request_scroll - Queues a hardware scroll request with triple buffering. Allegro game programming

       This function is used for triple buffering. It requests a hardware scroll to the specified position,  but
       returns  immediately  rather  than waiting for a retrace. The scroll will then take place during the next
       vertical retrace, but you can carry on running other code in  the  meantime  and  use  the  poll_scroll()
       routine to detect when the flip has actually taken place.

       Triple  buffering is only possible with certain drivers: you can look at the GFX_CAN_TRIPLE_BUFFER bit in
       the gfx_capabilities flag to see if it will work with the current driver.

       request_scroll  -  Queues  a  hardware  scroll  request  with  triple buffering. Allegro game programming
       library.

       This function returns zero on success, non-zero otherwise.

poll_scroll(3alleg4), request_video_bitmap(3alleg4), gfx_capabilities(3alleg4), scroll_screen(3alleg4)

Allegro                                           version 4.4.3                          request_scroll(3alleg4)

#include<allegro.h>intrequest_scroll(intx,inty);