1736174 - Extension popovers are very slow when fractional scaling is enabled

Status: UNCONFIRMED

(Core :: Graphics, defect)

Description

[Oliver Jensen]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:93.0) Gecko/20100101 Firefox/93.0

Steps to reproduce:

1. Fresh install of Firefox on fresh install of Arch Linux with Mate

2. Install extensions with popover UIs (e.g. BitWarden, Ublock Origin, etc)

3. Click BitWarden extension, observe popover is fast and responsive

4. Open a terminal and enable fractional scaling via:
   $ xrandr --output eDP-1 --scale 1.5x1.5

5. Return to Firefox and click BitWarden extension, observe popover renders one frame every 3-4 seconds, making typing your password / interacting with it difficult

6. Return to the terminal and disable fractional scaling via:
   $ xrandr --output eDP-1 --scale 1x1

7. Return to Firefox and click the BitWarden extension, observe popover is fast and responsive again

Actual results:

Extension popovers are extremely slow when fractional scaling is enabled. These are the only elements I can find which behave this way when fractional scaling is enabled -- everything else continues to be fast and snappy.

Expected results:

Extension popovers should not be extremely slow when fractional scaling is enabled.

Comment 1

[Oliver Jensen]

This was previously reported by someone else to gnome-shell (https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4518) because the reporter initially noticed this when using Gnome's fractional scaling. However, as I experience the same issue in Mate using xrandr directly for fractional scaling, I believe this is a Firefox bug.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'WebExtensions::Untriaged' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 3

[Alex Cornestean]

Hello,

I did not manage to reproduce the issue on the latest Release (93.0/20210927210923) under Ubuntu 16.04 LTS.

Setting scaling to 1.5x1.5 as you mentioned did not have any effect on the speed of the pop-ups of the add-ons I installed (Bitwarden and uBlock Origin). The pop-up comes out quick, as before, clicking on the available options will direct to the corresponding menus without delay and, in particular, for Bitwarden, typing characters in the login field of the add-on pop-up is snappy and no delay is perceived. Everything behaved as before enabling scaling.

Comment 4

[Tomislav Jovanovic :zombie]

This probably has something to do with layers or webrender or drivers, almost certainly not an extensions bug.

Comment 5

[Oliver Jensen]

Alex,

Thanks for trying to reproduce. I've been trying to play around with what triggers this.

In case it is helpful, I have a high-DPI display, so my typical setup is to have Mate scale everything up to 200% in the display settings, then have xrandr scale things back down again. I've also found that there seem to be specific thresholds at play.

With Display settings scaling up to 200%, I find the bug is triggered only when xrandr scales down > 1.4. That is:

$ xrandr --output eDP-1 --scale 1.40x1.40 # extension overlays are snappy
$ xrandr --output eDP-1 --scale 1.41x1.41 # extension overlays are slow

With Display settings scaling at 100%, I find the bug is triggered similarly but at a different limit:

$ xrandr --output eDP-1 --scale 1.20x1.20 # extension overlays are snappy
$ xrandr --output eDP-1 --scale 1.21x1.21 # extension overlays are slow

Could you please try experimenting with some other scaling factors to see if perhaps your thresholds are different from mine?

Comment 6

[Alex Cornestean]

Hello ojensen5115,

I tried different combinations with both Display settings scaling set to 100% and 200% and fractional scaling ranging from 0.5x0.5 up to 4.0x4.0. About 20 different scaling values. But could not trigger the issue.

The display I have available appears to have 84 DPI if this matters.

I'll keep trying different combinations and maybe hit the right one.

Comment 7

[Oliver Jensen]

After some more experimenting, I found that after installing hardware video acceleration drivers, the problem no longer seems to manifest (at least for me).