Pixel Ownership Test
The pixel ownership test determines whether the current OpenGL context owns the pixel in the framebuffer corresponding to a particular fragment. If so, the fragment proceeds to the next test. If not, the window system determines whether the fragment is discarded or whether any further fragment operations will be performed with that fragment. With this test, the window system controls behavior when, for example, an OpenGL window is obscured.
Build date: 3/6/2012