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This is how a system-triggered painting operation takes place: painting.

This is handled by to do incremental painting must ensure that lightweight descendents are recursively repainted if necessary.

Fortunately, few heavyweight container components need incremental painting, so this issue doesn't affect most programs.

For the most part, the Swing painting mechanism resembles and relies on the AWT's.

But it also introduces some differences in the mechanism, as well as new APIs that make it easier for applications to customize how painting works.

This means that a program should place the component's rendering code inside a particular overridden method, and the toolkit will invoke this method when it's time to paint.

The method to be overridden is in Developers who are new to AWT might want to take a peek at the Paint Demo example, which provides a runnable program example of how to use the paint callback in an AWT program.

The Lightweight Demo sample program demonstrates the transparency feature of lightweight components.

While the AWT attempts to make the process of rendering components as efficient as possible, a component's If your component is simple -- for example, if it's a pushbutton -- then it's not worth the effort to factor the rendering in order to only paint the portion that intersects the clip rectangle; it's preferable to just paint the entire component and let the graphics clip appropriately.

This scheme took care of details such as damage detection, clip calculation, and z-ordering.

With the introduction of components in JDK 1.1 (a "lightweight" component is one that reuses the native window of its closest heavyweight ancestor), the AWT needed to implement the paint processing for lightweight components in the shared Java code.

While the article covers the general paint mechanism ( components existed ("heavyweight" means that the component has it's own opaque native window).