200869 2019-08-18 09:46:23 -0700 Multiple scroll events during one requestAnimationFrame cycle 2021-10-15 16:30:16 -0700 1 1 1 Unclassified WebKit Scrolling Safari Technology Preview Unspecified macOS 10.14 NEW InRadar P2 Major --- 202843 1 alex webkit-unassigned alex rniwa sabouhallawa simon.fraser webkit-bug-importer oldest_to_newest 1562591 0 alex 2019-08-18 09:46:23 -0700 Safari dispatches multiple scroll events during one requestAnimationFrame "cycle". But the scroll event should be limited to the rAF. Steps to reproduce: 1. open page: Demo: https://jsbin.com/joculitacu/edit?console,output 2. Scroll the page What you see: You see multiple outputs `bug.` inside of the console. What I expect: No output. To me it is not entirely clear wether this is a bug with the scroll event or the rAF. 1562602 1 webkit-bug-importer 2019-08-18 11:36:32 -0700 <rdar://problem/54446269> 1562684 2 alex 2019-08-19 01:30:34 -0700 Here you find an updated testcase: https://jsbin.com/wiyehev/edit?console,output The old one said "success." although it is a bug. Having multiple scroll events in one render cycle can lead to performance problems and layout thrashing. Additionally it is not standard complaint. This bug only occurs in Safari not in Chrome, FF or Edge. 1805116 3 simon.fraser 2021-10-15 16:30:05 -0700 I suspect this only happens in cross-origin iframes where rAF is throttled to 30fps. Does it happen in the main frame? Attaching your testcase as an HTML file. 1805117 4 441451 simon.fraser 2021-10-15 16:30:16 -0700 Created attachment 441451 Test 441451 2021-10-15 16:30:16 -0700 2021-10-15 16:30:16 -0700 Test scroll-events-per-raf.html text/html 5973 simon.fraser PCFET0NUWVBFIGh0bWw+CjxodG1sPgo8aGVhZD4KICAgIDxtZXRhIG5hbWU9InZpZXdwb3J0IiBj b250ZW50PSJ3aWR0aD1kZXZpY2Utd2lkdGgsIGluaXRpYWwtc2NhbGU9MSwgc2hyaW5rLXRvLWZp dD1ubyI+CiAgICA8c2NyaXB0PgogICAgICAgIHZhciBzY2hlZHVsZWRBbmltYXRpb25GcmFtZTsK ICAgICAgICB2YXIgcmVhZEFuZFVwZGF0ZVBhZ2UgPSBmdW5jdGlvbigpIHsKICAgICAgICAJc2No ZWR1bGVkQW5pbWF0aW9uRnJhbWUgPSBmYWxzZTsKICAgICAgICAgICAgICAgLy8gZG8gc29tZXRo aW5nCiAgICAgICAgfTsKCiAgICAgICAgd2luZG93LmFkZEV2ZW50TGlzdGVuZXIoJ3Njcm9sbCcs IGZ1bmN0aW9uKCkgewogICAgICAgICAgLy8gUHJldmVudCBtdWx0aXBsZSByQUYgY2FsbGJhY2tz LgogICAgICAgICAgaWYgKHNjaGVkdWxlZEFuaW1hdGlvbkZyYW1lKSB7CiAgICAgICAgICAgIGNv bnNvbGUubG9nKCdidWcuJykKICAgICAgICAgICAgcmV0dXJuOwogICAgICAgICAgfQoKICAgICAg 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