Hello,

Still searching to fix that one.

I can now reproduce it at leasure: If I connect my laptop to an external monitor, launch the application, then unplug the external monitor and hover the mouse on the windows bar to make it appear (autohide is activated), my application AND QtCreator changes font, palette and style.

Then only way to get normal look back is to restart application. Reloading style, stylesheet, palette and font at application level does not fix existing widgets once they are corrupted.

I cannot find what trigger this, nor at qApp's event level or at QMainWindow level or at widget's level.

I am using qt 5.5.1 on windows 10. It does not seem to occur on Windows 7 as far as I can tell.

I have users complaining about that too so it is not just me ;)

Any idea how to catch what is causing that and avoid it? Since it occurs also in QtCreator maybe I should open a bug report...

Thanks
Philippe Lelong


Le 09-11-2015 16:45, maitai a écrit :
Thanks Robert for your reply,

In fact I succeeded to reproduce partly the problem. I have a laptop
with 2 graphic cards, switchable. Whenever the PC goes in power-saving
mode, it switches to the intel one. When this happens, my menubar
(regular QMenuBar) is changing font and becomes ugly, and the only way
to get it back to normal is to restart the application. It seems to
happen also from time to time if I switch from external monitor to
laptop monitor.

This app is not using opengl, it's just a plain QWidget app.

No signal or event as far as I can see is triggered when this happens,
just a paintEvent it seems.

The funny thing is that even QtCreator is impacted by that... It also
changes font or style.

Any clue on what is going on there?

Thanks
Philippe Lelong

Le 09-11-2015 12:03, Robert Iakobashvili a écrit :
On Mon, Nov 9, 2015 at 7:54 AM, maitai <mai...@virtual-winds.org> wrote:

Hello

On Windows, some users are reporting that the application style (font? palette?) is changing when laptop goes in energy saving mode, and becomes more or less unreadable (white font on white background, etc). I have seen that myself also a couple of times but I'm unable to reproduce it.

When it occurs, putting the laptop back on power does not fix anything, and the only way to get back the proper appearance is to restart the application. If you start the application when in battery saving mode, no problem. The application is widget-based (QMainWindow, QGraphicalScene, QMenubar, etc), Qt is 5.5.1 but that was reported also with previous Qt versions.

As I said this occurs only for a few users, and I cannot reproduce it. Maybe it's connected with the laptop changing GPU, I don't know.

Does anyone knows what could possibly trigger this, and if I can catch it somehow either to avoid it or reload style/palette/font/etc when it occurs?

Thanks
Philippe Lelong


Hi,

With which options Qt was configured and built?

Any plugins your software is using?

Is it correlating with any particular Windows versions
like on Windows-10 or 8.1?

That sounds like an aggressive memory optimization by OS.
Locking in memory sometimes could help against.

There is a Qt signal

QGuiApplication::on_applicationStateChanged(Qt::ApplicationState state);

and using it on Android.

Perhaps, coming to the state:Qt::ApplicationActive from
somewhere else and reloading fonts, etc could be a work-around?

Kind regards,
Robert
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