GLX_SGIS_shared_multisample
https://www.khronos.org/registry/egl/specs/eglspec.1.5.pdf
GLX_SGIS_shared_multisample

	GLX_MULTISAMPLE_SUB_RECT_WIDTH_SGIS 0x8026
	GLX_MULTISAMPLE_SUB_RECT_HEIGHT_SGIS 0x8027