QmlPuppet: Small optimization to rendering 2D content in 3D scene

There is no need to read back the texture into image when rendering
2D content for embedding into 3D scene, so don't do that.

Change-Id: If84619bdc20e6997733effc4745a496fab69e5b8
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>

share/qtcreator/qml/qmlpuppet/qml2puppet/instances/qt5informationnodeinstanceserver.cpp

@@ -800,8 +800,7 @@ void Qt5InformationNodeInstanceServer::doRender3DEditView()
 #else
         if (m_render2D) {
             // Render 2D content, as it might be used by 3D content
-            grabWindow();
-            m_render2D = false;
+            m_render2D = !renderWindow();
         }
         renderImage = grabRenderControl(m_editView3DData);
 #endif

share/qtcreator/qml/qmlpuppet/qml2puppet/instances/qt5nodeinstanceserver.cpp

@@ -308,6 +308,25 @@ QImage Qt5NodeInstanceServer::grabRenderControl(RenderViewData &viewData)
     return renderImage;
 }
 
+// This method simply renders the window without grabbing it
+bool Qt5NodeInstanceServer::renderWindow()
+{
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+    if (!m_viewData.rootItem || (m_viewData.bufferDirty && !initRhi(m_viewData)))
+        return false;
+
+    m_viewData.renderControl->polishItems();
+    m_viewData.renderControl->beginFrame();
+    m_viewData.renderControl->sync();
+    m_viewData.renderControl->render();
+    m_viewData.renderControl->endFrame();
+    return true;
+#else
+    Q_UNUSED(viewData)
+#endif
+    return false;
+}
+
 QImage Qt5NodeInstanceServer::grabWindow()
 {
     if (m_viewData.rootItem)

share/qtcreator/qml/qmlpuppet/qml2puppet/instances/qt5nodeinstanceserver.h

@@ -94,6 +94,7 @@ protected:
 
     virtual bool initRhi(RenderViewData &viewData);
     virtual QImage grabRenderControl(RenderViewData &viewData);
+    virtual bool renderWindow();
 
 private:
     RenderViewData m_viewData;