Ode to the Corner Radius API: A look at modern iOS design
summary
Explains that since iOS 11 Core Animation and Metal now handle rounded corners on the GPU so corner radius can be practically free when done right; shows two button implementations (pre-rasterized bitmap versus live clipping) and measures memory and off‑screen render costs, finds rasterizing images is costly and masksToBounds causes off‑screen passes, advises applying cornerRadius to the background layer (not the container) and only enabling masksToBounds when needed, and recommends the new continuous corner curve API for smoother shapes.
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chapters (10)
- 0:00Introduction to corner radius
- 3:10Evolution of rounded corners
- 5:39Early corner radius attempts
- 8:17Core Animation Lab insights
- 10:23Optimal corner radius implementation
- 12:26App Store’s corner radius tricks
- 14:12UIButton corner radius pitfalls
- 15:57Lessons from open source project
- 16:20Best practices and mindset shifts
- 19:15Modern corner curve API
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