OpenGL (QGLWindow) functionality in QDeclarativeView



  • Hi,
    I am working on a project for Sailfish OS (Qt 4.8) app.
    I need to integrate openGL into QML using a QDeclarativeView.
    Seen and tried the examples as shown in the Qt Forums.
    They all:
    set a QGLWidget as the viewport of the QDeclarativeView;
    Use a QDeclarativeItem and re-implement the paint function with:
    beginNativePainting() etc.;
    qmlRegisterType is used to bind the QDeclarativeItem class to a QML type.

    This looks nice (as in the examples) if you have some simple fixed pipeline rendering, but I need to use a lot of extra openGL functionality (like setAttribute, QGLShaderProgram, compileSourceCode, etc.).
    This is all neatly implemented in QGLWidget, but not in QDeclarativeItem which is now responsible for the openGL rendering/painting.
    So, is there a way have the QGLWidget available / accessible in QML?
    Thanks.



  • This may not be the answer you're looking for, but the kind of things you're trying to do is possible with little effort with QtQuick 2 (Qt5). With QtQuick2 your more or less directly manipulate OpenGL data in custom Qml items.

    Using Qt 4.8, i'm not sure how you could do that without creating your own QPainter+QGLWidget+QDeclarativeView+QDeclarativeItem to support custom advanced painting commands. And very likely need to modify private implementation of those classes too.



  • I have now made a MyDeclarativeView class derived from QDeclarativeView.
    Next I have added my QGLWindow as a child Widget to MyDeclarativeView.
    Further MyDeclarativeView sets a QGraphicsScene (setScene) to which I add QML items (addItem).
    Seems to work, but I am not sure if this is all sound....



  • (I guess you meant QDeclarative(View))

    Yes you can implement it manually that way. I'm not sure if making the QGLWindow a child of your view will render it or not. If not, you may want to make it a sibling of your View.

    I'm very curious about it if you succeed, interesting problem.



  • QDeclarative(View) corrected. Sorry.
    Yes it works as desktop app.
    Only had to:
    @view.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    view.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);@
    (view = MyDeclarativeView object).

    Now try it on Sailfish...
    I'll report back.



  • Does not crash on Sailfish, but QGLWindow stays black...
    Possibly a openGL issue with the simulator.
    And had to comment out:
    #ifdef HAS_BOOSTER
    view = MDeclarativeCache::qDeclarativeView();
    #else...
    because I have my own QDeclarativeView derived class.
    I'll ask about it on the Sailfish list.



  • Just found out that signals in QML (to c++) don't work.
    Changed QDeclarativeView->setScene etc. to QDeclarativeView->setSource
    Now it works.
    QGLWindow overlaps qml page.


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