NSTableView custom drag image with background and drop shadow based on contents of NSTableCellView -draggingImageComponents

gistfile1.m

#pragma mark -
#pragma mark NSTableViewDataSource

- (void)tableView:(NSTableView *)tableView draggingSession:(NSDraggingSession *)session willBeginAtPoint:(NSPoint)screenPoint forRowIndexes:(NSIndexSet *)rowIndexes
{
    // configure the drag image
    // we are only dragging one item
    NSTableCellView *cellView = [self.columnsTableView viewAtColumn:0 row:rowIndexes.firstIndex makeIfNecessary:NO];
    if (cellView) {
    
        [session enumerateDraggingItemsWithOptions:NSDraggingItemEnumerationConcurrent
                                           forView:tableView
                                           classes:[NSArray arrayWithObject:[NSPasteboardItem class]]
                                     searchOptions:nil
                                        usingBlock:^(NSDraggingItem *draggingItem, NSInteger idx, BOOL *stop)
         {
             // Note: we can set the drag image directly if desired rather than manipulating the tablecellview image
             //[draggingItem setDraggingFrame:NSMakeRect(0, 0, myWidth, myHeight) contents:myFunkyDragImage];
             
             // prepare context
             NSGraphicsContext* theContext = [NSGraphicsContext currentContext];
             [theContext saveGraphicsState];
             
             // drag image needs to be larger than the content in order to encapsulate the drop shadow
             CGFloat imageOffset = 5;
             
             // supply a drag background image
             NSSize contentSize = draggingItem.draggingFrame.size;
             NSSize imageSize = NSMakeSize(contentSize.width + imageOffset, contentSize.height + imageOffset);
             NSImage *image = [[NSImage alloc] initWithSize:imageSize];
             [image lockFocus];
             
             // define a shadow
             NSShadow *shadow = [NSShadow new];
             shadow.shadowColor = [[NSColor lightGrayColor] colorWithAlphaComponent:0.2];
             shadow.shadowOffset = NSMakeSize(imageOffset, -imageOffset);
             shadow.shadowBlurRadius = 3;
             [shadow set];
             
             // define content frame
             NSRect contentFrame = NSMakeRect(0, imageOffset, contentSize.width, contentSize.height);
             NSBezierPath *contentPath = [NSBezierPath bezierPathWithRect:contentFrame];
             
             // draw content border and sahdow
             [[[NSColor lightGrayColor] colorWithAlphaComponent:0.6] set];
             [contentPath stroke];
             [theContext restoreGraphicsState];
             
             // fill content
             [[NSColor whiteColor] set];
              contentPath = [NSBezierPath bezierPathWithRect:NSInsetRect(contentFrame, 1, 1)];
             [contentPath fill];
             
             [image unlockFocus];
             
             // update the dragging item frame to accomodate larger image
             draggingItem.draggingFrame = NSMakeRect(draggingItem.draggingFrame.origin.x, draggingItem.draggingFrame.origin.y, imageSize.width,imageSize.height);
             
             // define additional image component for drag
             NSDraggingImageComponent *backgroundImageComponent = [NSDraggingImageComponent draggingImageComponentWithKey:@"background"];
             backgroundImageComponent.contents = image;
             backgroundImageComponent.frame = NSMakeRect(0, 0, imageSize.width, imageSize.height);
             
             // we can provide custom content by overridding NSTableViewCell -draggingImageComponents
             // which defaults to only including the image and text fields
             draggingItem.imageComponentsProvider = ^NSArray*(void) {
                 
                 NSMutableArray *components = [NSMutableArray arrayWithArray:@[backgroundImageComponent]];
                 NSArray *cellViewComponents = cellView.draggingImageComponents;
                 [cellViewComponents enumerateObjectsUsingBlock:^(NSDraggingImageComponent *component, NSUInteger idx, BOOL *stop) {
                     component.frame = NSMakeRect(component.frame.origin.x, component.frame.origin.y + imageOffset, component.frame.size.width, component.frame.size.height);
                 }];

                 [components addObjectsFromArray:cellViewComponents];
                 return components;
             };
         }];
    }
     
}