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  = 1000000;                                      // = 
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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