From 2384b04415045b2203894b24a3743b03eeadbc88 Mon Sep 17 00:00:00 2001
From: Volker Hilsheimer <volker.hilsheimer@qt.io>
Date: Wed, 9 Nov 2022 15:34:11 +0100
Subject: [PATCH 11/26] QQuickItem: avoid emitting signals during destruction

If a QQuickItem is in the QQuickItem destructor, then it is both unsafe
and unnecessary to emit property change notifications. Connected code
can no longer rely on the state of the emitting object - if it was
originally a subclass of QQuickItem, then those subclass destructors
will already have run. And the QQuickItem destructor will also have
partially run, leaving the object in an undefined state.

Add a flag that we set to true at the top of ~QQuickItem, and don't emit
visibleChildrenChanged, parentChanged, visibleChanged, and
childrenChanged for items that are partially destroyed already.

[ChangeLog][Qt Quick][QQuickItem] QQuickItem no longer emits change
notifications for the parent, children, visible, and visibleChildren
properties while it is being destroyed.

Task-number: QTBUG-107850
Change-Id: I36ea98842c89ad89fcc1c4a328d138f66f2a0446
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
(cherry picked from commit 74873324bdf3399753f9fcaf7461c0e00df628b1)
---
 src/quick/items/qquickitem.cpp | 21 +++++++++++++--------
 src/quick/items/qquickitem_p.h |  1 +
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index 499fb61d1b..5ee2a440a3 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -2327,6 +2327,7 @@ QQuickItem::QQuickItem(QQuickItemPrivate &dd, QQuickItem *parent)
 QQuickItem::~QQuickItem()
 {
     Q_D(QQuickItem);
+    d->inDestructor = true;
 
     if (d->windowRefCount > 1)
         d->windowRefCount = 1; // Make sure window is set to null in next call to derefWindow().
@@ -2694,9 +2695,8 @@ void QQuickItem::setParentItem(QQuickItem *parentItem)
 
         const bool wasVisible = isVisible();
         op->removeChild(this);
-        if (wasVisible) {
+        if (wasVisible && !op->inDestructor)
             emit oldParentItem->visibleChildrenChanged();
-        }
     } else if (d->window) {
         QQuickWindowPrivate::get(d->window)->parentlessItems.remove(this);
     }
@@ -2773,8 +2773,9 @@ void QQuickItem::setParentItem(QQuickItem *parentItem)
 
     d->itemChange(ItemParentHasChanged, d->parentItem);
 
-    emit parentChanged(d->parentItem);
-    if (isVisible() && d->parentItem)
+    if (!d->inDestructor)
+        emit parentChanged(d->parentItem);
+    if (isVisible() && d->parentItem && !QQuickItemPrivate::get(d->parentItem)->inDestructor)
         emit d->parentItem->visibleChildrenChanged();
 }
 
@@ -2970,7 +2971,8 @@ void QQuickItemPrivate::removeChild(QQuickItem *child)
 
     itemChange(QQuickItem::ItemChildRemovedChange, child);
 
-    emit q->childrenChanged();
+    if (!inDestructor)
+        emit q->childrenChanged();
 }
 
 void QQuickItemPrivate::refWindow(QQuickWindow *c)
@@ -3199,6 +3201,7 @@ QQuickItemPrivate::QQuickItemPrivate()
     , touchEnabled(false)
 #endif
     , hasCursorHandler(false)
+    , inDestructor(false)
     , dirtyAttributes(0)
     , nextDirtyItem(nullptr)
     , prevDirtyItem(nullptr)
@@ -6118,9 +6121,11 @@ bool QQuickItemPrivate::setEffectiveVisibleRecur(bool newEffectiveVisible)
         QAccessible::updateAccessibility(&ev);
     }
 #endif
-    emit q->visibleChanged();
-    if (childVisibilityChanged)
-        emit q->visibleChildrenChanged();
+    if (!inDestructor) {
+        emit q->visibleChanged();
+        if (childVisibilityChanged)
+            emit q->visibleChildrenChanged();
+    }
 
     return true;    // effective visibility DID change
 }
diff --git a/src/quick/items/qquickitem_p.h b/src/quick/items/qquickitem_p.h
index 841d91bb40..ade8fb61f2 100644
--- a/src/quick/items/qquickitem_p.h
+++ b/src/quick/items/qquickitem_p.h
@@ -472,6 +472,7 @@ public:
     bool replayingPressEvent:1;
     bool touchEnabled:1;
     bool hasCursorHandler:1;
+    quint32 inDestructor:1; // has entered ~QQuickItem
 
     enum DirtyType {
         TransformOrigin         = 0x00000001,
-- 
2.40.1

