GMF > GMF Code Samples

If you have added a label to your GMF editor, but you want it to open up a sub-diagram when double-clicking (for example, when using GMF Diagram Partitioning), it is not too straightforward.

First, you need to add an OpenDiagramEditPolicy to the Label itself in your .gmfgen (similarly to how you need to add OpenDiagramEditPolicies to your nodes). This information is lost between .gmfgen generations.

Then, based on this newsgroup discussion about Label OpenEditPolicies, add this to the implementation of the OpenDiagramEditPolicy itself (probably through Dynamic Templates):

public EditPart getTargetEditPart(Request request) {
  if (understandsRequest(request) && (getHost() instanceof ShapeNodeEditPart || getHost() instanceof ConnectionNodeEditPart)) {
    return getHost();
  if (understandsRequest(request)) {
    return getHost().getParent();
  return super.getTargetEditPart(request);

Essentially, this means that if the current host is not a Node with an OpenDiagramEditPolicy (and the Node will contain the information on how to open a new diagram), it will select the parent element.

Make sure you don’t add an OpenDiagramEditPolicy to a Label which should not open a diagram, for example an editable field which double-click should normally edit the text field.

This was implemented in IAML in revision 651.