al_win_add_window_callback man page
al_win_add_window_callback — Allegro 5 API
#include <allegro5/allegro_windows.h> bool al_win_add_window_callback(ALLEGRO_DISPLAY *display, bool (*callback)(ALLEGRO_DISPLAY *display, UINT message, WPARAM wparam, LPARAM lparam, LRESULT *result, void *userdata), void *userdata)
The specified callback function will intercept the window's message before Allegro processes it. If the callback function consumes the event, then it should return true. In that case, Allegro will not do anything with the event.
Optionally, you may use
result to customize what Allegro will return return in response to this event. By default, Allegro returns
userdata pointer can be used to supply additional context to the callback function.
The callbacks are executed in the same order they were added.
Returns true if the callback was added.