HiDPI issues

[szlldm]

I recently upgraded my main setup, including a 4k monitor. Consequently HiDPI had to be turned on.
Overall the application looks ok, but i noticed some issues:

1) Graphical elements are pixel doubled, and for an unknown reason it use "nearest neighbour" scaling.
So icons, sliders, knobs and spinbox arrows looks very pixelated. I'm not sure is it Qt or system related?

2) The most serious issue is, that every QGraphicsView are also pixel doubled, therefore previews (both main window and filters) looks very bad.

On Ubuntu 20.04 LTS.

Thanks!

[szlldm]

I checked the nightly build, and sliders, knobs and spinbox arrows looks OK. 
My built from source version has pixelated Qt controls.

[eumagga0x2a]

I checked the nightly build

Which one of the two? If appImage4Buster: could you please compare Qt versions used by your build vs the official appImage? Would it be too much of a hassle to install Fedora 34 to be able to test with Qt6? You would need to explicitely request it with the --enable-qt6 switch for the bootstrap script.

Unfortunately, I don't have Linux-compatible equipment useful for HiDPI testing.

[szlldm]

Checked on avidemuxLinux_GLIBC_2.28_amd64_210426_0645.app

My Qt version is 5.12.8.

I try to install Fedora in VM.

Thanks!

[eumagga0x2a]

Thanks, so Buster is on an older Qt version (5.11.3). At the same time the Qt5 version in Ubuntu 20.04 LTS is still very old compared e.g. to Fedora 33.

[szlldm]

I did installed Fedora.
Running createRpmFromSourceFedora.bash, it can not install fdk-aac-devel xvidcore-devel x264-devel x265-devel.
The compiled avidemux could'nt open any files "Cannot find demuxer". -> install/usr/lib symlink was broken, had to fix manually. 

Qt controls are ok, icons scaled with nearest neighbor, previews are also looks bad.

By the way the theme/style is the same here as in appimage, while my build has different theme.

[eumagga0x2a]

Running createRpmFromSourceFedora.bash, it can not install fdk-aac-devel xvidcore-devel x264-devel x265-devel.

Due to patent / licensing problems, these packaged are in RPF Fusion repos. The script points out that these repositories (rpmfusion-free and rpmfusion-nonfree) need to be enabled prior to continuing.

The compiled avidemux could'nt open any files "Cannot find demuxer". -> install/usr/lib symlink was broken, had to fix manually.

Did you generate (and install) RPMs or did you use createRpmFromSourceFedora.bash just to install build dependencies? The symlink matters for portable mode only, not needed when running Avidemux installed system-wide to /usr/local/bin or /usr/bin. It looks for me as if you mixed both methods – built RPMs and tried to run as portable from the build directory. I'm not sure this can work.

Qt controls are ok, icons scaled with nearest neighbor, previews are also looks bad.

It looks like we cannot trust Qt with performing HiDPI scaling.

By the way the theme/style is the same here as in appimage, while my build has different theme.

There is no Adwaita Qt theme for Qt6 yet.