First guess would be not to explicitly set -anchorPosition. It defaults to
(0.5, 0.5), which refers to the middle of the bounds, and transforms (like
scaling) are applied relative to that position.
> On Sep 14, 2019, at 6:25 AM, Gabriel Zachmann via Cocoa-dev
> wrote:
>
> Maybe, I haven't understood how the animation of the bounds property works,
> or the bounds property of a CALayer itself ,
> or I am making a stupid mistake.
>
> Here is my code:
>
>CALayer * imgLayer = [CALayer layer];
>imgLayer.contents= (__bridge id) imageRef;
>imgLayer.delegate= nil;
>imgLayer.opacity = 1.0;
>imgLayer.anchorPoint = CGPointMake( 0.0, 0.0 );
>imgLayer.zPosition = -1.0;
>
>CABasicAnimation * anim = [CABasicAnimation animationWithKeyPath:
> @"bounds"];
>anim.timingFunction = [CAMediaTimingFunction functionWithName:
> kCAMediaTimingFunctionLinear];
>anim.duration = 5;// sec
>anim.autoreverses = YES;
>anim.repeatCount = 100; // =
> forever
>
>NSRect from_rect = NSMakeRect( 100.0, 100.0, 200.0, 200.0 );
>anim.fromValue= [NSValue valueWithRect: from_rect ];
>NSRect to_rect = NSMakeRect( 200.0, 200.0, 300.0, 300.0 );
>anim.toValue = [NSValue valueWithRect: to_rect ];
>
>[imgLayer addAnimation: anim forKey: @"myBoundsAnim"];
>
>
> What I am seeing is that the image gets scaled (from 200 to 300
> width/height) which is fine,
> but it always sits in the lower left corner of the screen (I am working under
> macOS).
>
> I want the lower left corner of the image to be animated , too.
> (Eventually, the animation will be a bit more complex, but for now I am just
> trying to understand this.)
>
> What am I missing? or going wrong?
>
> I guess I could achieve the effect by animating the position property of the
> layer,
> but I'd rather prefer to understand what is going on.
> I have also re-read the "Core Animation Basics" , but it doesn't explain the
> meaning of bounds.origin.
> In the drawings, it's always (0,0).
>
> Thanks a lot in advance for any insights.
>
> Best regards, Gabriel
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