a11y: Prevent one case of losing a11y interface when setting event child

9a369a25ddfac9352cabde65c8476c7433dc6c3a added a
QAccessibleEvent ctor that takes a QAccessibleInterface*
instead of a QObject*.

Retrieving the QAccessibleInterface* later is done using the
interface's unique ID stored in the m_uniqueId member.

However, the fact that m_uniqueId is a member
of the union alongside with m_child means that setting
a child via QAccessibleEvent::setChild also overwrites
the stored unique ID, which breaks retrieving the accessible
interface later.

Fix this for the case where the QAccessibleInterface has
an associated QObject by assigning m_object in the ctor as well.
This means that a QAccessibleEvent created using either of the two
constructors (the one taking the QObject* and the one taking
the QAccessibleInterface* associated with the object) now behaves
the same.

Fixing the case where there is no associated QObject would require
further changes (e.g. adding a member for the QAccessibleInterface*
or making the m_uniqueId member a separate member instead of having
it in a union with m_child). However, I see no way to do so without
breaking the ABI, so that is left unchanged.

This also adds a corresponding test case.

Fixes: QTBUG-105988
Pick-to: 6.4
Change-Id: I71a548af0277a5034e9e207f066fa3e25c5393f3
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/auto/other/qaccessibility/tst_qaccessibility.cpp b/tests/auto/other/qaccessibility/tst_qaccessibility.cpp
index 89ef57e29b..8479985c0e 100644
--- a/tests/auto/other/qaccessibility/tst_qaccessibility.cpp
+++ b/tests/auto/other/qaccessibility/tst_qaccessibility.cpp
@@ -163,6 +163,7 @@ public slots:
     void cleanup();
 private slots:
     void eventTest();
+    void eventWithChildTest();
     void customWidget();
     void deletedWidget();
     void subclassedWidget();
@@ -353,6 +354,33 @@ void tst_QAccessibility::eventTest()
     QTestAccessibility::clearEvents();
 }
 
+void tst_QAccessibility::eventWithChildTest()
+{
+    // make sure that QAccessibleEvent created using either of the two QAccessibleEvent
+    // behaves the same when the same underlying QObject is used
+    QWidget widget;
+    QWidget childWidget(&widget);
+
+    // QAccessibleEvent constructor called with the QObject*
+    QAccessibleEvent event1(&widget, QAccessible::Focus);
+
+    // QAccessibleEvent constructor called with the QAccessibleInterface* for the same QObject*
+    QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(&widget);
+    QAccessibleEvent event2(iface, QAccessible::Focus);
+
+    QVERIFY(event1.accessibleInterface() != nullptr);
+    QVERIFY(event2.accessibleInterface() != nullptr);
+    QCOMPARE(event1.accessibleInterface(), event2.accessibleInterface());
+
+    // set same child for both
+    event1.setChild(0);
+    event2.setChild(0);
+
+    QVERIFY(event1.accessibleInterface() != nullptr);
+    QVERIFY(event2.accessibleInterface() != nullptr);
+    QCOMPARE(event1.accessibleInterface(), event2.accessibleInterface());
+}
+
 void tst_QAccessibility::customWidget()
 {
     {