org.eclipse.emf.edit.ui.dnd
Class EditingDomainViewerDropAdapter

java.lang.Object
  org.eclipse.swt.dnd.DropTargetAdapter
      org.eclipse.emf.edit.ui.dnd.EditingDomainViewerDropAdapter

All Implemented Interfaces:

java.util.EventListener, DropTargetListener, org.eclipse.swt.internal.SWTEventListener

public class EditingDomainViewerDropAdapter
extends DropTargetAdapter

This implementation of a drop target listener is designed to turn a drag and drop operation into a Command based on the model objects of an EditingDomain and created by DragAndDropCommand.create(org.eclipse.emf.edit.domain.EditingDomain, java.lang.Object, float, int, int, java.util.Collection). It is designed to do early data transfer so the the enablement and feedback of the drag and drop interaction can intimately depend on the state of the model objects involved. On some platforms, however, early data transfer is not available, so this feedback cannot be provided.

The base implementation of this class should be sufficient for most applications. Any change in behaviour is typically accomplished by overriding ItemProviderAdapter.createDragAndDropCommand to return a derived implementation of DragAndDropCommand. This is how one these adapters is typically hooked up:

   viewer.addDropSupport
     (DND.DROP_COPY | DND.DROP_MOVE | DND.DROP_LINK,
      new Transfer [] { LocalTransfer.getInstance() },
      EditingDomainViewerDropAdapter(viewer));
 

This implementation prefers to use a LocalTransfer, which short-circuits the transfer process for simple transfers within the workbench, the method getDragSource(org.eclipse.swt.dnd.DropTargetEvent) can be overridden to change the behaviour. The implementation also only handles an IStructuredSelection, but the method extractDragSource(java.lang.Object) can be overridden to change the behaviour.

SWT's auto-scroll and auto-expand (hover) are enabled by default. The method getAutoFeedback() can be overridden to change this behaviour.

Nested Class Summary

protected static class

EditingDomainViewerDropAdapter.DragAndDropCommandInformation This holds all of the information used to create a DragAndDropCommand, but does not need to be disposed.

Field Summary

protected Command	command This is the command created during dragging which provides the feedback and will carry out the action upon completion.
protected java.lang.Object	commandTarget This records the object for which the command was created.
protected EditingDomain	domain This is the domain in which drag and drop commands will be executed.
protected EditingDomainViewerDropAdapter.DragAndDropCommandInformation	dragAndDropCommandInformation This keeps track of the information used to create command, but does not need to be disposed.
protected static boolean	IS_MOTIF This indicates whether the current platform is motif, which needs special treatment, since it cannot do early data transfer, but doesn't cleanly return null either.
protected int	originalOperation This keeps track of the original operation that the user requested, before we started changing the event.detail.
protected java.util.Collection<?>	source This is the collection of source objects being dragged.
protected Viewer	viewer This is the viewer for which this is a drop target listener.

Constructor Summary

EditingDomainViewerDropAdapter(EditingDomain domain, Viewer viewer)
This creates an instance with the given domain and viewer.

Method Summary

void	dragEnter(DropTargetEvent event) This is called when the mouse first enters or starts dragging in the viewer.
void	dragLeave(DropTargetEvent event) This is called when the mouse leaves or stops dragging in the viewer, whether the operation was aborted or is about to do a dropAccept and drop.
void	dragOperationChanged(DropTargetEvent event) This is called when the operation has changed in some way, typically because the user changes keyboard modifiers.
void	dragOver(DropTargetEvent event) This is called repeatedly, as the mouse moves over the viewer.
void	drop(DropTargetEvent event) This is called to indicate that the drop action should be invoked.
void	dropAccept(DropTargetEvent event) This is called when the mouse is released over the viewer to initiate a drop, between dragLeave and drop.
protected java.util.Collection<?>	extractDragSource(java.lang.Object object) This extracts a collection of dragged source objects from the given object retrieved from the transfer agent.
protected java.lang.Object	extractDropTarget(Widget item) This extracts an object from the given item widget, providing the special support required by an ExtendedTableTreeViewer.ExtendedTableTreeItem.
protected int	getAutoFeedback() This returns the bitwise OR'ed flags for desired auto-feedback effects.
protected java.util.Collection<?>	getDragSource(DropTargetEvent event) This attempts to extract the drag source from the event early, i.e., before the drop method.
protected float	getLocation(DropTargetEvent event) This returns the location of the mouse in the vertical direction, relative to the item widget, from 0 (top) to 1 (bottom).
protected void	helper(DropTargetEvent event) This method is called the same way for each of the DropTargetListener methods, except for leave and drop.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

IS_MOTIF

protected static final boolean IS_MOTIF

This indicates whether the current platform is motif, which needs special treatment, since it cannot do early data transfer, but doesn't cleanly return null either.

viewer

protected Viewer viewer

This is the viewer for which this is a drop target listener.

domain

protected EditingDomain domain

This is the domain in which drag and drop commands will be executed.

source

protected java.util.Collection<?> source

This is the collection of source objects being dragged.

command

protected Command command

This is the command created during dragging which provides the feedback and will carry out the action upon completion.

commandTarget

protected java.lang.Object commandTarget

This records the object for which the command was created.

originalOperation

protected int originalOperation

This keeps track of the original operation that the user requested, before we started changing the event.detail. We always try to create the command using this.

dragAndDropCommandInformation

protected EditingDomainViewerDropAdapter.DragAndDropCommandInformation dragAndDropCommandInformation

This keeps track of the information used to create command, but does not need to be disposed. This allows us to dispose of the command in dragLeave, and then, if we need to execute it, recreate it in drop.

Constructor Detail

EditingDomainViewerDropAdapter

public EditingDomainViewerDropAdapter(EditingDomain domain,
                                      Viewer viewer)

This creates an instance with the given domain and viewer.

Method Detail

dragEnter

public void dragEnter(DropTargetEvent event)

This is called when the mouse first enters or starts dragging in the viewer.

Specified by:

dragEnter in interface DropTargetListener

Overrides:

dragEnter in class DropTargetAdapter

dragLeave

public void dragLeave(DropTargetEvent event)

This is called when the mouse leaves or stops dragging in the viewer, whether the operation was aborted or is about to do a dropAccept and drop. The event argument is uninitialized, so it is impossible to distinguish between the two cases. So, we do the clean-up now and recreate the command later, if necessary.

Specified by:

dragLeave in interface DropTargetListener

Overrides:

dragLeave in class DropTargetAdapter

dragOperationChanged

public void dragOperationChanged(DropTargetEvent event)

This is called when the operation has changed in some way, typically because the user changes keyboard modifiers.

Specified by:

dragOperationChanged in interface DropTargetListener

Overrides:

dragOperationChanged in class DropTargetAdapter

dragOver

public void dragOver(DropTargetEvent event)

This is called repeatedly, as the mouse moves over the viewer.

Specified by:

dragOver in interface DropTargetListener

Overrides:

dragOver in class DropTargetAdapter

dropAccept

public void dropAccept(DropTargetEvent event)

This is called when the mouse is released over the viewer to initiate a drop, between dragLeave and drop.

Specified by:

dropAccept in interface DropTargetListener

Overrides:

dropAccept in class DropTargetAdapter

drop

public void drop(DropTargetEvent event)

This is called to indicate that the drop action should be invoked.

Specified by:

drop in interface DropTargetListener

Overrides:

drop in class DropTargetAdapter

helper

protected void helper(DropTargetEvent event)

This method is called the same way for each of the DropTargetListener methods, except for leave and drop. If the source is available early, it creates or revalidates the DragAndDropCommand, and updates the event's detail (operation) and feedback (drag under effect), appropriately.

getAutoFeedback

protected int getAutoFeedback()

This returns the bitwise OR'ed flags for desired auto-feedback effects. Drag under effect DND constants are always OR'ed with this to enable them. This implementation enables auto-scroll and auto-expand (hover).

getDragSource

protected java.util.Collection<?> getDragSource(DropTargetEvent event)

This attempts to extract the drag source from the event early, i.e., before the drop method. This implementation tries to use a LocalTransfer. If the data is not yet available (e.g. on platforms other than win32), it just returns null.

extractDragSource

protected java.util.Collection<?> extractDragSource(java.lang.Object object)

This extracts a collection of dragged source objects from the given object retrieved from the transfer agent. This default implementation converts a structured selection into a collection of elements.

extractDropTarget

protected java.lang.Object extractDropTarget(Widget item)

This extracts an object from the given item widget, providing the special support required by an ExtendedTableTreeViewer.ExtendedTableTreeItem.

getLocation

protected float getLocation(DropTargetEvent event)

This returns the location of the mouse in the vertical direction, relative to the item widget, from 0 (top) to 1 (bottom).