Fractional scaling

I have a high DPI display on my laptop and I’d like it to scale at 125%. Right now the only options are 100% (kinda small) and 200% (way too big). Any way to enable fractional scaling yet?

Trick way: Open Accessibility setting, switch the Large Text switch to on.
It works like 125% scale.

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Another way is via Tweaks (or gnome-tweaks from the command-line). Select “Fonts” and change the “Scaling Factor” to match your display. In my case, I have a 140 DPI display panel. Take the DPI value of your display and divide by 96; e.g. 140 / 96 = 1.46 rounded to two decimal places. Optionally, adjust in 0.01 increments to preferred setting.

I have the following environment settings so that QT-based applications scale to the display DPI value.

export QT_AUTO_SCREEN_SCALE_FACTOR=0
export QT_ENABLE_HIGHDPI_SCALING=0
export QT_SCALE_FACTOR_ROUNDING_POLICY=PassThrough
export QT_SCALE_FACTOR=1.0
export QT_FONT_DPI=140

Edit: QT 5 determines the DPI automatically. Thus not necessary to set environment variables. Running qtdiag requires libvulkan.so else a lot of errors stating vulkan missing.

$ sudo swupd bundle-add devpkg-Vulkan-Loader
$ qtdiag | grep DPI:
  Physical DPI: 139.937,139.959 Logical DPI: 140,140 Subpixel_None
  Physical DPI: 139.937,139.959 Logical DPI: 140,140 Subpixel_None
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