Avoid needless notifications when destroying layouts

When deleting a layout with children, it ends up in ~QQuickItem(), which in
turn will call setParentItem(0).  setParentItem(0) will in turn call
setEffectiveVisibleRecur(), which will recurse down all its descendants.
Therefore, deleting a top level layout might trigger item change listeners
for *all* its descendants, not only its direct children.

This behavior might even cause crashes: The visibility changes will then
trigger an invalidation of the layout, which will propagate up the parent
hierarchy, and potentially call invalidate() on a partially-destroyed
layout, which then might crash.

Change-Id: I48e11d57f69e9011ced6c3a0b51e3d89b24ad5c1
Task-number: QTBUG-55103
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 1 insertions, 5 deletions

diff --git a/src/imports/layouts/qquicklinearlayout.cpp b/src/imports/layouts/qquicklinearlayout.cpp
index 13fdd496c2..50b3eed87e 100644
--- a/src/imports/layouts/qquicklinearlayout.cpp
+++ b/src/imports/layouts/qquicklinearlayout.cpp
@@ -305,11 +305,7 @@ QQuickGridLayoutBase::~QQuickGridLayoutBase()
 
     // Remove item listeners so we do not act on signalling unnecessarily
     // (there is no point, as the layout will be torn down anyway).
-    for (int i = 0; i < itemCount(); ++i) {
-        QQuickItem *item = itemAt(i);
-        QQuickItemPrivate::get(item)->removeItemChangeListener(this, QQuickItemPrivate::SiblingOrder | QQuickItemPrivate::ImplicitWidth | QQuickItemPrivate::ImplicitHeight | QQuickItemPrivate::Destroyed | QQuickItemPrivate::Visibility);
-    }
-
+    deactivateRecur();
     delete d->styleInfo;
 }