1833164 - ui.textScaleFactor does not scale the browser chrome text independently of the system and UI scale like font.size.systemfontscale on Linux.

Status: REOPENED

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

Description

[Kestrel]

Attachment: Comparison showing ui.textScaleFactor not scaling UI text

STR:

1. Create pref ui.textScaleFactor = 150 on Nightly 115.0a1 (2023-05-14), Ubuntu 23.04.
2. Compare with font.size.systemfontscale = 150 on Nightly 115.0a1 (2023-05-11).

font.size.systemfontscale scaled only the text and made no exceptions.

ui.textScaleFactor does not scale browser chrome text as it gets overridden by the system setting /org/gnome/desktop/interface/font-name and instead scales the whole UI like layout.css.devPixelsPerPx. It is no longer possible to independently scale the text in the UI with the removal of font.size.systemfontscale.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=8ef61663212db748a7427b0f07fd6b5af28d0fa1&tochange=0b47bd87aa7734f9d1e459c608a0accfd94270ad

Regressed by Bug 1831136.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

There is tho. browser.display.os-zoom-behavior tweaks the behavior of the OS text scale.

Comment 2

[Kestrel]

Attachment: Browser chrome text not being scaled with ui.textScaleFactor

browser.display.os-zoom-behavior = 2 only produces the desired result when used in combination with /org/gnome/desktop/interface/text-scaling-factor. It cannot be overridden or applied directly with ui.textScaleFactor, all it does is make the content scale larger.

Comment 3

[Emilio Cobos Álvarez (:emilio)]

This accounts for the pref, maybe it shouldn't: https://searchfox.org/mozilla-central/rev/eb07633057d66ab25f9db4c5900eeb6913da7579/widget/gtk/nsLookAndFeel.cpp#1106

Comment 4

[Donal Meehan [:dmeehan]]

:emilio any follow-up on this? Could you set the priority/severity?

Comment 5

[Emilio Cobos Álvarez (:emilio)]

So the not accounting for the pref is intentional, see bug 1777902.

This is fairly low priority (we removed a pref that wasn't exposed in the UI). If we want to restore this functionality we could add an extra pref to the system font code to divide only by the native scale rather than accounting for the pref (effectively reverting https://hg.mozilla.org/integration/autoland/rev/68ec3d16cb3f).

I guess with bug 1777902 there isn't a great way of adjusting system font sizes and content font sizes unfortunately.