it was introduced in Mac OS X Tiger) is GPU acceleration for the Quartz 2D API. With QuartzGL enabled, all Quartz drawing commands are translated to OpenGL commands and executed on the GPU. This differs from Quartz Extreme, which still executes Quartz drawing commands on the CPU but performs final composition using the GPU.

In OS X Mountain Lion, QuartzGL was still not enabled by default. However, it was possible to enable it using the Quartz Debug