second attempt to fix all other shutdown QML warnings at once

libraries/qml/src/qml/OffscreenSurface.cpp

@@ -389,6 +389,10 @@ void OffscreenSurface::finishQmlLoad(QQmlComponent* qmlComponent,
         }
         // Allow child windows to be destroyed from JS
         QQmlEngine::setObjectOwnership(newObject, QQmlEngine::JavaScriptOwnership);
+
+        // add object to the manual deletion list
+        _sharedObject->addToDeletionList(newObject);
+
         newObject->setParent(parent);
         newItem->setParentItem(parent);
     } else {

libraries/qml/src/qml/impl/SharedObject.cpp

@@ -15,6 +15,7 @@
 #include <QtQml/QQmlEngine>
 
 #include <QtGui/QOpenGLContext>
+#include <QPointer>
 
 #include <NumericalConstants.h>
 #include <shared/NsightHelpers.h>
@@ -96,6 +97,15 @@ SharedObject::~SharedObject() {
     }
 #endif
 
+    // already deleted objects will be reset to null by QPointer so it should be safe just iterate here
+    for (auto qmlObject : _deletionList) {
+        if (qmlObject) {
+            // manually delete not-deleted-yet qml items
+            QQmlEngine::setObjectOwnership(qmlObject, QQmlEngine::CppOwnership);
+            delete qmlObject;
+        }
+    }
+
     if (_rootItem) {
         delete _rootItem;
         _rootItem = nullptr;
@@ -412,6 +422,11 @@ bool SharedObject::fetchTexture(TextureAndFence& textureAndFence) {
     return true;
 }
 
+void hifi::qml::impl::SharedObject::addToDeletionList(QObject * object)
+{
+    _deletionList.append(QPointer<QObject>(object));
+}
+
 void SharedObject::setProxyWindow(QWindow* window) {
 #ifndef DISABLE_QML
     _proxyWindow = window;

libraries/qml/src/qml/impl/SharedObject.h

@@ -66,7 +66,7 @@ public:
     void resume();
     bool isPaused() const;
     bool fetchTexture(TextureAndFence& textureAndFence);
-
+    void addToDeletionList(QObject* object);
 
 private:
     bool event(QEvent* e) override;
@@ -91,6 +91,8 @@ private:
     void onAboutToQuit();
     void updateTextureAndFence(const TextureAndFence& newTextureAndFence);
 
+    QList<QPointer<QObject>> _deletionList;
+
     // Texture management
     TextureAndFence _latestTextureAndFence{ 0, 0 };
     QQuickItem* _item{ nullptr };