Draw Qt widgets in DirectX/OpenGL context

  • Hello everyone,

    I'm working on a little utility that will inject itself into a given game and display information in an overlay.
    Now I'm wondering if I could use Qt to draw the items of this overlay.

    To keep this topic manageable, I'm assuming I've already acquired the DirectX/OpenGL context of the game.
    Given that, how can I draw a Qt widget into this context? Is there a way to set this context as "parent" for a widget?

    I've already found solutions that suggested using an QOpenGlWidget and add the widgets to that. However, this does not work for me, since I cannot change the actual executable, and therefore not the way the drawing context is presented to the user. Furthermore, I'm looking for solutions that also would work with DirectX.


  • Moderators

    Assuming you have an OpenGL context and you can draw/create objects in it you would make that context current, then create a QOpenGLPaintDevice and use it to render() the widget into that. Please note that a widgets require a QApplication instance and a running Qt's event loop, so you would need to ensure you have that.

    As for DirectX Qt doesn't have any direct support for it, but you could probably grab() a widget into a QPixmap, transfer the pixels to a DirectX texture and draw a quad with it.
    If you feel adventurous you could also implement your own QPaintEngine, then subclass QPaintDevice to return that engine and use it like with the OpenGL version.

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