This sample demonstrates one manner in which a diagram can show more detail where the mouse is. The diagram expands any Groups that intersect a rectangular area centered about the mouse.

The functionality is implemented by a custom default tool, LocallyExpandingToolManager. It replaces the standard Diagram.DefaultTool. This tool overrides the DoMouseMove method to look for Groups that overlap with the rectangular area near the mouse. Such Groups are expanded; all other Groups are collapsed.