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use relative scrolling to compensate when changing height

pull/21833/head
Bruno Windels 2020-03-03 15:42:22 +01:00 committed by J. Ryan Stinnett
parent aedd44addc
commit 91aa8d4a3a
1 changed files with 6 additions and 8 deletions
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14
src/components/structures/ScrollPanel.js
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@ -705,17 +705,15 @@ export default createReactClass({
// the currently filled piece of the timeline
if (trackedNode) {
const oldTop = trackedNode.offsetTop;
// changing the height might change the scrollTop
// if the new height is smaller than the scrollTop.
// We calculate the diff that needs to be applied
// ourselves, so be sure to measure the
// scrollTop before changing the height.
const preexistingScrollTop = sn.scrollTop;
itemlist.style.height = `${newHeight}px`;
const newTop = trackedNode.offsetTop;
const topDiff = newTop - oldTop;
sn.scrollTop = preexistingScrollTop + topDiff;
debuglog("updateHeight to", {newHeight, topDiff, preexistingScrollTop});
// important to scroll by a relative amount as
// reading scrollTop and then setting it might
// yield out of date values and cause a jump
// when setting it
sn.scrollBy(0, topDiff);
debuglog("updateHeight to", {newHeight, topDiff});
}
}
},