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LayersEach canvas pane contains a "stack" of layers laid one on top of the next. The Diva canvas provides a useful set of layers. A layer will generally implement the EventAcceptor interface, the VisibleComponent interface, or both. If it implements EventAcceptor, then the canvas pane will pass events from the JCanvas to it; if it implements VisibleComponent, then the canvas pane will ask it to paint itself when appropriate.
FigureLayer contains a collection of figures, and implements both EventAcceptor and FigureContainer (and therefore VisibleComponent). Each of the contained figures has the layer as its parent. Because there may be a large number of figures, the storage of figures is done by an implementation of the ZList interface. Currently there is only one implementation of ZList, BasicZList, but in future an optimized version will be written. EventLayer implements EventAccepter, and responds to events by passing them to any registered LayerListeners or LayerMotionListeners. This layer is shown in full in the section on events. OverlayLayer implements VisibleComponent, and is a simple layer that draws shapes on the screen. All the shapes are drawn with the same stroke and paint. This layer is intended for use in interactive applications where "rubber-banding" is required. GridLayer implements VisibleComponent, and draws a grid according to various parameters.
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