Notifies an appbar when an event has occurred that may effect the appbar’s size and position. Events include changes in the taskbar’s size, position, and visibility state, as well as the addition, removal, or resizing of another appbar on the same side of the screen.
No return value.
An appbar should respond to this notification message by sending the ABM_QUERYPOS and ABM_SETPOS messages. If its position has changed, the appbar should call the MoveWindow function to move itself to the new position.
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