Editing Decorator pattern (section)

=== Applying decorators === 
Adding or removing decorators on command (like a button press) is a common UI pattern, often implemented along with the [[Command pattern|Command design pattern]]. For example, a text editing application might have a button to highlight text. On button press, the individual text glyphs currently selected will all be wrapped in decorators that modify their draw() function, causing them to be drawn in a highlighted manner (a real implementation would probably also use a demarcation system to maximize efficiency). 

Applying or removing decorators based on changes in state is another common use case. Depending on the scope of the state, decorators can be applied or removed in bulk. Similarly, the [[State pattern|State design pattern]] can be implemented using decorators instead of subclassed objects encapsulating the changing functionality. The use of decorators in this manner makes the State object's internal state and functionality more compositional and capable of handling arbitrary complexity.