Man page - sdl_gl_getprocaddress(3)

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Manual

SDL_GL_GetProcAddress

NAME
HEADER FILE
SYNOPSIS
DESCRIPTION
FUNCTION PARAMETERS
RETURN VALUE
THREAD SAFETY
AVAILABILITY
SEE ALSO

NAME

SDL_GL_GetProcAddress - Get an OpenGL function by name.

HEADER FILE

Defined in SDL3/SDL_video.h

SYNOPSIS

#include "SDL3/SDL.h"

SDL_FunctionPointer SDL_GL_GetProcAddress(const char *proc);

DESCRIPTION

If the GL library is loaded at runtime with

SDL_GL_LoadLibrary (), then all GL functions must be retrieved this way. Usually this is used to retrieve function pointers to OpenGL extensions.

There are some quirks to looking up OpenGL functions that require some extra care from the application. If you code carefully, you can handle these quirks without any platform-specific code, though:

• On Windows, function pointers are specific to the current GL context;
this means you need to have created a GL context and made it current
before calling SDL_GL_GetProcAddress (). If you
recreate your context or create a second context, you should assume that
any existing function pointers aren’t valid to use with it. This is
(currently) a Windows-specific limitation, and in practice lots of
drivers don’t suffer this limitation, but it is still the way the wgl API
is documented to work and you should expect crashes if you don’t respect
it. Store a copy of the function pointers that comes and goes with
context lifespan.

• On X11, function pointers returned by this function are valid for any
context, and can even be looked up before a context is created at all.
This means that, for at least some common OpenGL implementations, if you
look up a function that doesn’t exist, you’ll get a non-NULL result that
is _NOT_ safe to call. You must always make sure the function is actually
available for a given GL context before calling it, by checking for the
existence of the appropriate extension with

SDL_GL_ExtensionSupported (), or verifying
that the version of OpenGL you’re using offers the function as core
functionality.

• Some OpenGL drivers, on all platforms, will return NULL if a function
isn’t supported, but you can’t count on this behavior. Check for
extensions you use, and if you get a NULL anyway, act as if that
extension wasn’t available. This is probably a bug in the driver, but you
can code defensively for this scenario anyhow.

• Just because you’re on Linux/Unix, don’t assume you’ll be using X11.
Next-gen display servers are waiting to replace it, and may or may not
make the same promises about function pointers.

• OpenGL function pointers must be declared APIENTRY as in the example
code. This will ensure the proper calling convention is followed on
platforms where this matters (Win32) thereby avoiding stack corruption.

FUNCTION PARAMETERS

proc

the name of an OpenGL function.

RETURN VALUE

( SDL_FunctionPointer ) Returns a pointer to the named OpenGL function. The returned pointer should be cast to the appropriate function signature.

THREAD SAFETY

This function should only be called on the main thread.

AVAILABILITY

This function is available since SDL 3.2.0.

SEE ALSO

• (3), SDL_GL_ExtensionSupported (3), • (3), SDL_GL_LoadLibrary (3), • (3), SDL_GL_UnloadLibrary (3)