Problem with picking when QRenderSettings::renderPolicy is set to OnDemand

iota142

Hi,

I'm trying to use the QObjectPicker to select a mesh in a Qt3DWindow.
All works as expected, but if I set the property QRenderSettings::renderPolicy to OnDemand then the signal QObjectPicker::clicked() is emitted only when the rendering is done (when something change, as says the documentation).
Is it the normal behavior? Do I something wrong?

I'm using the latest beta of Qt 5.9 (beta 3), on MacOSX.

A minimal example to reproduce the problem:

#include <QApplication>

#include <Qt3DExtras>
#include <Qt3DCore>
#include <Qt3DRender>

#include <QtDebug>

Qt3DCore::QEntity* createPickableMeshEntity(Qt3DCore::QNode* parent)
{
    Qt3DCore::QEntity* const entity = new Qt3DCore::QEntity(parent);
    Qt3DExtras::QCuboidMesh* const mesh = new Qt3DExtras::QCuboidMesh(entity);
    Qt3DExtras::QPhongMaterial* const material = new Qt3DExtras::QPhongMaterial(entity);
    Qt3DRender::QObjectPicker* const picker = new Qt3DRender::QObjectPicker(entity);

    entity->addComponent(mesh);
    entity->addComponent(material);
    entity->addComponent(picker);

    QObject::connect(picker, &Qt3DRender::QObjectPicker::clicked, [](Qt3DRender::QPickEvent*)
    {
        qDebug() << "Cube clicked.";
    });
    return entity;
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Qt3DExtras::Qt3DWindow window;
    Qt3DCore::QNode root;
    Qt3DRender::QCamera* const camera = new Qt3DRender::QCamera(&root);
    Qt3DExtras::QForwardRenderer renderer;

    renderer.setCamera(camera);
    renderer.setSurface(&window);
    // If the render policy is set to Qt3DRender::QRenderSettings::Always then when the user click on the cube
    // the message "Cube clicked" is immediatly displayed as expected.
    // But with the flag Qt3DRender::QRenderSettings::OnDemand, the message will be displayed only if
    // the rendering is triggered (in this example, when I resize the window).
    window.renderSettings()->setRenderPolicy(Qt3DRender::QRenderSettings::OnDemand);
    window.setRootEntity(createPickableMeshEntity(&root));
    window.setActiveFrameGraph(&renderer);
    window.show();
    return a.exec();
}

Thanks!

iota142

I have reported this issue on the Qt bug tracker.
If someone is interested: https://bugreports.qt.io/browse/QTBUG-60738