contextMenu property
      
      dynamic
      get
      contextMenu
      
    
    
This Adornment or HTMLInfo is shown when the use context clicks in the background. The default value is null, which means no context menu is shown. On touch devices, a special default context menu will appear even there is no context menu defined. See ContextMenuTool#defaultTouchContextMenu for details.
 diagram.contextMenu =
   $("ContextMenu",
     $("ContextMenuButton",
       $(go.TextBlock, "Undo"),
       { click: (e, obj) => e.diagram.commandHandler.undo() },
       new go.Binding("visible", "", o => o.diagram.commandHandler.canUndo()).ofObject()),
     $("ContextMenuButton",
       $(go.TextBlock, "Redo"),
       { click: (e, obj) => e.diagram.commandHandler.redo() },
       new go.Binding("visible", "", o => o.diagram.commandHandler.canRedo()).ofObject())
   );
Implementation
_i2.dynamic get contextMenu => _i4.getProperty(
      this,
      'contextMenu',
    );
      
      set
      contextMenu
      (dynamic value) 
      
    
    
    
Implementation
set contextMenu(_i2.dynamic value) {
  _i4.setProperty(
    this,
    'contextMenu',
    value,
  );
}