OpenGL extension SGIX.vertex_preclip
This module customises the behaviour of the OpenGL.raw.GL.SGIX.vertex_preclip to provide a more Python-friendly API
Overview (from the spec)
Certain graphics subsystems are capable of performing fast 2D viewport or, in some cases, 3D volume "scissoring" operations within some coordinate range much faster that the host CPU could re-tesselate clipped primitives.
This extension introduces the notion of an extended rasterizable view volume that is an expansion of the clip-space view volume. This volume is the space within which a particular graphics system is much more efficient at rejecting fragments that lie outside the view volume than it is at performing strict view volume clipping.
Clip-checking can be turned on or off through the glEnable/glDisable mechanism, and can be further controlled by using glHint.
The official definition of this extension is available here:
Return boolean indicating whether this extension is available