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Editorial Team
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Asked: 2026-06-16T00:50:18+00:00

I have a UICollectionView with some custom cells, it uses the flow layout and

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I have a UICollectionView with some custom cells, it uses the flow layout and it has 3 columns on landscape and 2 columns on portrait. When I started the app on landscape, scrolling gives me 55-60 FPS, which is fairly good. However, after I rotate for some reason it drops down to 30 FPS and under. Any idea how rotation could destroy FPS in scrolling?

I’ve heard some talk in WWDC video’s that rasterization might be causing it. Is it true that I’d have to turn off and on back rasterization on rotation?

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1 Answer

  1. Editorial Team
    • Are you running any other animations while scrolling? These will affect performance.
    • Are you using the CALayer shadow property on any elements? You may be better off using an shadow image instead.
    • Do your interface elements (or anything moving, for that matter) contain transparency? Check this by using the simulator and selecting Debug – Color Blended Layers.

    Blending slows down performance a great deal, so use opaque views wherever you can.

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