Scene3DView: fix shutdown crash

By using a QPointer to whatch whether the Entity was already destroyed.
Also had a ownsEntity property to control whether Scene3DView should
own the Entity ptr or not.

Patch provided by my colleague Tobias Koenig <tobias.koenig@kdab.com>

Change-Id: Ideb0e842419df73c8e1bc0608965859750195ca7
Task-number: QTBUG-85575
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

2 files changed, 39 insertions, 8 deletions

diff --git a/src/quick3d/imports/scene3d/scene3dview.cpp b/src/quick3d/imports/scene3d/scene3dview.cpp
index 19ef43757..3cdfbc01c 100644
--- a/src/quick3d/imports/scene3d/scene3dview.cpp
+++ b/src/quick3d/imports/scene3d/scene3dview.cpp
@@ -118,6 +118,10 @@ namespace Qt3DRender {
 
     There are no restriction on the sharing of elements between different scenes
     in different Scene3DView instances.
+
+    By default, you are in charge of ensuring the lifetime of the referenced
+    Entity. If you wish to transfer this duty to the Scene3DView, the
+    ownsEntity property can be set to true (defaults to false).
  */
 
 namespace {
@@ -146,6 +150,7 @@ Scene3DView::Scene3DView(QQuickItem *parent)
     , m_holderViewport(new Qt3DRender::QViewport())
     , m_dirtyFlags(DirtyNode|DirtyTexture)
     , m_texture(nullptr)
+    , m_ownsEntity(false)
 {
     setFlag(QQuickItem::ItemHasContents, true);\
 
@@ -157,8 +162,11 @@ Scene3DView::Scene3DView(QQuickItem *parent)
 
 Scene3DView::~Scene3DView()
 {
-    if (m_entity)
-        abandonSubtree(m_entity);
+    if (m_entity) {
+        abandonSubtree(m_entity.data());
+        if (m_ownsEntity)
+            m_entity->deleteLater();
+    }
 
     if (m_scene3D)
         m_scene3D->removeView(this);
@@ -166,7 +174,7 @@ Scene3DView::~Scene3DView()
 
 Qt3DCore::QEntity *Scene3DView::entity() const
 {
-    return m_entity;
+    return m_entity.data();
 }
 
 Scene3DItem *Scene3DView::scene3D() const
@@ -197,6 +205,11 @@ QSGTexture *Scene3DView::texture() const
     return m_texture;
 }
 
+bool Scene3DView::ownsEntity() const
+{
+    return m_ownsEntity;
+}
+
 // Called by Scene3DRender::beforeSynchronizing in RenderThread
 void Scene3DView::markSGNodeDirty()
 {
@@ -207,17 +220,20 @@ void Scene3DView::markSGNodeDirty()
 // Main Thread
 void Scene3DView::setEntity(Qt3DCore::QEntity *entity)
 {
-    if (m_entity == entity)
+    if (m_entity.data() == entity)
         return;
 
-    if (m_entity)
-        abandonSubtree(m_entity);
+    if (m_entity) {
+        abandonSubtree(m_entity.data());
+        if (m_ownsEntity)
+            m_entity->deleteLater();
+    }
 
     m_entity = entity;
     emit entityChanged();
 
     if (m_entity)
-        adoptSubtree(m_entity);
+        adoptSubtree(m_entity.data());
 }
 
 // Main Thread
@@ -247,6 +263,14 @@ void Scene3DView::setScene3D(Scene3DItem *scene3D)
     }
 }
 
+void Scene3DView::setOwnsEntity(bool ownsEntity)
+{
+    if (ownsEntity == m_ownsEntity)
+        return;
+    m_ownsEntity = ownsEntity;
+    emit ownsEntityChanged();
+}
+
 // Render Thread
 QSGNode *Scene3DView::updatePaintNode(QSGNode *node, QQuickItem::UpdatePaintNodeData *)
 {
diff --git a/src/quick3d/imports/scene3d/scene3dview_p.h b/src/quick3d/imports/scene3d/scene3dview_p.h
index 3278bc6c4..bec9b7846 100644
--- a/src/quick3d/imports/scene3d/scene3dview_p.h
+++ b/src/quick3d/imports/scene3d/scene3dview_p.h
@@ -53,6 +53,7 @@
 
 #include <QtQuick/QQuickItem>
 #include <QtCore/QFlags>
+#include <QtCore/QPointer>
 
 QT_BEGIN_NAMESPACE
 
@@ -76,6 +77,7 @@ class Scene3DView : public QQuickItem
     Q_OBJECT
     Q_PROPERTY(Qt3DCore::QEntity* entity READ entity WRITE setEntity NOTIFY entityChanged)
     Q_PROPERTY(Qt3DRender::Scene3DItem *scene3D READ scene3D WRITE setScene3D NOTIFY scene3DChanged)
+    Q_PROPERTY(bool ownsEntity READ ownsEntity WRITE setOwnsEntity NOTIFY ownsEntityChanged)
     Q_CLASSINFO("DefaultProperty", "entity")
 
 public:
@@ -97,15 +99,19 @@ public:
     void setTexture(QSGTexture *texture);
     QSGTexture *texture() const;
 
+    bool ownsEntity() const;
+
     void markSGNodeDirty();
 
 public Q_SLOTS:
     void setEntity(Qt3DCore::QEntity *entity);
     void setScene3D(Scene3DItem *scene3D);
+    void setOwnsEntity(bool ownsEntity);
 
 Q_SIGNALS:
     void entityChanged();
     void scene3DChanged();
+    void ownsEntityChanged();
 
 private:
     QSGNode *updatePaintNode(QSGNode *node, UpdatePaintNodeData *nodeData) override;
@@ -113,7 +119,7 @@ private:
     void abandonSubtree(Qt3DCore::QEntity *subtree);
 
     Scene3DItem *m_scene3D;
-    Qt3DCore::QEntity *m_entity;
+    QPointer<Qt3DCore::QEntity> m_entity;
     Qt3DCore::QNode *m_previousFGParent;
 
     Qt3DCore::QEntity *m_holderEntity;
@@ -125,6 +131,7 @@ private:
 
     DirtyFlags m_dirtyFlags;
     QSGTexture *m_texture;
+    bool m_ownsEntity;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(Scene3DView::DirtyFlags)