Affected versions

• 71.0b9 (20191111170815)
• 72.0a1 (20191111215252)

Affected platforms

• Ubuntu 18.04

Prerequisites:

• Ensure that in about:support at Graphics section “Compositing” has the “WebRender” attribute, if not set gfx.webrender.all to true.

Steps to reproduce

1. Open Firefox and go to Customize Menu.
2. Drag the “History” item and observe the rest of the items.

Expected result

• The rest of the items remains the same.

Actual result

• The text is moved in random directions for the rest of the items.

Regression range

• Will search for one ASAP.

Additional Notes

• Attached a screen recording with the issue.
• The issue is reproducible while having the Web Render disabled but it’s not so visible and it's different.
• I can’t reproduce the same issue on 70.0.1 (20191030021342), because the issue is different: after dragging a random item the icons and random text are moving too.
• Another thing is that the text under the icons is moving only after the dragged icon as seen in the recording (e.g if you drag the 4’th item the text from the first 3 items is not moved).

Andrew, this looks like a weird snapping issue. Something must be getting rendered directly during the drag phase, causing the text to snap differently until after it's dropped again?

I can reproduce on the latest nightly.

Webrender+Ubuntu so this is a small percentage of our Linux population that may be affected and are nearing the end of the beta cycle. Wontfix 71.

I have found a regression for this issue using the STR provided in the discription, here is the pushlog: https://hg.mozilla.org/mozilla-central/pushloghtml?changeset=caf55914ccddba34d462a1206530d7868b6c4992. As a side note to this issue is that even on the "good builds" there is a slight move with the text.

This was fixed for me as part of bug 1555376. It makes sense it would have an impact on glyph positioning (that is what it was in part about). Please reopen if you continue to experience it on current nightlies.