CALayer's contentsRect property


I’m having trouble visualizing what’s going on in these few lines of code:

[boxLayer setBounds:CGRectMake(0.0, 0.0, 85.0, 85.0)];
[boxLayer setPosition:CGPointMake(160.0, 100.0)];
// other code
[boxLayer setContentsRect:CGRectMake(-0.1, -0.1, 1.2, 1.2)];
[boxLayer setContentsGravity:kCAGravityResizeAspect];
  • From which point is the origin of the contentsRect -0.1, -0.1 away from? Which is the positive direction for each? What does 0.1 represent?
    I would have thought that would be left 10% of the width of the layer, and up 10% of the height of the layer, starting from the top-left corner of the layer, but that doesn’t seem to be the case.

  • What is the size 1.2, 1.2?
    I would have thought that this would be a Rect 120% the width and height of the layer, so that these two lines of code essentially cause you to zoom in on the image.

Here’s what I thought was going on:


I’ve been trying to wrap my head around that one too. Hopefully someone who knows will post.