Bug 119014

Comment 1 Paul E. Keyser 2005-12-28 15:03:41 EST

(In reply to comment #0)

I discovered that things seem to work if I do all of the following (not sure which part(s) are critical, as I only realised it worked after I had done it all): 

*dragStart()*: set event.doit to true (perhaps under some condition) 

*dragSetData()*: if event.dataType is OK, set event.data to the YourData[] to be dragged 

Then, override the following two methods as indicated: 

	public void dragEnter(final DropTargetEvent event) {
		selectDefault(event);
		super.dragEnter(event);
	}
	public void dragOperationChanged(final DropTargetEvent event) {
		selectDefault(event);
		super.dragOperationChanged(event);
	}

And here's the method selectDefault(): 

	protected void selectDefault(DropTargetEvent event) {
		if (maskEquals(event.detail, DND.DROP_DEFAULT)) {
			event.detail = DEFAULT_OP; 
		}
	}

I have this one in a module of useful utilities: 
	public static boolean maskEquals(int mask, int value) {
		return (mask & value) != 0;
	}

Can others verify that this works, or is a sensible way to proceed? 

Comment 2 Eric Moffatt 2007-06-25 10:09:25 EDT

I'll tag this for a look in 3.4 since there seem to be a fair number of gliches in the ViewDropAdapter...

Comment 3 Paul E. Keyser 2007-06-26 13:49:34 EDT

(In reply to comment #2)
> I'll tag this for a look in 3.4 since there seem to be a fair number of gliches
> in the ViewDropAdapter...
> 
Good to hear -- I am still interested in this bug, as we use DnD often, and for each implementation I must revisit all this. Thanks.

Comment 4 Eric Moffatt 2007-06-27 09:09:05 EDT

Dnd is near and dear to my heart...;-)

Comment 5 C. Lamont Gilbert 2007-07-11 16:25:50 EDT

Eclipse 3.2.2

I have a similar problem so rather than post a new bug, I'll ask here first if it is related.

I want to drop from one tree item onto another.  But the ViewerDropAdapter is configured such that it only recognizes the tree as a whole and not individual items.  So the second you hit a bad drop, the drop will stay bad until you leave and reenter the tree.  I want the drop to be reevaluated for each tree item.  I say this could be related because if you start your DND operation, and the first thing the system sees is you trying to drop an item ontop of itself, and you have disallowed items dropping on top of themselves, then the system will forbid the drop.  And as stated, once a drop is forbidden, it is permanently forbidden until you exit and reenter the tree.

My solution was to make a change which I think is proper.


private void doDropValidation(DropTargetEvent event) {
        //update last valid operation
        if (event.detail != DND.DROP_NONE) {
            lastValidOperation = event.detail;
        }
        //valid drop and set event detail accordingly
        if (validateDrop(currentTarget, event.operations, event.currentDataType)) {
            currentOperation = lastValidOperation;
        } else {
            currentOperation = DND.DROP_NONE;
        }
        event.detail = currentOperation;
    }


In the above method I have changed 

validateDrop(currentTarget, event.detail, event.currentDataType)

to

validateDrop(currentTarget, event.operations, event.currentDataType)

This gives the user an opportunity to indicate the drop is valid again.  If you use event.detail, once event.detail becomes DND.DROP_NONE, then it stays DND.DROP_NONE and the validator will always see DND.DROP_NONE and will never be able to reevaluate based on the actual drop target being over a different tree item.  Since he no longer knows the true requested drop operation.

Comment 6 C. Lamont Gilbert 2007-07-11 16:40:15 EDT

Patch is not so pretty so I just paste it here.  I don't have the project installed to create a proper patch.

--- C:\ViewerDropAdapter.java	2007-07-11 16:33:44.000000000 -0400
+++ C:\ViewerDropAdapter.java	2007-07-11 16:35:52.000000000 -0400
@@ -169,13 +169,13 @@
     private void doDropValidation(DropTargetEvent event) {
         //update last valid operation
         if (event.detail != DND.DROP_NONE) {
             lastValidOperation = event.detail;
         }
         //valid drop and set event detail accordingly
-        if (validateDrop(currentTarget, event.detail, event.currentDataType)) {
+        if (validateDrop(currentTarget, event.operations, event.currentDataType)) 

{
             currentOperation = lastValidOperation;
         } else {
             currentOperation = DND.DROP_NONE;
         }
         event.detail = currentOperation;
     }

Comment 7 Eric Moffatt 2008-06-09 10:52:57 EDT

*** Bug 92802 has been marked as a duplicate of this bug. ***

Comment 8 Chris Simmons 2008-06-10 09:06:51 EDT

Note that the suggested fix in bug 92802 is different.  It suggests to use lastValidOperation in validate drop.  This makes sense since we should be re-evaluating the validation for last (non-DND.DROP_NONE) operation on the current tree node.

I can't see how using event.operations makes any sense, this is isn't even a unique value since its the bitwise or of all supported operations.  It might appear to do the right thing if you have only set one operation but for the wrong reason.

eg in our tree we have all operations supported so

event.operations == DND.DROP_COPY | DND.DROP_MOVE | DND.DROP_DEFAULT | DND.DROP_LINK

Comment 9 Eric Moffatt 2008-06-10 14:55:32 EDT

Chris, for my money I think that 'validateDrop' should -return- the event.detail value rather than a boolean, making 'lastValidOperation'...umm...invalid...;-).

In any case I hope that the some flavor of the work around will help...

Comment 10 Eric Moffatt 2009-03-05 11:40:46 EST

Bug 263845 adds the ability to set the event.detail in 'validateDrop'. Try this out and re-open if there are issues that still cannot be solved.


*** This bug has been marked as a duplicate of bug 263845 ***