How Do I Set a Custom Drag Image When Doing an HFS Promise Drag in Cocoa?

NSView’s dragPromisedFilesOfTypes:fromRect:source:slideBack:event: method doesn't provide a way to set the drag image to be used when dragging an HFS promise file. However, this method calls another NSView method, dragImage:at:offset:event:pasteboard:source:slideBack: in its implementation, which does provide a parameter for an NSImage to be used as the drag image. So, to set a custom drag image, simply override dragImage:at:offset:event:pasteboard:source:slideBack:, setup your custom image, invoke super's dragImage:at:offset:event:pasteboard:source:slideBack: and pass in your custom drag image.

How Do I Add Other Pasteboard Types to an HFS Promise Drag in Cocoa?

NSView's dragPromisedFilesOfTypes:fromRect:source:slideBack:event: method doesn't provide a means to add other pasteboard types to the HFS Promise data, because it doesn't expose the pasteboard that it uses. However, there is a workaround to add other pasteboard type data. dragPromisedFilesOfTypes:fromRect:source:slideBack:event: calls NSView's dragImage:at:offset:event:pasteboard:source:slideBack: method in its implementation. So, you can override dragImage:at:offset:event:pasteboard:source:slideBack:, add any additional pasteboard types you need, and then invoke super's dragImage:at:offset:event:pasteboard:source:slideBack: to allow everything to continue as before.

When I Rebuild My application on OS X version 10.2, My NSTableView Loses the Ability to Drag-And-Drop to Other Applications. How Do I Fix This?

A bug in NSTableView in OS X version 10.2 and later causes cross-application drags to not work without additional code from the application developer. Drag-and-Drop within an application still works correctly.

You can work around the bug by subclassing NSTableView and overriding draggingSourceOperationMaskForLocal: to return the appropriate NSDragOperation (typically NSDragOperationCopy, depending upon what drag operation you want the drag-and-drop to perform). Only applications built on OS X version 10.2 and later are affected; applications built on OS X version 10.1.x are not affected.

In OS X v10.4 you can work around this bug without subclassing. By default the NSTableView implementation of draggingSourceOperationMaskForLocal: disallows dragging to destinations outside of the application while allowing any type of drag within the same application. You can change this behavior by sending the table view a setDraggingSourceOperationMask:forLocal: message. Passing a value of YES as the second parameter indicates that specified mask applies when the destination object is in the same application. Passing a value of NO indicates that the specified mask applies when the destination object in an application outside the receiver's application. The masks are archived with the table view.