Ubuntu GNOME and high resolution screen: icons in QT apps are too small. How to solve?

my brother got a new laptop, a Thinkpad X1 Carbon 4th generation. It features a screen with a rather large resolution of 2560x1440 px.

Out of the box, GNOME scales well the size of the text and the icons, as you may see from this screenshot of LibreOffice:

Unfortunately QT apps seem not to behave the same, as seen in this screenshot of TexMaker:

As you may see the icons are too small and rather difficult to reach.

How can he uniform the look&feel of the QT apps to the one of the GTK apps? Is there some compatibility package that he has to install? Or some configuration to make?

Thanks in advance

Solution 1:

Maybe you can play around with the QT_SCALE_FACTOR and QT_AUTO_SCREEN_SCALE_FACTOR environment variables.

I had the problem of a tiny UI font in calibre on the Gnome desktop on a 4K 15.6 display. I experimented with QT_SCALE_FACTOR=2.5 QT_AUTO_SCREEN_SCALE_FACTOR=0.8 calibre in the terminal and it worked!

So, basically (if my guess is correct), QT_AUTO_SCREEN_SCALE_FACTOR controls the overall scaling except the font, while QT_SCALE_FACTOR controls font scaling only.

I also added these two variables to the desktop file of calibre:

before:

Exec=calibre --detach %F

after:

Exec=env QT_SCALE_FACTOR=2.5 QT_AUTO_SCREEN_SCALE_FACTOR=0.8 calibre --detach %F

Also you may want to take a look at this github issue.

Solution 2:

The answer depends on which version of qt you are using, qt4 or qt5. The following will tell you which version of qt you are using.

ldd $(which $NAME) | grep qt -i

For qt5 you can use an environment variable QT_SCALE_FACTOR, for qt4 you can change font sizes using qtconfig-qt4, but it would appear that icon sizes don't scale. You might, however, be able to use a different icon set, or if you are very energetic scale up another icon set yourself.

See https://wiki.archlinux.org/index.php/HiDPI for more details and details for other toolkits.