Fix QAccessibleWidget::focusChild() to return focused descendant

This method should not ignore accessibility objects without
corresponding widget. The widget may have parts with their own
QAccessibilityInterface and these can be also focused.

VoiceOver ignores them if they are not returned by focusChild().

QAccessibleTabBar::focusChild() has been implemented to demonstrate
the concept and make tab titles of QTabBar readable by VoiceOver.

Task-number: QTBUG-78284
Change-Id: Id7c62d86154bbd5d47d6bbee8cb7d05268c2e151
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/widgets/accessible/complexwidgets.cpp

@@ -108,7 +108,10 @@ public:
             s.invalid = true;
             return s;
         }
-        return parent()->state();
+
+        QAccessible::State s = parent()->state();
+        s.focused = (m_index == m_parent->currentIndex());
+        return s;
     }
     QRect rect() const override {
         if (!isValid())
@@ -216,6 +219,16 @@ QTabBar *QAccessibleTabBar::tabBar() const
     return qobject_cast<QTabBar*>(object());
 }
 
+QAccessibleInterface* QAccessibleTabBar::focusChild() const
+{
+    for (int i = 0; i < childCount(); ++i) {
+        if (child(i)->state().focused)
+            return child(i);
+    }
+
+    return nullptr;
+}
+
 QAccessibleInterface* QAccessibleTabBar::child(int index) const
 {
     if (QAccessible::Id id = m_childInterfaces.value(index))

src/widgets/accessible/complexwidgets_p.h

@@ -112,6 +112,7 @@ public:
     explicit QAccessibleTabBar(QWidget *w);
     ~QAccessibleTabBar();
 
+    QAccessibleInterface *focusChild() const override;
     int childCount() const override;
     QString text(QAccessible::Text t) const override;
 

src/widgets/accessible/qaccessiblewidget.cpp

@@ -374,11 +374,15 @@ QAccessibleInterface *QAccessibleWidget::focusChild() const
 
     QWidget *fw = widget()->focusWidget();
     if (!fw)
-        return 0;
+        return nullptr;
 
-    if (isAncestor(widget(), fw) || fw == widget())
-        return QAccessible::queryAccessibleInterface(fw);
-    return 0;
+    if (isAncestor(widget(), fw)) {
+        QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(fw);
+        if (!iface || iface == this || !iface->focusChild())
+            return iface;
+        return iface->focusChild();
+    }
+    return nullptr;
 }
 
 /*! \reimp */

tests/auto/other/qaccessibility/tst_qaccessibility.cpp

@@ -237,6 +237,7 @@ private slots:
     void labelTest();
     void accelerators();
     void bridgeTest();
+    void focusChild();
 
 protected slots:
     void onClicked();
@@ -3913,5 +3914,173 @@ void tst_QAccessibility::bridgeTest()
 #endif
 }
 
+class FocusChildTestAccessibleInterface : public QAccessibleInterface
+{
+public:
+    FocusChildTestAccessibleInterface(int index, bool focus, QAccessibleInterface *parent)
+        : m_parent(parent)
+        , m_index(index)
+        , m_focus(focus)
+    {
+        QAccessible::registerAccessibleInterface(this);
+    }
+
+    bool isValid() const override { return true; }
+    QObject *object() const override { return nullptr; }
+    QAccessibleInterface *childAt(int, int) const override { return nullptr; }
+    QAccessibleInterface *parent() const override { return m_parent; }
+    QAccessibleInterface *child(int) const override { return nullptr; }
+    int childCount() const override { return 0; }
+    int indexOfChild(const QAccessibleInterface *) const override { return -1; }
+    QString text(QAccessible::Text) const override { return QStringLiteral("FocusChildTestAccessibleInterface %1").arg(m_index); }
+    void setText(QAccessible::Text, const QString &) override { }
+    QRect rect() const override { return QRect(); }
+    QAccessible::Role role() const override { return QAccessible::StaticText; }
+
+    QAccessible::State state() const override
+    {
+        QAccessible::State s;
+        s.focused = m_focus;
+        return s;
+    }
+
+private:
+    QAccessibleInterface *m_parent;
+    int m_index;
+    bool m_focus;
+};
+
+class FocusChildTestAccessibleWidget : public QAccessibleWidget
+{
+public:
+    static QAccessibleInterface *ifaceFactory(const QString &key, QObject *o)
+    {
+        if (key == "QtTestAccessibleWidget")
+            return new FocusChildTestAccessibleWidget(static_cast<QtTestAccessibleWidget *>(o));
+        return 0;
+    }
+
+    FocusChildTestAccessibleWidget(QtTestAccessibleWidget *w)
+        : QAccessibleWidget(w)
+    {
+        m_children.push_back(new FocusChildTestAccessibleInterface(0, false, this));
+        m_children.push_back(new FocusChildTestAccessibleInterface(1, true, this));
+        m_children.push_back(new FocusChildTestAccessibleInterface(2, false, this));
+    }
+
+    QAccessible::State state() const override
+    {
+        QAccessible::State s = QAccessibleWidget::state();
+        s.focused = false;
+        return s;
+    }
+
+    QAccessibleInterface *focusChild() const override
+    {
+        for (int i = 0; i < childCount(); ++i) {
+            if (child(i)->state().focused)
+                return child(i);
+        }
+
+        return nullptr;
+    }
+
+    QAccessibleInterface *child(int index) const override
+    {
+        return m_children[index];
+    }
+
+    int childCount() const override
+    {
+        return m_children.size();
+    }
+
+private:
+    QVector<QAccessibleInterface *> m_children;
+};
+
+void tst_QAccessibility::focusChild()
+{
+    {
+        QMainWindow mainWindow;
+        QtTestAccessibleWidget *widget1 = new QtTestAccessibleWidget(0, "Widget1");
+        QAccessibleInterface *iface1 = QAccessible::queryAccessibleInterface(widget1);
+        QtTestAccessibleWidget *widget2 = new QtTestAccessibleWidget(0, "Widget2");
+        QAccessibleInterface *iface2 = QAccessible::queryAccessibleInterface(widget2);
+
+        QWidget *centralWidget = new QWidget;
+        QHBoxLayout *centralLayout = new QHBoxLayout;
+        centralWidget->setLayout(centralLayout);
+        mainWindow.setCentralWidget(centralWidget);
+        centralLayout->addWidget(widget1);
+        centralLayout->addWidget(widget2);
+
+        mainWindow.show();
+        QVERIFY(QTest::qWaitForWindowExposed(&mainWindow));
+
+        // widget1 has not been focused yet -> it has no active focus nor focus widget.
+        QVERIFY(!iface1->focusChild());
+
+        // widget1 is focused -> it has active focus and focus widget.
+        widget1->setFocus();
+        QCOMPARE(iface1->focusChild(), iface1);
+        QCOMPARE(QAccessible::queryAccessibleInterface(&mainWindow)->focusChild(), iface1);
+
+        // widget1 lose focus -> it has no active focus but has focus widget what is itself.
+        // In this case, the focus child of widget1's interface is itself and the focusChild() call
+        // should not run into an infinite recursion.
+        widget2->setFocus();
+        QCOMPARE(iface1->focusChild(), iface1);
+        QCOMPARE(iface2->focusChild(), iface2);
+        QCOMPARE(QAccessible::queryAccessibleInterface(&mainWindow)->focusChild(), iface2);
+
+        delete widget1;
+        delete widget2;
+        delete centralWidget;
+        QTestAccessibility::clearEvents();
+    }
+
+    {
+        QMainWindow mainWindow;
+        QAccessible::installFactory(&FocusChildTestAccessibleWidget::ifaceFactory);
+        QtTestAccessibleWidget *widget = new QtTestAccessibleWidget(0, "FocusChildTestWidget");
+        mainWindow.setCentralWidget(widget);
+        mainWindow.show();
+        QVERIFY(QTest::qWaitForWindowExposed(&mainWindow));
+
+        QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(&mainWindow);
+        QVERIFY(!iface->focusChild());
+        widget->setFocus();
+        QCOMPARE(iface->focusChild(), QAccessible::queryAccessibleInterface(widget)->child(1));
+
+        delete widget;
+        QAccessible::removeFactory(FocusChildTestAccessibleWidget::ifaceFactory);
+        QTestAccessibility::clearEvents();
+    }
+
+    {
+        QMainWindow mainWindow;
+        QTabBar *tabBar = new QTabBar();
+        tabBar->insertTab(0, "First tab");
+        tabBar->insertTab(1, "Second tab");
+        tabBar->insertTab(2, "Third tab");
+        mainWindow.setCentralWidget(tabBar);
+        mainWindow.show();
+        QVERIFY(QTest::qWaitForWindowExposed(&mainWindow));
+
+        tabBar->setFocus();
+        QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(&mainWindow);
+        QCOMPARE(iface->focusChild()->text(QAccessible::Name), QStringLiteral("First tab"));
+        QCOMPARE(iface->focusChild()->role(), QAccessible::PageTab);
+        tabBar->setCurrentIndex(1);
+        QCOMPARE(iface->focusChild()->text(QAccessible::Name), QStringLiteral("Second tab"));
+        QCOMPARE(iface->focusChild()->role(), QAccessible::PageTab);
+
+        delete tabBar;
+        QTestAccessibility::clearEvents();
+    }
+}
+
+
 QTEST_MAIN(tst_QAccessibility)
 #include "tst_qaccessibility.moc"