Re: Drag & Drop Problem

[Andreas Höschler]

Hoi Fred,

> I tried to reproduce this problem with NSImageView and after removing
> the check for ([sender draggingSource] != self) in draggingEntered: it
> is possible to drag onto the same view.

My SRCalendarView is a subclass of NSImageView. I have overwritten (for 
test purposes) the following methods:

- (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender
{
   NSLog(@"draggingEntered %@", sender);
   return (NSDragOperationCopy | NSDragOperationLink | 
NSDragOperationMove);
}

- (void)draggingExited:(id <NSDraggingInfo>)sender;
{
   NSLog(@"draggingExited %@", sender);
}

- (BOOL)prepareForDragOperation:(id <NSDraggingInfo>)sender
{
   NSLog(@"prepareForDragOperation...");
   return YES;
}

- (NSDragOperation)draggingSourceOperationMask
{
   return (NSDragOperationCopy | NSDragOperationLink | 
NSDragOperationMove);
}
- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender
{
   NSPasteboard *thePasteboard = [sender draggingPasteboard];
   NSArray *types = [thePasteboard types];
   BOOL result = ([types firstObjectCommonWithArray:[self pboardTypes]] 
!= nil);
   NSLog(@"performDragOperation %d", result);
   return result;
}

/*- (NSDragOperation)draggingSourceOperationMask
{
   return _draggingSourceOperationMask;
}*/

- (void)concludeDragOperation:(id <NSDraggingInfo>)sender
{
}

I get draggingExited and draggingEntered, but the drag sign is "Do Not 
Enter" the whole time and when I let it go the drag image slides back. 
No luck! I am stuck!

> This means it isn't a general problem in GNUstep. Either it is related
> to you specific class or NSDragOperationLink isn't correctly propagated
> (which would surprise me with current GNUstep code).

I have no idea. I just know that the exact same code works great under 
MacOSX whatever that means.

> I will need more information from your side to make any further 
> progress.

What else can I provide?

Hey, I just dicovered something. I initiate the drag operation when the 
user presses the Ctrl-Key. That's by design (May be I should thing this 
over, but that how all drag and drop works an dall our applications so 
far). If I initiate the drag with the Ctrl-Key pressed and the let the 
Ctrl-Key go while still dragging, the "Do-Not-Enter" sign becomes a 
"Copy" sign and I can successfully drop.

Mac OS X behaves differently here. The drop works with a pressed 
Ctrl-Key. What exactly does a pressed Ctrl-Key mean to GNUstep?

Thanks,

  Andreas

> > > Are you referring to the same view that started the drag? It is 
> > > possible
> > > that GNUstep excludes this view from getting drag notifications.
> > > If you mean another view, is it in the same application, same window?
> > >
> > > Is this the first time you use drag&drop and if nto, what is the
> > > difference?
> >
> > Yes, I am referring to the same view/window. It is a caalendar view 
> > and
> > the drag and drop is supposed to move appointments from one day to
> > another. This works on MacOSX. Does the spec say the originating view
> > should be excluded?
> >
> > I also realized problems while dragging from this calendar view to
> > another view/window but haven't had time to dig into that any further.
> > The weird thing is, I can drag to these two views from even another
> > view/window (tableview) without problems. :-(
> >
> > All is the same application and everything works fine on MacOSX. I 
> > will
> > investigat ethe second case further, but IMHO there should be a way to
> > avoid the exclusion (dragging within a view).