All Qt-based programs unresponsive + mouse focus issues [Windows 7]



  • Since the last round normal and recommended Windows updates, it happens after some runtime that each and every QT-based program beomces unusable: After starting, the program only responds to the first input by mouse, then stays unresponsive to mouse clicks. Some keyboard input still works, depending which frame the mouse-click focused. Changing the focus in the main window is unsuccessful, dialog windows work sometimes, closing the application works in most cases. Non-Qt applications run fine, no antivirus program is running, etc.

    Tested with: Texstudio, Autodesk Maya, Oracle VirtualBox

    I confirmed that the same programs run fine on a similar machine without the latest updates, and since this behavior affects all Qt-based applications, it seems like a bug. I will report a bug once I can reproduce the problem. Unfortunately I could not yet find out when and why this kicks in, but after a restart everything works again for a while.

    The last round of updates also affected .NET, maybe there is a conflict? Has anyone seen something similar?


  • Moderators

    Things work OK for me. But I'm using windows in a virtual machine (VMware).



  • I have similar behavior in one Qt based application that we develop. I have not tested other Qt applications.

    Since the update I have also some issue with .Net to register some dll.

    Since the original post is from February it might not be exactly the same update issue but did you fine a way to fix it on your side?



  • I had a similar problem, and it seems to be related to this.
    We could identify two things deteriorating the problem (which eventually might be a bug):
    a) Using more than one screen
    b) Using 4K monitors
    c) Using Win GUI scaling anything else than the default

    A temporary though suboptimal workaround in Win7 is to change the GUI scaling whenever the problem appears.

    [EDIT: affecting QT versions 4.8.6 and to certain degree 5.5, too]



  • I am also having this issue, I've noticed with Virtualbox, and any other qt based application. I've also noticed that it will occasionally (read, this happened once, so I think it could happen again, but I haven't reproduced it) slip out and start affecting pretty much every app, but chrome was unaffected. This makes me think that it's related to some change in .NET.

    If there is anything that I can do to help move the fix along, or if anyone has an idea where in the qt source this might be, I will do whatever I can to fix it. It REALLY bothers me.

    Edit: It just spread into windows itself again. All keyboard interaction works fine, but only chrome will interact with my mouse. It happened while using Virtualbox.


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