mod(widget/Text): add alignment options for Text Widget

Updated exec example which uses centered text.

examples/exec.zig

@@ -44,7 +44,7 @@ pub fn main() !void {
                 Layout.createFrom(framing: {
                     var framing = Layout.Framing.init(allocator, .{}, .{
                         .widget = Widget.createFrom(blk: {
-                            var widget = Widget.Text.init(&[_]Cell{
+                            var widget = Widget.Text.init(.center, &[_]Cell{
                                 .{ .content = "Press " },
                                 .{ .content = "Ctrl+n", .style = .{ .fg = .{ .index = 6 } } },
                                 .{ .content = " to launch $EDITOR" },

src/widget/Text.zig

@@ -12,12 +12,23 @@ pub fn Widget(comptime Event: type, comptime Renderer: type) type {
         @compileError("Provided user event `Event` for `Layout(comptime Event: type)` is not of type `union(enum)`.");
     }
     return struct {
+        alignment: Alignment = undefined,
         contents: []const Cell = undefined,
         size: terminal.Size = undefined,
         require_render: bool = false,
 
-        pub fn init(contents: []const Cell) @This() {
+        const Alignment = enum {
+            default,
+            center,
+            top,
+            bottom,
+            left,
+            right,
+        };
+
+        pub fn init(alignment: Alignment, contents: []const Cell) @This() {
             return .{
+                .alignment = alignment,
                 .contents = contents,
             };
         }
@@ -43,7 +54,98 @@ pub fn Widget(comptime Event: type, comptime Renderer: type) type {
                 return;
             }
             try renderer.clear(this.size);
-            try renderer.render(this.size, this.contents);
+            // update size for aligned contents, default will not change size
+            const size: terminal.Size = blk: {
+                switch (this.alignment) {
+                    .default => break :blk this.size,
+                    .center => {
+                        var length_usize: usize = 0;
+                        for (this.contents) |content| {
+                            length_usize += content.content.len;
+                        }
+                        const length: u16 = @truncate(length_usize);
+                        const cols = @min(length, this.size.cols);
+                        const rows = @divExact(cols, length);
+                        break :blk .{
+                            .anchor = .{
+                                .col = this.size.anchor.col + @divTrunc(this.size.cols, 2) - @divTrunc(cols, 2),
+                                .row = this.size.anchor.row + @divTrunc(this.size.rows, 2),
+                            },
+                            .rows = rows,
+                            .cols = cols,
+                        };
+                    },
+                    .top => {
+                        var length_usize: usize = 0;
+                        for (this.contents) |content| {
+                            length_usize += content.content.len;
+                        }
+                        const length: u16 = @truncate(length_usize);
+                        const cols = @min(length, this.size.cols);
+                        const rows = @divExact(cols, length);
+                        break :blk .{
+                            .anchor = .{
+                                .col = this.size.anchor.col + @divTrunc(this.size.cols, 2) - @divTrunc(cols, 2),
+                                .row = this.size.anchor.row,
+                            },
+                            .rows = rows,
+                            .cols = cols,
+                        };
+                    },
+                    .bottom => {
+                        var length_usize: usize = 0;
+                        for (this.contents) |content| {
+                            length_usize += content.content.len;
+                        }
+                        const length: u16 = @truncate(length_usize);
+                        const cols = @min(length, this.size.cols);
+                        const rows = @divExact(cols, length);
+                        break :blk .{
+                            .anchor = .{
+                                .col = this.size.anchor.col + @divTrunc(this.size.cols, 2) - @divTrunc(cols, 2),
+                                .row = this.size.anchor.row + this.size.rows - rows,
+                            },
+                            .rows = rows,
+                            .cols = cols,
+                        };
+                    },
+                    .left => {
+                        var length_usize: usize = 0;
+                        for (this.contents) |content| {
+                            length_usize += content.content.len;
+                        }
+                        const length: u16 = @truncate(length_usize);
+                        const cols = @min(length, this.size.cols);
+                        const rows = @divExact(cols, length);
+                        break :blk .{
+                            .anchor = .{
+                                .col = this.size.anchor.col,
+                                .row = this.size.anchor.row + @divTrunc(this.size.rows, 2) - @divTrunc(rows, 2),
+                            },
+                            .rows = rows,
+                            .cols = cols,
+                        };
+                    },
+                    .right => {
+                        var length_usize: usize = 0;
+                        for (this.contents) |content| {
+                            length_usize += content.content.len;
+                        }
+                        const length: u16 = @truncate(length_usize);
+                        const cols = @min(length, this.size.cols);
+                        const rows = @divExact(cols, length);
+                        break :blk .{
+                            .anchor = .{
+                                .col = this.size.anchor.col + this.size.cols - cols,
+                                .row = this.size.anchor.row + @divTrunc(this.size.rows, 2) - @divTrunc(rows, 2),
+                            },
+                            .rows = rows,
+                            .cols = cols,
+                        };
+                    },
+                }
+            };
+            try renderer.render(size, this.contents);
             this.require_render = false;
         }
     };