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# Video Function Reference
Introduction | Function List | Function Reference | Examples
`extern SDL_Surface *SDL_GetVideoSurface(void);` This function returns a pointer to the current display surface. If SDL is doing format conversion on the display surface, this function returns the publicly visible surface, not the real video surface. `extern const SDL_VideoInfo *SDL_GetVideoInfo(void);` This function returns a read-only pointer to information about the video hardware. If this is called before `SDL_SetVideoMode()`, the '`vfmt`' member of the returned structure will contain the pixel format of the "best" video mode. `extern SDL_Rect **SDL_ListModes(SDL_PixelFormat *format, Uint32 flags);` Return a pointer to an array of available screen dimensions for the given format and video flags, sorted largest to smallest. Returns `NULL` if there are no dimensions available for a particular format, or if any dimension is okay for the given format. If '`format`' is `NULL`, the mode list will be for the format returned by `SDL_GetVideoInfo()->vfmt` `extern int SDL_VideoModeOK(int width, int height, int bpp, Uint32 flags);` Check to see if a particular video mode is supported. It returns `0` if the requested mode is not supported under any bit depth, or returns the bits-per-pixel of the closest available mode with the given width and height. If this bits-per-pixel is different from the one used when setting the video mode, `SDL_SetVideoMode()` will succeed, but will emulate the requested bits-per-pixel with a shadow surface. The arguments to `SDL_VideoModeOK()` are the same ones you would pass to `SDL_SetVideoMode()` `extern SDL_Surface *SDL_SetVideoMode(int width, int height, int bpp, Uint32 flags);` Set up a video mode with the specified width, height and bits-per-pixel. If '`bpp`' is `0`, it is treated as the current display bits per pixel. If `SDL_ANYFORMAT` is set in '`flags`', the SDL library will try to set the requested bits-per-pixel, but will return whatever video pixel format is available. The default is to emulate the requested pixel format if it is not natively available. If `SDL_HWSURFACE` is set in '`flags`', the video surface will be placed in video memory, if possible, and you may have to call `SDL_LockSurface()` in order to access the raw framebuffer. Otherwise, the video surface will be created in system memory. If `SDL_HWPALETTE` is set in '`flags`', the SDL library will guarantee that the colors set by `SDL_SetColors()` will be the colors you get. Otherwise, in 8-bit mode, `SDL_SetColors()` may not be able to set all of the colors exactly the way they are requested, and you should look at the video surface structure to determine the actual palette. If SDL cannot guarantee that the colors you request can be set, i.e. if the colormap is shared, then the video surface may be created under emulation in system memory, overriding the `SDL_HWSURFACE` flag. If `SDL_FULLSCREEN` is set in '`flags`', the SDL library will try to set a fullscreen video mode. The default is to create a windowed mode if the current graphics system has a window manager. If the SDL library is able to set a fullscreen video mode, this flag will be set in the surface that is returned. If `SDL_DOUBLEBUF` is set in '`flags`', the SDL library will try to set up two surfaces in video memory and swap between them when you call `SDL_Flip()`. This is usually slower than the normal single-buffering scheme, but prevents "tearing" artifacts caused by modifying video memory while the monitor is refreshing. It should only be used by applications that redraw the entire screen on every update. This function returns the frambuffer surface, or `NULL` if it fails. `extern void SDL_UpdateRects(SDL_Surface *screen, int numrects, SDL_Rect *rects); extern void SDL_UpdateRect(SDL_Surface *screen, Sint32 x, Sint32 y, Uint32 w, Uint32 h);` Makes sure the given list of rectangles is updated on the given screen. If '`x`', '`y`', '`w`' and '`h`' are all `0`, `SDL_UpdateRect()` will update the entire screen. These functions should not be called while '`screen`' is locked. `extern int SDL_Flip(SDL_Surface *screen);` On hardware that supports double-buffering, this function sets up a flip and returns. The hardware will wait for vertical retrace, and then swap video buffers before the next video surface blit or lock will return. On hardware that doesn not support double-buffering, this is equivalent to calling `SDL_UpdateRect (screen, 0, 0, 0, 0)`; The `SDL_DOUBLEBUF` flag must have been passed to `SDL_SetVideoMode()` when setting the video mode for this function to perform hardware flipping. This function returns `0` if successful, or `-1` if there was an error. `extern int SDL_SetColors(SDL_Surface *surface, SDL_Color *colors, int firstcolor, int ncolors);` Sets a portion of the colormap for the given 8-bit surface. If '`surface`' is not a palettized surface, this function does nothing, returning `0`. If all of the colors were set as passed to `SDL_SetColors()`, it will return `1`. If not all the color entries were set exactly as given, it will return `0`, and you should look at the surface palette to determine the actual color palette. When '`surface`' is the surface associated with the current display, the display colormap will be updated with the requested colors. If `SDL_HWPALETTE` was set in `SDL_SetVideoMode()` flags, `SDL_SetColors()` will always return `1`, and the palette is guaranteed to be set the way you desire, even if the window colormap has to be warped or run under emulation. `extern Uint32 SDL_MapRGB(SDL_PixelFormat *fmt, Uint8 r, Uint8 g, Uint8 b);` Maps an RGB value to a 32-bit pixel for a given pixel format `extern void SDL_GetRGB(Uint32 pixel, SDL_PixelFormat *fmt, Uint8 *r, Uint8 *g, Uint8 *b);` Maps a 32-bit pixel into the RGB components for a given pixel format `extern SDL_Surface *SDL_CreateRGBSurface (Uint32 flags, int width, int height, int depth, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask); extern SDL_Surface *SDL_CreateRGBSurfaceFrom( void *pixels, int width, int height, int depth, int pitch, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask); extern void SDL_FreeSurface(SDL_Surface *surface);` Allocate and free an RGB surface (must be called after SDL_SetVideoMode) If '`depth`' is 4 or 8 bits, an empty palette is allocated for the surface. If '`depth`' is greater than 8 bits, the pixel format is set using the flags '`[RGB]mask`'. The '`flags`' tell what kind of surface to create. `SDL_SWSURFACE` means that the surface should be created in system memory. `SDL_HWSURFACE` means that the surface should be created in video memory, with the same format as the display surface. This is useful for surfaces that will not change much, to take advantage of hardware acceleration when being blitted to the display surface. `SDL_SRCCOLORKEY` means that the surface will be used for colorkey blits and if the hardware supports hardware acceleration of colorkey blits between two surfaces in video memory, to place the surface in video memory if possible, otherwise it will be placed in system memory. `SDL_SRCALPHA` means that the surface will be used for alpha blits and if the hardware supports hardware acceleration of alpha blits between two surfaces in video memory, to place the surface in video memory if possible, otherwise it will be placed in system memory. `SDL_SRCCOLORKEY` and `SDL_SRCALPHA` will only be honored if the display surface is in video video memory (the surface returned by `SDL_SetVideoMode()` has the `SDL_HWSURFACE` flag set.) If the surface is created in video memory, blits will be _much_ faster, but the surface format must be identical to the video surface format, and the only way to access the pixels member of the surface is to use the `SDL_LockSurface()` and `SDL_UnlockSurface()` calls. If the requested surface actually resides in video memory, `SDL_HWSURFACE` will be set in the flags member of the returned surface. If for some reason the surface could not be placed in video memory, it will not have the `SDL_HWSURFACE` flag set, but will be created in system memory and returned anyway. If the function runs out of memory, it will return `NULL`. `extern int SDL_LockSurface(SDL_Surface *surface); extern void SDL_UnlockSurface(SDL_Surface *surface);` `SDL_LockSurface()` sets up a surface for directly accessing the pixels. Between calls to `SDL_LockSurface()`/ `SDL_UnlockSurface()`, you can write to and read from '`surface->pixels`', using the pixel format stored in '`surface->format`'. Once you are done accessing the surface, you should use `SDL_UnlockSurface()` to release it. Not all surfaces require locking. If `SDL_MUSTLOCK(surface)` evaluates to `0`, then you can read and write to the surface at any time, and the pixel format of the surface will not change. In particular, if the `SDL_HWSURFACE` flag is not given when calling SDL_SetVideoMode(), you will not need to lock the display surface before accessing it. No operating system or library calls should be made between lock/unlock pairs, as critical system locks may be held during this time. `SDL_LockSurface()` returns `0`, or `-1` if the surface couldn't be locked. `extern SDL_Surface *SDL_LoadBMP(const char *file);` Load a surface from a named Windows BMP file. Returns the new surface, or `NULL` if there was an error. The new surface should be freed with `SDL_FreeSurface()`. `extern int SDL_SaveBMP(SDL_Surface *surface, const char *file);` Save a surface to the named Windows BMP file. Returns `0` if successful or `-1` if there was an error. `extern int SDL_SetColorKey(SDL_Surface *surface, Uint32 flag, Uint32 key);` Sets the color key (transparent pixel) in a blittable surface. If '`flag`' is `SDL_SRCCOLORKEY` (optionally OR'd with `SDL_RLEACCEL`), the '`key`' is the transparent pixel in the source image of a blit. If '`flag`' is `0`, this function clears any current color key. This function returns `0`, or `-1` if there was an error. `extern int SDL_SetAlpha(SDL_Surface *surface, Uint32 flag, Uint8 alpha);` If '`alpha`' is non-zero, this function sets the alpha value for the entire surface, as opposed to using the alpha component of each pixel. This value measures the range of transparency of the surface, `0` being completely opaque to `255` being completely transparent. If '`flag`' is `0`, alpha blending is disabled for the surface. If '`flag`' is `SDL_SRCALPHA`, alpha blending is enabled for the surface. `extern void SDL_SetClipping(SDL_Surface *surface, int top, int left, int bottom, int right);` Sets the clipping rectangle for the source surface in a blit. If the destination rectangle falls outside this rectangle, the source surface will be clipped so the blit doesn't write outside the clipping rectangle. If the clip rectangle is { 0, 0, 0, 0 }, clipping will be disabled. Note that blits are automatically clipped to the edges of the source and destination surfaces. `extern SDL_Surface *SDL_ConvertSurface(SDL_Surface *src, SDL_PixelFormat *fmt, Uint32 flags);` Creates a new surface of the specified format, and then copies and maps the given surface to it so the blit of the converted surface will be as fast as possible. If this function fails, it returns `NULL`. The '`flags`' parameter is passed to `SDL_CreateRGBSurface()` and has those semantics. This function is used internally by `SDL_DisplayFormat()`. `extern int SDL_BlitSurface(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect);` This performs a fast blit from the source surface to the destination surface. It assumes that the source and destination rectangles are the same size. If either '`srcrect`' or '`dstrect`' are `NULL`, the entire surface (src or dst) is copied. The final blit rectangles are saved in '`srcrect`' and '`dstrect`' after all clipping is performed. If the blit is successful, it returns `0`, otherwise it returns `-1`. The blit function should not be called on a locked surface. If either of the surfaces were in video memory, and the blit returns -2, the video memory was lost, so it should be reloaded with artwork and re-blitted: ``
    	while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {
    		while ( SDL_LockSurface(image)) < 0 )
    			Sleep(10);
    		-- Write image pixels to image->pixels --
    		SDL_UnlockSurface(image);
    	}
This happens under DirectX 5.0 when the system switches away from your fullscreen application. Locking the surface will also fail until you have access to the video memory again. `extern int SDL_FillRect(SDL_Surface *dst, SDL_Rect *dstrect, Uint32 color);` This function performs a fast fill of the given rectangle with '`color`'. If '`dstrect`' is `NULL`, the whole surface will be filled with '`color`' The color should be a pixel of the format used by the surface, and can be generated by the `SDL_MapRGB()` function. This function returns `0` on success, or `-1` on error. `extern SDL_Surface *SDL_DisplayFormat(SDL_Surface *surface);` This function takes a surface and copies it to a new surface of the pixel format and colors of the video framebuffer, suitable for fast blitting onto the display surface. It calls `SDL_ConvertSurface()` If you want to take advantage of hardware colorkey or alpha blit acceleration, you should set the colorkey and alpha value before calling this function. If the conversion fails or runs out of memory, it returns `NULL` `extern void SDL_UnmapSurface(SDL_Surface *src);` This should never be necessary, but is included for completeness, and is used internally. `extern void SDL_WM_SetCaption(const char *title, const char *icon); extern void SDL_WM_GetCaption(char **title, char **icon);` Sets/Gets the title-bar of the display window, if any. `extern void SDL_WM_SetIcon(SDL_Surface *icon, Uint8 *mask);` Sets the icon for the display window. This function must be called before the first call to SDL_SetVideoMode(). It takes an icon surface, and a mask in MSB format. If '`mask`' is `NULL`, the entire icon surface will be used as the icon. `extern void SDL_WarpMouse(Uint16 x, Uint16 y);` Set the position of the mouse cursor (generates a mouse motion event) `extern SDL_Cursor *SDL_CreateCursor(Uint8 *data, Uint8 *mask, int w, int h, int hot_x, int hot_y);` Create a cursor using the specified data and mask (in MSB format). The cursor width must be a multiple of 8 bits. The cursor is created in black and white according to the following:
data | mask | resulting pixel on screen
--- | --- | ---
0 | 1 | White
1 | 1 | Black
0 | 0 | Transparent
1 | 0 | Inverted color if possible, black if not.
Cursors created with this function must be freed with `SDL_FreeCursor()`. `extern void SDL_SetCursor(SDL_Cursor *cursor);` Set the currently active cursor to the specified one. If the cursor is currently visible, the change will be immediately represented on the display. `extern SDL_Cursor *SDL_GetCursor(void);` Returns the currently active cursor. `extern void SDL_FreeCursor(SDL_Cursor *cursor);` Deallocates a cursor created with `SDL_CreateCursor()`. `extern int SDL_ShowCursor(int toggle);` Toggle whether or not the cursor is shown on the screen. The cursor start off displayed, but can be turned off. `SDL_ShowCursor()` returns `1` if the cursor was being displayed before the call, or `0` if it was not. ### Structure definitions:
    typedef struct {
            Sint16 x, y;
            Uint16 w, h;
    } SDL_Rect;

    typedef struct {
            Uint8 r;
            Uint8 g;
            Uint8 b;
            Uint8 unused;
    } SDL_Color;

    typedef struct {
            int       ncolors;
            SDL_Color *colors;
    } SDL_Palette;

    typedef struct SDL_PixelFormat {
            SDL_Palette *palette;
            Uint8  BitsPerPixel;
            Uint8  BytesPerPixel;
            Uint8  Rloss;
            Uint8  Gloss;
            Uint8  Bloss;
            Uint8  Aloss;
            Uint8  Rshift;
            Uint8  Gshift;
            Uint8  Bshift;
            Uint8  Ashift;
            Uint32 Rmask;
            Uint32 Gmask;
            Uint32 Bmask;
            Uint32 Amask;

            /* RGB color key information */
            Uint32 colorkey;
            /* Alpha value information (per-surface alpha) */
            Uint8  alpha;
    } SDL_PixelFormat;

    /* This structure should be treated as read-only, except for 'pixels',
       which, if not NULL, contains the raw pixel data for the surface.
    */
    typedef struct SDL_Surface {
            Uint32 flags;                           /* Read-only */
            SDL_PixelFormat *format;                /* Read-only */
            int w, h;                               /* Read-only */
            Uint16 pitch;                           /* Read-only */
            void *pixels;                           /* Read-write */
            int offset;                             /* Private */

            /* Hardware-specific surface info */
            struct private_hwdata *hwdata;

            /* clipping information */
            int clip_minx;                          /* Read-only */
            int clip_maxx;                          /* Read-only */
            int clip_miny;                          /* Read-only */
            int clip_maxy;                          /* Read-only */

            /* info for fast blit mapping to other surfaces */
            struct SDL_BlitMap *map;                /* Private */

            /* List of surfaces mapped */
            struct map_list *mapped;                /* Private */

            /* Reference count -- used when freeing surface */
            int refcount;                           /* Read-mostly */
    } SDL_Surface;

    /* These are the currently supported flags for the SDL_surface */
    /* Available for SDL_CreateRGBSurface() or SDL_SetVideoMode() */
    #define SDL_SWSURFACE   0x00000000      /* Surface is in system memory */
    #define SDL_HWSURFACE   0x00000001      /* Surface is in video memory */
    /* Available for SDL_SetVideoMode() */
    #define SDL_ANYFORMAT   0x10000000      /* Allow any video pixel format */
    #define SDL_HWPALETTE   0x00000002      /* Surface has exclusive palette */
    #define SDL_DOUBLEBUF   0x40000000      /* Set up double-buffered video mode */
    #define SDL_FULLSCREEN  0x80000000      /* Surface is a full screen display */

    /* Useful for determining the video hardware capabilities */
     typedef struct {
            Uint32 hw_available :1; /* Flag: Can you create hardware surfaces? */
            Uint32 wm_available :1; /* Flag: Can you talk to a window manager? */
            Uint32 UnusedBits1  :6;
            Uint32 UnusedBits2  :1;
            Uint32 blit_hw      :1; /* Flag: Accelerated blits HW --> HW */
            Uint32 blit_hw_CC   :1; /* Flag: Accelerated blits with Colorkey */
            Uint32 blit_hw_A    :1; /* Flag: Accelerated blits with Alpha */
            Uint32 blit_sw      :1; /* Flag: Accelerated blits SW --> HW */
            Uint32 blit_sw_CC   :1; /* Flag: Accelerated blits with Colorkey */
            Uint32 blit_sw_A    :1; /* Flag: Accelerated blits with Alpha */
            Uint32 blit_fill    :1; /* Flag: Accelerated color fill */
            Uint32 UnusedBits3  :16;
            Uint32 video_mem;       /* The total amount of video memory (in K) */
            SDL_PixelFormat *vfmt;  /* Value: The format of the video surface */
    } SDL_VideoInfo;

    typedef struct WMcursor WMcursor;       /* Implementation dependent */
    typedef struct {
            SDL_Rect area;                  /* The area of the mouse cursor */
            Sint16 hot_x, hot_y;            /* The "tip" of the cursor */
            Uint8 *data;                    /* B/W cursor data */
            Uint8 *mask;                    /* B/W cursor mask */
            Uint8 *save[2];                 /* Place to save cursor area */
            WMcursor *wm_cursor;            /* Window-manager cursor */
    } SDL_Cursor;