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

	GLXDrawable glXGetCurrentReadDrawableSGI (void)
	Bool glXMakeCurrentReadSGI (Display* dpy, GLXDrawable draw, GLXDrawable read, GLXContext ctx)