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Graphics Contexts

Graphics contexts are a fundamental part of the drawing infrastructure in Cocoa applications. As the name suggests, a graphics context provides the context for subsequent drawing operations. It identifies the current drawing destination (screen, printer, file, and so on), the coordinate system and boundaries for the underlying canvas, and any graphics attributes associated with the destination.

For most of the drawing you do in Cocoa, you never need to create a graphics context yourself. The normal drawing cycle in Cocoa automatically creates and configures a graphics context for you to use. For some advanced drawing, however, you may need to create your own graphics context prior to drawing.

In a Cocoa application, graphics contexts for nearly all types of canvas are represented by the NSGraphicsContext class. You use graphics context objects to manipulate graphics attributes and to get information about the current drawing environment.

This chapter provides an overview of Cocoa graphics contexts and how you use them in your application. It includes information on how to create custom graphics contexts and when it might be appropriate to do so.

Contents:

Graphics Context Basics
Modifying the Current Graphics State
Creating Graphics Contexts
Threading and Graphics Contexts

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