Viewport Pane (Drawing on the display)

The ViewportPane is the class that draws the map on the screen. It is not responsible for rendering, it only draws the results of the rendered map when it is provided with the rendered image. However it is used to provide feedback for the user. The tools draw on the ViewportPane, such as the zoom box, to provide the user some meaningful feedback. Another example is the vertex manipulation tool. It draws the feature on the ViewportPane along with the vertex handles.
The ViewportPane allows listeners to register and receive events from the ViewportPane. The event most listeners are interested in are the various mouse events, however there are, or will be, key events as well that the ViewportPane will issue.
The ViewportGraphics object is the graphics object used to draw on the viewport pane. The reason a UDIG defines its own graphics object is because currently there are two VuiewportPane implementations, one is a java canvas and one is a swt canvas. The ViewportGraphics allows the tools to work with both implementations and future implementations, if they evolve.

ViewportPane Classes and Interfaces