NSDraggingSession

gistfile1.m

- (void)mouseDown:(NSEvent*)event
{

    //create a NSPasteboardItem
    NSPasteboardItem *pbItem = [NSPasteboardItem new];
    [pbItem setDataProvider:self forTypes:[NSArray arrayWithObjects:NSPasteboardTypeTIFF, nil]];
    
    //create a new NSDraggingItem with our pasteboard item.
    NSDraggingItem *dragItem = [[NSDraggingItem alloc] initWithPasteboardWriter:pbItem];
    NSPoint dragPosition = [self convertPoint:[event locationInWindow] fromView:nil];
    dragPosition.x -= self.image.size.width/5/2;
    dragPosition.y -= self.image.size.height/5/2;
    NSRect draggingRect = NSMakeRect(dragPosition.x, dragPosition.y, self.image.size.width/5, self.image.size.height/5);
    [dragItem setDraggingFrame:draggingRect contents:self.image];
    
    //create a dragging session with our drag item and ourself as the source.
    NSDraggingSession *draggingSession = [self beginDraggingSessionWithItems:[NSArray arrayWithObject:dragItem] event:event source:self];
    
    //causes the dragging item to slide back to the source if the drag fails.
    draggingSession.animatesToStartingPositionsOnCancelOrFail = YES;
    
}

- (NSDragOperation)draggingSession:(NSDraggingSession *)session sourceOperationMaskForDraggingContext:(NSDraggingContext)context
{
    if (context == NSDraggingContextOutsideApplication) {
        return NSDragOperationCopy;
    }
    
    return NSDragOperationNone;
}


-(void) draggingSession:(NSDraggingSession *)session willBeginAtPoint:(NSPoint) screenPoint
{
    for (NSPasteboardItem *item in [[NSPasteboard pasteboardWithName:NSDragPboard] pasteboardItems]) {
        NSLog(@"%@",[item types]);
    }
}

- (void)draggingSession:(NSDraggingSession *)session endedAtPoint:(NSPoint)screenPoint operation:(NSDragOperation)operation
{
        NSLog(@"%@",session);
}

- (void)pasteboard:(NSPasteboard *)sender item:(NSPasteboardItem *)item provideDataForType:(NSString *)type
{
    
    NSLog(@"FIRED ! %@",type);

    //sender has accepted the drag and now we need to send the data for the type we promised
    if ( [type compare: NSPasteboardTypeTIFF] == NSOrderedSame ) {
        [sender setData:[[self image] TIFFRepresentation] forType:NSPasteboardTypeTIFF];
    }    
}