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Diagram Developer Documentation

Snap To Grid Enhancement

By Default Snap To Grid allows to snap on the grid using the top left corner of the figure (in case of Rctangle).

To improve this behavior, you should subclass the GMF Class org.eclipse.gmf.runtime.diagram.ui.tools.DragEditPartsTrackerEx or one of its superclass. Then you must ovveride the method org.eclipse.gef.EditPart.getDragTracker(Request) in the edit part concerned by your specific SnapToGrid.

In Papyrus we change this class to be able to snap on the 4 corners, the four middle and the center of a rectangle. Have a look to these classes to get examples.

  • org.eclipse.papyrus.infra.gmfdiag.common.editpart.NodeEditPart.java
  • org.eclipse.papyrus.infra.gmfdiag.common.snap.PapyrusDragBorderNodeEditPartTrackerEx.java
  • org.eclipse.papyrus.infra.gmfdiag.common.snap.PapyrusDragEditPartsTrackerEx.java
  • org.eclipse.papyrus.uml.diagram.common.editparts.BorderNodeEditPart.java

To improve the connection of the endPoint of the link, Papyrus provides its own EditPolicy (in ConnectionEditPart) : org.eclipse.papyrus.infra.gmfdiag.common.editpolicies.PapyrusConnectionEndEditPolicy.PapyrusConnectionEndEditPolicy, with the role EditPolicy.CONNECTION_ENDPOINTS_ROLE (see this class for details)

User tricks

ALT allows to ignore Snap To Grid when your are moving an element