The Cocoa Text System, MLTE, and ATSUI

The Cocoa text system is an object-oriented framework designed to provide all the text services needed by Cocoa applications. Carbon applications, on the other hand, use the APIs of other text-oriented components such as the Multilingual Text Engine (MLTE), which provides editing features, and Apple Type Services for Unicode Imaging (ATSUI), which provides typography and layout services.

From the developer’s perspective, the Cocoa text system and ATSUI are two parallel APIs that both handle line layout and character-to-glyph transformations, calling into the Quartz Core Graphics library for text rendering. A developer using the Cocoa text system for a given project is not likely to use ATSUI and vice versa.

The relationships among the Cocoa text system, MLTE, ATSUI, and other text-related components of the Mac OS X development environment are shown in Figure 1.

For more information about the Core Graphics rendering engine, see the Quartz 2D documentation.

---