We’re using ProseMirror with Y.js for collaborative editing. In a somewhat extreme case which unfortunately happens often, a remote transaction (one coming from another connected client via Y.js) will override a user’s cursor position after they have clicked. What this looks like in practice is user A will click to change their cursor position while user B edits the document. User A sees their cursor move to the new position under their mouse, but then it bounces back to its previous position. With a lot of concurrent edits, it’s near impossible to move the cursor.
I’ve tracked down when this happens, but I’m unsure if it’s a bug in ProseMirror or if there’s something we can do about it on our end. The sequence of events for user A is as follows:
mousedownevent fires, indicating to the browser to change the selection in the DOM- browser changes the selection in the DOM
- remote transaction from user B comes in, changes the doc
- because the doc has changed, ProseMirror modifies the DOM selection to match the changed state (with the old selection) using
selectionToDOM selectionchangeevent fires, because browser has changed the selectionDOMObserver.onSelectionfires in response to theselectionchangeevent, but the selection in the DOM matches the previous selection (modified in step 4), so nothing happens
I realize it’s quite an edge case to have a transaction change the document between the mousedown trigger and the selectionchange event. It happens reliably with CPU throttling and often enough that it’s noticeable. I’d appreciate guidance on how we can fix it.