Silky Smooth (Part 1)

In this presentation I outline some common causes of poor scroll performance in iOS applications and some useful tips on measuring and comparing performance.

Transcript

1. Silky Smooth Tricks for measuring and improving scroll performance Part 1
2. Measure & Analyse
3. 2 common symptoms
4. 1. Low, but consistent frame rates
5. can be caused by... •excessive compositing •layer blending •pixel misalignment
6. Blended Layers
7. Misaligned Images
8. Offscreen Rendering
9. 2. Stuttering frame rate when new cells come on screen
10. can be caused by... •expensive cell creation •complex cell layout •loading/scaling images
11. When you try and fix these things...
12. ...change one thing at a time
13. ...and compare Apples with Apples
14. I’ll let you in on a little secret...
15. UIAutomation isn’t just for testing
18. Close your eyes!
19. var target = UIATarget.localTarget(); target.delay(10); target.flickFromTo({x:160, y:460},{x:160, y:160}); target.delay(4); target.flickFromTo({x:160, y:460},{x:160, y:160}); target.delay(4); target.flickFromTo({x:160, y:160},{x:160, y:460}); target.delay(4); target.flickFromTo({x:160, y:460},{x:160, y:160}); target.delay(4); target.flickFromTo({x:160, y:160},{x:160, y:460}); target.delay(4); target.flickFromTo({x:160, y:460},{x:160, y:160}); target.delay(4); target.flickFromTo({x:160, y:160},{x:160, y:460}); target.delay(4); target.flickFromTo({x:160, y:460},{x:160, y:160}); target.delay(4);
20. Test on multiple devices
21. Some are CPU constrained iPhone 3GS
22. iPhone 4 Some are GPU constrained
23. Some are CPU & GPU constrained 4th Gen iPod Touch
24. 2% 78% 20% iPhone 4 iPhone 4s & 5 iPhone 3 & 3GS Choose a minimum hardware spec to optimise for based on your userbase:
25. We consider iPhone 4 our low-end target
26. Remember
27. 1. Don't prematurely optimise!
28. 2. Each app is different.
29. Part 2 will look at optimisations and their effect.
30. Homework
31. 2011 •121 “Understanding UIKit Rendering” •129 “Practical Drawing for iOS Developers” 2012 •240 “Polishing Your Interface Rotations” WWDC videos
32. References Designing for iOS: Graphics & Performance http://goo.gl/xDFtF Tips for improving performance of your iOS application http://goo.gl/X5q4F Customizing UITableViewCells: a better way. http://goo.gl/FNymk
33. References Mac QuartzGL (2D drawing on the graphics card) performance http://goo.gl/ks4Mb iOS vs. Android ICS: Hardware Accelerated Graphics Pipelines http://goo.gl/4zMb9 View Programming Guide for iOS: View and Window Architecture http://goo.gl/zJifp
34. References Simple Strategies for Smooth Animation on the iPhone http://goo.gl/4NwGR
35. Tools ImageOptim http://imageoptim.com/ ImageOptim optimizes images — so they take up less disk space and load faster — by finding best compression parameters and by removing unnecessary comments and color profiles. It handles PNG, JPEG and GIF animations.
36. sean@ittybittyapps.com seanwoodhouse