User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

• Open the sidebar
• Go to https://oui.sncf
• Click on the menu on top left
• Move the cursor over menu items or links in the top bar

Actual results:

Transparent black boxes are displayed

Expected results:

No black boxes should be displayed

Mozregression :
https://phabricator.services.mozilla.com/D45287
app_name: firefox
build_date: 2019-09-14
build_file: C:\Users\Foo.mozilla\mozregression\persist\2019-09-14--mozilla-central--firefox-71.0a1.en-US.win64.zip
build_type: nightly
build_url: https://archive.mozilla.org/pub/firefox/nightly/2019/09/2019-09-14-21-24-52-mozilla-central/firefox-71.0a1.en-US.win64.zip
changeset: 6cbf1430a66ef5aa5f066ed77677f47ea44fc0e1
repo_name: mozilla-central
repo_url: https://hg.mozilla.org/mozilla-central

I can't reproduce this on Linux with current m-c, but it might be dependent on GPU / drivers / resolution etc.

Could you post the output of your about:support and also the resolution you're running with?

The window on the screenshot is at 1286x970 and my screen at 1920x1080.
It's on a Win 10 + NVIDIA GeForce GTX 1060 6GB.
I have the same issue with a Win 10 + Intel GPU.

Thanks for the info! I can reproduce this on Windows, but not on Linux.

It's unlikely to be a driver bug if it occurs with both the nVidia and Intel GPUs. It's possible the display list / theme on Windows makes the display list different enough from Linux to expose this bug. I'll investigate this week.

This fixes a case where the is_same_content field was no longer
being reset to true before dependency calculation could occur.

In some cases, this could result in a tile being updated, but
the dirty rect being empty, which meant all primitives in that
tile would fail the visibility culling test.

I uploaded a patch that fixes this problem.

Pending try runs:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=a2172f67c4a1d46d41f43eb6bb0d146eef23c78e
https://treeherder.mozilla.org/#/jobs?repo=try&revision=d3739e1319759eb8e7f462ee64b1fd330f856b0e

I think these have build artifacts available if you want to download them to confirm that it fixes it for you too.

Otherwise, this should hopefully get reviewed soon and get into a nightly build shortly after that.

https://hg.mozilla.org/mozilla-central/rev/43d18e14f370

Hello!
Reproduced the issues with Firefox 71.0a1 (20190916155843) on Windows 10x64.
The issue is verified fixed with Firefox 71.0b9 (20191111170815) on Windows 10x64. No black boxes are displayed while following STR from comment 0 with Webrender.