kylefang/AsyncDisplayKit
1
0
Fork 0
mirror of https://github.com/HackPlan/AsyncDisplayKit.git synced 2026-04-01 22:36:03 +08:00
Code Issues Packages Projects Releases Wiki Activity

Update corner-rounding.md

Browse Source
This commit is contained in:
Hannah Troisi
2016-07-06 18:26:53 -07:00
committed by GitHub
parent c9627a118a
commit 6b59cfb0fb
1 changed files with 1 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
_docs/corner-rounding.md
View File

@@ -19,7 +19,7 @@ If you've worked with Scott Goodson before, you will know that CALayer’s `.cor
When it comes to corner rounding, many developers stick with CALayer's `.cornerRadius` property. Unfortunately, this convenient property greatly taxes performance and should only be used when there is _no_ alternative.
Why is `.cornerRadius` so expensive? Use of CALayer's `.cornerRadius` property triggers off-screen rendering to perform the clipping operation on every frame - 60 FPS during scrolling - even if the content in that area isn't changing! This means that the GPU has to switch contexts on every frame, between compositing the overall frame + additional passes for each use of `.cornerRadius`. Importantly, these costs don't show up in the Time Profiler, because they affect work done by the CoreAnimation Render Server on your app's behalf. This intensive thrash annihilates performance for a lot of devices. On the iPhone 4, 4S, and 5 / 5C (along with comparable iPads / iPods), expect to see notably degraded performance. On the iPhone 5S and newer, even if you can't see the impact directly, it will reduce headroom so that it takes less to cause a frame drop.
Why is `.cornerRadius` so expensive? Use of CALayer's `.cornerRadius` property triggers off-screen rendering to perform the clipping operation on every frame - 60 FPS during scrolling - even if the content in that area isn't changing! This means that the GPU has to switch contexts on every frame, between compositing the overall frame + additional passes for each use of `.cornerRadius`. Importantly, these costs don't show up in the Time Profiler, because they affect work done by the CoreAnimation Render Server on your app's behalf. This intensive thrash annihilates performance for a lot of devices. On the iPhone 4, 4S, and 5 / 5C (along with comparable iPads / iPods), expect to see notably degraded performance. On the iPhone 5S and newer, even if you can't see the impact directly, it will reduce headroom so that it takes less to cause a frame drop.
## Performant Corner Rounding Strategies