,
+            },
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+            .direction = .vertical,
+        },
+    }, quit_text.element());
+    defer container.deinit();
+
+    // place empty container containing the element of the scrollable Container.
+    var scrollable_top: App.Scrollable = .init(top_box, .enabled(.default, false));
+    try container.append(try App.Container.init(allocator, .{}, scrollable_top.element()));
+
+    var scrollable_bottom: App.Scrollable = .init(bottom_box, .enabled(.white, true));
+    try container.append(try App.Container.init(allocator, .{}, scrollable_bottom.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const input = zterm.input;
+const App = zterm.App(struct {}, union(enum) {});

examples/elements/selection.zig

@@ -0,0 +1,97 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var selection: App.Selection(enum {
+        one,
+        two,
+        three,
+    }) = .init(.{
+        .label = "Selection",
+    });
+    var quit_text: QuitText = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .grey },
+        .layout = .{ .padding = .all(5) },
+    }, quit_text.element());
+    defer container.deinit();
+    try container.append(try .init(allocator, .{}, selection.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const Error = zterm.Error;
+const App = zterm.App(struct {}, union(enum) {});

examples/errors.zig

@@ -0,0 +1,159 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+const InfoText = struct {
+    const text = "Press any key; Non-Ascii inputs (i.e. `Enter` or `Backspace`) to trigger an exception";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+const ErrorNotification = struct {
+    msg: ?[]const u8 = null,
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .handle = handle, .content = content } };
+    }
+
+    fn handle(ctx: *anyopaque, _: *App.Model, event: App.Event) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        switch (event) {
+            .key => |key| if (!key.isAscii()) return zterm.Error.TooSmall,
+            .err => |err| this.msg = err.msg,
+            else => {},
+        }
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        const this: *@This() = @ptrCast(@alignCast(ctx));
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        if (this.msg) |msg| {
+            const row = size.y -| 2;
+            const col = size.x -| 2 -| msg.len;
+            const anchor = (row * size.x) + col;
+
+            for (msg, 0..) |cp, idx| {
+                cells[anchor + idx].style.fg = .white;
+                cells[anchor + idx].style.bg = .black;
+                cells[anchor + idx].cp = cp;
+
+                // NOTE do not write over the contents of this `Container`'s `Size`
+                if (anchor + idx == cells.len - 1) break;
+            }
+
+            this.msg = null;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+    var info_text: InfoText = .{};
+    var error_notification: ErrorNotification = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            .gap = 2,
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+        },
+    }, quit_text.element());
+    defer container.deinit();
+
+    try container.append(try App.Container.init(allocator, .{}, info_text.element()));
+    try container.append(try App.Container.init(allocator, .{}, error_notification.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {});

examples/layouts/grid.zig

@@ -0,0 +1,115 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{ .content = content },
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+    const element = quit_text.element();
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            .separator = .{ .enabled = true },
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+            .direction = .horizontal,
+        },
+    }, element);
+    for (0..3) |_| {
+        var column = try App.Container.init(allocator, .{
+            .layout = .{
+                .separator = .{ .enabled = true },
+                .direction = .vertical,
+            },
+        }, .{});
+        try column.append(try App.Container.init(allocator, .{
+            .rectangle = .{ .fill = .blue },
+        }, .{}));
+        try column.append(try App.Container.init(allocator, .{
+            .rectangle = .{ .fill = .blue },
+        }, .{}));
+        try column.append(try App.Container.init(allocator, .{
+            .rectangle = .{ .fill = .blue },
+        }, .{}));
+        try container.append(column);
+    }
+    defer container.deinit(); // also de-initializes the children
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        // NOTE returned errors should be propagated back to the application
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {});

examples/layouts/horizontal.zig

@@ -0,0 +1,107 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{ .content = content },
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+    const element = quit_text.element();
+
+    var container = try App.Container.init(allocator, .{
+        .border = .{},
+        .layout = .{
+            .gap = 2,
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+            .direction = .horizontal,
+        },
+    }, element);
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+    }, .{}));
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+    }, .{}));
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+    }, .{}));
+    defer container.deinit(); // also de-initializes the children
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        // NOTE returned errors should be propagated back to the application
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {});

examples/layouts/mixed.zig

@@ -0,0 +1,123 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{ .content = content },
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+    const element = quit_text.element();
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            .gap = 2,
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+        },
+    }, element);
+    for (0..3) |i| {
+        var column = try App.Container.init(allocator, .{
+            .layout = .{
+                .separator = .{ .enabled = true },
+                .direction = if (i > 0) .vertical else .horizontal,
+            },
+        }, .{});
+        if (i != 1) {
+            try column.append(try App.Container.init(allocator, .{
+                .rectangle = .{ .fill = .green },
+            }, .{}));
+            try column.append(try App.Container.init(allocator, .{
+                .rectangle = .{ .fill = .yellow },
+            }, .{}));
+        } else {
+            try column.append(try App.Container.init(allocator, .{
+                .size = .{
+                    .dim = .{ .y = 4 },
+                    .grow = .horizontal,
+                },
+            }, .{}));
+        }
+        try column.append(try App.Container.init(allocator, .{
+            .rectangle = .{ .fill = .blue },
+        }, .{}));
+        try container.append(column);
+    }
+    defer container.deinit(); // also de-initializes the children
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        // NOTE returned errors should be propagated back to the application
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {});

examples/layouts/vertical.zig

@@ -0,0 +1,106 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{ .content = content },
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+    const element = quit_text.element();
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            .gap = 2,
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+            .direction = .vertical,
+        },
+    }, element);
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+    }, .{}));
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+    }, .{}));
+    try container.append(try App.Container.init(allocator, .{
+        .rectangle = .{ .fill = .blue },
+    }, .{}));
+    defer container.deinit(); // also de-initializes the children
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            // NOTE errors could be displayed in another container in case one was received, etc. to provide the user with feedback
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        // NOTE returned errors should be propagated back to the application
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {});

examples/styles/palette.zig

@@ -0,0 +1,101 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+    const element = quit_text.element();
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            .gap = 2,
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+        },
+    }, element);
+    defer container.deinit();
+
+    var box = try App.Container.init(allocator, .{
+        .layout = .{ .direction = .horizontal },
+    }, .{});
+
+    inline for (std.meta.fields(zterm.Color)) |field| {
+        if (field.value == 0) continue; // zterm.Color.default == 0 -> skip
+        try box.append(try App.Container.init(allocator, .{ .rectangle = .{ .fill = @enumFromInt(field.value) } }, .{}));
+    }
+    var scrollable: App.Scrollable = .init(box, .disabled);
+    try container.append(try App.Container.init(allocator, .{}, scrollable.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    while (true) {
+        const event = app.nextEvent();
+        log.debug("received event: {s}", .{@tagName(event)});
+
+        // pre event handling
+        switch (event) {
+            .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+            .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+            else => {},
+        }
+
+        container.handle(&app.model, event) catch |err| app.postEvent(.{
+            .err = .{
+                .err = err,
+                .msg = "Container Event handling failed",
+            },
+        });
+
+        // post event handling
+        switch (event) {
+            .quit => break,
+            else => {},
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+const App = zterm.App(struct {}, union(enum) {});

examples/styles/text.zig

@@ -0,0 +1,264 @@
+const QuitText = struct {
+    const text = "Press ctrl+c to quit.";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{ .ptr = this, .vtable = &.{ .content = content } };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        const row = 2;
+        const col = size.x / 2 -| (text.len / 2);
+        const anchor = (row * size.x) + col;
+
+        for (text, 0..) |cp, idx| {
+            cells[anchor + idx].style.fg = .white;
+            cells[anchor + idx].style.bg = .black;
+            cells[anchor + idx].cp = cp;
+
+            // NOTE do not write over the contents of this `Container`'s `Size`
+            if (anchor + idx == cells.len - 1) break;
+        }
+    }
+};
+
+const TableText = struct {
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                .content = content,
+            },
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        _ = ctx;
+        _ = size;
+        var idx: usize = 0;
+        {
+            const text = "Normal ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Bold   ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Dim    ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Italic ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Underl ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Blink  ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Invert ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Hidden ";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+        {
+            const text = "Strikethrough";
+            for (text) |cp| {
+                cells[idx].cp = cp;
+                idx += 1;
+            }
+        }
+    }
+};
+
+const TextStyles = struct {
+    const text = "Example";
+
+    pub fn element(this: *@This()) App.Element {
+        return .{
+            .ptr = this,
+            .vtable = &.{
+                .minSize = minSize,
+                .content = content,
+            },
+        };
+    }
+
+    fn minSize(ctx: *anyopaque, _: *const App.Model, size: zterm.Point) zterm.Point {
+        _ = ctx;
+        _ = size;
+        return .{
+            .x = std.meta.fields(zterm.Style.Emphasis).len * TextStyles.text.len,
+            .y = (std.meta.fields(zterm.Color).len - 1) * (std.meta.fields(zterm.Color).len - 2),
+        };
+    }
+
+    fn content(ctx: *anyopaque, _: *const App.Model, cells: []zterm.Cell, size: zterm.Point) !void {
+        @setEvalBranchQuota(10000);
+        _ = ctx;
+        assert(cells.len == @as(usize, size.x) * @as(usize, size.y));
+
+        var row: usize = 0;
+        var col: usize = 0;
+
+        // Color
+        inline for (std.meta.fields(zterm.Color)) |bg_field| {
+            if (bg_field.value == 0) continue; // zterm.Color.default == 0 -> skip
+
+            inline for (std.meta.fields(zterm.Color)) |fg_field| {
+                if (fg_field.value == 0) continue; // zterm.Color.default == 0 -> skip
+                if (fg_field.value == bg_field.value) continue;
+
+                // witouth any emphasis
+                for (text) |cp| {
+                    cells[(row * size.x) + col].style.bg = @enumFromInt(bg_field.value);
+                    cells[(row * size.x) + col].style.fg = @enumFromInt(fg_field.value);
+                    cells[(row * size.x) + col].cp = cp;
+                    col += 1;
+                }
+
+                // emphasis (no combinations)
+                inline for (std.meta.fields(zterm.Style.Emphasis)) |emp_field| {
+                    if (emp_field.value == 0) continue; // zterm.Style.Emphasis.reset == 0 -> skip
+                    const emphasis: zterm.Style.Emphasis = @enumFromInt(emp_field.value);
+
+                    for (text) |cp| {
+                        cells[(row * size.x) + col].style.bg = @enumFromInt(bg_field.value);
+                        cells[(row * size.x) + col].style.fg = @enumFromInt(fg_field.value);
+                        cells[(row * size.x) + col].style.emphasis = &.{emphasis};
+                        cells[(row * size.x) + col].cp = cp;
+                        col += 1;
+                    }
+                }
+                row += 1;
+                col = 0;
+            }
+        }
+    }
+};
+
+pub fn main() !void {
+    errdefer |err| log.err("Application Error: {any}", .{err});
+
+    var gpa: std.heap.DebugAllocator(.{}) = .init;
+    defer if (gpa.deinit() == .leak) log.err("memory leak", .{});
+
+    const allocator = gpa.allocator();
+
+    var app: App = .init(allocator, .{}, .{});
+    var renderer = zterm.Renderer.Buffered.init(allocator);
+    defer renderer.deinit();
+
+    var quit_text: QuitText = .{};
+    const element = quit_text.element();
+
+    var text_styles: TextStyles = .{};
+
+    var container = try App.Container.init(allocator, .{
+        .layout = .{
+            // .gap = 2,
+            .padding = .{ .top = 5, .bottom = 3, .left = 3, .right = 3 },
+            .direction = .vertical,
+        },
+    }, element);
+    defer container.deinit();
+
+    var table_head: TableText = .{};
+    try container.append(try .init(allocator, .{
+        .size = .{
+            .dim = .{ .y = 1 },
+            .grow = .horizontal,
+        },
+    }, table_head.element()));
+
+    var scrollable: App.Scrollable = .init(try .init(allocator, .{
+        .layout = .{ .direction = .vertical },
+    }, text_styles.element()), .enabled(.white, true));
+    try container.append(try App.Container.init(allocator, .{}, scrollable.element()));
+
+    try app.start(.full);
+    defer app.stop() catch |err| log.err("Failed to stop application: {any}", .{err});
+
+    // event loop
+    loop: while (true) {
+        // batch events since last iteration
+        const len = blk: {
+            app.queue.poll();
+            app.queue.lock();
+            defer app.queue.unlock();
+            break :blk app.queue.len();
+        };
+
+        // handle events
+        for (0..len) |_| {
+            const event = app.queue.pop();
+            log.debug("handling event: {s}", .{@tagName(event)});
+            // pre event handling
+            switch (event) {
+                .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit(),
+                .err => |err| log.err("Received {s} with message: {s}", .{ @errorName(err.err), err.msg }),
+                else => {},
+            }
+
+            container.handle(&app.model, event) catch |err| app.postEvent(.{
+                .err = .{
+                    .err = err,
+                    .msg = "Container Event handling failed",
+                },
+            });
+
+            // post event handling
+            switch (event) {
+                .quit => break :loop,
+                else => {},
+            }
+        }
+
+        container.resize(&app.model, try renderer.resize());
+        container.reposition(&app.model, .{});
+        try renderer.render(@TypeOf(container), &container, App.Model, &app.model);
+        try renderer.flush();
+    }
+}
+
+pub const panic = App.panic_handler;
+const log = std.log.scoped(.default);
+
+const std = @import("std");
+const assert = std.debug.assert;
+const zterm = @import("zterm");
+
+const App = zterm.App(struct {}, union(enum) {});

src/app.zig

@@ -1,16 +1,4 @@
 //! Application type for TUI-applications
-const std = @import("std");
-const terminal = @import("terminal.zig");
-const event = @import("event.zig");
-
-const mergeTaggedUnions = event.mergeTaggedUnions;
-const isTaggedUnion = event.isTaggedUnion;
-
-const Key = @import("key.zig");
-const Size = @import("size.zig").Size;
-const Queue = @import("queue.zig").Queue;
-
-const log = std.log.scoped(.app);
 
 /// Create the App Type with the associated user events _E_ which describes
 /// an tagged union for all the user events that can be send through the
@@ -24,76 +12,118 @@ const log = std.log.scoped(.app);
 /// ```zig
 ///   const zterm = @import("zterm");
 ///   const App = zterm.App(
-///       union(enum) {},
+///       struct {}, // empty model
+///       union(enum) {}, // no additional user event's
 ///   );
 ///   // later on create an `App` instance and start the event loop
-///   var app: App = .{};
-///   try app.start(null);
-///   defer app.stop() catch unreachable;
+///   var app: App = .init(io, .{}); // provide instance of the `std.Io` and `App` model that shall be used
+///   try app.start(.full);
+///   defer app.stop() catch unreachable; // does not clean-up the resources used in the model
 /// ```
-pub fn App(comptime E: type) type {
-    if (!isTaggedUnion(E)) {
-        @compileError("Provided user event `E` for `App(comptime E: type)` is not of type `union(enum)`.");
-    }
+pub fn App(comptime M: type, comptime E: type) type {
+    if (!isStruct(M)) @compileError("Provided model `M` for `App(comptime M: type, comptime E: type)` is not of type `struct`");
+    if (!isTaggedUnion(E)) @compileError("Provided user event `E` for `App(comptime M: type, comptime E: type)` is not of type `union(enum)`.");
     return struct {
-        pub const Event = mergeTaggedUnions(event.SystemEvent, E);
-        pub const Container = @import("container.zig").Container(Event);
+        gpa: Allocator,
+        io: std.Io,
+        model: Model,
+        queue: Queue,
+        thread: ?Thread = null,
+        quit_event: Thread.ResetEvent,
+        termios: ?posix.termios = null,
+        handler_registered: bool = false,
+        config: TerminalConfiguration,
 
-        queue: Queue(Event, 256) = .{},
-        thread: ?std.Thread = null,
-        quit_event: std.Thread.ResetEvent = .{},
-        termios: ?std.posix.termios = null,
-        attached_handler: bool = false,
-        prev_size: Size = .{ .cols = 0, .rows = 0 },
+        pub const TerminalConfiguration = struct {
+            altScreen: bool,
+            saveScreen: bool,
+            rawMode: bool,
+            hideCursor: bool,
 
-        pub const SignalHandler = struct {
-            context: *anyopaque,
-            callback: *const fn (context: *anyopaque) void,
+            pub const full: @This() = .{
+                .altScreen = true,
+                .saveScreen = true,
+                .rawMode = true,
+                .hideCursor = true,
+            };
+
+            pub const direct: @This() = .{
+                .altScreen = false,
+                .saveScreen = false,
+                .rawMode = false,
+                .hideCursor = false,
+            };
         };
 
-        pub fn start(this: *@This()) !void {
+        // global variable for the registered handler for WINCH
+        var handler_ctx: *anyopaque = undefined;
+        /// registered WINCH handler to report resize events
+        fn handleWinch(_: i32) callconv(.c) void {
+            const this: *@This() = @ptrCast(@alignCast(handler_ctx));
+            // NOTE this does not have to be done if in-band resize events are supported
+            // -> the signal might not work correctly when hosting the application over ssh!
+            this.postEvent(.resize);
+        }
+        /// registered CONT handler to force a complete redraw
+        fn handleCont(_: i32) callconv(.c) void {
+            const this: *@This() = @ptrCast(@alignCast(handler_ctx));
+            // NOTE this does not have to be done if in-band resize events are supported
+            // -> the signal might not work correctly when hosting the application over ssh!
+            this.postEvent(.resize);
+        }
+
+        pub fn init(gpa: Allocator, io: std.Io, model: Model) @This() {
+            return .{
+                .gpa = gpa,
+                .io = io,
+                .model = model,
+                .queue = .{},
+                .quit_event = .{},
+                .config = undefined,
+            };
+        }
+
+        pub fn start(this: *@This(), config: TerminalConfiguration) !void {
+            this.config = config;
             if (this.thread) |_| return;
 
-            if (!this.attached_handler) {
-                var winch_act = std.posix.Sigaction{
-                    .handler = .{ .handler = @This().handleWinch },
-                    .mask = std.posix.empty_sigset,
+            // post init event (as the very first element to be in the queue - event loop)
+            this.postEvent(.init);
+
+            if (!this.handler_registered) {
+                handler_ctx = this;
+                posix.sigaction(posix.SIG.WINCH, &.{
+                    .handler = .{ .handler = handleWinch },
+                    .mask = posix.sigemptyset(),
                     .flags = 0,
-                };
-                std.posix.sigaction(std.posix.SIG.WINCH, &winch_act, null);
-
-                try registerWinch(.{
-                    .context = this,
-                    .callback = @This().winsizeCallback,
-                });
-                this.attached_handler = true;
-
-                // post init event (as the very first element to be in the queue - event loop)
-                this.postEvent(.init);
+                }, null);
+                posix.sigaction(posix.SIG.CONT, &.{
+                    .handler = .{ .handler = handleCont },
+                    .mask = posix.sigemptyset(),
+                    .flags = 0,
+                }, null);
+                this.handler_registered = true;
             }
 
             this.quit_event.reset();
-            this.thread = try std.Thread.spawn(.{}, @This().run, .{this});
+            this.thread = try Thread.spawn(.{}, @This().run, .{this});
 
-            var termios: std.posix.termios = undefined;
-            try terminal.enableRawMode(&termios);
+            var termios: posix.termios = undefined;
+            if (this.config.rawMode) try terminal.enableRawMode(&termios);
             if (this.termios) |_| {} else this.termios = termios;
 
-            try terminal.saveScreen();
-            try terminal.enterAltScreen();
-            try terminal.hideCursor();
-
-            // send initial size afterwards
-            const size = terminal.getTerminalSize();
-            this.postEvent(.{ .resize = size });
-            this.prev_size = size;
+            if (this.config.altScreen) try terminal.enterAltScreen();
+            if (this.config.saveScreen) try terminal.saveScreen();
+            if (this.config.hideCursor) try terminal.hideCursor();
+            if (this.config.altScreen and this.config.rawMode) try terminal.enableMouseSupport();
         }
 
         pub fn interrupt(this: *@This()) !void {
             this.quit_event.set();
-            try terminal.exitAltScreen();
-            try terminal.restoreScreen();
-            if (this.thread) |thread| {
+            if (this.config.altScreen and this.config.rawMode) try terminal.disableMouseSupport();
+            if (this.config.saveScreen) try terminal.restoreScreen();
+            if (this.config.altScreen) try terminal.exitAltScreen();
+            if (this.thread) |*thread| {
                 thread.join();
                 this.thread = null;
             }
@@ -101,17 +131,16 @@ pub fn App(comptime E: type) type {
 
         pub fn stop(this: *@This()) !void {
             try this.interrupt();
-            if (this.termios) |*termios| {
-                try terminal.disableRawMode(termios);
-                try terminal.showCursor();
-                try terminal.exitAltScreen();
-                try terminal.restoreScreen();
+            if (this.config.hideCursor) try terminal.showCursor();
+            if (this.config.saveScreen) try terminal.resetCursor();
+            if (this.termios) |termios| {
+                if (this.config.rawMode) try terminal.disableRawMode(&termios);
+                this.termios = null;
             }
-            this.termios = null;
         }
 
         /// Quit the application loop.
-        /// This will stop the internal input thread and post a **.quit** `Event`.
+        /// This will cancel the internal input thread and post a **.quit** `Event`.
         pub fn quit(this: *@This()) void {
             this.quit_event.set();
             this.postEvent(.quit);
@@ -127,72 +156,83 @@ pub fn App(comptime E: type) type {
             this.queue.push(e);
         }
 
-        fn winsizeCallback(ptr: *anyopaque) void {
-            const this: *@This() = @ptrCast(@alignCast(ptr));
-            const size = terminal.getTerminalSize();
-            if (size.cols != this.prev_size.cols or size.rows != this.prev_size.rows) {
-                this.postEvent(.{ .resize = size });
-                this.prev_size = size;
-            }
-        }
-
-        var winch_handler: ?SignalHandler = null;
-
-        fn registerWinch(handler: SignalHandler) !void {
-            if (winch_handler) |_| {
-                @panic("Cannot register another WINCH handler.");
-            }
-            winch_handler = handler;
-        }
-
-        fn handleWinch(_: c_int) callconv(.C) void {
-            if (winch_handler) |handler| {
-                handler.callback(handler.context);
-            }
-        }
-
         fn run(this: *@This()) !void {
-            // send initial terminal size
-            // changes are handled by the winch signal handler
-            // see `App.start` and `App.registerWinch` for details
-            {}
-
             // thread to read user inputs
-            var buf: [256]u8 = undefined;
+            var buf: [512]u8 = undefined;
+            // NOTE set the `NONBLOCK` option for the stdin file, such that reading is not blocking!
+            if (this.config.rawMode) {
+                // TODO is there a better way to do this through the `std.Io` interface?
+                var fl_flags = posix.fcntl(posix.STDIN_FILENO, posix.F.GETFL, 0) catch |err| switch (err) {
+                    error.FileBusy => unreachable,
+                    error.Locked => unreachable,
+                    error.PermissionDenied => unreachable,
+                    error.DeadLock => unreachable,
+                    error.LockedRegionLimitExceeded => unreachable,
+                    else => |e| return e,
+                };
+                fl_flags |= 1 << @bitOffsetOf(posix.system.O, "NONBLOCK");
+                _ = posix.fcntl(posix.STDIN_FILENO, posix.F.SETFL, fl_flags) catch |err| switch (err) {
+                    error.FileBusy => unreachable,
+                    error.Locked => unreachable,
+                    error.PermissionDenied => unreachable,
+                    error.DeadLock => unreachable,
+                    error.LockedRegionLimitExceeded => unreachable,
+                    else => |e| return e,
+                };
+            }
+
+            var remaining_bytes: usize = 0;
+            var lines: std.ArrayList(u8) = .empty;
+            defer lines.deinit(this.gpa);
+
             while (true) {
-                // FIX: I still think that there is a race condition (I'm just waiting 'long' enough)
                 this.quit_event.timedWait(20 * std.time.ns_per_ms) catch {
-                    const read_bytes = try terminal.read(buf[0..]);
+                    // non-blocking read
+                    const read_bytes = terminal.read(buf[remaining_bytes..]) catch |err| switch (err) {
+                        error.WouldBlock => {
+                            // wait a bit
+                            std.Thread.sleep(20);
+                            continue;
+                        },
+                        else => return err,
+                    } + remaining_bytes;
+                    remaining_bytes = 0;
+
+                    if (read_bytes == 0) {
+                        // received <EOF>
+                        this.postEvent(.cancel);
+                        continue;
+                    }
+
                     // escape key presses
                     if (buf[0] == 0x1b and read_bytes > 1) {
                         switch (buf[1]) {
                             0x4F => { // ss3
                                 if (read_bytes < 3) continue;
 
-                                const key: ?Key = switch (buf[2]) {
-                                    0x1B => null,
-                                    'A' => .{ .cp = Key.up },
-                                    'B' => .{ .cp = Key.down },
-                                    'C' => .{ .cp = Key.right },
-                                    'D' => .{ .cp = Key.left },
-                                    'E' => .{ .cp = Key.kp_begin },
-                                    'F' => .{ .cp = Key.end },
-                                    'H' => .{ .cp = Key.home },
-                                    'P' => .{ .cp = Key.f1 },
-                                    'Q' => .{ .cp = Key.f2 },
-                                    'R' => .{ .cp = Key.f3 },
-                                    'S' => .{ .cp = Key.f4 },
-                                    else => null,
+                                const key: Key = switch (buf[2]) {
+                                    'A' => .{ .cp = input.Up },
+                                    'B' => .{ .cp = input.Down },
+                                    'C' => .{ .cp = input.Right },
+                                    'D' => .{ .cp = input.Left },
+                                    'E' => .{ .cp = input.KpBegin },
+                                    'F' => .{ .cp = input.End },
+                                    'H' => .{ .cp = input.Home },
+                                    'P' => .{ .cp = input.F1 },
+                                    'Q' => .{ .cp = input.F2 },
+                                    'R' => .{ .cp = input.F3 },
+                                    'S' => .{ .cp = input.F4 },
+                                    else => continue,
                                 };
-                                if (key) |k| this.postEvent(.{ .key = k });
+                                this.postEvent(.{ .key = key });
                             },
                             0x5B => { // csi
                                 if (read_bytes < 3) continue;
 
                                 // We start iterating at index 2 to get past the '['
-                                const sequence = for (buf[2..], 2..) |b, i| {
+                                const sequence: []u8 = blk: for (buf[2..], 2..) |b, i| {
                                     switch (b) {
-                                        0x40...0xFF => break buf[0 .. i + 1],
+                                        0x40...0xFF => break :blk buf[0 .. i + 1],
                                         else => continue,
                                     }
                                 } else continue;
@@ -203,64 +243,140 @@ pub fn App(comptime E: type) type {
                                         // Legacy keys
                                         // CSI {ABCDEFHPQS}
                                         // CSI 1 ; modifier:event_type {ABCDEFHPQS}
+                                        var field_iter = std.mem.splitScalar(u8, sequence[2 .. sequence.len - 1], ';');
+                                        _ = field_iter.next(); // skip first field
+
                                         const key: Key = .{
                                             .cp = switch (final) {
-                                                'A' => Key.up,
-                                                'B' => Key.down,
-                                                'C' => Key.right,
-                                                'D' => Key.left,
-                                                'E' => Key.kp_begin,
-                                                'F' => Key.end,
-                                                'H' => Key.home,
-                                                'P' => Key.f1,
-                                                'Q' => Key.f2,
-                                                'R' => Key.f3,
-                                                'S' => Key.f4,
-                                                else => unreachable, // switch case prevents in this case form ever happening
+                                                'A' => input.Up,
+                                                'B' => input.Down,
+                                                'C' => input.Right,
+                                                'D' => input.Left,
+                                                'E' => input.KpBegin,
+                                                'F' => input.End,
+                                                'H' => input.Home,
+                                                'P' => input.F1,
+                                                'Q' => input.F2,
+                                                'R' => input.F3,
+                                                'S' => input.F4,
+                                                else => unreachable,
+                                            },
+                                            .mod = blk: {
+                                                // modifier_mask:event_type
+                                                var mod: Key.Modifier = .{};
+                                                const field_buf = field_iter.next() orelse break :blk mod;
+                                                var param_iter = std.mem.splitScalar(u8, field_buf, ':');
+                                                const modifier_buf = param_iter.next() orelse unreachable;
+                                                const modifier_mask = fmt.parseUnsigned(u8, modifier_buf, 10) catch break :blk mod;
+                                                if ((modifier_mask -| 1) & 1 != 0) mod.shift = true;
+                                                if ((modifier_mask -| 1) & 2 != 0) mod.alt = true;
+                                                if ((modifier_mask -| 1) & 4 != 0) mod.ctrl = true;
+                                                break :blk mod;
                                             },
                                         };
                                         this.postEvent(.{ .key = key });
                                     },
+                                    'Z' => this.postEvent(.{ .key = .{ .cp = input.Tab, .mod = .{ .shift = true } } }),
                                     '~' => {
                                         // Legacy keys
                                         // CSI number ~
                                         // CSI number ; modifier ~
                                         // CSI number ; modifier:event_type ; text_as_codepoint ~
-                                        var field_iter = std.mem.splitScalar(u8, sequence[2 .. sequence.len - 1], ';');
-                                        const number_buf = field_iter.next() orelse unreachable; // always will have one field
-                                        const number = std.fmt.parseUnsigned(u16, number_buf, 10) catch break;
+                                        var field_iter = mem.splitScalar(u8, sequence[2 .. sequence.len - 1], ';');
 
                                         const key: Key = .{
-                                            .cp = switch (number) {
-                                                2 => Key.insert,
-                                                3 => Key.delete,
-                                                5 => Key.page_up,
-                                                6 => Key.page_down,
-                                                7 => Key.home,
-                                                8 => Key.end,
-                                                11 => Key.f1,
-                                                12 => Key.f2,
-                                                13 => Key.f3,
-                                                14 => Key.f4,
-                                                15 => Key.f5,
-                                                17 => Key.f6,
-                                                18 => Key.f7,
-                                                19 => Key.f8,
-                                                20 => Key.f9,
-                                                21 => Key.f10,
-                                                23 => Key.f11,
-                                                24 => Key.f12,
-                                                // 200 => return .{ .event = .paste_start, .n = sequence.len },
-                                                // 201 => return .{ .event = .paste_end, .n = sequence.len },
-                                                57427 => Key.kp_begin,
-                                                else => unreachable,
+                                            .cp = blk: {
+                                                const number_buf = field_iter.next() orelse unreachable; // always will have one field
+                                                const number = fmt.parseUnsigned(u16, number_buf, 10) catch break;
+                                                break :blk switch (number) {
+                                                    2 => input.Insert,
+                                                    3 => input.Delete,
+                                                    5 => input.PageUp,
+                                                    6 => input.PageDown,
+                                                    7 => input.Home,
+                                                    8 => input.End,
+                                                    11 => input.F1,
+                                                    12 => input.F2,
+                                                    13 => input.F3,
+                                                    14 => input.F4,
+                                                    15 => input.F5,
+                                                    17 => input.F6,
+                                                    18 => input.F7,
+                                                    19 => input.F8,
+                                                    20 => input.F9,
+                                                    21 => input.F10,
+                                                    23 => input.F11,
+                                                    24 => input.F12,
+                                                    25 => input.F13,
+                                                    26 => input.F14,
+                                                    28 => input.F15,
+                                                    29 => input.F16,
+                                                    31 => input.F17,
+                                                    32 => input.F18,
+                                                    33 => input.F19,
+                                                    34 => input.F20,
+                                                    // 200 => return .{ .event = .paste_start, .n = sequence.len },
+                                                    // 201 => return .{ .event = .paste_end, .n = sequence.len },
+                                                    57399...57454 => |code| code,
+                                                    else => unreachable,
+                                                };
+                                            },
+                                            .mod = blk: {
+                                                // modifier_mask:event_type
+                                                var mod: Key.Modifier = .{};
+                                                const field_buf = field_iter.next() orelse break :blk mod;
+                                                var param_iter = std.mem.splitScalar(u8, field_buf, ':');
+                                                const modifier_buf = param_iter.next() orelse unreachable;
+                                                const modifier_mask = fmt.parseUnsigned(u8, modifier_buf, 10) catch break :blk mod;
+                                                if ((modifier_mask -| 1) & 1 != 0) mod.shift = true;
+                                                if ((modifier_mask -| 1) & 2 != 0) mod.alt = true;
+                                                if ((modifier_mask -| 1) & 4 != 0) mod.ctrl = true;
+                                                break :blk mod;
                                             },
                                         };
                                         this.postEvent(.{ .key = key });
                                     },
+                                    // TODO focus usage? should this even be in the default event system?
                                     'I' => this.postEvent(.{ .focus = true }),
                                     'O' => this.postEvent(.{ .focus = false }),
-                                    // 'M', 'm' => return parseMouse(sequence), // TODO: parse mouse inputs
+                                    'M', 'm' => {
+                                        assert(sequence.len >= 4);
+                                        if (sequence[2] != '<') break;
+
+                                        const delim1 = mem.indexOfScalarPos(u8, sequence, 3, ';') orelse break;
+                                        const button_mask = fmt.parseUnsigned(u16, sequence[3..delim1], 10) catch break;
+                                        const delim2 = mem.indexOfScalarPos(u8, sequence, delim1 + 1, ';') orelse break;
+                                        const px = fmt.parseUnsigned(u16, sequence[delim1 + 1 .. delim2], 10) catch break;
+                                        const py = fmt.parseUnsigned(u16, sequence[delim2 + 1 .. sequence.len - 1], 10) catch break;
+
+                                        const mouse_bits = packed struct {
+                                            const motion: u8 = 0b00100000;
+                                            const buttons: u8 = 0b11000011;
+                                            const shift: u8 = 0b00000100;
+                                            const alt: u8 = 0b00001000;
+                                            const ctrl: u8 = 0b00010000;
+                                        };
+
+                                        const button: Mouse.Button = @enumFromInt(button_mask & mouse_bits.buttons);
+                                        const motion = button_mask & mouse_bits.motion > 0;
+                                        // const shift = button_mask & mouse_bits.shift > 0;
+                                        // const alt = button_mask & mouse_bits.alt > 0;
+                                        // const ctrl = button_mask & mouse_bits.ctrl > 0;
+
+                                        this.postEvent(.{
+                                            .mouse = .{
+                                                .button = button,
+                                                .x = px -| 1,
+                                                .y = py -| 1,
+                                                .kind = blk: {
+                                                    if (motion and button != Mouse.Button.none) break :blk .drag;
+                                                    if (motion and button == Mouse.Button.none) break :blk .motion;
+                                                    if (sequence[sequence.len - 1] == 'm') break :blk .release;
+                                                    break :blk .press;
+                                                },
+                                            },
+                                        });
+                                    },
                                     'c' => {
                                         // Primary DA (CSI ? Pm c)
                                     },
@@ -268,29 +384,26 @@ pub fn App(comptime E: type) type {
                                         // Device Status Report
                                         // CSI Ps n
                                         // CSI ? Ps n
-                                        std.debug.assert(sequence.len >= 3);
+                                        assert(sequence.len >= 3);
                                     },
                                     't' => {
                                         // XTWINOPS
                                         // Split first into fields delimited by ';'
-                                        var iter = std.mem.splitScalar(u8, sequence[2 .. sequence.len - 1], ';');
+                                        var iter = mem.splitScalar(u8, sequence[2 .. sequence.len - 1], ';');
                                         const ps = iter.first();
-                                        if (std.mem.eql(u8, "48", ps)) {
+                                        if (mem.eql(u8, "48", ps)) {
                                             // in band window resize
                                             // CSI 48 ; height ; width ; height_pix ; width_pix t
-                                            const height_char = iter.next() orelse break;
                                             const width_char = iter.next() orelse break;
+                                            const height_char = iter.next() orelse break;
 
-                                            // TODO: only post the event if the size has changed?
-                                            // because there might be too many resize events (which force a re-draw of the entire screen)
-                                            const size: Size = .{
-                                                .rows = std.fmt.parseUnsigned(u16, height_char, 10) catch break,
-                                                .cols = std.fmt.parseUnsigned(u16, width_char, 10) catch break,
-                                            };
-                                            if (size.cols != this.prev_size.cols or size.rows != this.prev_size.rows) {
-                                                this.postEvent(.{ .resize = size });
-                                                this.prev_size = size;
-                                            }
+                                            _ = width_char;
+                                            _ = height_char;
+                                            this.postEvent(.resize);
+                                            // this.postEvent(.{ .size = .{
+                                            //     .x = fmt.parseUnsigned(u16, width_char, 10) catch break,
+                                            //     .y = fmt.parseUnsigned(u16, height_char, 10) catch break,
+                                            // } });
                                         }
                                     },
                                     'u' => {
@@ -305,35 +418,133 @@ pub fn App(comptime E: type) type {
                                     else => {},
                                 }
                             },
-                            // TODO: parse corresponding codes
-                            // 0x5B => parseCsi(input, &self.buf), // CSI see https://github.com/rockorager/libvaxis/blob/main/src/Parser.zig
-                            else => {},
+                            0x50 => {
+                                // DCS
+                            },
+                            0x58 => {
+                                // SOS
+                            },
+                            0x5D => {
+                                // OSC
+                            },
+                            // TODO parse corresponding codes
+                            0x5F => {
+                                // APC
+                                // parse for kitty graphics capabilities
+                            },
+                            else => {
+                                // alt + <char> keypress
+                                this.postEvent(.{
+                                    .key = .{
+                                        .cp = buf[1],
+                                        .mod = .{ .alt = true },
+                                    },
+                                });
+                            },
                         }
                     } else {
-                        const b = buf[0];
-                        const key: Key = switch (b) {
-                            0x00 => .{ .cp = '@', .mod = .{ .ctrl = true } },
-                            0x08 => .{ .cp = Key.backspace },
-                            0x09 => .{ .cp = Key.tab },
-                            0x0a, 0x0d => .{ .cp = Key.enter },
-                            0x01...0x07, 0x0b...0x0c, 0x0e...0x1a => .{ .cp = b + 0x60, .mod = .{ .ctrl = true } },
-                            0x1b => escape: {
-                                std.debug.assert(read_bytes == 1);
-                                break :escape .{ .cp = Key.escape };
-                            },
-                            0x7f => .{ .cp = Key.backspace },
-                            else => {
-                                var iter = terminal.code_point.Iterator{ .bytes = buf[0..read_bytes] };
-                                while (iter.next()) |cp| this.postEvent(.{ .key = .{ .cp = cp.code } });
-                                continue;
-                            },
-                        };
-                        this.postEvent(.{ .key = key });
+                        if (this.config.rawMode) {
+                            const b = buf[0];
+                            const key: Key = switch (b) {
+                                0x00 => .{ .cp = '@', .mod = .{ .ctrl = true } },
+                                0x08 => .{ .cp = input.Backspace },
+                                0x09 => .{ .cp = input.Tab },
+                                0x0a => .{ .cp = 'j', .mod = .{ .ctrl = true } },
+                                0x0d => .{ .cp = input.Enter },
+                                0x01...0x07, 0x0b...0x0c, 0x0e...0x1a => .{ .cp = b + 0x60, .mod = .{ .ctrl = true } },
+                                0x1b => escape: {
+                                    assert(read_bytes == 1);
+                                    break :escape .{ .cp = input.Escape };
+                                },
+                                0x7f => .{ .cp = input.Backspace },
+                                else => {
+                                    var len = read_bytes;
+                                    while (!std.unicode.utf8ValidateSlice(buf[0..len])) len -= 1;
+                                    remaining_bytes = read_bytes - len;
+                                    var iter: std.unicode.Utf8Iterator = .{ .bytes = buf[0..len], .i = 0 };
+                                    while (iter.nextCodepoint()) |cp| this.postEvent(.{ .key = .{ .cp = cp } });
+                                    if (remaining_bytes > 0) {
+                                        @memmove(buf[0..remaining_bytes], buf[len .. len + remaining_bytes]);
+                                    }
+                                    continue; // this switch block does not return a `Key` we continue with loop
+                                },
+                            };
+                            this.postEvent(.{ .key = key });
+                        } else {
+                            var len = read_bytes;
+                            while (!std.unicode.utf8ValidateSlice(buf[0..len])) len -= 1;
+                            remaining_bytes = read_bytes - len;
+                            try lines.appendSlice(this.gpa, buf[0..len]);
+                            if (remaining_bytes > 0) {
+                                @memmove(buf[0..remaining_bytes], buf[len .. len + remaining_bytes]);
+                            } else {
+                                if (read_bytes != 512 and buf[len - 1] == '\n') this.postEvent(.{ .line = try lines.toOwnedSlice(this.gpa) });
+                                // NOTE line did not end with `\n` but with EOF, meaning the user canceled
+                                if (read_bytes != 512 and buf[len - 1] != '\n') {
+                                    lines.clearRetainingCapacity();
+                                    this.postEvent(.cancel);
+                                }
+                            }
+                        }
                     }
                     continue;
                 };
                 break;
             }
         }
+
+        pub fn panic_handler(msg: []const u8, _: ?*std.builtin.StackTrace, ret_addr: ?usize) noreturn {
+            terminal.disableMouseSupport() catch {};
+            terminal.showCursor() catch {};
+            terminal.resetCursor() catch {};
+            terminal.restoreScreen() catch {};
+            terminal.disableRawMode(&.{
+                .iflag = .{},
+                .lflag = .{},
+                .cflag = .{},
+                .oflag = .{},
+                .cc = undefined,
+                .line = 0,
+                .ispeed = undefined,
+                .ospeed = undefined,
+            }) catch {};
+            terminal.exitAltScreen() catch {};
+            std.debug.defaultPanic(msg, ret_addr);
+        }
+
+        const element = @import("element.zig");
+        pub const Model = M;
+        pub const Event = mergeTaggedUnions(event.SystemEvent, E);
+        pub const Container = @import("container.zig").Container(Model, Event);
+        pub const Element = element.Element(Model, Event);
+        pub const Alignment = element.Alignment(Model, Event);
+        pub const Button = element.Button(Model, Event, Queue);
+        pub const TextField = element.TextField(Model, Event);
+        pub const Input = element.Input(Model, Event, Queue);
+        pub const Progress = element.Progress(Model, Event, Queue);
+        pub const RadioButton = element.RadioButton(Model, Event);
+        pub const Scrollable = element.Scrollable(Model, Event);
+        pub const Selection = element.Selection(Model, Event);
+        pub const Queue = queue.Queue(Event, 512);
     };
 }
+
+const log = std.log.scoped(.app);
+
+const std = @import("std");
+const mem = std.mem;
+const fmt = std.fmt;
+const posix = std.posix;
+const Thread = std.Thread;
+const Allocator = mem.Allocator;
+const assert = std.debug.assert;
+const event = @import("event.zig");
+const input = @import("input.zig");
+const terminal = @import("terminal.zig");
+const queue = @import("queue.zig");
+const mergeTaggedUnions = event.mergeTaggedUnions;
+const isTaggedUnion = event.isTaggedUnion;
+const isStruct = event.isStruct;
+const Mouse = input.Mouse;
+const Key = input.Key;
+const Point = @import("point.zig").Point;

src/cell.zig

@@ -1,21 +1,61 @@
-const std = @import("std");
-const Style = @import("style.zig");
+//! Cell type containing content and formatting for each character in the terminal screen.
 
-pub const Cell = @This();
-
-style: Style = .{ .attributes = &.{} },
-// TODO: embrace `zg` dependency more due to utf-8 encoding
 cp: u21 = ' ',
+style: Style = .{ .emphasis = &.{} },
 
 pub fn eql(this: Cell, other: Cell) bool {
     return this.cp == other.cp and this.style.eql(other.style);
 }
 
 pub fn reset(this: *Cell) void {
-    this.style = .{ .attributes = &.{} };
+    this.style = .{ .emphasis = &.{} };
     this.cp = ' ';
 }
 
-pub fn value(this: Cell, writer: anytype) !void {
+pub fn value(this: Cell, writer: *std.Io.Writer) !void {
     try this.style.value(writer, this.cp);
 }
+
+const std = @import("std");
+const Style = @import("style.zig");
+const Cell = @This();
+
+test "ascii styled text" {
+    const cells: [4]Cell = .{
+        .{ .cp = 'Y', .style = .{ .fg = .green, .bg = .grey, .emphasis = &.{} } },
+        .{ .cp = 'v', .style = .{ .emphasis = &.{ .bold, .underline } } },
+        .{ .cp = 'e', .style = .{ .emphasis = &.{.italic} } },
+        .{ .cp = 's', .style = .{ .fg = .lightgreen, .bg = .black, .emphasis = &.{.underline} } },
+    };
+
+    var writer = std.Io.Writer.Allocating.init(std.testing.allocator);
+    defer writer.deinit();
+    for (cells) |cell| {
+        try cell.value(&writer.writer);
+    }
+    try std.testing.expectEqualSlices(
+        u8,
+        "\x1b[38;5;10;48;5;8;59mY\x1b[0m\x1b[39;49;59;1;4mv\x1b[0m\x1b[39;49;59;3me\x1b[0m\x1b[38;5;2;48;5;16;59;4ms\x1b[0m",
+        writer.writer.buffer[0..writer.writer.end],
+    );
+}
+
+test "utf-8 styled text" {
+    const cells: [4]Cell = .{
+        .{ .cp = '╭', .style = .{ .fg = .green, .bg = .grey, .emphasis = &.{} } },
+        .{ .cp = '─', .style = .{ .emphasis = &.{} } },
+        .{ .cp = '┄', .style = .{ .emphasis = &.{} } },
+        .{ .cp = '┘', .style = .{ .fg = .lightgreen, .bg = .black, .emphasis = &.{.underline} } },
+    };
+
+    var writer = std.Io.Writer.Allocating.init(std.testing.allocator);
+    defer writer.deinit();
+    for (cells) |cell| {
+        try cell.value(&writer.writer);
+    }
+    try std.testing.expectEqualSlices(
+        u8,
+        "\x1b[38;5;10;48;5;8;59m╭\x1b[0m\x1b[39;49;59m─\x1b[0m\x1b[39;49;59m┄\x1b[0m\x1b[38;5;2;48;5;16;59;4m┘\x1b[0m",
+        writer.writer.buffer[0..writer.writer.end],
+    );
+}

src/color.zig

@@ -1,15 +1,13 @@
-const std = @import("std");
-
 pub const Color = enum(u8) {
     default = 0,
     black = 16,
-    light_red = 1,
-    light_green,
-    light_yellow,
-    light_blue,
-    light_magenta,
-    light_cyan,
-    light_grey,
+    lightred = 1,
+    lightgreen,
+    lightyellow,
+    lightblue,
+    lightmagenta,
+    lightcyan,
+    lightgrey,
     grey,
     red,
     green,
@@ -18,21 +16,23 @@ pub const Color = enum(u8) {
     magenta,
     cyan,
     white,
-    // TODO: add further colors as described in https://gist.github.com/ConnerWill/d4b6c776b509add763e17f9f113fd25b # Color / Graphics Mode - 256 Colors
+    // TODO add further colors as described in https://gist.github.com/ConnerWill/d4b6c776b509add763e17f9f113fd25b # Color / Graphics Mode - 256 Colors
 
-    pub inline fn write(this: Color, writer: anytype, comptime coloring: enum { fg, bg, ul }) !void {
+    pub inline fn write(this: Color, writer: *std.Io.Writer, comptime coloring: enum { fg, bg, ul }) !void {
         if (this == .default) {
             switch (coloring) {
-                .fg => try std.fmt.format(writer, "39", .{}),
-                .bg => try std.fmt.format(writer, "49", .{}),
-                .ul => try std.fmt.format(writer, "59", .{}),
+                .fg => try writer.printAscii("39", .{}),
+                .bg => try writer.printAscii("49", .{}),
+                .ul => try writer.printAscii("59", .{}),
             }
         } else {
             switch (coloring) {
-                .fg => try std.fmt.format(writer, "38;5;{d}", .{@intFromEnum(this)}),
-                .bg => try std.fmt.format(writer, "48;5;{d}", .{@intFromEnum(this)}),
-                .ul => try std.fmt.format(writer, "58;5;{d}", .{@intFromEnum(this)}),
+                .fg => try writer.print("38;5;{d}", .{@intFromEnum(this)}),
+                .bg => try writer.print("48;5;{d}", .{@intFromEnum(this)}),
+                .ul => try writer.print("58;5;{d}", .{@intFromEnum(this)}),
             }
         }
     }
 };
+
+const std = @import("std");

src/ctlseqs.zig

@@ -50,6 +50,7 @@ pub const home = "\x1b[H";
 pub const cup = "\x1b[{d};{d}H";
 pub const hide_cursor = "\x1b[?25l";
 pub const show_cursor = "\x1b[?25h";
+pub const reset_cursor_shape = "\x1b[0 q";
 pub const cursor_shape = "\x1b[{d} q";
 pub const ri = "\x1bM";
 pub const ind = "\n";
@@ -58,8 +59,11 @@ pub const cub = "\x1b[{d}D";
 
 // Erase
 pub const erase_below_cursor = "\x1b[J";
+pub const clear_screen = "\x1b[2J";
 
 // alt screen
+pub const save_screen = "\x1b[?47h";
+pub const restore_screen = "\x1b[?47l";
 pub const smcup = "\x1b[?1049h";
 pub const rmcup = "\x1b[?1049l";
 
@@ -89,7 +93,7 @@ pub const bg_rgb_legacy = "\x1b[48;2;{d};{d};{d}m";
 pub const ul_rgb_legacy = "\x1b[58;2;{d};{d};{d}m";
 
 // Underlines
-pub const ul_off = "\x1b[24m"; // NOTE: this could be \x1b[4:0m but is not as widely supported
+pub const ul_off = "\x1b[24m"; // NOTE this could be \x1b[4:0m but is not as widely supported
 pub const ul_single = "\x1b[4m";
 pub const ul_double = "\x1b[4:2m";
 pub const ul_curly = "\x1b[4:3m";
@@ -136,5 +140,6 @@ pub const osc10_reset = "\x1b]110\x1b\\"; // reset fg to terminal default
 pub const osc11_query = "\x1b]11;?\x1b\\"; // bg
 pub const osc11_set = "\x1b]11;rgb:{x:0>2}{x:0>2}/{x:0>2}{x:0>2}/{x:0>2}{x:0>2}\x1b\\"; // set default terminal bg
 pub const osc11_reset = "\x1b]111\x1b\\"; // reset bg to terminal default
+pub const osc12_set = "\x1b]12;{s}\x1b\\"; // set the cursor color through the name of the 8 base colors!
 pub const osc12_query = "\x1b]12;?\x1b\\"; // cursor color
 pub const osc12_reset = "\x1b]112\x1b\\"; // reset cursor to terminal default

src/error.zig

@@ -0,0 +1,4 @@
+pub const Error = error{
+    /// Thrown when a `Container` is too small to be rendered in the current screen part.
+    TooSmall,
+};

src/event.zig

@@ -1,37 +1,55 @@
 //! Events which are defined by the library. They might be extended by user
 //! events. See `App` for more details about user defined events.
-const std = @import("std");
-const terminal = @import("terminal.zig");
-
-const Size = @import("size.zig").Size;
-const Key = @import("key.zig");
 
 /// System events available to every `zterm.App`
 pub const SystemEvent = union(enum) {
     /// Initialize event, which is send once at the beginning of the event loop and before the first render loop
-    /// TODO: not sure if this is necessary or if there is an actual usecase for this - for now it will remain
+    /// TODO not sure if this is necessary or if there is an actual usecase for this - for now it will remain
     init,
     /// Quit event to signify the end of the event loop (rendering should stop afterwards)
     quit,
+    /// Cancel event to signify that the user provided an EOF
+    ///
+    /// Usually this event is only triggered by the system in *non raw mode*
+    /// renderings otherwise the corresponding `.key` event would be fired instead.
+    cancel,
+    /// Resize event to signify that the application should re-draw to resize
+    ///
+    /// Usually no `Container` nor `Element` should act on that event, as it
+    /// only serves for event based loops to force a re-draw with a new `Event`.
+    resize,
+    /// Ring the terminal bell to notify the user. This `Event` is handled by
+    /// every `Container` and will not be passed through the container tree.
+    bell,
     /// Error event to notify other containers about a recoverable error
     err: struct {
+        /// actual error
         err: anyerror,
         /// associated error message
         msg: []const u8,
     },
-    /// Resize event emitted by the terminal to derive the `Size` of the current terminal the application is rendered in
-    resize: Size,
+    /// Input line event received in *non raw mode* (instead of individual `key` events)
+    ///
+    /// This event contains the entire line until the ending newline character
+    /// (which is included in the payload of this event).
+    line: []const u8,
     /// Input key event received from the user
     key: Key,
-    /// Focus event for mouse interaction
-    /// TODO: this should instead be a union with a `Size` to derive which container / element the focus meant for
+    /// Mouse input event
+    mouse: Mouse,
+    /// Focus event indicating that the application has gained the focus of the user
     focus: bool,
 };
 
+/// Merge the two provided `union(enum)` `A` and `B` to a tagged union containing all fields of both tagged unions in `comptime`.
+/// Declarations are not supported for `comptime` created types, see https://github.com/ziglang/zig/issues/6709 for details.
 pub fn mergeTaggedUnions(comptime A: type, comptime B: type) type {
-    if (!isTaggedUnion(A) or !isTaggedUnion(B)) {
-        @compileError("Both types for merging tagged unions need to be of type `union(enum)`.");
-    }
+    // TODO maybe it makes sense to have a nested tagged union type (i.e. system: union(enum) and event: union(enum))
+    // - allows re-definition of system / built-in events
+    // - clearly shows which events are system / built-in ones and which are user defined events
+    // - the memory footprint for the nesting is not really harmful
+    if (!isTaggedUnion(A) or !isTaggedUnion(B)) @compileError("Both types for merging tagged unions need to be of type `union(enum)`.");
+
     const a_fields = @typeInfo(A).@"union".fields;
     const a_fields_tag = @typeInfo(A).@"union".tag_type.?;
     const a_enum_fields = @typeInfo(a_fields_tag).@"enum".fields;
@@ -56,11 +74,27 @@ pub fn mergeTaggedUnions(comptime A: type, comptime B: type) type {
         i += 1;
     }
 
-    const log2_i = @bitSizeOf(@TypeOf(i)) - @clz(i);
+    // NOTE declarations are not supported for `comptime` types: https://github.com/ziglang/zig/issues/6709
+    // -> will lead to a compilation error when constructing the tagged union
+    //    at the end of this function in case at least one of the provided tagged
+    //    unions to merge contains declarations (which in this case can only be the
+    //    user provided one)
+    const a_enum_decls = @typeInfo(A).@"union".decls;
+    const b_enum_decls = @typeInfo(B).@"union".decls;
+    var decls: [a_enum_decls.len + b_enum_decls.len]std.builtin.Type.Declaration = undefined;
+    var j: usize = 0;
+    for (a_enum_decls) |decl| {
+        decls[j] = decl;
+        j += 1;
+    }
+    for (b_enum_decls) |decl| {
+        decls[j] = decl;
+        j += 1;
+    }
 
     const EventType = @Type(.{ .int = .{
         .signedness = .unsigned,
-        .bits = log2_i,
+        .bits = @bitSizeOf(@TypeOf(i)) - @clz(i),
     } });
 
     const Event = @Type(.{ .@"enum" = .{
@@ -78,15 +112,28 @@ pub fn mergeTaggedUnions(comptime A: type, comptime B: type) type {
     } });
 }
 
-// Determine at `comptime` whether the provided type `E` is an `union(enum)`.
-pub fn isTaggedUnion(comptime E: type) bool {
-    switch (@typeInfo(E)) {
-        .@"union" => |u| {
-            if (u.tag_type) |_| {} else {
-                return false;
-            }
+/// Determine whether the provided type `T` is a tagged union: `union(enum)`.
+pub fn isTaggedUnion(comptime T: type) bool {
+    switch (@typeInfo(T)) {
+        .@"union" => |u| if (u.tag_type) |_| {} else {
+            return false;
         },
         else => return false,
     }
     return true;
 }
+
+/// Determine whether the provided type `T` is a `struct`.
+pub fn isStruct(comptime T: type) bool {
+    return switch (@typeInfo(T)) {
+        .@"struct" => true,
+        else => false,
+    };
+}
+
+const std = @import("std");
+const input = @import("input.zig");
+const terminal = @import("terminal.zig");
+const Key = input.Key;
+const Mouse = input.Mouse;
+const Point = @import("point.zig").Point;

src/input.zig

@@ -0,0 +1,238 @@
+//! Input module for `zterm`. Contains structs to represent key events and mouse events.
+
+pub const Mouse = packed struct {
+    x: u16,
+    y: u16,
+    button: Button,
+    kind: Kind,
+
+    pub const Button = enum(u8) {
+        left,
+        middle,
+        right,
+        none,
+        wheel_up = 64,
+        wheel_down = 65,
+        wheel_right = 66,
+        wheel_left = 67,
+        button_8 = 128,
+        button_9 = 129,
+        button_10 = 130,
+        button_11 = 131,
+    };
+
+    pub const Kind = enum(u2) {
+        press,
+        release,
+        motion,
+        drag,
+    };
+
+    pub fn eql(this: @This(), other: @This()) bool {
+        return meta.eql(this, other);
+    }
+
+    pub fn in(this: @This(), origin: Point, size: Point) bool {
+        return this.x >= origin.x and this.x < size.x + origin.x and
+            this.y >= origin.y and this.y < size.y + origin.y;
+    }
+};
+
+pub const Key = packed struct {
+    cp: u21,
+    mod: Modifier = .{},
+
+    pub const Modifier = packed struct {
+        shift: bool = false,
+        alt: bool = false,
+        ctrl: bool = false,
+    };
+
+    /// Compare _this_ `Key` with an _other_ `Key`.
+    ///
+    /// # Example
+    ///
+    /// Configure `ctrl+c` to quit the application (done in main event loop of the application):
+    ///
+    /// ```zig
+    /// switch (event) {
+    ///     .quit => break,
+    ///     .key => |key| if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) app.quit.set(),
+    ///     else => {},
+    /// }
+    /// ```
+    pub fn eql(this: @This(), other: @This()) bool {
+        return meta.eql(this, other);
+    }
+
+    /// Determine if the `Key` is an unicode character that can be printed to
+    /// the screen. This means that the code point of the `Key` is an ascii
+    /// character between 32 - 255 (with the exception of 127 = Delete) and no
+    /// modifiers (alt and/or ctrl) are used.
+    ///
+    /// # Example
+    ///
+    /// Get user input's from the .key event from the application event loop:
+    ///
+    /// ```zig
+    /// switch (event) {
+    ///   .key => |key| if (key.isUnicode()) try this.input.append(key.cp),
+    ///   else => {},
+    /// }
+    /// ```
+    pub fn isUnicode(this: @This()) bool {
+        return this.mod.alt == false and this.mod.ctrl == false and // no modifier keys
+            (this.cp >= 32 and this.cp <= 126 or // ascii printable characters (except for input.Delete)
+                this.cp >= 128 and this.cp <= 255) or // extended ascii codes
+            ((this.cp >= 0x0080 and this.cp <= 0x07FF) or
+                (this.cp >= 0x0800 and this.cp <= 0xFFFF) or
+                (this.cp >= 0x100000 and this.cp <= 0x10FFFF)) and // allowed unicode character ranges (2 - 4 byte characters)
+                (this.cp < 57348 or this.cp > 57454); // no other predefined meanings (i.e. arrow keys, etc.)
+    }
+
+    /// Determine if the `Key` is an ascii character that can be printed to
+    /// the screen. This means that the code point of the `Key` is an ascii
+    /// character between 32 - 255 (with the exception of 127 = Delete) and no
+    /// modifiers (alt and/or ctrl) are used.
+    ///
+    /// # Example
+    ///
+    /// Get user input's from the .key event from the application event loop:
+    ///
+    /// ```zig
+    /// switch (event) {
+    ///   .key => |key| if (key.isAscii()) try this.input.append(key.cp),
+    ///   else => {},
+    /// }
+    /// ```
+    pub fn isAscii(this: @This()) bool {
+        return this.mod.alt == false and this.mod.ctrl == false and // no modifier keys
+            (this.cp >= 32 and this.cp <= 126 or // ascii printable characters (except for input.Delete)
+                this.cp >= 128 and this.cp <= 255); // extended ascii codes
+    }
+
+    test "isAscii with ascii character" {
+        try testing.expectEqual(true, isAscii(.{ .cp = 'c' }));
+        try testing.expectEqual(false, isAscii(.{ .cp = 'c', .mod = .{ .ctrl = true } }));
+        try testing.expectEqual(false, isAscii(.{ .cp = 'c', .mod = .{ .alt = true } }));
+        try testing.expectEqual(false, isAscii(.{ .cp = 'c', .mod = .{ .alt = true, .ctrl = true } }));
+    }
+
+    test "isAscii with non-ascii character" {
+        try testing.expectEqual(false, isAscii(.{ .cp = Escape }));
+        try testing.expectEqual(false, isAscii(.{ .cp = Enter }));
+        try testing.expectEqual(false, isAscii(.{ .cp = Enter, .mod = .{ .alt = true } }));
+    }
+
+    test "isAscii with excluded input.Delete" {
+        try testing.expectEqual(false, isAscii(.{ .cp = Delete }));
+        try testing.expectEqual(false, isAscii(.{ .cp = Delete, .mod = .{ .alt = false, .ctrl = false } }));
+    }
+};
+
+// TODO: std.ascii has the escape codes too!
+// codepoints for keys
+pub const Tab: u21 = 0x09;
+pub const Enter: u21 = 0x0D;
+pub const Escape: u21 = 0x1B;
+pub const Space: u21 = 0x20;
+pub const Backspace: u21 = 0x7F;
+
+// kitty key encodings (re-used here)
+pub const Insert: u21 = 57348;
+pub const Delete: u21 = 57349;
+pub const Left: u21 = 57350;
+pub const Right: u21 = 57351;
+pub const Up: u21 = 57352;
+pub const Down: u21 = 57353;
+pub const PageUp: u21 = 57354;
+pub const PageDown: u21 = 57355;
+pub const Home: u21 = 57356;
+pub const End: u21 = 57357;
+pub const CapsLock: u21 = 57358;
+pub const ScrollLock: u21 = 57359;
+pub const NumLock: u21 = 57360;
+pub const PrintScreen: u21 = 57361;
+pub const Pause: u21 = 57362;
+pub const Menu: u21 = 57363;
+pub const F1: u21 = 57364;
+pub const F2: u21 = 57365;
+pub const F3: u21 = 57366;
+pub const F4: u21 = 57367;
+pub const F5: u21 = 57368;
+pub const F6: u21 = 57369;
+pub const F7: u21 = 57370;
+pub const F8: u21 = 57371;
+pub const F9: u21 = 57372;
+pub const F10: u21 = 57373;
+pub const F11: u21 = 57374;
+pub const F12: u21 = 57375;
+pub const F13: u21 = 57376;
+pub const F14: u21 = 57377;
+pub const F15: u21 = 57378;
+pub const F16: u21 = 57379;
+pub const F17: u21 = 57380;
+pub const F18: u21 = 57381;
+pub const F19: u21 = 57382;
+pub const F20: u21 = 57383;
+pub const Kp0: u21 = 57399;
+pub const Kp1: u21 = 57400;
+pub const Kp2: u21 = 57401;
+pub const Kp3: u21 = 57402;
+pub const Kp4: u21 = 57403;
+pub const Kp5: u21 = 57404;
+pub const Kp6: u21 = 57405;
+pub const Kp7: u21 = 57406;
+pub const Kp8: u21 = 57407;
+pub const Kp9: u21 = 57408;
+pub const KpDecimal: u21 = 57409;
+pub const KpDivide: u21 = 57410;
+pub const KpMultiply: u21 = 57411;
+pub const KpSubtract: u21 = 57412;
+pub const KpAdd: u21 = 57413;
+pub const KpEnter: u21 = 57414;
+pub const KpEqual: u21 = 57415;
+pub const KpSeparator: u21 = 57416;
+pub const KpLeft: u21 = 57417;
+pub const KpRight: u21 = 57418;
+pub const KpUp: u21 = 57419;
+pub const KpDown: u21 = 57420;
+pub const KpPageUp: u21 = 57421;
+pub const KpPageDown: u21 = 57422;
+pub const KpHome: u21 = 57423;
+pub const KpEnd: u21 = 57424;
+pub const KpInsert: u21 = 57425;
+pub const KpDelete: u21 = 57426;
+pub const KpBegin: u21 = 57427;
+pub const MediaPlay: u21 = 57428;
+pub const MediaPause: u21 = 57429;
+pub const MediaPlayPause: u21 = 57430;
+pub const MediaReverse: u21 = 57431;
+pub const MediaStop: u21 = 57432;
+pub const MediaFastForward: u21 = 57433;
+pub const MediaRewind: u21 = 57434;
+pub const MediaTrackNext: u21 = 57435;
+pub const MediaTrackPrevious: u21 = 57436;
+pub const MediaRecord: u21 = 57437;
+pub const LowerVolume: u21 = 57438;
+pub const RaiseVolume: u21 = 57439;
+pub const MuteVolume: u21 = 57440;
+pub const LeftShift: u21 = 57441;
+pub const LeftControl: u21 = 57442;
+pub const LeftAlt: u21 = 57443;
+pub const LeftSuper: u21 = 57444;
+pub const LeftHyper: u21 = 57445;
+pub const LeftMeta: u21 = 57446;
+pub const RightShift: u21 = 57447;
+pub const RightControl: u21 = 57448;
+pub const RightAlt: u21 = 57449;
+pub const RightSuper: u21 = 57450;
+pub const RightHyper: u21 = 57451;
+pub const RightMeta: u21 = 57452;
+pub const IsoLevel3Shift: u21 = 57453;
+pub const IsoLevel5Shift: u21 = 57454;
+
+const std = @import("std");
+const meta = std.meta;
+const Point = @import("point.zig").Point;
+const testing = std.testing;

src/key.zig

@@ -1,151 +0,0 @@
-//! Keybindings and Modifiers for user input detection and selection.
-const std = @import("std");
-
-pub const Key = @This();
-
-pub const Modifier = struct {
-    shift: bool = false,
-    alt: bool = false,
-    ctrl: bool = false,
-};
-
-cp: u21,
-mod: Modifier = .{},
-
-/// Compare _this_ `Key` with an _other_ `Key`.
-///
-/// # Example
-///
-/// Configure `ctrl+c` to quit the application (done in main event loop of the application):
-///
-/// ```zig
-/// switch (event) {
-///     .quit => break,
-///     .key => |key| {
-///         // ctrl+c to quit
-///         if (terminal.Key.matches(key, .{ .cp = 'c', .mod = .{ .ctrl = true } })) {
-///             app.quit.set();
-///         }
-///     },
-///     else => {},
-/// }
-/// ```
-pub fn matches(this: @This(), other: @This()) bool {
-    return std.meta.eql(this, other);
-}
-
-// codepoints for keys
-pub const tab: u21 = 0x09;
-pub const enter: u21 = 0x0D;
-pub const escape: u21 = 0x1B;
-pub const space: u21 = 0x20;
-pub const backspace: u21 = 0x7F;
-
-// kitty key encodings (re-used here)
-pub const insert: u21 = 57348;
-pub const delete: u21 = 57349;
-pub const left: u21 = 57350;
-pub const right: u21 = 57351;
-pub const up: u21 = 57352;
-pub const down: u21 = 57353;
-pub const page_up: u21 = 57354;
-pub const page_down: u21 = 57355;
-pub const home: u21 = 57356;
-pub const end: u21 = 57357;
-pub const caps_lock: u21 = 57358;
-pub const scroll_lock: u21 = 57359;
-pub const num_lock: u21 = 57360;
-pub const print_screen: u21 = 57361;
-pub const pause: u21 = 57362;
-pub const menu: u21 = 57363;
-pub const f1: u21 = 57364;
-pub const f2: u21 = 57365;
-pub const f3: u21 = 57366;
-pub const f4: u21 = 57367;
-pub const f5: u21 = 57368;
-pub const f6: u21 = 57369;
-pub const f7: u21 = 57370;
-pub const f8: u21 = 57371;
-pub const f9: u21 = 57372;
-pub const f10: u21 = 57373;
-pub const f11: u21 = 57374;
-pub const f12: u21 = 57375;
-pub const f13: u21 = 57376;
-pub const f14: u21 = 57377;
-pub const f15: u21 = 57378;
-pub const @"f16": u21 = 57379;
-pub const f17: u21 = 57380;
-pub const f18: u21 = 57381;
-pub const f19: u21 = 57382;
-pub const f20: u21 = 57383;
-pub const f21: u21 = 57384;
-pub const f22: u21 = 57385;
-pub const f23: u21 = 57386;
-pub const f24: u21 = 57387;
-pub const f25: u21 = 57388;
-pub const f26: u21 = 57389;
-pub const f27: u21 = 57390;
-pub const f28: u21 = 57391;
-pub const f29: u21 = 57392;
-pub const f30: u21 = 57393;
-pub const f31: u21 = 57394;
-pub const @"f32": u21 = 57395;
-pub const f33: u21 = 57396;
-pub const f34: u21 = 57397;
-pub const f35: u21 = 57398;
-pub const kp_0: u21 = 57399;
-pub const kp_1: u21 = 57400;
-pub const kp_2: u21 = 57401;
-pub const kp_3: u21 = 57402;
-pub const kp_4: u21 = 57403;
-pub const kp_5: u21 = 57404;
-pub const kp_6: u21 = 57405;
-pub const kp_7: u21 = 57406;
-pub const kp_8: u21 = 57407;
-pub const kp_9: u21 = 57408;
-pub const kp_decimal: u21 = 57409;
-pub const kp_divide: u21 = 57410;
-pub const kp_multiply: u21 = 57411;
-pub const kp_subtract: u21 = 57412;
-pub const kp_add: u21 = 57413;
-pub const kp_enter: u21 = 57414;
-pub const kp_equal: u21 = 57415;
-pub const kp_separator: u21 = 57416;
-pub const kp_left: u21 = 57417;
-pub const kp_right: u21 = 57418;
-pub const kp_up: u21 = 57419;
-pub const kp_down: u21 = 57420;
-pub const kp_page_up: u21 = 57421;
-pub const kp_page_down: u21 = 57422;
-pub const kp_home: u21 = 57423;
-pub const kp_end: u21 = 57424;
-pub const kp_insert: u21 = 57425;
-pub const kp_delete: u21 = 57426;
-pub const kp_begin: u21 = 57427;
-pub const media_play: u21 = 57428;
-pub const media_pause: u21 = 57429;
-pub const media_play_pause: u21 = 57430;
-pub const media_reverse: u21 = 57431;
-pub const media_stop: u21 = 57432;
-pub const media_fast_forward: u21 = 57433;
-pub const media_rewind: u21 = 57434;
-pub const media_track_next: u21 = 57435;
-pub const media_track_previous: u21 = 57436;
-pub const media_record: u21 = 57437;
-pub const lower_volume: u21 = 57438;
-pub const raise_volume: u21 = 57439;
-pub const mute_volume: u21 = 57440;
-pub const left_shift: u21 = 57441;
-pub const left_control: u21 = 57442;
-pub const left_alt: u21 = 57443;
-pub const left_super: u21 = 57444;
-pub const left_hyper: u21 = 57445;
-pub const left_meta: u21 = 57446;
-pub const right_shift: u21 = 57447;
-pub const right_control: u21 = 57448;
-pub const right_alt: u21 = 57449;
-pub const right_super: u21 = 57450;
-pub const right_hyper: u21 = 57451;
-pub const right_meta: u21 = 57452;
-pub const iso_level_3_shift: u21 = 57453;
-pub const iso_level_5_shift: u21 = 57454;

src/point.zig

@@ -0,0 +1,60 @@
+pub const Point = packed struct {
+    x: u16 = 0,
+    y: u16 = 0,
+
+    pub fn add(a: @This(), b: @This()) @This() {
+        return .{
+            .x = a.x + b.x,
+            .y = a.y + b.y,
+        };
+    }
+
+    pub fn max(a: @This(), b: @This()) @This() {
+        return .{
+            .x = @max(a.x, b.x),
+            .y = @max(a.y, b.y),
+        };
+    }
+
+    test "adding" {
+        const testing = @import("std").testing;
+
+        const a: @This() = .{
+            .x = 10,
+            .y = 20,
+        };
+
+        const b: @This() = .{
+            .x = 20,
+            .y = 10,
+        };
+
+        try testing.expectEqual(@This(){
+            .x = 30,
+            .y = 30,
+        }, a.add(b));
+    }
+
+    test "maximum" {
+        const testing = @import("std").testing;
+
+        const a: @This() = .{
+            .x = 10,
+            .y = 20,
+        };
+
+        const b: @This() = .{
+            .x = 20,
+            .y = 10,
+        };
+
+        try testing.expectEqual(@This(){
+            .x = 20,
+            .y = 20,
+        }, a.max(b));
+    }
+};
+
+test {
+    _ = Point;
+}

src/queue.zig

@@ -1,9 +1,7 @@
 // taken from https://github.com/rockorager/libvaxis/blob/main/src/queue.zig (MIT-License)
 // with slight modifications
-const std = @import("std");
-const assert = std.debug.assert;
 
-/// Thread safe. Fixed size. Blocking push and pop.
+/// Queue implementation. Thread safe. Fixed size. _Blocking_ `push` and `pop`. _Polling_ through `tryPop` and `tryPush`.
 pub fn Queue(comptime T: type, comptime size: usize) type {
     return struct {
         buf: [size]T = undefined,
@@ -92,6 +90,23 @@ pub fn Queue(comptime T: type, comptime size: usize) type {
             assert(!this.isEmptyLH());
         }
 
+        pub fn lock(this: *QueueType) void {
+            this.mutex.lock();
+        }
+
+        pub fn unlock(this: *QueueType) void {
+            this.mutex.unlock();
+        }
+
+        /// Used to efficiently drain the queue
+        pub fn drain(this: *QueueType) ?T {
+            if (this.isEmptyLH()) return null;
+
+            const result = this.buf[this.mask(this.read_index)];
+            this.read_index = this.mask2(this.read_index + 1);
+            return result;
+        }
+
         fn isEmptyLH(this: QueueType) bool {
             return this.write_index == this.read_index;
         }
@@ -116,7 +131,7 @@ pub fn Queue(comptime T: type, comptime size: usize) type {
         }
 
         /// Returns the length
-        fn len(this: QueueType) usize {
+        pub fn len(this: QueueType) usize {
             const wrap_offset = 2 * this.buf.len *
                 @intFromBool(this.write_index < this.read_index);
             const adjusted_write_index = this.write_index + wrap_offset;
@@ -135,8 +150,12 @@ pub fn Queue(comptime T: type, comptime size: usize) type {
     };
 }
 
+const std = @import("std");
 const testing = std.testing;
+const assert = std.debug.assert;
+const Thread = std.Thread;
 const cfg = Thread.SpawnConfig{ .allocator = testing.allocator };
+
 test "Queue: simple push / pop" {
     var queue: Queue(u8, 16) = .{};
     queue.push(1);
@@ -146,7 +165,6 @@ test "Queue: simple push / pop" {
     try testing.expectEqual(2, queue.pop());
 }
 
-const Thread = std.Thread;
 fn testPushPop(q: *Queue(u8, 2)) !void {
     q.push(3);
     try testing.expectEqual(2, q.pop());
@@ -197,9 +215,9 @@ fn sleepyPop(q: *Queue(u8, 2)) !void {
     // still full and the push in the other thread is still blocked
     // waiting for space.
     try Thread.yield();
-    std.time.sleep(std.time.ns_per_s);
+    std.Thread.sleep(std.time.ns_per_s);
     // Finally, let that other thread go.
-    try std.testing.expectEqual(1, q.pop());
+    try testing.expectEqual(1, q.pop());
 
     // This won't continue until the other thread has had a chance to
     // put at least one item in the queue.
@@ -207,7 +225,7 @@ fn sleepyPop(q: *Queue(u8, 2)) !void {
         try Thread.yield();
     // But we want to ensure that there's a second push waiting, so
     // here's another sleep.
-    std.time.sleep(std.time.ns_per_s / 2);
+    std.Thread.sleep(std.time.ns_per_s / 2);
 
     // Another spurious wake...
     q.not_full.signal();
@@ -215,10 +233,10 @@ fn sleepyPop(q: *Queue(u8, 2)) !void {
     // And another chance for the other thread to see that it's
     // spurious and go back to sleep.
     try Thread.yield();
-    std.time.sleep(std.time.ns_per_s / 2);
+    std.Thread.sleep(std.time.ns_per_s / 2);
 
     // Pop that thing and we're done.
-    try std.testing.expectEqual(2, q.pop());
+    try testing.expectEqual(2, q.pop());
 }
 
 test "Fill, block, fill, block" {
@@ -238,28 +256,28 @@ test "Fill, block, fill, block" {
 
     // Just to make sure the sleeps are yielding to this thread, make
     // sure it took at least 900ms to do the push.
-    try std.testing.expect(then - now > 900);
+    try testing.expect(then - now > 900);
 
     // This should block again, waiting for the other thread.
     queue.push(4);
 
     // And once that push has gone through, the other thread's done.
     thread.join();
-    try std.testing.expectEqual(3, queue.pop());
-    try std.testing.expectEqual(4, queue.pop());
+    try testing.expectEqual(3, queue.pop());
+    try testing.expectEqual(4, queue.pop());
 }
 
 fn sleepyPush(q: *Queue(u8, 1)) !void {
     // Try to ensure the other thread has already started trying to pop.
     try Thread.yield();
-    std.time.sleep(std.time.ns_per_s / 2);
+    std.Thread.sleep(std.time.ns_per_s / 2);
 
     // Spurious wake
     q.not_full.signal();
     q.not_empty.signal();
 
     try Thread.yield();
-    std.time.sleep(std.time.ns_per_s / 2);
+    std.Thread.sleep(std.time.ns_per_s / 2);
 
     // Stick something in the queue so it can be popped.
     q.push(1);
@@ -268,7 +286,7 @@ fn sleepyPush(q: *Queue(u8, 1)) !void {
         try Thread.yield();
     // Give the other thread time to block again.
     try Thread.yield();
-    std.time.sleep(std.time.ns_per_s / 2);
+    std.Thread.sleep(std.time.ns_per_s / 2);
 
     // Spurious wake
     q.not_full.signal();
@@ -284,8 +302,8 @@ test "Drain, block, drain, block" {
 
     var queue: Queue(u8, 1) = .{};
     const thread = try Thread.spawn(cfg, sleepyPush, .{&queue});
-    try std.testing.expectEqual(1, queue.pop());
-    try std.testing.expectEqual(2, queue.pop());
+    try testing.expectEqual(1, queue.pop());
+    try testing.expectEqual(2, queue.pop());
     thread.join();
 }
 
@@ -299,7 +317,7 @@ test "2 readers" {
     const t1 = try Thread.spawn(cfg, readerThread, .{&queue});
     const t2 = try Thread.spawn(cfg, readerThread, .{&queue});
     try Thread.yield();
-    std.time.sleep(std.time.ns_per_s / 2);
+    std.Thread.sleep(std.time.ns_per_s / 2);
     queue.push(1);
     queue.push(1);
     t1.join();

src/render.zig

@@ -1,21 +1,14 @@
-const std = @import("std");
-const terminal = @import("terminal.zig");
-
-const Cell = @import("cell.zig");
-const Position = @import("size.zig").Position;
-const Size = @import("size.zig").Size;
+//! Renderer for `zterm`.
 
 /// Double-buffered intermediate rendering pipeline
 pub const Buffered = struct {
-    const log = std.log.scoped(.renderer_buffered);
-    // _ = log;
-    allocator: std.mem.Allocator,
+    allocator: Allocator,
     created: bool,
-    size: Size,
+    size: Point,
     screen: []Cell,
     virtual_screen: []Cell,
 
-    pub fn init(allocator: std.mem.Allocator) @This() {
+    pub fn init(allocator: Allocator) @This() {
         return .{
             .allocator = allocator,
             .created = false,
@@ -32,84 +25,198 @@ pub const Buffered = struct {
         }
     }
 
-    pub fn resize(this: *@This(), size: Size) !void {
-        log.debug("renderer::resize", .{});
-        defer this.size = size;
+    pub fn resize(this: *@This()) !Point {
+        const size = terminal.getTerminalSize();
+        if (meta.eql(this.size, size)) return this.size;
+
+        this.size = size;
+        const n = @as(usize, this.size.x) * @as(usize, this.size.y);
 
         if (!this.created) {
-            this.screen = this.allocator.alloc(Cell, @as(usize, size.cols) * @as(usize, size.rows)) catch @panic("render.zig: Out of memory.");
-            @memset(this.screen, .{});
-            this.virtual_screen = this.allocator.alloc(Cell, @as(usize, size.cols) * @as(usize, size.rows)) catch @panic("render.zig: Out of memory.");
+            this.screen = this.allocator.alloc(Cell, n) catch @panic("render.zig: Out of memory.");
+
+            this.virtual_screen = this.allocator.alloc(Cell, n) catch @panic("render.zig: Out of memory.");
             @memset(this.virtual_screen, .{});
+
             this.created = true;
         } else {
             this.allocator.free(this.screen);
-            this.screen = this.allocator.alloc(Cell, @as(usize, size.cols) * @as(usize, size.rows)) catch @panic("render.zig: Out of memory.");
-            @memset(this.screen, .{});
+            this.screen = this.allocator.alloc(Cell, n) catch @panic("render.zig: Out of memory.");
+
             this.allocator.free(this.virtual_screen);
-            this.virtual_screen = this.allocator.alloc(Cell, @as(usize, size.cols) * @as(usize, size.rows)) catch @panic("render.zig: Out of memory.");
+            this.virtual_screen = this.allocator.alloc(Cell, n) catch @panic("render.zig: Out of memory.");
             @memset(this.virtual_screen, .{});
         }
         try this.clear();
+        return size;
     }
 
     /// Clear the entire screen and reset the screen buffer, to force a re-draw with the next `flush` call.
     pub fn clear(this: *@This()) !void {
-        log.debug("renderer::clear", .{});
         try terminal.clearScreen();
         @memset(this.screen, .{});
     }
 
     /// Render provided cells at size (anchor and dimension) into the *virtual screen*.
-    pub fn render(this: *@This(), comptime T: type, container: *T) !void {
-        const viewport: Size = container.viewport;
-        const cells: []const Cell = try container.contents();
+    pub fn render(this: *@This(), comptime Container: type, container: *Container, comptime Model: type, model: *const Model) !void {
+        const size: Point = container.size;
+        const origin: Point = container.origin;
+        const cells: []const Cell = try container.content(model);
 
         if (cells.len == 0) return;
 
         var idx: usize = 0;
         var vs = this.virtual_screen;
-        const anchor: usize = (@as(usize, viewport.anchor.row) * @as(usize, this.size.cols)) + @as(usize, viewport.anchor.col);
+        const anchor: usize = (@as(usize, origin.y) * @as(usize, this.size.x)) + @as(usize, origin.x);
 
-        blk: for (0..viewport.rows) |row| {
-            for (0..viewport.cols) |col| {
-                const cell = cells[idx];
+        blk: for (0..size.y) |row| {
+            for (0..size.x) |col| {
+                vs[anchor + (row * this.size.x) + col] = cells[idx];
                 idx += 1;
 
-                vs[anchor + (row * this.size.cols) + col].style = cell.style;
-                vs[anchor + (row * this.size.cols) + col].cp = cell.cp;
-
                 if (cells.len == idx) break :blk;
             }
         }
         // free immediately
         container.allocator.free(cells);
 
-        for (container.elements.items) |*element| {
-            try this.render(T, element);
-        }
+        for (container.elements.items) |*element| try this.render(Container, element, Model, model);
     }
 
     /// Write *virtual screen* to alternate screen (should be called once and last during each render loop iteration in the main loop).
     pub fn flush(this: *@This()) !void {
-        // TODO: measure timings of rendered frames?
-        log.debug("renderer::flush", .{});
-        const writer = terminal.writer();
+        try terminal.hideCursor();
+        // TODO measure timings of rendered frames?
+        var cursor_position: ?Point = null;
+        var writer = terminal.writer();
         const s = this.screen;
         const vs = this.virtual_screen;
-        for (0..this.size.rows) |row| {
-            for (0..this.size.cols) |col| {
-                const idx = (row * this.size.cols) + col;
+
+        for (0..this.size.y) |row| {
+            for (0..this.size.x) |col| {
+                const idx = (row * this.size.x) + col;
                 const cs = s[idx];
                 const cvs = vs[idx];
+
+                // update the latest found cursor position
+                if (cvs.style.cursor) {
+                    assert(cursor_position == null);
+                    cursor_position = .{
+                        .x = @truncate(col),
+                        .y = @truncate(row),
+                    };
+                    try cvs.style.set_cursor_style(&writer);
+                }
+
                 if (cs.eql(cvs)) continue;
 
                 // render differences found in virtual screen
-                try terminal.setCursorPosition(.{ .row = @truncate(row + 1), .col = @truncate(col + 1) });
-                try cvs.value(writer);
+                try terminal.setCursorPosition(.{ .y = @truncate(row), .x = @truncate(col) });
+                try cvs.value(&writer);
                 // update screen to be the virtual screen for the next frame
                 s[idx] = vs[idx];
             }
         }
+        if (cursor_position) |point| {
+            try terminal.showCursor();
+            try terminal.setCursorPosition(point);
+        }
     }
 };
+
+pub const Direct = struct {
+    gpa: Allocator,
+    size: Point,
+    resized: bool,
+    screen: []Cell,
+
+    pub fn init(gpa: Allocator) @This() {
+        return .{
+            .gpa = gpa,
+            .size = .{},
+            .resized = true,
+            .screen = undefined,
+        };
+    }
+
+    pub fn deinit(this: *@This()) void {
+        this.gpa.free(this.screen);
+    }
+
+    pub fn resize(this: *@This()) !Point {
+        this.size = .{};
+        if (!this.resized) {
+            this.gpa.free(this.screen);
+            this.screen = undefined;
+        }
+        this.resized = true;
+        return terminal.getTerminalSize();
+    }
+
+    pub fn clear(this: *@This()) !void {
+        _ = this;
+        try terminal.clearScreen();
+    }
+
+    pub fn writeCtrlDWithNewline(this: *@This()) !void {
+        _ = this;
+        _ = try terminal.write("^D\n");
+    }
+
+    pub fn writeNewline(this: *@This()) !void {
+        _ = this;
+        _ = try terminal.write("\n");
+    }
+
+    /// Render provided cells at size (anchor and dimension) into the *screen*.
+    pub fn render(this: *@This(), comptime Container: type, container: *Container, comptime Model: type, model: *const Model) !void {
+        const size: Point = container.size;
+        const origin: Point = container.origin;
+
+        if (this.resized) {
+            this.size = size;
+            const n = @as(usize, this.size.x) * @as(usize, this.size.y);
+            this.screen = try this.gpa.alloc(Cell, n);
+            @memset(this.screen, .{});
+            this.resized = false;
+        }
+
+        const cells: []const Cell = try container.content(model);
+
+        var idx: usize = 0;
+        var vs = this.screen;
+        const anchor: usize = (@as(usize, origin.y) * @as(usize, this.size.x)) + @as(usize, origin.x);
+
+        blk: for (0..size.y) |row| {
+            for (0..size.x) |col| {
+                vs[anchor + (row * this.size.x) + col] = cells[idx];
+                idx += 1;
+
+                if (cells.len == idx) break :blk;
+            }
+        }
+        // free immediately
+        container.allocator.free(cells);
+        for (container.elements.items) |*element| try this.render(Container, element, Model, model);
+    }
+
+    pub fn flush(this: *@This()) !void {
+        var writer = terminal.writer();
+        for (0..this.size.y) |row| {
+            for (0..this.size.x) |col| {
+                const idx = (row * this.size.x) + col;
+                const cvs = this.screen[idx];
+                try cvs.value(&writer);
+                if (cvs.style.cursor) return; // that's where the cursor should be left!
+            }
+        }
+    }
+};
+
+const std = @import("std");
+const meta = std.meta;
+const assert = std.debug.assert;
+const Allocator = std.mem.Allocator;
+const terminal = @import("terminal.zig");
+const Cell = @import("cell.zig");
+const Point = @import("point.zig").Point;

src/root.zig

@@ -1,30 +1,39 @@
 // private imports
 const container = @import("container.zig");
 const color = @import("color.zig");
-const size = @import("size.zig");
+const size = @import("point.zig");
 
 // public exports
+pub const input = @import("input.zig");
+pub const testing = @import("testing.zig");
+
 pub const App = @import("app.zig").App;
+pub const Error = @import("error.zig").Error;
+// App also exports further types once initialized with the user events at compile time:
+// `App.Container`
+// `App.Element`
 pub const Renderer = @import("render.zig");
 
 // Container Configurations
 pub const Border = container.Border;
 pub const Rectangle = container.Rectangle;
-pub const Scroll = container.Scroll;
 pub const Layout = container.Layout;
 
 pub const Cell = @import("cell.zig");
 pub const Color = color.Color;
-pub const Key = @import("key.zig");
-pub const Size = size.Size;
+pub const Key = input.Key;
+pub const Mouse = input.Mouse;
+pub const Point = @import("point.zig").Point;
 pub const Style = @import("style.zig");
 
 test {
     _ = @import("terminal.zig");
+    _ = @import("container.zig");
     _ = @import("queue.zig");
+    _ = @import("error.zig");
+    _ = @import("point.zig");
 
     _ = color;
-    _ = size;
 
     _ = Cell;
     _ = Key;

src/size.zig

@@ -1,10 +0,0 @@
-pub const Size = packed struct {
-    anchor: Position = .{},
-    cols: u16 = 0,
-    rows: u16 = 0,
-};
-
-pub const Position = packed struct {
-    col: u16 = 0,
-    row: u16 = 0,
-};

src/style.zig

@@ -7,11 +7,15 @@
 
 // taken from https://github.com/rockorager/libvaxis/blob/main/src/Cell.zig (MIT-License)
 // with slight modifications
-const std = @import("std");
 
-const Color = @import("color.zig").Color;
-
-pub const Style = @This();
+fg: Color = .default,
+bg: Color = .default,
+ul: Color = .default,
+cursor: bool = false,
+cursor_color: Color = .default,
+cursor_shape: CursorShape = .default,
+ul_style: Underline = .off,
+emphasis: []const Emphasis,
 
 pub const Underline = enum {
     off,
@@ -22,7 +26,7 @@ pub const Underline = enum {
     dashed,
 };
 
-pub const Attribute = enum(u8) {
+pub const Emphasis = enum(u8) {
     reset = 0,
     bold = 1,
     dim,
@@ -34,40 +38,61 @@ pub const Attribute = enum(u8) {
     strikethrough,
 };
 
-fg: Color = .white,
-bg: Color = .default,
-ul: Color = .default,
-ul_style: Underline = .off,
-attributes: []const Attribute,
+pub const CursorShape = enum(u4) {
+    default = 0,
+    block_blinking = 1,
+    block_steady,
+    underline_blinking,
+    underline_steady,
+    bar_blinking,
+    bar_steady,
+};
 
 pub fn eql(this: Style, other: Style) bool {
-    return std.meta.eql(this, other);
+    // TODO should there be a compare for every field?
+    return meta.eql(this, other);
 }
 
-pub fn value(this: Style, writer: anytype, cp: u21) !void {
+pub fn set_cursor_style(this: Style, writer: *std.Io.Writer) !void {
+    if (!this.cursor) return;
+    switch (this.cursor_color) {
+        .default => try writer.print(ctlseqs.osc12_reset, .{}),
+        else => try writer.print(ctlseqs.osc12_set, .{@tagName(this.cursor_color)}),
+    }
+    try writer.print(ctlseqs.cursor_shape, .{@intFromEnum(this.cursor_shape)});
+}
+
+pub fn value(this: Style, writer: *std.Io.Writer, cp: u21) !void {
     var buffer: [4]u8 = undefined;
-    const bytes = try std.unicode.utf8Encode(cp, &buffer);
-    std.debug.assert(bytes > 0);
+    const bytes = try unicode.utf8Encode(cp, &buffer);
+    assert(bytes > 0);
     // build ansi sequence for 256 colors ...
     // foreground
-    try std.fmt.format(writer, "\x1b[", .{});
+    try writer.printAscii("\x1b[", .{});
     try this.fg.write(writer, .fg);
     // background
-    try std.fmt.format(writer, ";", .{});
+    try writer.printAsciiChar(';', .{});
     try this.bg.write(writer, .bg);
     // underline
-    // FIX: assert that if the underline property is set that the ul style and the attribute for underlining is available
-    try std.fmt.format(writer, ";", .{});
+    // FIX assert that if the underline property is set that the ul style and the attribute for underlining is available
+    try writer.printAsciiChar(';', .{});
     try this.ul.write(writer, .ul);
     // append styles (aka attributes like bold, italic, strikethrough, etc.)
-    for (this.attributes) |attribute| {
-        try std.fmt.format(writer, ";{d}", .{@intFromEnum(attribute)});
-    }
-    try std.fmt.format(writer, "m", .{});
+    for (this.emphasis) |attribute| try writer.print(";{d}", .{@intFromEnum(attribute)});
+    try writer.printAsciiChar('m', .{});
     // content
-    try std.fmt.format(writer, "{s}", .{buffer});
+    try writer.printAscii(buffer[0..bytes], .{});
+    try writer.printAscii("\x1b[0m", .{});
 }
 
-// TODO: implement helper functions for terminal capabilities:
+// TODO implement helper functions for terminal capabilities:
 // - links / url display (osc 8)
 // - show / hide cursor?
+
+const std = @import("std");
+const unicode = std.unicode;
+const meta = std.meta;
+const assert = std.debug.assert;
+const Color = @import("color.zig").Color;
+const ctlseqs = @import("ctlseqs.zig");
+const Style = @This();

src/terminal.zig

@@ -1,13 +1,3 @@
-const std = @import("std");
-pub const code_point = @import("code_point");
-
-const Key = @import("key.zig");
-const Position = @import("size.zig").Position;
-const Size = @import("size.zig").Size;
-const Cell = @import("cell.zig");
-
-const log = std.log.scoped(.terminal);
-
 // Ref: https://vt100.net/docs/vt510-rm/DECRPM.html
 pub const ReportMode = enum {
     not_recognized,
@@ -19,81 +9,104 @@ pub const ReportMode = enum {
 
 /// Gets number of rows and columns in the terminal
 pub fn getTerminalSize() Size {
-    var ws: std.posix.winsize = undefined;
-    _ = std.posix.system.ioctl(std.posix.STDIN_FILENO, std.posix.T.IOCGWINSZ, @intFromPtr(&ws));
-    return .{ .cols = ws.col, .rows = ws.row };
+    var ws: posix.winsize = undefined;
+    _ = posix.system.ioctl(posix.STDIN_FILENO, posix.T.IOCGWINSZ, @intFromPtr(&ws));
+    return .{ .x = ws.col, .y = ws.row };
 }
 
 pub fn saveScreen() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[?47h");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.save_screen);
 }
 
 pub fn restoreScreen() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[?47l");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.restore_screen);
 }
 
 pub fn enterAltScreen() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[?1049h");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.smcup);
 }
 
 pub fn exitAltScreen() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[?1049l");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.rmcup);
 }
 
 pub fn clearScreen() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[2J");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.clear_screen);
 }
 
 pub fn hideCursor() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[?25l");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.hide_cursor);
 }
 
 pub fn showCursor() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[?25h");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.show_cursor);
+}
+
+pub fn resetCursor() !void {
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.reset_cursor_shape);
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.osc12_reset);
 }
 
 pub fn setCursorPositionHome() !void {
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[H");
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.home);
+}
+
+pub fn enableMouseSupport() !void {
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.mouse_set);
+}
+
+pub fn disableMouseSupport() !void {
+    _ = try posix.write(posix.STDIN_FILENO, ctlseqs.mouse_reset);
+}
+
+pub fn ringBell() !void {
+    _ = try posix.write(posix.STDIN_FILENO, &.{7});
 }
 
 pub fn read(buf: []u8) !usize {
-    return try std.posix.read(std.posix.STDIN_FILENO, buf);
+    return try posix.read(posix.STDIN_FILENO, buf);
 }
 
 pub fn write(buf: []const u8) !usize {
-    return try std.posix.write(std.posix.STDIN_FILENO, buf);
+    return try posix.write(posix.STDIN_FILENO, buf);
 }
 
-fn contextWrite(context: @This(), data: []const u8) anyerror!usize {
-    _ = context;
-    return try std.posix.write(std.posix.STDOUT_FILENO, data);
+fn drainFn(w: *std.Io.Writer, data: []const []const u8, splat: usize) error{WriteFailed}!usize {
+    _ = w;
+    if (data.len == 0 or splat == 0) return 0;
+    var len: usize = 0;
+
+    for (data) |bytes| len += posix.write(posix.STDOUT_FILENO, bytes) catch return error.WriteFailed;
+
+    return len;
 }
 
-const Writer = std.io.Writer(
-    @This(),
-    anyerror,
-    contextWrite,
-);
-
-pub fn writer() Writer {
-    return .{ .context = .{} };
+// TODO I now need to add that much, for just the one function above?
+pub fn writer() std.Io.Writer {
+    return .{
+        .vtable = &.{
+            .drain = drainFn,
+            .flush = std.Io.Writer.noopFlush,
+        },
+        .buffer = &.{},
+    };
 }
 
-pub fn setCursorPosition(pos: Position) !void {
+pub fn setCursorPosition(pos: Point) !void {
     var buf: [64]u8 = undefined;
-    const value = try std.fmt.bufPrint(&buf, "\x1b[{d};{d}H", .{ pos.row, pos.col });
-    _ = try std.posix.write(std.posix.STDIN_FILENO, value);
+    const value = try std.fmt.bufPrint(&buf, "\x1b[{d};{d}H", .{ pos.y + 1, pos.x + 1 });
+    _ = try posix.write(posix.STDIN_FILENO, value);
 }
 
-pub fn getCursorPosition() !Size.Position {
+pub fn getCursorPosition() !Size {
     // Needs Raw mode (no wait for \n) to work properly cause
     // control sequence will not be written without it.
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[6n");
+    _ = try posix.write(posix.STDIN_FILENO, "\x1b[6n");
 
     var buf: [64]u8 = undefined;
 
     // format: \x1b, "[", R1,..., Rn, ";", C1, ..., Cn, "R"
-    const len = try std.posix.read(std.posix.STDIN_FILENO, &buf);
+    const len = try posix.read(posix.STDIN_FILENO, &buf);
 
     if (!isCursorPosition(buf[0..len])) {
         return error.InvalidValueReturned;
@@ -127,8 +140,8 @@ pub fn getCursorPosition() !Size.Position {
     }
 
     return .{
-        .row = try std.fmt.parseInt(u16, row[0..ridx], 10) - 1,
-        .col = try std.fmt.parseInt(u16, col[0..cidx], 10) - 1,
+        .x = try std.fmt.parseInt(u16, col[0..cidx], 10) - 1,
+        .y = try std.fmt.parseInt(u16, row[0..ridx], 10) - 1,
     };
 }
 
@@ -156,8 +169,8 @@ pub fn isCursorPosition(buf: []u8) bool {
 ///
 /// `bak`: pointer to store termios struct backup before
 /// altering, this is used to disable raw mode.
-pub fn enableRawMode(bak: *std.posix.termios) !void {
-    var termios = try std.posix.tcgetattr(std.posix.STDIN_FILENO);
+pub fn enableRawMode(bak: *posix.termios) !void {
+    var termios = try posix.tcgetattr(posix.STDIN_FILENO);
     bak.* = termios;
 
     // termios flags used by termios(3)
@@ -182,20 +195,20 @@ pub fn enableRawMode(bak: *std.posix.termios) !void {
     termios.cflag.CSIZE = .CS8;
     termios.cflag.PARENB = false;
 
-    termios.cc[@intFromEnum(std.posix.V.MIN)] = 1;
-    termios.cc[@intFromEnum(std.posix.V.TIME)] = 0;
+    termios.cc[@intFromEnum(posix.V.MIN)] = 1;
+    termios.cc[@intFromEnum(posix.V.TIME)] = 0;
 
-    try std.posix.tcsetattr(
-        std.posix.STDIN_FILENO,
+    try posix.tcsetattr(
+        posix.STDIN_FILENO,
         .FLUSH,
         termios,
     );
 }
 
 /// Reverts `enableRawMode` to restore initial functionality.
-pub fn disableRawMode(bak: *std.posix.termios) !void {
-    try std.posix.tcsetattr(
-        std.posix.STDIN_FILENO,
+pub fn disableRawMode(bak: *const posix.termios) !void {
+    try posix.tcsetattr(
+        posix.STDIN_FILENO,
         .FLUSH,
         bak.*,
     );
@@ -205,13 +218,13 @@ pub fn disableRawMode(bak: *std.posix.termios) !void {
 pub fn canSynchornizeOutput() !bool {
     // Needs Raw mode (no wait for \n) to work properly cause
     // control sequence will not be written without it.
-    _ = try std.posix.write(std.posix.STDIN_FILENO, "\x1b[?2026$p");
+    _ = try posix.write(posix.STDIN_FILENO, "\x1b[?2026$p");
 
     var buf: [64]u8 = undefined;
 
     // format: \x1b, "[", "?", "2", "0", "2", "6", ";", n, "$", "y"
-    const len = try std.posix.read(std.posix.STDIN_FILENO, &buf);
-    if (!std.mem.eql(u8, buf[0..len], "\x1b[?2026;") or len < 9) {
+    const len = try posix.read(posix.STDIN_FILENO, &buf);
+    if (!mem.eql(u8, buf[0..len], "\x1b[?2026;") or len < 9) {
         return false;
     }
 
@@ -228,3 +241,16 @@ fn getReportMode(ps: u8) ReportMode {
         else => ReportMode.not_recognized,
     };
 }
+
+const log = std.log.scoped(.terminal);
+
+const std = @import("std");
+const mem = std.mem;
+const posix = std.posix;
+const assert = std.debug.assert;
+const ctlseqs = @import("ctlseqs.zig");
+const input = @import("input.zig");
+const Key = input.Key;
+const Point = @import("point.zig").Point;
+const Size = @import("point.zig").Point;
+const Cell = @import("cell.zig");

src/testing.zig

@@ -0,0 +1,234 @@
+//! Testing namespace for `zterm` to provide testing capabilities for `Containers`, `Event` handling, `App`s and `Element` implementations.
+
+/// Single-buffer test rendering pipeline for testing purposes.
+pub const Renderer = struct {
+    allocator: Allocator,
+    size: Point,
+    screen: []Cell,
+
+    pub fn init(allocator: Allocator, size: Point) @This() {
+        const screen = allocator.alloc(Cell, @as(usize, size.x) * @as(usize, size.y)) catch @panic("testing.zig: Out of memory.");
+        @memset(screen, .{});
+
+        return .{
+            .allocator = allocator,
+            .size = size,
+            .screen = screen,
+        };
+    }
+
+    pub fn deinit(this: *@This()) void {
+        this.allocator.free(this.screen);
+    }
+
+    pub fn resize(this: *@This(), size: Point) !void {
+        this.size = size;
+        const n = @as(usize, size.x) * @as(usize, size.y);
+
+        this.allocator.free(this.screen);
+        this.screen = this.allocator.alloc(Cell, n) catch @panic("testing.zig: Out of memory.");
+        @memset(this.screen, .{});
+    }
+
+    pub fn clear(this: *@This()) !void {
+        @memset(this.screen, .{});
+    }
+
+    pub fn render(this: *@This(), comptime T: type, container: *const T, comptime Model: type, model: *const Model) !void {
+        const size: Point = container.size;
+        const origin: Point = container.origin;
+        const cells: []const Cell = try container.content(model);
+
+        if (cells.len == 0) return;
+
+        var idx: usize = 0;
+        const anchor = (@as(usize, origin.y) * @as(usize, this.size.x)) + @as(usize, origin.x);
+
+        blk: for (0..size.y) |row| {
+            for (0..size.x) |col| {
+                const cell = cells[idx];
+                idx += 1;
+
+                this.screen[anchor + (row * this.size.x) + col].style = cell.style;
+                this.screen[anchor + (row * this.size.x) + col].cp = cell.cp;
+
+                if (cells.len == idx) break :blk;
+            }
+        }
+        // free immediately
+        container.allocator.free(cells);
+
+        for (container.elements.items) |*element| try this.render(T, element, Model, model);
+    }
+
+    pub fn save(this: @This(), writer: anytype) !void {
+        try std.zon.stringify.serialize(this.screen, .{ .whitespace = false }, writer);
+    }
+};
+
+/// This function is intended to be used only in tests. Test if a `Container`'s
+/// rendered contents are equal to the expected `Cell` slice.
+///
+/// # Test data creation
+///
+/// Create a .zon file containing the expected `Cell` slice using the `zterm.testing.Renderer.save` method:
+///
+/// ```zig
+/// const Model = struct {};
+/// var model: Model = .{};
+/// const file = try std.fs.cwd().createFile("test/container/border/all.zon", .{ .truncate = true });
+/// defer file.close();
+///
+/// const allocator = std.testing.allocator;
+/// var renderer: testing.Renderer = .init(allocator, size);
+/// defer renderer.deinit();
+///
+/// try container.handle(&model, .{ .size = size });
+/// try renderer.render(@TypeOf(container), &container, Model, &.{});
+/// try renderer.save(file.writer());
+/// ```
+///
+/// # Testing against created data
+///
+/// Then later load that .zon file at compile time and run your test against this `Cell` slice.
+///
+/// ```zig
+/// const Model = struct {};
+/// var container: Container(Model, event.SystemEvent) = try .init(std.testing.allocator, .{
+///     .border = .{
+///         .color = .green,
+///         .sides = .all,
+///     },
+/// }, .{});
+/// defer container.deinit();
+///
+/// try testing.expectContainerScreen(.{
+///     .rows = 20,
+///     .cols = 30,
+/// }, @TypeOf(container), &container, Model, @import("test/container/border.all.zon"));
+/// ```
+pub fn expectContainerScreen(size: Point, comptime T: type, container: *T, comptime Model: type, expected: []const Cell) !void {
+    const allocator = testing.allocator;
+    var renderer: Renderer = .init(allocator, size);
+    defer renderer.deinit();
+
+    const model: Model = .{};
+
+    container.resize(&model, size);
+    container.reposition(&model, .{});
+    try renderer.render(T, container, Model, &model);
+
+    try expectEqualCells(.{}, renderer.size, expected, renderer.screen);
+}
+
+/// Taken from: https://codeberg.org/atman/zg/src/branch/master/src/DisplayWidth.zig
+/// Owned by https://codeberg.org/atman licensed under MIT all credits for this function go to him
+fn center(allocator: Allocator, str: []const u8, total_width: usize, pad: []const u8) ![]u8 {
+    if (str.len > total_width) return error.StrTooLong;
+    if (str.len == total_width) return try allocator.dupe(u8, str);
+
+    if (pad.len > total_width or str.len + pad.len > total_width) return error.PadTooLong;
+
+    const margin_width = @divFloor((total_width - str.len), 2);
+    if (pad.len > margin_width) return error.PadTooLong;
+
+    const extra_pad: usize = if (total_width % 2 != str.len % 2) 1 else 0;
+    const pads = @divFloor(margin_width, pad.len) * 2 + extra_pad;
+
+    var result = try allocator.alloc(u8, pads * pad.len + str.len);
+    var bytes_index: usize = 0;
+    var pads_index: usize = 0;
+
+    while (pads_index < pads / 2) : (pads_index += 1) {
+        @memcpy(result[bytes_index..][0..pad.len], pad);
+        bytes_index += pad.len;
+    }
+
+    @memcpy(result[bytes_index..][0..str.len], str);
+    bytes_index += str.len;
+
+    pads_index = 0;
+    while (pads_index < pads / 2 + extra_pad) : (pads_index += 1) {
+        @memcpy(result[bytes_index..][0..pad.len], pad);
+        bytes_index += pad.len;
+    }
+
+    return result;
+}
+
+/// This function is intended to be used only in tests. Test if the two
+/// provided cell arrays are identical. Usually the `Cell` slices are
+/// the contents of a given screen from the `zterm.testing.Renderer`. See
+/// `zterm.testing.expectContainerScreen` for an example usage.
+pub fn expectEqualCells(origin: Point, size: Point, expected: []const Cell, actual: []const Cell) !void {
+    const allocator = testing.allocator;
+
+    try testing.expectEqual(expected.len, actual.len);
+    try testing.expectEqual(expected.len, @as(usize, size.y) * @as(usize, size.x));
+
+    var expected_cps = try std.ArrayList(Cell).initCapacity(allocator, size.x);
+    defer expected_cps.deinit(allocator);
+
+    var actual_cps = try std.ArrayList(Cell).initCapacity(allocator, size.x);
+    defer actual_cps.deinit(allocator);
+
+    var allocating_writer = std.Io.Writer.Allocating.init(allocator);
+    defer allocating_writer.deinit();
+
+    var writer = &allocating_writer.writer;
+    var differ = false;
+
+    const expected_centered = try center(allocator, "Expected Screen", size.x, " ");
+    defer allocator.free(expected_centered);
+
+    const actual_centered = try center(allocator, "Actual Screen", size.x, " ");
+    defer allocator.free(actual_centered);
+
+    try writer.print("Screens are not equivalent.\n{s} ┆ {s}\n", .{ expected_centered, actual_centered });
+
+    for (origin.y..size.y) |row| {
+        defer {
+            expected_cps.clearRetainingCapacity();
+            actual_cps.clearRetainingCapacity();
+        }
+        for (origin.x..size.x) |col| {
+            const expected_cell = expected[(row * size.x) + col];
+            const actual_cell = actual[(row * size.x) + col];
+
+            if (!expected_cell.eql(actual_cell)) differ = true;
+
+            try expected_cps.append(allocator, expected_cell);
+            try actual_cps.append(allocator, actual_cell);
+        }
+
+        // write screens both formatted to buffer
+        for (expected_cps.items) |cell| try cell.value(writer);
+        _ = try writer.write(" ┆ ");
+        for (actual_cps.items) |cell| try cell.value(writer);
+        _ = try writer.write("\n");
+    }
+
+    if (!differ) return;
+
+    // test failed
+    var buf: [1024]u8 = undefined;
+
+    std.debug.lockStdErr();
+    defer std.debug.unlockStdErr();
+
+    var buffer = std.fs.File.stderr().writer(&buf);
+    var error_writer = &buffer.interface;
+    try error_writer.writeAll(writer.buffer[0..writer.end]);
+    try error_writer.flush();
+
+    return error.TestExpectEqualCells;
+}
+
+const std = @import("std");
+const debug = std.debug;
+const testing = std.testing;
+const Allocator = std.mem.Allocator;
+const event = @import("event.zig");
+const Container = @import("container.zig").Container;
+const Cell = @import("cell.zig");
+const Point = @import("point.zig").Point;