I'm updating some older code that uses the now-deprecated [NSView
dragImage:at:offset:pasteboard:source:slideback:] to use NSDraggingSession and
pals. Note that this older code works just fine, I've never had any issues with
it. I'm doing this mostly just to clear out compiler warnings, though my
instinct tells me not to "fix" code that isn't broken.
Sadly its replacement is broken.
In order to use NSDraggingItem, I first need to make sure the stuff I'm
dragging supports NSPasteboardWriting. I've done that, it seems straightforward
enough. Then I build a NSDraggingItem and use the same image I previously used,
so there's nothing new there. Finally I use [NSView
beginDraggingSessionWithItems:event:source:].
Nothing shows up. No image, nothing drags. I can break on the
NSPasteboardWriting methods and see that they are being called, so it seems to
be trying to write the correct things to the pasteboard. Nothing is logged.
After this, use of the legacy dragging methods elsewhere in the app also fail
to work - it's like whatever I did in this drag session messes up the dragging
system altogether. Obviously I'm doing something wrong, but I've been over the
docs and am just not getting it.
One thing is that the docs state that this new dragging method returns
immediately and the drag itself is somehow magically handled on the next turn
of the event loop. I think the older approach kept control for the duration of
the drag. That seems like a very different situation from the app's point of
view, and makes updating legacy code that expects it to keep control quite
difficult. That might be where things are messing up, so I'll look into that...
unless anyone can spot an obvious problem otherwise. Or would it just be better
to stick with working code and ignore the deprecation warnings? Those warnings
really go against the grain of everything I've ever learned about coding which
is "if it ain't broke don't fix it".
Here's the code:
- (void) dragStyleOrSymbol:(id<DKOLibraryObjectProtocol>) obj
event:(NSEvent*) event source:(id) sourceObject slideBack:(BOOL) slideBack
{
NSAssert( obj != nil, @"can't drag a nil style or symbol");
// can pass in nil to mean self
if( sourceObject == nil )
sourceObject = self;
// create the drag image
NSImage* dragImage = [obj image];
NSPoint mdLoc = [self convertPoint:[event locationInWindow]
fromView:nil];
mdLoc.x -= [dragImage size].width * 0.5;
mdLoc.y -= [dragImage size].height * 0.5;
#if (LEGACY_ CODE)
NSPasteboard* dragPBoard = [NSPasteboard
pasteboardWithName:NSDragPboard];
// put the object on the pasteboard
[obj copyToPasteboard:dragPBoard];
// start dragging it
[self dragImage:dragImage at:mdLoc offset:NSZeroSize event:event
pasteboard:dragPBoard source:sourceObject slideBack:slideBack];
#else
NSDraggingItem* dragItem = [[[NSDraggingItem alloc]
initWithPasteboardWriter:obj] autorelease];
NSRect dragFrame;
dragFrame.origin = mdLoc;
dragFrame.size = dragImage.size;
[dragItem setDraggingFrame:dragFrame contents:dragImage];
NSDraggingSession* session = [self
beginDraggingSessionWithItems:@[dragItem] event:event source:sourceObject];
session.animatesToStartingPositionsOnCancelOrFail = slideBack;
#endif
}
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