I think you're wrong. 1. How do you know the size of the menubar? Width and height are not constant.
Height difference between screen and desktop work area. The width of the screen is constant.
2. The menubar-area might have changed during full-screen (top-app might haveexited or whatever)
I assume that a fullscreen application that doesn't relocate the framebuffer locks the screen. So you restore the saved area and then unlock the screen. Then the AES will update as necessary if there has been any changes to the menubar.
Jo Even