Any GWidget can have a tooltip and it will automatically pop up below the
center of the widget when hovered. GActions added to GToolBars will use
the action text() as their tooltip automagically. :^)
The window is simply ignored in the painting and hit testing traversal
when in minimized state, same as we do for invisible windows.
The WM_SetActiveWindow message (sent by Taskbar) brings it back into the
non-minimized state. :^)
I originally thought I would do this inside WindowServer, but let's try to
make it as a standalone app that communicates with WindowServer instead.
That will allow us to use LibGUI. :^)
Now that everything is nice and mature, the WindowServer can just use the
client PID it receives in the Greeting message, and we can get rid of this
hacky ioctl. :^)