| <!DOCTYPE html> |
| <link rel="help" src="https://drafts.csswg.org/scroll-animations-1/#scroll-timeline-at-rule"> |
| <link rel="help" src="https://drafts.csswg.org/scroll-animations-1/#avoiding-cycles"> |
| <script src="/resources/testharness.js"></script> |
| <script src="/resources/testharnessreport.js"></script> |
| <script src="/web-animations/testcommon.js"></script> |
| <style> |
| #scroller { |
| overflow: scroll; |
| width: 100px; |
| height: 100px; |
| } |
| #contents { |
| height: 200px; |
| } |
| @keyframes expand { |
| from { width: 100px; } |
| to { width: 200px; } |
| } |
| @scroll-timeline timeline { |
| source: selector(#scroller); |
| time-range: 10s; |
| start: 0px; |
| end: 100px; |
| } |
| #element { |
| width: 0px; |
| animation: expand 10s linear; |
| animation-timeline: timeline; |
| } |
| /* Ensure stable expectations if feature is not supported */ |
| @supports not (animation-timeline:foo) { |
| #element { animation-play-state: paused; } |
| } |
| </style> |
| <div id=scroller> |
| <div id=contents></div> |
| </div> |
| <div id=element></div> |
| <script> |
| promise_test(async (t) => { |
| // The scroll timeline is initially inactive until the first frame. |
| assert_equals(getComputedStyle(element).width, '0px'); |
| await waitForNextFrame(); |
| scroller.scrollTop = 50; |
| // Scrolling position should not yet be reflected in the animation, |
| // since the new scroll position has not yet been sampled. |
| assert_equals(getComputedStyle(element).width, '100px'); |
| await waitForNextFrame(); |
| assert_equals(getComputedStyle(element).width, '150px'); |
| }, 'Scroll position is sampled once per frame'); |
| </script> |
