Stuck in HDPI mode with GNOME

[benjamindaines]

Quite simply, as the title states newest version of Cantata displays incorrectly with HDPI scaling when launched under GNOME using qt5ct style plugin version 0.33-2.

[CDrummond]

Well, works fine under GNOME shell in Ubuntu 17.04 - both in a VM, and my full HD (1080p) laptop. This issue looks similar to #1063

• Which version of Qt5?
• What is your screen size? Is it HighDPI
• Which version of GNOME shell? (Probably irrelevant, but...)

Can you please try with the following variations, and let me know the results of each:

• without qt5ct (I don't think this is the cause, but helps to reduce differences) Run QT_QPA_PLATFORMTHEME= cantata (This sets QT_QPA_PLATFORMTHEME to an empty string, so should disable qt5ct)

• With fusion style cantata --style fusion

• With QT_AUTO_SCREEN_SCALE_FACTOR=0, - e.g. QT_AUTO_SCREEN_SCALE_FACTOR=0 cantata This should disable Qt's auto scale setting.

If you don't mind compiling the code, please:

• Try git/master? Probably no difference, but worth a check.

• After the initial build, please edit the code and remove QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling); from gui/main.cpp - then recompile, and try again. Works now?

[benjamindaines]

Qt version 5.9.1-3
Screen size is 1920x1080, so not HDPI
Shell version is 3.24 (does it under 3.25.90 as well)

QT_AUTO_SCREEN_SCALE_FACTOR=0 cantata launches properly, however throwing QT_AUTO_SCREEN_SCALE_FACTOR=0 in /etc/enviornment does not.

Recompiled after commenting out QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling); and scaling looks correct, however some icons do not display properly and opening the preferences window causes a crash ASSERT: "!qFuzzyIsNull(c)" in file /usr/include/qt/QtCore/qsize.h, line 196

Hopefully at least some of that is helpful.

[CDrummond]

Try also removing QGuiApplication::setAttribute(Qt::AA_UseHighDpiPixmaps); from gui/main.cpp

[CDrummond]

When you built Cantata, did you install it? If not, then that is why some icons are missing.

[CDrummond]

I've updated git/master (for 2.2.0) to only set Qt::AA_EnableHighDpiScaling under Linux if QT_AUTO_SCREEN_SCALE_FACTOR is set and non-zero.

[benjamindaines]

Same issue unfortunately. I can't see anywhere that any scaling is set on my system. I've even tried explicitly setting it to 0 in /etc/environment and still getting the massive UI.

[CDrummond]

This looks like something in your system is setting 'QT_AUTO_SCREEN_SCALE_FACTOR=1' (or some other number).

If setting 'QT_AUTO_SCREEN_SCALE_FACTOR' before Cantata works, but not placing in /etc/environment then something must be setting this to a non-zero value.

---

If you revert to just removing the line from gui/main.cpp, rebuilding, and installing - is it now ok? Does the crash still happen when you have Cantata installed?

If the crash still happens please:

1. Create a new build folder for Cantata
2. When calling cmake, also pass -DCMAKE_BUILD_TYPE=Debug
3. Perform a make install
4. Run cantata from withing gdb, e.g. (assuming cantata is installed to /usr/local)

    > gdb /usr/local/bin/cantata
    (gdb) run
   

5. When Cantata crashes gdb should trap this, and show some text. In the terminal with gdb type where - and paste the results here.

Thanks.

[benjamindaines]

I'm going to be away for a few days where the internet connection is awful, but I'll set ya know what happens when I get back.

I can say though, that I have no idea where qt_scaling would have been set.

[ben@pluto ~]$ printenv
XDG_MENU_PREFIX=gnome-
LANG=en_US.utf8
GDM_LANG=en_US.utf8
DISPLAY=:0
COLORTERM=truecolor
DESKTOP_AUTOSTART_ID=10884813e8629d5691150339782276287700000309850008
USERNAME=ben
MOZ_PLUGIN_PATH=/usr/lib/mozilla/plugins
XDG_VTNR=2
SSH_AUTH_SOCK=/run/user/1000/keyring/ssh
XDG_SESSION_ID=c6
USER=ben
DESKTOP_SESSION=gnome-xorg
QT_QPA_PLATFORMTHEME=qt5ct
PWD=/home/ben
HOME=/home/ben
JOURNAL_STREAM=8:759436
XDG_SESSION_TYPE=x11
XDG_DATA_DIRS=/home/ben/.local/share/flatpak/exports/share/:/var/lib/flatpak/exports/share/:/usr/local/share/:/usr/share/
XDG_SESSION_DESKTOP=gnome-xorg
SAL_USE_VCLPLUGIN=gtk3
MAIL=/var/spool/mail/ben
WINDOWPATH=2
TERM=xterm-256color
SHELL=/bin/bash
VTE_VERSION=4901
XDG_CURRENT_DESKTOP=GNOME
XDG_SEAT=seat0
SHLVL=1
WINDOWID=67108870
GDMSESSION=gnome-xorg
GNOME_DESKTOP_SESSION_ID=this-is-deprecated
LOGNAME=ben
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
XDG_RUNTIME_DIR=/run/user/1000
XAUTHORITY=/run/user/1000/gdm/Xauthority
QT_AUTO_SCREEN_SCALE_FACTOR=0 
PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl
SESSION_MANAGER=local/pluto:@/tmp/.ICE-unix/30985,unix/pluto:/tmp/.ICE-unix/30985
_=/usr/bin/printenv

[benjamindaines]

Latest source works fine.