linphone: UI scaling issue

[Nivalux]

Nixpkgs version

• Stable (25.11)

Describe the bug

On my PC I often have the issue, that the linphone UI is way to small scaled (the text and all ui elements really).
I am currently using the AppImage version (#487595) and also tested it in the updated PR for the linphone package (#487626).

When starting the binary from the linphone PR, it uses wayland and also is too small scaled:

2026-02-06 15:31:19:564 [app] MESSAGE [App]: Display server : wayland
2026-02-06 15:31:19:564 [app] MESSAGE Starting application Linphone (bin: linphone). Version:6.1.0 Os:nixos/25.11 Qt:6.10.1

If I use the linphone-bin via the AppImage, then it looks like it uses the xwayland version:

2026-02-06 15:26:47:255 [app] MESSAGE [App]: Display server : xcb
2026-02-06 15:26:47:255 [app] MESSAGE Starting application Linphone (bin: linphone). Version:6.1.0 Os:nixos/25.11 Qt:6.10.0

In the AppImage version I added export QT_SCALE_FACTOR=1 to the profile and with that the scale issue seems solved. Using the same env variable does not seem to do anything for the version build in this PR.

Linphone is the only Qt app that I'm using that has this issue. Not really sure why.

Steps to reproduce

Just starting linphone on niri.
I have 3 outputs (monitors), all with Scale set to 1.
One monitor I have is a tiny one, with a resolution of 1024x600.

Expected behaviour

The UI being scaled correctly

Screenshots

Here a screenshot snipped of what I mean with it being to small scaled:

Relevant log output

Additional context

No response

System metadata

• system: "x86_64-linux"
• host os: Linux 6.18.8, NixOS, 25.11 (Xantusia), 25.11.20260203.e576e3c
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.32.4
• nixpkgs: /nix/store/kgp2lkqawayipws2p64flyp06sgzzf0r-source

Notify maintainers

@jluttine @Naxdy

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[Naxdy]

I cannot reproduce on nixos-unstable with my fork of niri, text looks scaled correctly to me:

This may be an environment / Qt thing that's going on. Other than niri, I have the entire KDE desktop suite installed (services.desktopManager.plasma6.enable = true;), and I'm running my session with:

environment.sessionVariables = {
  KDE_FULL_SESSION = "true";
  KDE_SESSION_VERSION = "6";
};

Without these env vars set, I used to have font scaling issues in Ardour. Perhaps this could be related?

[Nivalux]

That does not seem to fix it.
Interestingly enough it is inconsistent.
I just now also tried the the linphone 5.x from the nixpkgs and it was scaled correctly.
Starting the PR version via nix run github:NixOS/nixpkgs/pull/487626/head#linphone or nix-review were both scaled wrong.

[Nivalux]

This works to scale it up:
QT_SCALE_FACTOR=2 nix run github:NixOS/nixpkgs/pull/487626/head#linphone

via DPI it works as well:
QT_WAYLAND_FORCE_DPI=192 nix run github:NixOS/nixpkgs/pull/487626/head#linphone

This is how it looks with scale 2.5

[Nivalux]

I feel like the ui looks a little bit blurry, compared to your image. The text is not as sharp.

[Nivalux]

Which platform did you use for your screenshot @Naxdy ?

If I launch it with QT_QPA_PLATFORM=xcb nix run github:NixOS/nixpkgs/pull/487626/head#linphone, then it is scaled correctly.

What does it say in log, when starting it?
2026-02-06 17:39:03:954 [app] MESSAGE [App]: Display server : xcb