Function 18, subfunction 7 - get active window.
Parameters:
- eax = 18 - function number
- ebx = 7 - subfunction number
Returned value:
- eax = number of the active window
(number of the slot of the thread with active window)
Remarks:
- Active window is at the top of the window stack and receives
messages on all keyboard input.
- To make a window active, use subfunction 3.