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core-animationcalayer

How to force a CALayer to redraw at a higher resolution?

Two CALayers

I have two instances of a CALayer subclass.

The only difference between them is this line:

[self setTransform:CATransform3DMakeScale(2, 2, 2)];

What else do I need so that the large layer looks good at scale 2x ?

PS: (to avoid any confusion) The layers also include a few control buttons, shadows and rounded corner to mimic the look of windows in a windowing system, but those are not NSWindows instances.

Solution

  • The short answer is, don't use transforms. Transforms scale the layer by magnifying it, without re-rendering.

    You could get a very similar effect by using a CAShapeLayer and animating changes to the path. That would give you sharp rendering, however, because it path animation does re-render the pixels.

    I say "similar" effect because CAShapeLayers use a lineWidth property for the whole layer. You can animate the line width between values, and use fractional values, but you'll have to do some fine-tuning to get the line thickness to animate up and down in proportion to the size of the shape. Another consideration is that the graphics system uses anti-aliasing to draw fractional width paths, so when the line width is not an integer value they will look slightly soft. You could turn off antialiasing, but then they would look really jaggy.