I was playing around with some things and noticed that all al_acknowledge_resize appears to do in X is reset the OpenGL coordinates so that (0,0) is the upper-left corner. Perhaps for some people this is necessary to resize the drawing surface, but it was not the case for me, and the actual window will be changing size whether you want it to or not.
This led me to believe that al_acknowledge_resize is unnecessary, and could instead be called at the same time the ALLEGRO_EVENT_DISPLAY_RESIZE event is fired. Is there a case to be made for
a) A user needing to perform cleanup work before correcting the screen coordinates?
b) A user wanting their coordinates to be messed up in a most likely platform-dependant manner?
Also, if the event is not acknowledged, it will continue to fire for any X ConfigureNotify events (such as moving the window) until it has been acknowledged. I don't know if this is something that really matters or not, since I am proposing removing this function completely (at least from the public interface).