qt a11y: Clear XAccessible reference when disposing

The `XEventListener::disposing` doc
(in `./udkapi/com/sun/star/lang/XEventListener.idl`) says:

> /** gets called when the broadcaster is about to be disposed.
>
>     <p>All listeners and all other objects, which reference the
>     broadcaster should release the reference to the source.
>     No method should be invoked anymore on this object (
>     including XComponent::removeEventListener() ).
>     </p>
>
>     <p>This method is called for every listener registration
>     of derived listener interfaced, not only for registrations
>     at XComponent. </p>
>  */

Therefore, clear the `XAccessible` reference held in
the associated `QtAccessibleWidget`
in `QtAccessibleEventListener::disposing`.

This also implies that `QtAccessibleWidget::isValid()`
(overriding the `QAccessibleInterface` method)
will return `false` from that point on.

Change-Id: I077dffe6ca3e887707d1f578e947ccf3c2c2a492
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/138364
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

3 files changed, 11 insertions, 1 deletions

diff --git a/vcl/inc/qt5/QtAccessibleWidget.hxx b/vcl/inc/qt5/QtAccessibleWidget.hxx
index fdd97b0b407d..0ca17b394123 100644
--- a/vcl/inc/qt5/QtAccessibleWidget.hxx
+++ b/vcl/inc/qt5/QtAccessibleWidget.hxx
@@ -50,6 +50,10 @@ class QtAccessibleWidget final : public QObject,
 public:
     QtAccessibleWidget(const css::uno::Reference<css::accessibility::XAccessible> xAccessible,
                        QObject* pObject);
+
+    void invalidate();
+
+    // QAccessibleInterface
     QWindow* window() const override;
     int childCount() const override;
     int indexOfChild(const QAccessibleInterface* child) const override;
diff --git a/vcl/qt5/QtAccessibleEventListener.cxx b/vcl/qt5/QtAccessibleEventListener.cxx
index ee562a4eca38..53256181ea4e 100644
--- a/vcl/qt5/QtAccessibleEventListener.cxx
+++ b/vcl/qt5/QtAccessibleEventListener.cxx
@@ -353,6 +353,10 @@ void QtAccessibleEventListener::notifyEvent(const css::accessibility::Accessible
     }
 }
 
-void QtAccessibleEventListener::disposing(const EventObject& /* Source */) {}
+void QtAccessibleEventListener::disposing(const EventObject& /* Source */)
+{
+    assert(m_pAccessibleWidget);
+    m_pAccessibleWidget->invalidate();
+}
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/qt5/QtAccessibleWidget.cxx b/vcl/qt5/QtAccessibleWidget.cxx
index d6370877f449..83733e04c285 100644
--- a/vcl/qt5/QtAccessibleWidget.cxx
+++ b/vcl/qt5/QtAccessibleWidget.cxx
@@ -73,6 +73,8 @@ QtAccessibleWidget::QtAccessibleWidget(const Reference<XAccessible> xAccessible,
     }
 }
 
+void QtAccessibleWidget::invalidate() { m_xAccessible.clear(); }
+
 Reference<XAccessibleContext> QtAccessibleWidget::getAccessibleContextImpl() const
 {
     Reference<XAccessibleContext> xAc;