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Qt Virtual Keyboard's strange transparency under Debian

  • Hello,

    I'm testing the Qt Virtual keyboard 5.7.

    After building and deployment, the keyboard works properly. The only problem is that the keyboard panel's background is transparent under my debian system(GNOME,KDE, ... tested with all the desktops). If the background before the keyboard pops up was dark, then we can see the keys on the dark background, but if the background was white, we can see nothing but the buttons are still there and can be operated.


    I also tested it under ubuntu, no such problem occurs.

    And all my other Qt 5.7 built applications have no such problem.

  • Lifetime Qt Champion

    Hi and welcome to devnet,

    Does it also happen if you build your application with your distribution provided Qt ?

  • @SGaist Hello,

    Thanks for replying. No, so far all my applications are nornal. And all the Qt examples I built myself are also normal. Only have the Qt keyboard problem

  • Lifetime Qt Champion


    Can you reproduce that with a minimal compilable example ?

  • @SGaist Hi, if you mean testing the keyboard with a simple example, yes I did that already. Using an example with only on text input field, and also tested with many different Qt5.7 applications with text edit Field, all the same. THe keyboard is transparent above white background.

  • I almost believe that this problem has something todo with the d->view->setcolor(QtColor(Qt::transparent)) statement in the source code. If I change that, it has different effects under windows, ubuntu and debian. Does some on also use debian to test the virtual keyboard?

  • Lifetime Qt Champion

    That I don't know and might be not relevant. Ubuntu is a Debian derivative but they implement their own replacement of the X server with Mir.

    There are several window managers for Linux that behaves differently so you may have found something on the ones you are running.

  • @SGaist Thank you for your answer and I've found that I could avoid this problem by adding view.setcolor(QtColor(Qt::transparent)) to any application who wants to invoke the keyboard, that must be unormal, so I reported this as a bug.

    More details are described there:

  • Lifetime Qt Champion

    Thanks for the workaround and report !

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