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screen(3alleg4) 						  Allegro manual						   screen(3alleg4)

screen - Global pointer to the screen hardware video memory. Allegro game programming library. SYNOPSIS
#include <allegro.h> extern BITMAP *screen; DESCRIPTION
Global pointer to a bitmap, sized VIRTUAL_W x VIRTUAL_H. This is created by set_gfx_mode(), and represents the hardware video memory. Only a part of this bitmap will actually be visible, sized SCREEN_W x SCREEN_H. Normally this is the top left corner of the larger virtual screen, so you can ignore the extra invisible virtual size of the bitmap if you aren't interested in hardware scrolling or page flipping. To move the visible window to other parts of the screen bitmap, call scroll_screen(). Initially the clipping rectangle will be limited to the physical screen size, so if you want to draw onto a larger virtual screen space outside this rectangle, you will need to adjust the clipping. For example, to draw a pixel onto the screen you would write: putpixel(screen, x, y, color); Or to implement a double-buffered system: /* Make a bitmap in RAM. */ BITMAP *bmp = create_bitmap(320, 200); /* Clean the memory bitmap. */ clear_bitmap(bmp); /* Draw onto the memory bitmap. */ putpixel(bmp, x, y, color); /* Copy it to the screen. */ blit(bmp, screen, 0, 0, 0, 0, 320, 200); Warning: be very careful when using this pointer at the same time as any bitmaps created by the create_video_bitmap() function (see the description of this function for more detailed information). And never try to destroy it with destroy_bitmap(). SEE ALSO
set_gfx_mode(3alleg4), is_screen_bitmap(3alleg4), create_video_bitmap(3alleg4), scroll_screen(3alleg4) Allegro version 4.4.2 screen(3alleg4)

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create_video_bitmap(3alleg4)					  Allegro manual				      create_video_bitmap(3alleg4)

create_video_bitmap - Creates a video memory bitmap. Allegro game programming library. SYNOPSIS
#include <allegro.h> BITMAP *create_video_bitmap(int width, int height); DESCRIPTION
Allocates a video memory bitmap of the specified size. This can be used to allocate offscreen video memory for storing source graphics ready for a hardware accelerated blitting operation, or to create multiple video memory pages which can then be displayed by calling show_video_bitmap(). Read the introduction of this chapter for a comparison with other types of bitmaps and other specific details. Warning: video memory bitmaps are usually allocated from the same space as the screen bitmap, so they may overlap with it; it is therefore not a good idea to use the global screen at the same time as any surfaces returned by this function. RETURN VALUE
Returns a pointer to the bitmap on success, or NULL if you have run out of video ram. Remember to destroy this bitmap before any subsequent call to set_gfx_mode(). SEE ALSO
create_bitmap(3alleg4), create_bitmap_ex(3alleg4), create_system_bitmap(3alleg4), create_sub_bitmap(3alleg4), destroy_bitmap(3alleg4), screen(3alleg4), show_video_bitmap(3alleg4), gfx_capabilities(3alleg4), is_video_bitmap(3alleg4), clear_bitmap(3alleg4), clear_to_color(3alleg4), ex3buf(3alleg4), exaccel(3alleg4), exflip(3alleg4), exupdate(3alleg4) Allegro version 4.4.2 create_video_bitmap(3alleg4)
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