Quartz Compositor is the display server (and at the same time the compositing window manager) in macOS. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other renderers in the Quartz technologies family. Overview The bitmap output from Quartz 2D, OpenGL, Core Image, QuickTime, or other process is written to a specific memory location, or backing store. The Compositor then reads the data from the backing stores and assembles each into one image for the display, writing that image to the frame buffer memory of the graphics card. Quartz Compositor only accepts raster data, and is the only process that can directly access the graphics frame buffer. In managing individual windows, Quartz Compositor accepts a bitmap image of the window's contents from its renderer, along with its position. The choice of the renderer is up to the individual application, although most use Quartz 2D. Quartz Compositor then acts as a "visual mixing board," by adding the given window to the whole scene for the display. In its role as window manager, Quartz Compositor also has an event queue which receives events, such as key strokes and mouse clicks. The Quartz Compositor takes the events from the queue, determines which process owns the window where the event occurred, and passes the event on to the process. Quartz Extreme Mac OS X v10.2 introduced Quartz Extreme: graphics processor (GPU) acceleration for the Quartz Compositor. With Quartz Extreme, far fewer central processing unit (CPU) cycles are needed for scene composition. Instead, the Quartz Compositor encapsulates each rendered backing store in an OpenGL texture map or surface. It then directs the GPU to compose the surfaces and maps to provide the final image, which is delivered to the frame buffer. Quartz Extreme only uses OpenGL commands, and requires a graphics card connected to an AGP 2X or faster bus (including AGP 4X, 8X, and PCI Express), supporting textures and maps of arbitrary size, since many of the renderers have no size limitation (Quartz 2D for example). In Mac OS X Tiger, it is automatically enabled on Mac systems with one of the following types of graphics cards: AMD (ATI) Radeon, AGP-based, 16 MB VRAM minimum, or better NVIDIA GeForce2 MX, 16 MB VRAM minimum, or better As of OS X El Capitan, Quartz Extreme is enabled on all supported Macs. QuartzGL QuartzGL (called Quartz