Provided by: allegro4-doc_4.4.2-10_all bug


       scroll_screen - Requests a hardware scroll request. Allegro game programming library.


       #include <allegro.h>

       int scroll_screen(int x, int y);


       Attempts  to  scroll the hardware screen to display a different part of the virtual screen
       (initially it will be positioned at 0, 0, which is the top left corner). You can use  this
       to  move  the  screen display around in a large virtual screen space, or to page flip back
       and forth between two non-overlapping areas of the  virtual  screen.  Note  that  to  draw
       outside  the  original  position  in the screen bitmap you will have to alter the clipping
       rectangle with set_clip_rect().

       Mode-X scrolling is reliable and will work on any card, other drivers may not work or  not
       work reliably. See the platform-specific section of the docs for more information.

       Allegro  will  handle  any  necessary  vertical retrace synchronisation when scrolling the
       screen, so you don't need to call vsync() before it. This means that  scroll_screen()  has
       the same time delay effects as vsync().


       Returns  zero  on  success.  Returns non-zero if the graphics driver can't handle hardware
       scrolling or the virtual screen is not large enough.


       set_gfx_mode(3alleg4),        show_video_bitmap(3alleg4),         request_scroll(3alleg4),
       request_video_bitmap(3alleg4), exscroll(3alleg4)