[arch-general] xrandr with XPS 13" (3840x2160) HiDPI and 30" (2560x1600) LowDPI

[Bruno Pagani]

Le 02/08/2018 à 10:10, Tyler a écrit :

> So,
>
> Using:
>
> Xft.dpi: 220
> GDK_SCALE=2
> GDK_DPI_SCALE=0.5
> QT_AUTO_SCREEN_SCALE_FACTOR=1
>
> xrandr --output DP1 --scale 2x2 --auto --pos 0x0 --primary \
>        --output eDP1 --scale 1x1 --mode 3840x2160 --pos 5120x0
>
> I noticed that Qt5 apps look now fine on my external screen (Low DPI)
> but now super huge on my laptop screen HiDPI.
>
> I think the reason I avoided using QT_AUTO_SCREEN_SCALE_FACTOR and set
> that to 0 was because it was being scaled twice (hence the super
> hugeness on my laptop) as apparently it looks at the DPI in xrdb, but I
> need that for rxvt, i3 etc.
>
> Without doing what you've done and dropping the resolution on my HiDPI
> screen. I found this, using:
>
> GDK_SCALE=2
> GDK_DPI_SCALE=0.5
>
> QT_AUTO_SCREEN_SCALE_FACTOR=0
> QT_SCREEN_SCALE_FACTORS=2
>
> Single Screen Laptop:
>
> xrandr --output eDP1 --scale 1x1 --mode 3840x2160 \
>        --output DP1 --off
>
> All good.
>
> Single Screen External:
>
> xrandr --output eDP1 --off \
>        --output DP1 --scale 2x2 --mode 2560x1600
>
> All good.
>
> Both screens!
>
> xrandr --output eDP1 --scale 1x1 --mode 3840x2160 --pos 5120x0 --primary \
>        --output DP1 --scale 2x2 --mode 2560x1600 --pos 0x0
>
> Small fonts on external screen with Qt5.
>
> xrandr --output eDP1 --scale 1x1 --mode 3840x2160 --pos 5120x0 \
>        --output DP1 --scale 2x2 --mode 2560x1600 --pos 0x0 --primary
>
> Small fonts on laptop using Qt5. So it seems tied to Primary switch as
> to which screen it scales for. Fortunately when using dual monitors I
> basically never use virtualbox, wireshark or nvim-qt on the laptop screen.

Ah, small fonts is something different:
https://bugreports.qt.io/browse/QTBUG-67928