Run plasmashell with "PLASMA_USE_QT_SCALING=1" : Wait until 18.10; re-test
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Description

Right now, Plasma doesn't respect the system scale factor on X, only Wayland. However there is actually support; you just need to run plasmashell with PLASMA_USE_QT_SCALING=1.

There were two major blockers that have both been resolved upstream of us:

If we ship with Frameworks 5.45 and take the trivial, two-line patch from https://codereview.qt-project.org/#/c/222827/ into whatever Qt version we ship with, then we can turn on Qt scaling in plasmashell and fix a significant amount of bugs with running Plasma with a HiDPI screen.

To turn this on, we would patch /etc/xdg/autostart/org.kde.plasmashell.desktop to replace plasmashell with PLASMA_USE_QT_SCALING=1 plasmashell.

ngraham created this task.Mar 10 2018, 11:59 PM
ngraham updated the task description. (Show Details)Mar 11 2018, 12:02 AM

Yes yes yes! I had no idea about this variable. It fixes a bunch of icon scaling and spacing issues. Lots of people will still be using Xorg for a while due to missing features in Wayland (such as myself). Enabling this for them will go a long way to making Plasma look good on newer computers. The only thing I noticed that happened to me, was my panel reset it's width (it's on the left of my screen).

ngraham added a comment.EditedMar 11 2018, 3:19 PM

Andrew, would you mind testing at multiple scale factors (including non-integer ones) and see if you can find any glaring regressions? I fear that at non-integer scale factors, we'll run into blurry pixellated text all over the place due to PlasmaComponenets Labels not using the right Qt Text rendering (see https://bugs.kde.org/show_bug.cgi?id=391691).

Even so, I wonder if there's a way to only allow this to be on with integer scale factors, which would seem to work around that issue.

ngraham updated the task description. (Show Details)Mar 11 2018, 3:20 PM

Just tested, and text does indeed look awful when a non-integer scale factor is used and PLASMA_USE_QT_SCALING=true is active. So that would be a regression for people who use non-integer scale factors.

I've just submitted a patch that fixes this: D11244

So if D11244 lands, then we can do this if we ship with Frameworks 5.45, or if we cherry-pick that patch into 5.44.

ngraham updated the task description. (Show Details)Mar 11 2018, 8:19 PM

Yep, landed in Frameworks 5.45. So if we want to do this, and we don't ship with 5.45, we'll need to cherry-pick that patch.

ngraham renamed this task from Run plasmashell with "PLASMA_USE_QT_SCALING=true" to Run plasmashell with "PLASMA_USE_QT_SCALING=1".Mar 19 2018, 3:48 PM
ngraham updated the task description. (Show Details)
ngraham updated the task description. (Show Details)Mar 19 2018, 4:56 PM
ngraham updated the task description. (Show Details)Mar 19 2018, 6:08 PM
tsimonq2 moved this task from Inbox to Packaging / Devel on the Kubuntu board.Mar 20 2018, 9:37 PM
valorie renamed this task from Run plasmashell with "PLASMA_USE_QT_SCALING=1" to Run plasmashell with "PLASMA_USE_QT_SCALING=1" : Wait until 18.10; re-test.Mar 31 2018, 8:36 PM
rikmills moved this task from Packaging / Devel to Inbox on the Kubuntu board.Apr 7 2018, 12:06 PM

I just wanted to mention this still works fine for me and resolves numerous icon scaling issues.