Thanks for the detailed information. It’s very helpful. KDE + multiple monitors + fractional scale + JavaFX. A perfect storm. In an effort to get certain legacy applications to scale KDE is setting the old “scaling-factor” to the floor of the actual scale. JavaFX is reading that faulty value which is preventing it from computing the correct UI scale on a per-monitor basis. Things go downhill from there. (For the record that’s what KDE in Ubuntu 24 is doing. In Ubuntu 22 it’s setting GDK_SCALE instead.)
The GDK_SCALE and “scaling-factor” settings are obsolete within their respective toolkits and for some time they were never set. KDE resurrected them and now they’re interfering with fractional scaling and multiple monitor support in JavaFX. I’m putting together a PR to de-emphasize them. (Along those lines we should probably deprecate “glass.gtk.uiScale” since it doesn’t work well with multiple monitors. A better approach would be to allow the user to specify a multiplier to be applied to the per-monitor scales that JavaFX computes internally.) > On Nov 22, 2025, at 12:57 PM, Chad Preisler <[email protected]> wrote: > > I'm running on a brand new Infinity Book Pro from Tuxedo Computers. Here is > the system info. > > DISTRIB_ID=Ubuntu > DISTRIB_RELEASE=24.04 > DISTRIB_CODENAME=noble > DISTRIB_DESCRIPTION="TUXEDO OS 24.04.3 LTS" > NAME="TUXEDO OS" > VERSION="24.04.3 LTS" > ID=tuxedo > ID_LIKE="ubuntu debian" > PRETTY_NAME="TUXEDO OS" > VERSION_ID="24.04" > > KDE Plasma Version: 6.4.5 > KDE Frameworks Version: 6.17.0 > Qt Version: 6.8.2 > Kernel: 6.14.0-116036-tuxedo (64-bit) > Graphics: Wayland > > I did some more testing and found that the scaling issues happen in a dual > monitor environment where the scaling factor is different between the two > monitors. Here is my setup. > > Built-in Screen: 2653x1600, 130% > Samsung Odyssey G5 2560x1440, 0% > > When running with two monitors with "Scaled by system" off: > - Things look sharp on the monitor with scaling (Built-in). However, fonts > get pretty blurry on the unscaled monitor (G5). > - If I scale up the unscaled monitor (G5) to 130%, things look sharp. > However, everything is huge on the huge monitor. Not ideal. > - As a side note, Netbeans exhibits the same behavior. It's sharp with tiny > fonts on the scaled monitor and looks terrible on the unscaled. > > Running the app on a single screen (built-in) with "Scaled by system" off, > the fonts are sharp, but they are also very small. > Running the app on a single screen (built-in) with "Scaled by system" on, the > font size is larger (perfect in my opinion) but it's not as sharp. > > The pop-up is probably not an issue. It seems like it always appears in about > the middle of the screen. I don't use a lot of pop-ups, but a quick search > said that is the default behavior. At some point my app was probably off > center when I noticed the behavior. >
