* New and completed widgets: Menu, MenuButton and MenuBar.
* MenuButton is a kind of Button that opens a popup Menu when clicked.
* MenuBar is a container of buttons designed to be attached to the top
of an application window ("File, Edit, View, Help")
* Supervisor manages the popup menus with its new concept of a Modal
Widget. Modal widgets take exclusive event priority for all mouse and
key events. The pop-up menu is a modal window, which means you must
click an option inside the menu OR clicking outside the menu will
close it and eat your click event (widgets outside the modal don't
receive events, but the modal itself gets an event that you've done
this).
* Fix Supervisor event issues wrt. the window manager feature: if a
focused window exists and Supervisor is running events for the "other"
widgets not in managed windows, and the mouse cursor is over the
rectangle of THE focused window, no widget under the cursor receives
active (hover, click) events. Prevents being able to click "through"
the window and interact with widgets and other windows below.
* Adds Close, Maximize and Minimize buttons to windows. Maximize is
still buggy and Minimize is implementation-defined behavior with no
default event handler configured.
* eg/windows has an example of the Window Manager for SDL2 and
WebAssembly targets.
Noah