Make QGuiApplication to use an external QOpenGLContext?

Timothy

I'd like to be able to set up a QOpenGLContext and then tell my QGuiApplication to use said context. Is this possible?

Timothy

I ended up solving this myself. Here's sample code which shows how to set up context sharing between Qt's context and some external context:

// These functions would wrap some other library that can create windows and contexts, like glfw for example
void create_external_context();
HGLRC get_native_context_handle();
HWND get_native_window_handle();

int main(int argc, char* argv[]) {
    // create an opengl context
    create_external_context();

    // set opengl version and options
    QSurfaceFormat format;
    format.setVersion(4, 5);
    format.setProfile(QSurfaceFormat::CoreProfile);
    format.setDepthBufferSize(24);
    format.setStencilBufferSize(8);
    QSurfaceFormat::setDefaultFormat(format);

    // this must be set to enable context sharing
    QGuiApplication::setAttribute(Qt::AA_ShareOpenGLContexts, true);

    QGuiApplication app(argc, argv);

    // Create a Qt context which wraps the external native context.
    QOpenGLContext nativeContext;
    // This will be platform specific. The following is windows only
    QWGLNativeContext wglcontext(get_native_context_handle(), get_native_window_handle());
    QVariant qv;
    qv.setValue<QWGLNativeContext>(wglcontext);
    nativeContext.setNativeHandle(qv);
    nativeContext.create();

    // Tell Qt to use the external context as the global sharing context
    QOpenGLContext * qtGlobalContex = QOpenGLContext::globalShareContext();
    qtGlobalContex->setShareContext(&nativeContext);
    // recreate after setting native shared context
    qtGlobalContex->create();

    // at this point it is safe to start a separate thread and bind the external context to it
    // start the app only after the contexts have been set up
    engine.load(QUrl("qrc:/main.qml"));
    return app.exec();
}