add(widget): Text widget to display static Cell contents

src/widget/Text.zig

@@ -0,0 +1,50 @@
+const std = @import("std");
+const terminal = @import("../terminal.zig");
+
+const isTaggedUnion = @import("../event.zig").isTaggedUnion;
+const Error = @import("../event.zig").Error;
+const Cell = terminal.Cell;
+
+const log = std.log.scoped(.widget_text);
+
+pub fn Widget(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)`.");
+    }
+    return struct {
+        contents: []const Cell = undefined,
+        size: terminal.Size = undefined,
+        require_render: bool = false,
+
+        pub fn init(contents: []const Cell) @This() {
+            return .{
+                .contents = contents,
+            };
+        }
+
+        pub fn deinit(this: *@This()) void {
+            this.* = undefined;
+        }
+
+        pub fn handle(this: *@This(), event: Event) ?Event {
+            switch (event) {
+                // store the received size
+                .resize => |size| {
+                    this.size = size;
+                    this.require_render = true;
+                },
+                else => {},
+            }
+            return null;
+        }
+
+        pub fn render(this: *@This(), renderer: *Renderer) !void {
+            if (!this.require_render) {
+                return;
+            }
+            try renderer.clear(this.size);
+            try renderer.render(this.size, this.contents);
+            this.require_render = false;
+        }
+    };
+}