editor lines out of sync in merge view

I believe the MergeView editor has a bug related to virtualization. Based on how the content is virtualized, multiple mergeSpacers can start pushing the content on one document and make the 2 documents out of sync.

I’ve made the following recordings using the demo website you’ve put up for @codemirror/merge.

It’s a bit hard to tell what is going on in the video above. After modifying the background color of cm-mergeSpacer you can start seeing that the content jumps around whenever a spacer is introduced or removed.

I’ve put together a Gist with 2 documents for repro. Hope this helps!

Does the same issue occur in the current version of the merge view code? (That demo hadn’t been updated since the initial announcement. I’ve deleted it to avoid future confusion.)

I just recreated the repro in the official CM6 playground and the issue occurs there too:

The generated share link is too long to paste in the browser (out of scope), but you can use this playground configured with MergeView and get the text documents from my Gist.

It’s easiest to repro when one of the documents has multiple mergeSpacers which are big in height.

Thanks, I managed to reproduce it now (it only showed up for me when I scrolled back up from the bottom). This patch overhauls how spacers are handled, and seems to help.

Just bumped to 6.1.3 and works like a charm! Thank you so much for the swift responses and implementing the patch so quickly :raised_hands: