Mac OS X Graphics Stack 本文介绍了 Mac OS X 的图形栈，分析了它的原理和体系结构。

简介

Mac OS X 总体结构

图形栈体系结构

Quartz Compositor：窗口管理器¹²

Quartz Compositor is the windowing system in Mac OS X. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the CoreGraphics framework and other renderers in the Quartz technologies family.

Quartz Compositor is the sole facilitator for the placement ofrendered bitmaps into the memory of the graphics card.

整体渲染流程遵从如下步骤：

1. The bitmap output from Quartz 2D, OpenGL, Core Image, QuickTime,or other process is written to a specific memory location, orbacking store.
2. The Compositor then reads the data from the backing stores andassembles each into one image for the display;
3. The Compositor writes that image to the frame buffer memory of thegraphics 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 : GPU Acceleration for Quartz Compositor¹²

Mac OS X v10.2 introduced Quartz Extreme: graphics processor (GPU)acceleration for the Quartz Compositor.

With Quartz Extreme, no central processor (CPU) cycles are utilized for scene composition. Quartz Compositor runs using the graphics processor (GPU) by encapsulating each rendered backing store in an OpenGL texture map or surface. The GPU then composes the surfaces and maps to provide the final image, which is delivered to its frame buffer.

Quartz Extreme only uses OpenGL commands, and requires a graphics cardconnected to an AGP 2X or faster bus (including AGP 4X, 8X, and PCIExpress), supporting textures and maps of arbitrary size, since manyof the renderers have no size limitation (Quartz 2D for example).It isautomatically enabled on Mac systems with one of the following typesof graphics cards:

• AMD (ATI) Radeon, AGP-based, 16MB VRAM minimum, or better
• NVIDIA GeForce2 MX, 16MB VRAM minimum, or better

SeeAlso

1. Apple OpenGL and Quartz Extreme
2. Quartz Compositor
3. Mac OS X OpenGL Capabilities Tables