NAME

request_video_bitmap - Triple buffering page flip request. Allegro game programming library.

SYNOPSIS

#include <allegro.h>

int request_video_bitmap(BITMAP *bitmap);

DESCRIPTION

This function is used for triple buffering. It requests a page flip to display the specified video bitmap object, but returns immediately rather than waiting for a retrace. The flip 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 on certain hardware: see the comments about request_scroll(). Example:

   int current_page;


   BITMAP *video_page[3];


   ...


   /* Create pages for page flipping */


   video_page[0] = create_video_bitmap(SCREEN_W, SCREEN_H);


   video_page[1] = create_video_bitmap(SCREEN_W, SCREEN_H);


   video_page[2] = create_video_bitmap(SCREEN_W, SCREEN_H);


   current_page = 0;


   ...


   /* draw the screen and flip pages */


   draw_screen(video_page[current_page]);


   do {


   } while (poll_scroll());


   request_video_bitmap(video_page[current_page]);


   current_page = (current_page+1)%3;


   ...

RETURN VALUE

Returns zero on success and non-zero on failure.

SEE ALSO

poll_scroll(3), request_scroll(3), gfx_capabilities(3), create_video_bitmap(3), scroll_screen(3), ex3buf(3), exupdate(3)