MainWindow

repaints the screen.

called when this control becomes the active control. It will start receiving keystrokes after this point.

MainWindow is not directly interactive, though being the top-level parent, it does see keystrokes.

modeled after bubbling events in web browsers. Send the key to the currently active control, and continue sending it up the control's parents, so long as each control returns :continue. If any control sets it's dirty flag, trigger a refresh.

Sets focus to the nearest child/sibling control.

exit the program. Not named exit because that is a crystal kernel method.

Keys are processed in their own fiber.

MainWindow holds other controls so has no text of it's own.