Icons rendering in plasmoid has lower quality than the tray application

[mrpink17]

Relevant components

• Standalone tray application (based on Qt Widgets)
• Plasmoid/applet for Plasma desktop
• Dolphin integration
• Command line tool (syncthingctl)
• Integrated Syncthing instance (libsyncthing)
• Backend libraries

Environment and versions

• gcc 14.2.1+r134+gab884fffe3fc-1
• glibc 2.40+r16+gaa533d58ff-2
• syncthingtray-qt6 1.6.2-1
• qt6-base 6.7.2-2
• c++utilities 5.26.1-1
• qtutilities-qt6 6.14.3-1
• Operating System: Arch Linux
• KDE Plasma Version: 6.1.5
• KDE Frameworks Version: 6.6.0
• Qt Version: 6.7.2
• Kernel Version: 6.10.10-arch1-1 (64-bit)
• Graphics Platform: Wayland

Bug description
The rendering of some icons in plasmoid is not as good as in tray application

Plasmoid

Tray application

[Martchus]

Looks like the icon rendering is broken in the Plasmoid. For me the icon rendering generally¹ works within the Plasmoid as well. Does it work under X11?

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¹ Today I noticed that Plasma falls back to software rendering on my Arch system when using Wayland. With this the entire shell looks quite broken when it comes to icons. Switching to X11 helped but I'm wondering what's wrong with Plasma on Wayland since the last update. The issue I am experiencing is definitely not specific to this Plasmoid but means I can currently not develop/test under KDE/Wayland. And under KDE/X11 I cannot reproduce any rendering issues with the Plasmoid.

[mrpink17]

No, Wayland and X11 look the same

[Martchus]

Then probably related to the way this renders ForkAwesome icons considering only these icons are affected. It looks like you enabled to prefer system icons instead of ForkAwesome icons. Maybe that is not working with the Plasmoid. I haven't tested this config for ages so it might be broken.

[Martchus]

Looks like the Wayland-related issue I mentioned is actually more NVIDIA-related and tracked on https://gitlab.archlinux.org/archlinux/packaging/packages/linux/-/issues/80.

I can reproduce the issue you've mentioned when enabling the setting to prefer system icons over ForkAwesome icons. So as a workaround I suggest you disable this setting. You'll need to restart plasmashell for this to have an effect.

[Martchus]

I have no idea why the icon rendering doesn't work in this case. I tried to play around with the rendering code but it looks like it might be a Qt bug.

Do you know since when this issue is occurring? Maybe this is even a regression of Qt because I vaguely remember that this worked at some point. (Since I don't use the prefer system icons setting I can't really tell myself.)

[mrpink17]

I can confirm it used to work, but it was many months ago. I feel it happened after upgrading the synchthingtray package, not a Qt upgrade, but I'm not 100% sure

[Martchus]

The relevant code on my side is actually this line in qtforkawesome: Martchus/qtforkawesome@v0.1.0...v0.2.1#diff-bbdda2a0a28454037de0dc03c0077fd4b526a8b0027652e04e8d3e88c70ad8ecR151

But it hasn't changed for quite a while in it is merely using QIcon::pixmap().