SDL_SetVideoMode

The flags parameter is the same as the flags field of the SDL_Surface structure. OR'd combinations of the following values are valid.

SDL_SWSURFACE	Create the video surface in system memory.
SDL_HWSURFACE	Create the video surface in video memory.
SDL_ASYNCBLIT	Enables the use of asynchronous updates of the display surface. This will usually slow down blitting on single CPU machines, but may provide a speed increase on SMP systems.
SDL_ANYFORMAT	Normally, if a video surface of the requested bits-per-pixel (bpp) is not available, SDL will emulate one with a shadow surface. Passing SDL_ANYFORMAT prevents this and causes SDL to use the video surface, regardless of its pixel depth.
SDL_HWPALETTE	Give SDL exclusive palette access. Without this flag you may not always get the the colors you request with SDL_SetColors or SDL_SetPalette.
SDL_DOUBLEBUF	Enable hardware double buffering; only valid with SDL_HWSURFACE. Calling SDL_Flip will flip the buffers and update the screen. All drawing will take place on the surface that is not displayed at the moment. If double buffering could not be enabled then SDL_Flip will just perform a SDL_UpdateRect on the entire screen.
SDL_FULLSCREEN	SDL will attempt to use a fullscreen mode. If a hardware resolution change is not possible (for whatever reason), the next higher resolution will be used and the display window centered on a black background.
SDL_OPENGL	Create an OpenGL rendering context. You should have previously set OpenGL video attributes with SDL_GL_SetAttribute.
SDL_OPENGLBLIT	Create an OpenGL rendering context, like above, but allow normal blitting operations. The screen (2D) surface may have an alpha channel, and SDL_UpdateRects must be used for updating changes to the screen surface. NOTE: This option is kept for compatibility only, and will be removed in next versions. Is not recommended for new code.
SDL_RESIZABLE	Create a resizable window. When the window is resized by the user a SDL_VIDEORESIZE event is generated and SDL_SetVideoMode can be called again with the new size.
SDL_NOFRAME	If possible, SDL_NOFRAME causes SDL to create a window with no title bar or frame decoration. Fullscreen modes automatically have this flag set.

Note: Whatever flags SDL_SetVideoMode could satisfy are set in the flags member of the returned surface.

Note: A bitsperpixel of 24 uses the packed representation of 3 bytes/pixel. For the more common 4 bytes/pixel mode, use a bitsperpixel of 32. Somewhat oddly, both 15 and 16 will request a 2 bytes/pixel mode, but different pixel formats.

Note: Use SDL_SWSURFACE if you plan on doing per-pixel manipulations, or blit surfaces with alpha channels, and require a high framerate. When you use hardware surfaces (SDL_HWSURFACE), SDL copies the surfaces from video memory to system memory when you lock them, and back when you unlock them. This can cause a major performance hit. (Be aware that you may request a hardware surface, but receive a software surface. Many platforms can only provide a hardware surface when using SDL_FULLSCREEN.) SDL_HWSURFACE is best used when the surfaces you'll be blitting can also be stored in video memory.

Note: If you want to control the position on the screen when creating a windowed surface, you may do so by setting the environment variables "SDL_VIDEO_CENTERED = center" or "SDL_VIDEO_WINDOW_POS = x,y".

A pointer to the framebuffer surface, or NULL if it fails. The surface returned is freed by SDL_Quit and should not be freed by the caller. Note: This rule includes consecutive calls to SDL_SetVideoMode (i.e. resize or resolution change) - the pre-existing surface will be released automatically.

In Windows, setting the video mode "resets" OpenGL context. You must execute again the OpenGL initialization code (set the clear color or the shade model, or reload textures, for example) after calling SDL_SetVideoMode.