Expose skin scaling options to the preferences

[Nico Schlömer]

I've got a 12 inch laptop with a 1080p (1920x1080) display (which I think are fairly common nowadays). In the mixxx interface, unfortunately, everything is really small. The fonts are small, and the clickable buttons are between 10 and 20 pixels wide. For comparison, the back, forth and reload buttons on this chrome browser are about 30 pixels wide.

I know that I can adjust the library font size. What other knobs are there? Can I adjust, for example, the font size in the other parts of the interface?

[Daniel Schürmann (daschuer)]

This is an other aspect of https://bugs.launchpad.net/mixxx/+bug/1793954

I think it is really required to expose the scaling options again.

A intermediate solution was proposed here:
https://github.com/mixxxdj/mixxx/pull/1741

[Nico Schlömer (nschloe)]

```
export QT_AUTO_SCREEN_SCALE_FACTOR=0
export QT_SCREEN_SCALE_FACTORS=1.4
```
works for me.

[Be (be.ing)]

Once again, this is Qt's responsibility, not the responsibility of every application. We only need to inform users how to manually adjust scaling when Qt's automatic scaling fails, which it inevitably will in some cases with the wide variety of resolutions and physical screen sizes available.

[Uwe Klotz (uklotzde-deactivatedaccount)]

It is not only Qt's responsibility since we decided to explicitly opt-in into auto-scaling with unforeseeable side effects. Now one has to set QT_AUTO_SCREEN_SCALE_FACTOR=0 to restore the default behavior in order to follow the instructions documented by Qt.

That's the problem with those half-baked solutions. Either you provide the full scale of configuration options or entirely leave it to someone else.

[ronso0 (ronso0)]

why "won't fix"?

> this is Qt's responsibility ... inform users how to manually adjust scaling

I disagree. Even though Qt's scaling might work if every screen also supplies info about its physical size, there are use cases where manual adjust of the scaling is required and we may not expect users to mess with the command line or .bat/.desktop files. Because, if they are simply not skilled or brave enough to go to this level of their OS they will just drop Mixxx and re-try the DJ app which probably came with their controller.

+1 for scaling controls in Preferences

[Be (be.ing)]

If we can change Qt's scale factor from the preferences, okay, but not elaborate hacks duplicating what Qt already does for us (like https://github.com/mixxxdj/mixxx/pull/1741). However I am doubtful we can adjust Qt's scale factor within a Qt application. IIRC it needs to be set before any GUI is shown.

[Daniel Schürmann (daschuer)]

It is OK to restart Mixxx after tweaking the preferences option.
It is better than fiddling with a batch file.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/9640