Affected versions

• 100.0a1
• 99.0

Affected platforms

• Windows 10
• macOS 12
• Ubuntu 20.04

Steps to reproduce

1. Open any website
2. Go to Connection security (icon lock) - More information - Media tab
3. Select (CTRL +A) the content inside the Address section
4. Scroll down the panel

Expected result

• The panel can be scrolled down without any issue.

Actual result:

• The scrolling action looks like it gets stuck, the scroll-thumb won't go down to the edge of the scrollbar, but the bottom content is releaveled entirely.

Regression range

• Last good revision: 3c08edf74d039af79f9daad8ff5b57ffb64fdab6 (2019-12-03)
• First bad revision: 32f84899fc000d95337a25c14a27470d0c52e3ee (2019-12-04)
• Pushlog:
  https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=3c08edf74d039af79f9daad8ff5b57ffb64fdab6&tochange=32f84899fc000d95337a25c14a27470d0c52e3ee

Other notes

• Panel resizing fixes the issue.

Looks like a bug in the xul tree code that when it gets resized it doesn't recalculate it's scrollbars.

:Anca, since this bug is a regression, could you fill (if possible) the regressed_by field?
For more information, please visit auto_nag documentation.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=dfa7714e0543412adf6ee9e065069f9fe5d1b025&tochange=2d39de2be1ae9fa8063a19b459d8712fa90bc851

Set release status flags based on info from the regressing bug 1593060

:dholbert, since you are the author of the regressor, bug 1593060, could you take a look?
For more information, please visit auto_nag documentation.

(In reply to Release mgmt bot [:suhaib / :marco/ :calixte] from comment #5)

:dholbert, since you are the author of the regressor, bug 1593060, could you take a look?

I'll try, but it doesn't seem super high-severity (no content is actually unreachable), so I probably won't get to it right away. Note that the regressing bug is in a kinda fiddly & un-tested area of code (at the border between CSS Grid and XUL code), so strange behaviors don't surprise me super-much, and I would be somewhat cautious when making additional adjustments to fix this.

I can reproduce, though I initially overlooked the "Select-all" crucial portion of the STR.

A few notes on the STR scenario: if you explicitly click and drag the scroll thumb itself (as a user might do after hitting this bug), then you can indeed drag it all the way to the bottom of the scroll-track (with the last chunk of scrolling not actually revealing any additional entries). It's only other forms of scrolling (like mousewheel-scrolling) that triggers this issue.

Set release status flags based on info from the regressing bug 1593060

FWIW this happens if you just do a regular multi-select, too (e.g. ctrl+click several entries).