window: add some doc comments

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

src/Screen.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const assert = std.debug.assert;
 
 const Cell = @import("cell.zig").Cell;
 
@@ -38,6 +39,6 @@ pub fn writeCell(self: *Screen, cell: Cell, row: usize, col: usize) void {
         return;
     }
     const i = (col * self.width) + row;
-    std.debug.assert(i < self.buf.len);
+    assert(i < self.buf.len);
     self.buf[i] = cell;
 }

src/Window.zig

@@ -10,15 +10,20 @@ pub const Size = union(enum) {
     limit: usize,
 };
 
+/// horizontal offset from the screen
 x_off: usize,
+/// vertical offset from the screen
 y_off: usize,
+/// width of the window. This can't be larger than the terminal screen
 width: usize,
+/// height of the window. This can't be larger than the terminal screen
 height: usize,
 
 screen: *Screen,
 
 /// Creates a new window with offset relative to parent and size clamped to the
-/// parents' size
+/// parent's size. Windows do not retain a reference to their parent and are
+/// unaware of resizes.
 pub fn initChild(
     self: *Window,
     x_off: usize,