Disabling NSView fade animation for NSView `setHidden:`

Question

I am working on a project that has the concept of draggable controls, everything is working fine except that NSView seems to employ a fade in/out animation when calling setHidden:.

I have been able to work around the problem by changing the line session.animatesToStartingPositionsOnCancelOrFail = YES; to NO and implementing the image snapback myself with a custom animated NSWindow subclass. it looks great, but I know there must be an easier way.

I have tried:

1. using NSAnimationContext grouping with duration of 0 around the setHidden: calls
2. setting the view animations dictionary using various keys (alpha, hidden, isHidden) on the control and superview
3. overriding animationForKey: for both the control and its superview

I am not using CALayers and have even tried explicitly setting wantsLayer: to NO.

Does anybody know how to either disable this animation, or have a simpler solution then my animated NSWindow?

here is my stripped down altered code with the bare minimum to see what I'm talking about.

@implementation NSControl (DragControl)

- (NSDraggingSession*)beginDraggingSessionWithDraggingCell:(NSActionCell <NSDraggingSource> *)cell event:(NSEvent*) theEvent
{
    NSImage* image = [self imageForCell:cell];
    NSDraggingItem* di = [[NSDraggingItem alloc] initWithPasteboardWriter:image];
    NSRect dragFrame = [self frameForCell:cell];
    dragFrame.size = image.size;
    [di setDraggingFrame:dragFrame contents:image];

    NSArray* items = [NSArray arrayWithObject:di];

    [self setHidden:YES];
    return [self beginDraggingSessionWithItems:items event:theEvent source:cell];
}

- (NSRect)frameForCell:(NSCell*)cell
{
    // override in multi-cell cubclasses!
    return self.bounds;
}

- (NSImage*)imageForCell:(NSCell*)cell
{
    return [self imageForCell:cell highlighted:[cell isHighlighted]];
}

- (NSImage*)imageForCell:(NSCell*)cell highlighted:(BOOL) highlight
{
    // override in multicell cubclasses to just get an image of the dragged cell.
    // for any single cell control we can just make sure that cell is the controls cell

    if (cell == self.cell || cell == nil) { // nil signifies entire control
                                            // basically a bitmap of the control
                                            // NOTE: the cell is irrelevant when dealing with a single cell control
        BOOL isHighlighted = [cell isHighlighted];
        [cell setHighlighted:highlight];

        NSRect cellFrame = [self frameForCell:cell];

        // We COULD just draw the cell, to an NSImage, but button cells draw their content
        // in a special way that would complicate that implementation (ex text alignment).
        // subclasses that have multiple cells may wish to override this to only draw the cell
        NSBitmapImageRep* rep = [self bitmapImageRepForCachingDisplayInRect:cellFrame];
        NSImage* image = [[NSImage alloc] initWithSize:rep.size];

        [self cacheDisplayInRect:cellFrame toBitmapImageRep:rep];
        [image addRepresentation:rep];
        // reset the original cell state
        [cell setHighlighted:isHighlighted];
        return image;
    }
    // cell doesnt belong to this control!
    return nil;
}

#pragma mark NSDraggingDestination

- (void)draggingEnded:(id < NSDraggingInfo >)sender
{
    [self setHidden:NO];
}

@end

@implementation NSActionCell (DragCell)

- (void)setControlView:(NSView *)view
{
    // this is a bit of a hack, but the easiest way to make the control dragging work.
    // force the control to accept image drags.
    // the control will forward us the drag destination events via our DragControl category

    [view registerForDraggedTypes:[NSImage imagePasteboardTypes]];
    [super setControlView:view];
}

- (BOOL)trackMouse:(NSEvent *)theEvent inRect:(NSRect)cellFrame ofView:(NSView *)controlView untilMouseUp:(BOOL)untilMouseUp
{
    BOOL result = NO;
    NSPoint currentPoint = theEvent.locationInWindow;
    BOOL done = NO;
    BOOL trackContinously = [self startTrackingAt:currentPoint inView:controlView];

    BOOL mouseIsUp = NO;
    NSEvent *event = nil;
    while (!done)
    {
        NSPoint lastPoint = currentPoint;

        event = [NSApp nextEventMatchingMask:(NSLeftMouseUpMask|NSLeftMouseDraggedMask)
                                   untilDate:[NSDate distantFuture]
                                      inMode:NSEventTrackingRunLoopMode
                                     dequeue:YES];

        if (event)
        {
            currentPoint = event.locationInWindow;

            // Send continueTracking.../stopTracking...
            if (trackContinously)
            {
                if (![self continueTracking:lastPoint
                                         at:currentPoint
                                     inView:controlView])
                {
                    done = YES;
                    [self stopTracking:lastPoint
                                    at:currentPoint
                                inView:controlView
                             mouseIsUp:mouseIsUp];
                }
                if (self.isContinuous)
                {
                    [NSApp sendAction:self.action
                                   to:self.target
                                 from:controlView];
                }
            }

            mouseIsUp = (event.type == NSLeftMouseUp);
            done = done || mouseIsUp;

            if (untilMouseUp)
            {
                result = mouseIsUp;
            } else {
                // Check if the mouse left our cell rect
                result = NSPointInRect([controlView
                                        convertPoint:currentPoint
                                        fromView:nil], cellFrame);
                if (!result)
                    done = YES;
            }

            if (done && result && ![self isContinuous])
                [NSApp sendAction:self.action
                               to:self.target
                             from:controlView];
            else {
                done = YES;
                result = YES;

                // this bit-o-magic executes on either a drag event or immidiately following timer expiration
                // this initiates the control drag event using NSDragging protocols
                NSControl* cv = (NSControl*)self.controlView;
                NSDraggingSession* session = [cv beginDraggingSessionWithDraggingCell:self
                                                                                event:theEvent];
                // Note that you will get an ugly flash effect when the image returns if this is set to yes
                // you can work around it by setting NO and faking the release by animating an NSWindowSubclass with the image as the content
                // create the window in the drag ended method for NSDragOperationNone
                // there is [probably a better and easier way around this behavior by playing with view animation properties.
                session.animatesToStartingPositionsOnCancelOrFail = YES;
            }

        }
    }
    return result;
}

#pragma mark - NSDraggingSource Methods
- (NSDragOperation)draggingSession:(NSDraggingSession *)session sourceOperationMaskForDraggingContext:(NSDraggingContext)context
{
    switch(context) {
        case NSDraggingContextOutsideApplication:
            return NSDragOperationNone;
            break;

        case NSDraggingContextWithinApplication:
        default:
            return NSDragOperationPrivate;
            break;
    }
}

- (void)draggingSession:(NSDraggingSession *)session endedAtPoint:(NSPoint)screenPoint operation:(NSDragOperation)operation
{
    // now tell the control view the drag ended so it can do any cleanup it needs
    // this is somewhat hackish
    [self.controlView draggingEnded:nil];
}

@end

Answer 1

Ok. I figured out that the animation I'm seeing is not the control, the superview, nor the control's window. It appears that animatesToStartingPositionsOnCancelOrFail causes NSDraggingSession to create a window (observed with QuartzDebug) and put the drag image in it and it is this window that animates back to the origin and fades out before the setHidden: call is executed (i.e. before the drag operation is concluded).

Unfortunately, the window that it creates is not an NSWindow so creating a category on NSWindow doesn't disable the fade animation.

Secondly, there is no public way that I know of to get a handle on the window, so I can't attempt directly manipulating the window instance.

It looks like maybe my workaround is the best way to do this, after all its not far from what AppKit does for you anyway.

If anybody knows how to get a handle on this window, or what class it is I would be interested to know.

Answer 2

There must be a layer enabled somewhere in your view hierarchy, otherwise there wouldn't be a fade animation. Here is my way of disabling such animations:

@interface NoAnimationImageView : NSImageView

@end

@implementation NoAnimationImageView

+ (id)defaultAnimationForKey: (NSString *)key
{
    return nil;
}

@end

Answer 3

The solution you already tried by setting the view animations dictionary should work. But not for the keys you mention but for the following. Use it somewhere before the animation is triggered the first time. If you have to do it on the window or view or both, I don't know.

NSMutableDictionary *animations = [NSMutableDictionary dictionaryWithDictionary:[[theViewOrTheWindow animator] animations];
[animations setObject:[NSNull null] forKey: NSAnimationTriggerOrderIn];
[animations setObject:[NSNull null] forKey: NSAnimationTriggerOrderOut];
[[theViewOrTheWindow animator] setAnimations:animations];

Or also just remove the keys if they are there (might not be the case as they are implicit / default):

NSMutableDictionary *animations = [NSMutableDictionary dictionaryWithDictionary:[[theViewOrTheWindow animator] animations];
[animations removeObjectForKey:NSAnimationTriggerOrderIn];
[animations removeObjectForKey:NSAnimationTriggerOrderOut];
[[theViewOrTheWindow animator] setAnimations:animations];