qt a11y: Clear QtXAccessible's ref to XAccessible once passed on

The `QtXAccessible` only needs to hold a reference to
the `XAccessible` in order to pass it to the
`QtAccessibleWidget` ctor in `QtAccessibleWidget::customFactory`
(which gets called via `QAccessible::queryAccessibleInterface`).

After that has happened, the `QtAccessibleWidget` holds
its own reference in its `m_xAccessible` member and is the
only class in the context of the qt a11y bridge that needs
access to the `XAccessible`, so drop the reference
in the `QtXAccessible` to avoid any references being
held even after `QtAccessibleEventListener::disposing`
has been called, s.a.
Change-Id I077dffe6ca3e887707d1f578e947ccf3c2c2a492
"qt a11y: Clear XAccessible reference when disposing" for
some more context.

Change-Id: Ief80b2939e4c509fc4bc68e67500dbad66498506
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/138365
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

2 files changed, 11 insertions, 1 deletions

diff --git a/vcl/inc/qt5/QtXAccessible.hxx b/vcl/inc/qt5/QtXAccessible.hxx
index 4f4285e8065b..ddb7849b641c 100644
--- a/vcl/inc/qt5/QtXAccessible.hxx
+++ b/vcl/inc/qt5/QtXAccessible.hxx
@@ -28,6 +28,11 @@ class QtXAccessible : public QObject
 
 public:
     QtXAccessible(css::uno::Reference<css::accessibility::XAccessible> xAccessible);
+
+    /** Reference to the XAccessible.
+      * This is cleared once it has been passed to the QtAccessibleWidget,
+      * which then keeps an own reference and takes care of all required
+      * access to the XAccessible for the Qt a11y bridge. */
     css::uno::Reference<css::accessibility::XAccessible> m_xAccessible;
 };
 
diff --git a/vcl/qt5/QtAccessibleWidget.cxx b/vcl/qt5/QtAccessibleWidget.cxx
index 83733e04c285..09d01c6e496f 100644
--- a/vcl/qt5/QtAccessibleWidget.cxx
+++ b/vcl/qt5/QtAccessibleWidget.cxx
@@ -749,7 +749,12 @@ QAccessibleInterface* QtAccessibleWidget::customFactory(const QString& classname
     {
         QtXAccessible* pXAccessible = static_cast<QtXAccessible*>(object);
         if (pXAccessible && pXAccessible->m_xAccessible.is())
-            return new QtAccessibleWidget(pXAccessible->m_xAccessible, object);
+        {
+            QtAccessibleWidget* pRet = new QtAccessibleWidget(pXAccessible->m_xAccessible, object);
+            // clear the reference in the QtXAccessible, no longer needed now that the QtAccessibleWidget holds one
+            pXAccessible->m_xAccessible.clear();
+            return pRet;
+        }
     }
 
     return nullptr;