hi

I have a 2K monitor (1560x1440) and on my right a Full Hd monitor (1920x1080).

In Kde 5.5, i set
Increase font dpi : 210
Change Scale: 2

Everything is big, on my both computer.

Don't know if we need xrandr?

Any tips to get correct setting?

Not sure about the supposed question, but if you want things to have have the same (similar) physical size across screens with different resolutions, there's no client solution to this possible for principal reasons (you'd have different pixel meanings inside the same application; and this local attribute driven by a global parameter - the global position)

You need to drive outputs at the same resolution, ie. set the "2k" monitor to (really? That's the screens resolution???) 780x720px OR "pin" applications to certain screens (ie. you know you want dolphin to run on the HiDPI screen *only*) and invoke it with an explicit scale factor:

QT_DEVICE_PIXEL_RATIO=2 dolphin

In case that's not the problem: do not set the scale factor AND the font DPI, since they'll be multiplied (and you get a 4x scale instead of ad 2x one)

There's another issue I'm not sure how to solve:
Imagine you have an external display for your laptop. The external display has a max resolution of 1920x1080 while the laptop's display is 2k or more. Now whenever you change location (external display/internal display) with suspend/resume your applications are either too small or too big.

The scale factor should be switchable at runtime on demand (e.g. when changing screens are detected).

maybe http://blog.qt.io/blog/2015/12/18/qt-5-6-beta-released/

High-DPI Support

One of the biggest new features coming with Qt 5.6 is a fully rewritten cross-platform High-DPI support. It allows applications written for standard resolution displays to be automatically scaled when shown on high-pixel-density displays. Using the new High-DPI support, Qt automatically adjusts font sizes, window elements, icons and graphics in general in a Qt application based on the pixel density. High-DPI support allows applications to adjust automatically even when the user moves a window from one display to another with a different pixel density.

google01103 wrote:maybe http://blog.qt.io/blog/2015/12/18/qt-5-6-beta-released/

High-DPI Support

One of the biggest new features coming with Qt 5.6 is a fully rewritten cross-platform High-DPI support. It allows applications written for standard resolution displays to be automatically scaled when shown on high-pixel-density displays. Using the new High-DPI support, Qt automatically adjusts font sizes, window elements, icons and graphics in general in a Qt application based on the pixel density. High-DPI support allows applications to adjust automatically even when the user moves a window from one display to another with a different pixel density.

Anyone got a chance to play with this? I've documented my tempts here viewtopic.php?f=66&t=132457&p=362953&hilit=hidpi#p362953
Wither I can't figure it out (quite likely) or Qt5.6 is still missing something for actually scaling between DPIs. Maybe someone can point me towards a tutorial or documentation on setting up HiDPI + LowDPI monitors?

I am facing same issue here, having laptop at 3840x2160 and external monitor at 2560x1440. I already make the view on 4k laptop screen to meet my requirements, but when moving to external monitor with lower resolution, everything stays too big. I will look into docs as well deeper and lets discuss here this issue. I will report any progress.

After reading trough documentation I have feeling the font automatically scale following resolution, but I don't see explicitly stated that multi screens with different resolutions are supported at the same time.

It looks to me like this works only when you for example change the resolution on your screen in case of laptop, or unplug old monitor and plug new monitor.

Can someone clearly explain if realized?

Thanks.

Any update on this functionality? I have 4k laptop, 1 4k external monitor and 1 2560 x 1440. So auto-scaling between different resolutions would be handy.

I raised a bug:
https://bugs.kde.org/show_bug.cgi?id=377272