An Overview is a Diagram that displays all of a different diagram, with a rectangular box showing the viewport displayed by that other diagram.
All you need to do is set Overview.observed. For example:
var myDiagram = new go.Diagram("myDiagramDIV"); . . . other initialization . . . // create and initialize the Overview: new go.Overview("myOverviewDIV").observed = myDiagram;
The Overview draws what the observed Diagram is displaying, so setting or modifying any diagram templates or template Maps has no effect. At the current time methods such as Diagram.makeImage, Diagram.makeImageData and Diagram.makeSvg do not work on Overviews.
A reference to a div or its ID as a string.
Gets or sets whether this overview draws the temporary layers of the observed Diagram.
Gets or sets the Diagram for which this Overview is displaying a model and showing its viewport into that model.
The value must be null or another Diagram, but may not be an Overview.