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QSpinBox buttons and arrows on EGLFS, XCB and Wayland backend



  • Dear all,

    I need help to understand the display of the up and down buttons and arrows of a QSpinBox on different backends.

    My application runs on a Raspberry Pi4 with a 4.3" display and touch screen. I have chosen EGLFS (the "fake" one). I have no X11, no wayland compositor installed. The application works. When I increase the font size of a QSpinBox, the box gets bigger and so do the up and down buttons and arrows. This allows the use with the touch screen. So far, so good.

    As I have learned, when there is no window manager, there are no window decorations (e.g. borders, title bars). This is one reason why I would like to run my application on X11 or wayland. This works when I choose the right platform on program startup. However, there is an important and very annoying difference between EGLFS and X11 or wayland. On X11 and wayland, the up and down buttons and arrows of the QSpinBox are far too small to be usable with the touch screen and the arrows are barely visible.

    On my Linux development box (Linux Mint 20, X11), I have the same problem. When I increase the font size of the QSpinBox, the box gets bigger but the buttons and arrows remain too small. On my Windows computer the buttons are larger but the arrows are still too small.

    Can anybody explain me why this is the case and how I can avoid this problem? For information, the QT version is 5.15.1 and I don't use style sheets.

    Thank you very much for your help!

    Kind regards,

    Ralf


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