1818229 - [Partial scale/KDE] Firefox UI elements seem too big on KDE Display scaling

Status: RESOLVED DUPLICATE of bug 1211547

(Core :: Widget: Gtk, defect, P3)

Description

[Lyubomir [:mystiquewolf]]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/110.0

Steps to reproduce:

Recently switched to Fedora and at first i tried Gnome for a day, before switching to KDE.

Actual results:

On Gnome Firefox looks okay while on KDE it has its window elements bigger than usual.
Additionally i've noticed that changing layout.css.devPixelsPerPx from the default -1 to 1.75 fixes this.

Comment 1

[Lyubomir [:mystiquewolf]]

Attachment: firefox with devpixes 1.75.png

Comment 2

[Lyubomir [:mystiquewolf]]

Attachment: firefox with devpixes -1.png

Comment 3

[Lyubomir [:mystiquewolf]]

I use KDE display scaling 125%.

Comment 4

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

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Gtk' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 5

[Emilio Cobos Álvarez (:emilio)]

With -1, what's your window.devicePixelRatio? Also, can you attach about:support? Are you using Wayland or X11?

Comment 6

[Lyubomir [:mystiquewolf]]

Attachment: about:support

With -1 it is 2.5 and with 1.75 it is 2.2222222222222223. Using Wayland.

Comment 7

[Lyubomir [:mystiquewolf]]

Let's wait until 5.27.1 to see if it'll fix things. Meanwhile i can live with this hack..

Comment 8

[Emilio Cobos Álvarez (:emilio)]

What is your global scale in the Plasma settings?

Comment 9

[Lyubomir [:mystiquewolf]]

125%. I took a quick glance over the KDE bugs and they got a real mess, even some saying 5.27.1 is worse ¯_(ツ)_/¯

Comment 10

[Tobias Schula]

Attachment: On the left, Firefox at 175 % desktop scaling and 90 % text scaling, on the right, Edge at 175 % desktop scaling

I can confirm this behaviour. On plasma desktop 5.27 under X11, when I set global scaling to 175 %, firefox will scale its interface and the content to 200 %. Edge and other chromium based browsers give me the correct scaling. The settings 100 %, 125 % and 150 % work as expected. As a workaround, if I set the global text scaling in firefox to 90 %, everything looks almost correct. Of course, 1.75 / 2 = 0.87, so it's almost 90 %.

Comment 11

[Lyubomir [:mystiquewolf]]

(In reply to Tobias Schula from comment #10)

I can confirm this behaviour. On plasma desktop 5.27 under X11...

What's your distro? I've switched to openSUSE TW and with current Plasma 5.27.7, KDE Frameworks 5.108.0 and Qt 5.15.10 it's good with -1 as a setting.

Comment 12

[Tobias Schula]

TW, up to date. I saw in your earlier comment, you are using 125 % global scaling? Please try the other scaling options, too. What I found out so far, Firefox and Seamonkey (Thunderbird to some extent, the interface font is the correct size, the other elements, including the mail body are too big) work fine with 100 %, 125 % and 150 %. 175 % and 200 % display the same. Finer scaling factors, offered by plasma-desktop are rounded down to the next quarter of an integer, e.g. 117 % to 100 %, 168 % to 150 %.

Everything >= 175 % will get scaled to 200 %.

It's an annoyance on quite common 27" 4k screens. For 27" 5k would offer proper 200 % scaling, but there are no manufacturers outside Apple and LG, and these screens have limited availability and high prices.

Comment 13

[Tobias Schula]

With the fix of bug 1211547, this bug here is also fixed for me. Scaling works now flawlessly in KDE Plasma, be it X11 or Wayland.