window: implement initial window data structure

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>

src/Window.zig

@@ -0,0 +1,111 @@
+const std = @import("std");
+
+const Screen = @import("Screen.zig");
+const Cell = @import("cell.zig").Cell;
+
+const Window = @This();
+
+pub const Size = union(enum) {
+    expand,
+    limit: usize,
+};
+
+x_off: usize,
+y_off: usize,
+width: usize,
+height: usize,
+
+parent: ?*Window,
+screen: *Screen,
+
+/// Creates a new window with offset relative to parent and size clamped to the
+/// parents' size
+pub fn initChild(
+    self: *Window,
+    x_off: usize,
+    y_off: usize,
+    width: Size,
+    height: Size,
+) Window {
+    const resolved_width = switch (width) {
+        .expand => self.width - x_off,
+        .limit => |w| blk: {
+            if (w + x_off > self.width) {
+                break :blk self.width - x_off;
+            }
+            break :blk w;
+        },
+    };
+    const resolved_height = switch (height) {
+        .expand => self.height - y_off,
+        .limit => |h| blk: {
+            if (h + y_off > self.height) {
+                break :blk self.height - y_off;
+            }
+            break :blk h;
+        },
+    };
+    return Window{
+        .x_off = x_off,
+        .y_off = y_off,
+        .width = resolved_width,
+        .height = resolved_height,
+        .parent = self,
+        .screen = self.screen,
+    };
+}
+
+/// writes a cell to the location in the window
+pub fn writeCell(self: Window, cell: Cell, row: usize, col: usize) void {
+    if (self.h < row or self.w < col) return;
+    if (self.parent) |p| {
+        p.writeCell(cell, row + self.y_off, col + self.x_off);
+    } else {
+        self.screen.writeCell(cell, row + self.y_off, col + self.x_off);
+    }
+}
+
+test "Window size set" {
+    var parent = Window{
+        .x_off = 0,
+        .y_off = 0,
+        .width = 20,
+        .height = 20,
+        .parent = null,
+        .screen = undefined,
+    };
+
+    const child = parent.initChild(1, 1, .expand, .expand);
+    try std.testing.expectEqual(19, child.width);
+    try std.testing.expectEqual(19, child.height);
+}
+
+test "Window size set too big" {
+    var parent = Window{
+        .x_off = 0,
+        .y_off = 0,
+        .width = 20,
+        .height = 20,
+        .parent = null,
+        .screen = undefined,
+    };
+
+    const child = parent.initChild(0, 0, .{ .limit = 21 }, .{ .limit = 21 });
+    try std.testing.expectEqual(20, child.width);
+    try std.testing.expectEqual(20, child.height);
+}
+
+test "Window size set too big with offset" {
+    var parent = Window{
+        .x_off = 0,
+        .y_off = 0,
+        .width = 20,
+        .height = 20,
+        .parent = null,
+        .screen = undefined,
+    };
+
+    const child = parent.initChild(10, 10, .{ .limit = 21 }, .{ .limit = 21 });
+    try std.testing.expectEqual(10, child.width);
+    try std.testing.expectEqual(10, child.height);
+}

src/app.zig

@@ -4,6 +4,7 @@ const queue = @import("queue.zig");
 const Tty = @import("Tty.zig");
 const Key = @import("Key.zig");
 const Screen = @import("Screen.zig");
+const Window = @import("Window.zig");
 
 /// App is the entrypoint for an odditui application. The provided type T should
 /// be a tagged union which contains all of the events the application will
@@ -83,6 +84,17 @@ pub fn App(comptime T: type) type {
         pub fn resize(self: *Self, alloc: std.mem.Allocator, w: usize, h: usize) !void {
             try self.screen.resize(alloc, w, h);
         }
+
+        pub fn window(self: *Self) Window {
+            return Window{
+                .x_off = 0,
+                .y_off = 0,
+                .w = .{.expand},
+                .h = .{.expand},
+                .parent = null,
+                .screen = &self.screen,
+            };
+        }
     };
 }
 
@@ -90,8 +102,9 @@ test "App: event queueing" {
     const Event = union(enum) {
         key,
     };
+    const alloc = std.testing.allocator;
     var app: App(Event) = try App(Event).init(.{});
-    defer app.deinit();
+    defer app.deinit(alloc);
     app.postEvent(.key);
     const event = app.nextEvent();
     try std.testing.expect(event == .key);

src/main.zig

@@ -4,7 +4,10 @@ pub const Winsize = @import("Tty.zig").Winsize;
 
 test {
     _ = @import("Key.zig");
+    _ = @import("Screen.zig");
     _ = @import("Tty.zig");
+    _ = @import("Window.zig");
     _ = @import("app.zig");
+    _ = @import("cell.zig");
     _ = @import("queue.zig");
 }