mod: replace Layout.content with Layout.render

The App.Renderer is used for the new `Layout.render` method. Each layout
renders itself now with corresponding renderers which might only update
parts of the screen, etc.

src/layout.zig

@@ -1,7 +1,7 @@
 //! Dynamic dispatch for layout implementations.
 //! Each layout should at last implement these functions:
 //! - handle(this: *@This(), event: Event) anyerror!*std.ArrayList(Event) {}
-//! - content(this: *@This()) anyerror!*std.ArrayList(u8) {}
+//! - render(this: *@This(), renderer: Renderer) anyerror!void {}
 //! - deinit(this: *@This()) void {}
 //!
 //! Create a `Layout` using `createFrom(object: anytype)` and use them through
@@ -11,10 +11,13 @@
 //! Each `Layout` is responsible for clearing the allocated memory of the used
 //! widgets when deallocated. This means that `deinit()` will also deallocate
 //! every used widget too.
+//!
+//! When `Layout.render` is called the provided `Renderer` type is expected
+//! which handles how contents are rendered for a given layout.
 const std = @import("std");
 const isTaggedUnion = @import("event.zig").isTaggedUnion;
 
-pub fn Layout(comptime Event: type) type {
+pub fn Layout(comptime Event: type, comptime Renderer: type) type {
     if (!isTaggedUnion(Event)) {
         @compileError("Provided user event `Event` for `Layout(comptime Event: type)` is not of type `union(enum)`.");
     }
@@ -25,7 +28,7 @@ pub fn Layout(comptime Event: type) type {
 
         const VTable = struct {
             handle: *const fn (this: *LayoutType, event: Event) anyerror!*Events,
-            content: *const fn (this: *LayoutType) anyerror!*std.ArrayList(u8),
+            render: *const fn (this: *LayoutType, renderer: Renderer) anyerror!void,
             deinit: *const fn (this: *LayoutType) void,
         };
 
@@ -37,9 +40,9 @@ pub fn Layout(comptime Event: type) type {
             return try this.vtable.handle(this, event);
         }
 
-        // Return the entire content of this `Layout`.
-        pub fn content(this: *LayoutType) !*std.ArrayList(u8) {
-            return try this.vtable.content(this);
+        // Render this `Layout` completely. This will render contained sub-elements too.
+        pub fn render(this: *LayoutType, renderer: Renderer) !void {
+            return try this.vtable.render(this, renderer);
         }
 
         pub fn deinit(this: *LayoutType) void {
@@ -58,13 +61,13 @@ pub fn Layout(comptime Event: type) type {
                             return try layout.handle(event);
                         }
                     }.handle,
-                    .content = struct {
-                        // Return the entire content of this `Layout`.
-                        fn content(this: *LayoutType) !*std.ArrayList(u8) {
+                    .render = struct {
+                        // Render the contents of this `Layout`.
+                        fn render(this: *LayoutType, renderer: Renderer) !void {
                             const layout: @TypeOf(object) = @ptrFromInt(this.object);
-                            return try layout.content();
+                            try layout.render(renderer);
                         }
-                    }.content,
+                    }.render,
                     .deinit = struct {
                         fn deinit(this: *LayoutType) void {
                             const layout: @TypeOf(object) = @ptrFromInt(this.object);
@@ -76,9 +79,9 @@ pub fn Layout(comptime Event: type) type {
         }
 
         // import and export of `Layout` implementations
-        pub const HStack = @import("layout/HStack.zig").Layout(Event);
-        pub const VStack = @import("layout/VStack.zig").Layout(Event);
-        pub const Padding = @import("layout/Padding.zig").Layout(Event);
-        pub const Framing = @import("layout/Framing.zig").Layout(Event);
+        pub const HStack = @import("layout/HStack.zig").Layout(Event, Renderer);
+        pub const VStack = @import("layout/VStack.zig").Layout(Event, Renderer);
+        pub const Padding = @import("layout/Padding.zig").Layout(Event, Renderer);
+        pub const Framing = @import("layout/Framing.zig").Layout(Event, Renderer);
     };
 }