OpenGL configuration attributes.
Defined in SDL_video.h
typedef enum SDL_GLattr
{
SDL_GL_RED_SIZE, /**< the minimum number of bits for the red channel of the color buffer; defaults to 3. */
SDL_GL_GREEN_SIZE, /**< the minimum number of bits for the green channel of the color buffer; defaults to 3. */
SDL_GL_BLUE_SIZE, /**< the minimum number of bits for the blue channel of the color buffer; defaults to 2. */
SDL_GL_ALPHA_SIZE, /**< the minimum number of bits for the alpha channel of the color buffer; defaults to 0. */
SDL_GL_BUFFER_SIZE, /**< the minimum number of bits for frame buffer size; defaults to 0. */
SDL_GL_DOUBLEBUFFER, /**< whether the output is single or double buffered; defaults to double buffering on. */
SDL_GL_DEPTH_SIZE, /**< the minimum number of bits in the depth buffer; defaults to 16. */
SDL_GL_STENCIL_SIZE, /**< the minimum number of bits in the stencil buffer; defaults to 0. */
SDL_GL_ACCUM_RED_SIZE, /**< the minimum number of bits for the red channel of the accumulation buffer; defaults to 0. */
SDL_GL_ACCUM_GREEN_SIZE, /**< the minimum number of bits for the green channel of the accumulation buffer; defaults to 0. */
SDL_GL_ACCUM_BLUE_SIZE, /**< the minimum number of bits for the blue channel of the accumulation buffer; defaults to 0. */
SDL_GL_ACCUM_ALPHA_SIZE, /**< the minimum number of bits for the alpha channel of the accumulation buffer; defaults to 0. */
SDL_GL_STEREO, /**< whether the output is stereo 3D; defaults to off. */
SDL_GL_MULTISAMPLEBUFFERS, /**< the number of buffers used for multisample anti-aliasing; defaults to 0. */
SDL_GL_MULTISAMPLESAMPLES, /**< the number of samples used around the current pixel used for multisample anti-aliasing. */
SDL_GL_ACCELERATED_VISUAL, /**< set to 1 to require hardware acceleration, set to 0 to force software rendering; defaults to allow either. */
SDL_GL_RETAINED_BACKING, /**< not used (deprecated). */
SDL_GL_CONTEXT_MAJOR_VERSION, /**< OpenGL context major version. */
SDL_GL_CONTEXT_MINOR_VERSION, /**< OpenGL context minor version. */
SDL_GL_CONTEXT_EGL, /**< deprecated: set SDL_GL_CONTEXT_PROFILE_MASK to SDL_GL_CONTEXT_PROFILE_ES to enable instead. */
SDL_GL_CONTEXT_FLAGS, /**< some combination of 0 or more of elements of the SDL_GLcontextFlag enumeration; defaults to 0. */
SDL_GL_CONTEXT_PROFILE_MASK, /**< type of GL context (Core, Compatibility, ES). See SDL_GLprofile; default value depends on platform. */
SDL_GL_SHARE_WITH_CURRENT_CONTEXT, /**< OpenGL context sharing; defaults to 0. */
SDL_GL_FRAMEBUFFER_SRGB_CAPABLE, /**< requests sRGB capable visual; defaults to 0. (>= SDL 2.0.1) */
SDL_GL_CONTEXT_RELEASE_BEHAVIOR, /**< sets context the release behavior; defaults to 1. (>= SDL 2.0.4) */
SDL_GL_CONTEXT_RESET_NOTIFICATION,
SDL_GL_CONTEXT_NO_ERROR,
SDL_GL_FLOATBUFFERS
} SDL_GLattr;While you can set most OpenGL attributes normally, the attributes listed above must be known before SDL creates the window that will be used with the OpenGL context. These attributes are set and read with SDL_GL_SetAttribute and SDL_GL_GetAttribute.
In some cases, these attributes are minimum requests; the GL does not promise to give you exactly what you asked for. It's possible to ask for a 16-bit depth buffer and get a 24-bit one instead, for example, or to ask for no stencil buffer and still have one available. Context creation should fail if the GL can't provide your requested attributes at a minimum, but you should check to see exactly what you got.
Multisample anti-aliasing is a type of full screen anti-aliasing. Multipsampling defaults to off but can be turned on by setting SDL_GL_MULTISAMPLEBUFFERS to 1 and SDL_GL_MULTISAMPLESAMPLES to a value greater than 0. Typical values are 2 and 4.
SDL_GL_CONTEXT_PROFILE_MASK determines the type of context created, while both SDL_GL_CONTEXT_MAJOR_VERSION and SDL_GL_CONTEXT_MINOR_VERSION determine which version. All three attributes must be set prior to creating the first window, and in general you can't change the value of SDL_GL_CONTEXT_PROFILE_MASK without first destroying all windows created with the previous setting.
SDL_GL_CONTEXT_RELEASE_BEHAVIOR can be set to SDL_GL_CONTEXT_RELEASE_BEHAVIOR_NONE or SDL_GL_CONTEXT_RELEASE_BEHAVIOR_FLUSH.