set_mouse_cursor_bitmap (3) - Linux Man Pages
set_mouse_cursor_bitmap: Changes the image Allegro uses for mouse cursors.
NAMEset_mouse_cursor_bitmap - Changes the image Allegro uses for mouse cursors.
DESCRIPTIONThis function changes the cursor image Allegro uses if select_mouse_cursor() is called but no native operating system cursor can be used, e.g. because you did not call enable_hardware_cursor().
The cursor argument can be one of:
MOUSE_CURSOR_ALLEGRO MOUSE_CURSOR_ARROW MOUSE_CURSOR_BUSY MOUSE_CURSOR_QUESTION MOUSE_CURSOR_EDIT
but not MOUSE_CURSOR_NONE.
The bmp argument can either point to a valid bitmap or it can be NULL. Passing a bitmap makes Allegro use that image in place of its own default substitution (should the operating system's native cursor be unavailable). The bitmap must remain available for the duration in which it could be used. Passing NULL lets Allegro revert to its default substitutions.
The effect of this function will not be apparent until show_mouse() is called.