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Revert "remove fix for old chrome bug"

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This reverts commit ecb074862e.
This commit is contained in:
Bruno Windels 2019-03-01 16:08:41 +01:00
parent 60c4c55010
commit 37593c117a
1 changed files with 18 additions and 0 deletions
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18
src/components/structures/ScrollPanel.js
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@ -215,6 +215,24 @@ module.exports = React.createClass({
debuglog("Scroll event: offset now:", sn.scrollTop, debuglog("Scroll event: offset now:", sn.scrollTop,
"_lastSetScroll:", this._lastSetScroll); "_lastSetScroll:", this._lastSetScroll);
// Sometimes we see attempts to write to scrollTop essentially being
// ignored. (Or rather, it is successfully written, but on the next
// scroll event, it's been reset again).
//
// This was observed on Chrome 47, when scrolling using the trackpad in OS
// X Yosemite. Can't reproduce on El Capitan. Our theory is that this is
// due to Chrome not being able to cope with the scroll offset being reset
// while a two-finger drag is in progress.
//
// By way of a workaround, we detect this situation and just keep
// resetting scrollTop until we see the scroll node have the right
// value.
if (this._lastSetScroll !== undefined && sn.scrollTop < this._lastSetScroll-200) {
console.log("Working around vector-im/vector-web#528");
this._restoreSavedScrollState();
return;
}
// If there weren't enough children to fill the viewport, the scroll we // If there weren't enough children to fill the viewport, the scroll we
// got might be different to the scroll we wanted; we don't want to // got might be different to the scroll we wanted; we don't want to
// forget what we wanted, so don't overwrite the saved state unless // forget what we wanted, so don't overwrite the saved state unless