From 0c0eadc484ab7143801593ccdbe8e96eeb9f6cf7 Mon Sep 17 00:00:00 2001
From: Michael Weghorn <m.weghorn@posteo.de>
Date: Fri, 26 Aug 2022 14:51:04 +0200
Subject: [PATCH] a11y: Prevent one case of losing a11y interface when setting
 event child
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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>
---
 src/gui/accessible/qaccessible.h              |  3 +-
 .../qaccessibility/tst_qaccessibility.cpp     | 28 +++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/gui/accessible/qaccessible.h b/src/gui/accessible/qaccessible.h
index 2700b5c0807..b5e155c01e4 100644
--- a/src/gui/accessible/qaccessible.h
+++ b/src/gui/accessible/qaccessible.h
@@ -287,7 +287,7 @@ public:
     }
 
     inline QAccessibleEvent(QAccessibleInterface *iface, QAccessible::Event typ)
-        : m_type(typ), m_object(nullptr)
+        : m_type(typ)
     {
         Q_ASSERT(iface);
         Q_ASSERT(m_type != QAccessible::ValueChanged);
@@ -299,6 +299,7 @@ public:
         Q_ASSERT(m_type != QAccessible::TextUpdated);
         Q_ASSERT(m_type != QAccessible::TableModelChanged);
         m_uniqueId = QAccessible::uniqueId(iface);
+        m_object = iface->object();
     }
 
     virtual ~QAccessibleEvent();
diff --git a/tests/auto/other/qaccessibility/tst_qaccessibility.cpp b/tests/auto/other/qaccessibility/tst_qaccessibility.cpp
index 89ef57e29b3..8479985c0e8 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()
 {
     {