HiDPI monitors

[Elvis Stansvik]

Den lör 16 jan. 2021 kl 14:26 skrev Elvis Stansvik <elvstone at gmail.com>:
>
> Nice! Just a small comment about
>
> > MySetting = 100 / int(QScreen.devicePixelRatio(app.primaryScreen()))
>
> Here you are assuming that the application is on the primary screen.
> In a multi-monitor setup, it may be on another screen with a different
> device pixel ratio. It's possibly a better idea to call
> QPaintDevice::devicePixelRatio() on the widget that will hold your
> matplotlib plots.
>
> Also, the application may be moved between screens, which you should
> ideally listen for (there are some Qt mechanisms for this I believe,
> screenChanged signal, though I've found it a bit unreliable at times),
> and if it happens, re-create your matplotlib plots with the correct
> DPI passed in (calculated from the new screen the widget is on), and
> also re-create any pixmaps you may have created in terms of physical
> pixels (if you have any like that).

I see now that you said "and the user says he can even move it back
and forth between an 8K and a FullHD monitor without distortion except
for a wobble in the transition !!?", so perhaps matplotlib takes care
of this on its own once the plot has been shown, which is great.

Elvis

>
> How much of this you want to bother with is up to you of course :) You
> may decide it's enough if the user has to restart the application if
> he/she wants it on another screen.
>
> HiDPI really is a pain :)
>
> Cheers,
> Elvis
>
> Den fre 15 jan. 2021 kl 17:34 skrev ullix <ullix at urkam.de>:
> >
> > My struggle with HiDPI monitors has come to an at least workaround solution thanks to your responses, so many thanks!
> > I'll try to summarize:
> >
> > PyQt(5) applications will behave well with this command:
> >
> > QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling, True)
> >
> > Whether this next command will also be needed depends on your explicit (perhaps implicit) use of pixmaps with HiDPIs available
> > I had no benefit from it
> >
> > QtWidgets.QApplication.setAttribute(QtCore.Qt.AA_UseHighDpiPixmaps, True)
> >
> > Unfortunately, matplotlib is separate from this and needs its own adaptation of settings. This can be done by setting the 'dpi=' parameter in every call to figure:
> > matplotlib.pyplot.figure(num=None, figsize=None, dpi=MySetting, .... )
> >
> > But MySetting is a bit tricky: it basically must reverse the scaling. The default dpi is: MySetting = 100. So, when your scaling is 200%, then set MySetting=50. Is your scaling 300%, then set MySetting=33.
> >
> > I don't know if there is a single command which could set dpi for the session?
> >
> > Thankfully the "devicePixelRatio" of QScreen basically has Scaling/100, i.e. the values 1, 2, 3 for the above examples. Therefore you can set:
> > MySetting = 100 / int(QScreen.devicePixelRatio(app.primaryScreen()))
> >
> > In the rare case that you do not have several 4k and 8k monitors to test with :-( you can use Xephyr as suggested by VA.
> > Though when I tried the examples refernenced by him  https://indigo.re/posts/2020-05-18-hidpi-testing.html each one crashed on my system! But in my need I came back and just tried the small script and it worked! Script: https://gitlab.com/hydrargyrum/attic/blob/master/xephyr-run-cmd/xephyr-run-cmd
> >
> > I can now start my program and run it in proper scale with this command:
> > ./xephyr-run-cmd -dpi 200 -screen 4000x2000 -- ./geigerlog
> >
> > And lastly a screenshot on a real 8k monitor on Win10:
> > Full WidthxHeight is 2732x1443 (open it);
> > and the user says he can even move it back and forth between an 8K and a FullHD monitor without distortion except for a wobble in the transition !!?
> >
> > Thanks again,
> >
> > ullix
> >
> >