Decorating GEF figure using EditPolicy

In GMF there is a nifty DragDropEditPolicy that allows you to decorate EditPart's figure by changing background color thus indicating to the user that he is hovering over particular figure. I wanted to use this in my GEF editor, but unfortunately this policy does not exist in GEF.

To make use of this policy I made my plugin depend on import org.eclipse.gmf.runtime.diagram.ui.editpolicies and extended DragDropEditPolicy with my own

public class DesignerDragDropEditPolicty extends DragDropEditPolicy {
 private Label connectionLabel;
 private PolylineConnection relationFigure;
 private DesignerEditor editor;
 private Image image;

 public DesignerDragDropEditPolicty() {
  connectionLabel = new Label();
  connectionLabel.setOpaque(false);
  image = DesignerUIPlugin.getDefault().getImageRegistry().get(ImageConstants.DROP_ICON);
  connectionLabel.setIcon(image);
  
 }
 
 @Override
 // remove icon when edit policy is done
 public void eraseTargetFeedback(Request request) {
  if(relationFigure != null){
   if(relationFigure.getChildren().contains(connectionLabel)){
    relationFigure.remove(connectionLabel);
   }
  }
 }
 
 // add icon on filtered edit part. Remove it when another edit part is hovered over.
 public void showTargetFeedback(Request request) {
  if(request instanceof CreateRequest){
   editor = (DesignerEditor) DesignerUtil.getActiveDesignerTab();
   Point location = ((CreateRequest)request).getLocation();
   EditPart part = editor.getViewer().findObjectAt(location);

   if(part instanceof RelationEditPart){
    relationFigure = ((RelationEditPart)part).getConnection();
    relationFigure.add(connectionLabel, new MidpointLocator(relationFigure, 0));
    relationFigure.repaint();
   }
   else{
    if(relationFigure != null){
     if(relationFigure.getChildren().contains(connectionLabel)){
      relationFigure.remove(connectionLabel);
     }
    }
   }
  }
 }
}

Instead of changing background of the figure as DragDropEditPolicy does I did something different. Whenever user passes inside an EditPart, in my case it's a relation, I put an icon signifying that in this case an object can be dropped onto existing connection an be created in the middle of the relation. I could have put a label saying "Drop here", but I think icons work better than words and after you get used to seeing a particular label with words it gets annoying.

Notice that in showTargetFeedback I filter out EditPart that I am interested in, so here code can be added to add different behavior for other parts.

Implementing “select on focus” behavior for an Eclipse Text control

http://stackoverflow.com/questions/10038570/implementing-select-on-focus-behavior-for-an-eclipse-text-control/10049615#10049615

Examine Eclipse via OSGi console

• Launch eclipse with just the osgi console (eclipse -console -noexit) 
• Run 'ss' to figure out what hasn't been resolved 
• 'diag [bundle #]' will give you some details on the problem

Adding 'Collapse All' button to a view

Start by adding extension point to plugin.xml of plugin where View lives:

Then add service code to the View's createPartControl method:

 
 IWorkbenchPartSite site = getSite();
        if (site != null) {
         IHandlerService handlerService = (IHandlerService) site.getService(
           IHandlerService.class);
         if (handlerService != null) {
          CollapseAllHandler fCollapseHandler = new CollapseAllHandler(viewer);
          handlerService.activateHandler(CollapseAllHandler.COMMAND_ID ,
            fCollapseHandler);
         }
        }

Find out plugin and id of menu item

ALT+SHIFT+F2 and then click on the item

Removing horizontal line above compartment

In addFixedChild method of EditPart that contains compartment extract figure that is added to the pane (primary figure) and set its border to null.

Eclipse builders

When creating builder as in every other extension point make sure that IDs of builder and IDs in extension point match up. Otherwise your builders will not work and you will not know what went wrong. One place to check is project properties (right-click project -> properties -> Builders. If your build is listed as "Missing Builder" then chances are IDs are screwed up.