Last active
October 16, 2018 20:49
-
-
Save jsantell/23edd6d5ec3e2a1f76c60cfe0057e661 to your computer and use it in GitHub Desktop.
Why is there (usually) two rAF callbacks before the next frame? This happens when triggering a transition from a timer (setTimeout) and does not occur when triggering from a rAF
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| <html><head> | |
| <style> | |
| div { | |
| height: 100px; | |
| width: 100px; | |
| background-color: #35baf6; | |
| transition: width 0.5s; | |
| } | |
| </style> | |
| </head><body> | |
| <div id="test"></div> | |
| <script> | |
| const test = document.querySelector('#test'); | |
| let startTransition = 0; | |
| setTimeout(() => { | |
| startTransition = performance.now(); | |
| test.style.width = '200px'; | |
| requestAnimationFrame(frame); | |
| }, 100); | |
| function frame(t) { | |
| performance.mark('raf-start'); | |
| const style = getComputedStyle(test).width; | |
| console.timeStamp(`width: ${style}`); | |
| console.log(`width: ${style}`); | |
| if ((t - startTransition) < 750) { | |
| requestAnimationFrame(frame); | |
| } | |
| performance.mark('raf-end'); | |
| performance.measure('rAF', 'raf-start', 'raf-end'); | |
| } | |
| </script> | |
| </body> | |
| </html> |
I was wrong there, you'll see it twice times :-/
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
@jsantell OK I'm on the same page now... comment out line 20 (the rAF) and you still get a delay between when that callback executes and when the actual frame starts, ya?
1000 / 60fps = 16.6ms (the rAF target framerate)
100ms (your setTimeout) is usually right after a frame ended, and a new one started. Change your setTimeout to 99 or 98, I think you'll see the artifact disappear.