DraggingImageOutOfNSImageView

Is there any sample code to demonstrate being able to drag an image OUT of an NSImageView and drop it into other apps as an image?

You just have to put the image data on the pasteboard in mouseDragged:

http://developer.apple.com/documentation/Cocoa/Conceptual/DragandDrop/Concepts/dragsource.html

http://developer.apple.com/documentation/Cocoa/Reference/ApplicationKit/ObjC_classic/Classes/NSView.html#//apple_ref/doc/uid/20000014/BBCDEIEF

How do you detect the dragging?

subclass NSImageView and override mouseDragged:

I tried that, but it’s not catching the event - do I have to make it a responder or something?

Putting

(void)mouseDragged:(NSEvent *)event { NSLog(@”hi”); }

Into the implementation of the NSImageView subclass doesn’t work…any ideas?

Try also catching mouse downs. Make sure a mouse down event is properly handled before mouseDragged is called.

-(void)mouseDown:(NSEvent*)event { NSLog(@”Wassup”); [super mouseDown:event]; }

It appears to be catching mouse downs properly - but still no go with the mouse drags. Thanks.

Here’s some (slightly modified) code from the Basic Event Handling docs…

(void)mouseDown:(NSEvent *)theEvent { BOOL keepOn = YES;

while (keepOn) { theEvent = self window] nextEventMatchingMask: [[NSLeftMouseUpMask | NSLeftMouseDraggedMask];

  switch ([theEvent type]) {
      case NSLeftMouseDragged:
               [self mouseDragged:theEvent];
               keepOn = NO;
              break;
      case NSLeftMouseUp:
              keepOn = NO;
              break;
      default:
              /* Ignore any other kind of event. */
              break;
  }   }   return; }

Here’s another (PyObjC; should be obvious how to translate to straight Objective-C, and ignore the ‘self’ arguments) version that I’ve implemented. It’s still not perfect (I’m sure I’m not doing the ‘at’ and/or ‘offset’ arguments correctly, for example) but it works.

class Dragger(NSImageView): def mouseDown_(self,theEvent): return NSResponder.mouseDown_(self,theEvent)

def mouseDragged_(self,theEvent):
    pb = NSPasteboard.pasteboardWithName_(NSDragPboard)
    pb.declareTypes_owner_(NSArray.arrayWithObject_(NSTIFFPboardType),self)
    pb.setData_forType_(self.image().TIFFRepresentation(),NSTIFFPboardType)
    
    NSView.dragImage_at_offset_event_pasteboard_source_slideBack_(self,self.image(),
        NSPoint(0.0,0.0),self.image().size(),theEvent,pb,self.window(),objc.YES)

    return NSResponder.mouseDragged_(self,theEvent)

def draggingSourceOperationMaskForLocal_(self,isLocal):
    return NSDragOperationCopy

Isn’t that implementation of mouseDown: basically redundant? After all, it just calls NSResponder’s implementation. Maybe this is just a Python quirk… –JediKnil

Half-newbie here: Can anyone suggest how to drag FROM NSImageViews?

Well, it really wasn’t intended for that purpose, just to accept an image. It IS however a descendant of NSView. Just look up how to do drag and drop with a view. One thing you’ll learn is that you need to provide a “drag image” for the drag op. Just use the NSImageView’s -image to grab the current image.

I have successfully subclassed NSImageView to allow it to act as a drag source. Drop an email to jeff [at] bitprophet [dot] org if you’d like to see what I did. In the end it was very simple to implement, however finding out the correct thing to do was a bit of a pain (I’m also a newbie).

CocoaDev