When content is inserted/deleted above the current viewport, Firefox will anchor the scroll position so that the visible content doesn't jump around. However, the anchoring seems to stop happening when focus a contenteditable element. Attached HTML page demonstrates this—the view is stable initially, but starts shifting as soon as you focus the content. See also https://bugzilla.mozilla.org/show_bug.cgi?id=1971861 , though that one seems to talk about anchoring *within* editable elements, and the problem here also occurs when content is inserted above the element. Focusing it seems to turn off anchoring altogether.
Bug 1988109 Comment 0 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
When content is inserted/deleted above the current viewport, Firefox will anchor the scroll position so that the visible content doesn't jump around. However, the anchoring seems to stop happening when the user focuses a contenteditable element. Attached HTML page demonstrates this—the view is stable initially, but starts shifting as soon as you focus the content. See also https://bugzilla.mozilla.org/show_bug.cgi?id=1971861 , though that one seems to talk about anchoring *within* editable elements, and the problem here also occurs when content is inserted above the element. Focusing it seems to turn off anchoring altogether.