Disabling implicit animations in -[CALayer setNeedsDisplayInRect:]

Question

I've got a layer with some complex drawing code in its -drawInContext: method. I'm trying to minimize the amount of drawing I need to do, so I'm using -setNeedsDisplayInRect: to update just the changed parts. This is working splendidly. However, when the graphics system updates my layer, it's transitioning from the old to the new image using a cross-fade. I'd like it to switch over instantly.

I've tried using CATransaction to turn off actions and set the duration to zero, and neither work. Here's the code I'm using:

[CATransaction begin];
[CATransaction setDisableActions: YES];
[self setNeedsDisplayInRect: rect];
[CATransaction commit];

Is there a different method on CATransaction I should use instead (I also tried -setValue:forKey: with kCATransactionDisableActions, same result).

Answer 1

You can do this by setting the actions dictionary on the layer to return [NSNull null] as an animation for the appropriate key. For example, I use

NSDictionary *newActions = @{
    @"onOrderIn": [NSNull null],
    @"onOrderOut": [NSNull null],
    @"sublayers": [NSNull null],
    @"contents": [NSNull null],
    @"bounds": [NSNull null]
};

layer.actions = newActions;

to disable fade in / out animations on insertion or change of sublayers within one of my layers, as well as changes in the size and contents of the layer. I believe the contents key is the one you're looking for in order to prevent the crossfade on updated drawing.

---

Swift version:

let newActions = [
        "onOrderIn": NSNull(),
        "onOrderOut": NSNull(),
        "sublayers": NSNull(),
        "contents": NSNull(),
        "bounds": NSNull(),
    ]

Answer 2

Also:

[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];

//foo

[CATransaction commit];

Answer 3

When you change the property of a layer, CA usually creates an implicit transaction object to animate the change. If you do not want to animate the change, you can disable implicit animations by creating an explicit transaction and setting its kCATransactionDisableActions property to true.

Objective-C

[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];
// change properties here without animation
[CATransaction commit];

Swift

CATransaction.begin()
CATransaction.setValue(kCFBooleanTrue, forKey: kCATransactionDisableActions)
// change properties here without animation
CATransaction.commit()