OpenGL Interface Implementation

See OpenGL Interface for details on the publically-visible modules.

See ctypes Wrapper Generation for details on some of these modules are generated.

ctypes linkage

Most functions link to libGL.so (Linux), opengl32.dll (Windows) or OpenGL.framework (OS X). pyglet.gl.lib provides some helper types then imports linker functions for the appropriate platform: one of pyglet.gl.lib_agl, pyglet.gl.lib_glx, pyglet.gl.lib_wgl.

On any platform, the following steps are taken to link each function during import:

  1. Look in the appropriate library (e.g. libGL.so, opengl32.dll, etc.) using cdll or windll.

  2. If not found, call wglGetProcAddress or glxGetProcAddress to try to resolve the function’s address dynamically. On OS X, skip this step.

  3. On Windows, this will fail if the context hasn’t been created yet. Create and return a proxy object WGLFunctionProxy which will try the same resolution again when the object is __call__’d.

    The proxy object caches its result so that subsequent calls have only a single extra function-call overhead.

  4. If the function is still not found (either during import or proxy call), the function is replaced with MissingFunction (defined in pyglet.gl.lib), which raises an exception. The exception message details the name of the function, and optionally the name of the extension or OpenGL version it requires.

    We currently include all functions and enums from OpenGL 4.6 in separate modules. gl.g exposes the core api and gl_compat.py exposes the compatibility profile (no deprecation).

    What extensions are included can be found in gengl.py.

To access the linking function, import pyglet.gl.lib and use one of link_AGL, link_GLX, link_WGL or link_GL. This is what the generated modules do.

Missing extensions

Missing extensions can be added to the extensions list in gengl.py.