Public bug reported:
I have a system that was upgraded from 16.04 -> 16.10 -> 17.04 -> 17.10. So now
running on 17.10.
I upgraded to 17.10 because I hoped for better HiDPI scaling support.
My laptop is Dell Precision 5520 with 4k 3840x2160 15" screen, with
Intel graphics (it has nvidia too, but disabled).
Additionally, I have an external Dell U3011 2560x1600 30" display
connected to it.
When I logged into graphical session (selected the default Ubuntu session), I
confirmed wayland is running by checking loginctl:
loginctl show-session 2 -p Type
Type=wayland
With external display connected, display settings show that the high DPI
laptop screen got scaling set automatically to 200%, and the external
low DPI display got scaling set to 100%. So far, looks good - automatic
detection of hi dpi screens did the right thing.
The built-in Ubuntu applications like terminal, file browser or setting
window work fine. When I start e.g. the terminal, it appears first on
the laptop screen - it is scaled properly, then I drag it to the
external screen and once I release the mouse button, the window shrinks
to 2x smaller, so it adapts to lower DPI of that screen. Everything is
sharp and crispy and the sizes are ok.
Problems:
* Firefox, Chrome, Chromium, Intellij IDEA all do not scale correctly on
the external screen. Everything is twice too big. When started, they
appear first on the built-in hiDPI screen with the correct size, but
after dragging to the external screen, they remain scaled by 200%.
* When I enabled dock to be displayed on all screens, the dock icons are
twice too big on the external screen. So, 200% scaling seems to be
applied to the dock on both screens.
* Sometimes the mouse pointer is twice as large. Sometimes it is twice
too small. I didn't figure out yet when it happens. Sometimes it is only
twice too large when over the desktop background, but ok when over an
application window. This is a very minor issue, but looks funny.
-----
What I tried so far:
Resetting dconf to factory settings with:
dconf reset -f /org/gnome/
did not help.
Then I tried enabling experimental fractional scaling, with 200% / 100%
scales set (I do not really need fractional scaling, but I hoped it
changes how things are rendered and where scaling is applied). This
actually helped for both scaling issues - including the dock scaling
problem. Windows get even properly scaled in the *middle of dragging*
between displays. Everything is the right size with this setting on.
Really cool.
Unfortunately now the image on the builtin display for the non-native
applications like Firefox, Chrome or Idea is severely blurred. And it is
blurred even if I disconnect the external display. It looks as if it
rendered these apps at half the resolution (I noticed xrandr shows
1920x1080 for that screen, but ubuntu display settings window shows
3840x2160) and then upscaled twice the bitmap to reach higher 4k real
screen resolution. The blur does not happen for native Ubuntu apps like
terminal.
Unfortunately the blurring effect is much stronger than if I just
manually force the builtin screen to 1920x1080. In this case everything
is a bit lower resolution, but still sharp enough.
Therefore so far, Ubuntu 17.10 and Wayland did not improve hi dpi
support for me at all, despite some rumours it should have. I still have
to switch to lower resolution on the builtin display to get everything
crisp and the right size.
** Affects: gnome-control-center (Ubuntu)
Importance: Undecided
Status: New
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You received this bug notification because you are a member of Ubuntu
Desktop Bugs, which is subscribed to gnome-control-center in Ubuntu.
https://bugs.launchpad.net/bugs/1735986
Title:
Ubuntu 17.10 on Wayland doesn't scale some applications properly on
external low DPI display
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