wasm: a11y - Implement ParentChanged callback

Implement the QAccessible::ParentChanged callback.

Probably not possible with a perfect implementation.

What  can reasonably be done is to issue ParentChanged on;
QWidget::setParent, QWindow::setParent, QQuickItem::setParentItem.

However calling these functions do not necessarily map 1:1 to QAccessibleInterface::parent().

Fixes: QTBUG-138802
Fixes: QTBUG-134923
Change-Id: Iac4ac7843ba904bf0b7aa9964ee68a94294ad979
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/gui/kernel/qwindow.cpp

@@ -856,6 +856,12 @@ void QWindow::setParent(QWindow *parent)
 
     QEvent parentChangedEvent(QEvent::ParentWindowChange);
     QCoreApplication::sendEvent(this, &parentChangedEvent);
+#if QT_CONFIG(accessibility)
+    if (QGuiApplicationPrivate::is_app_running && !QGuiApplicationPrivate::is_app_closing) {
+        QAccessibleEvent qaEvent(this, QAccessible::ParentChanged);
+        QAccessible::updateAccessibility(&qaEvent);
+    }
+#endif
 }
 
 /*!

src/plugins/platforms/wasm/qwasmaccessibility.cpp

@@ -955,6 +955,35 @@ void QWasmAccessibility::removeObject(QAccessibleInterface *iface)
     }
 }
 
+void QWasmAccessibility::unlinkParentForChildren(QAccessibleInterface *iface)
+{
+    auto element = getHtmlElement(iface);
+    if (!element.isUndefined()) {
+        auto oldContainer = element["parentElement"];
+        auto newContainer = getElementContainer(iface);
+        if (!oldContainer.isUndefined() &&
+            !oldContainer.isNull() &&
+            oldContainer != newContainer) {
+            oldContainer.call<void>("removeChild", element);
+        }
+    }
+    for (int i = 0; i < iface->childCount(); ++i)
+        unlinkParentForChildren(iface->child(i));
+}
+
+void QWasmAccessibility::relinkParentForChildren(QAccessibleInterface *iface)
+{
+    auto element = getHtmlElement(iface);
+    if (!element.isUndefined()) {
+        if (element["parentElement"].isUndefined() ||
+            element["parentElement"].isNull()) {
+            linkToParent(iface);
+        }
+    }
+    for (int i = 0; i < iface->childCount(); ++i)
+        relinkParentForChildren(iface->child(i));
+}
+
 void QWasmAccessibility::notifyAccessibilityUpdate(QAccessibleEvent *event)
 {
     if (!m_accessibilityEnabled)
@@ -983,6 +1012,11 @@ void QWasmAccessibility::notifyAccessibilityUpdate(QAccessibleEvent *event)
         createObject(iface);
         break;
 
+    case QAccessible::ParentChanged:
+        unlinkParentForChildren(iface);
+        relinkParentForChildren(iface);
+        break;
+
     default:
         break;
     };

src/plugins/platforms/wasm/qwasmaccessibility.h

@@ -94,6 +94,9 @@ private:
     void populateAccessibilityTree(QAccessibleInterface *iface);
     void createObject(QAccessibleInterface *iface);
     void removeObject(QAccessibleInterface *iface);
+    void unlinkParentForChildren(QAccessibleInterface *iface);
+    void relinkParentForChildren(QAccessibleInterface *iface);
+
     void notifyAccessibilityUpdate(QAccessibleEvent *event) override;
     void setRootObject(QObject *o) override;
     void initialize() override;

src/widgets/kernel/qwidget.cpp

@@ -10960,6 +10960,14 @@ void QWidget::setParent(QWidget *parent, Qt::WindowFlags f)
             }
         }
     }
+
+#if QT_CONFIG(accessibility)
+    if (QGuiApplicationPrivate::is_app_running && !QGuiApplicationPrivate::is_app_closing) {
+        QAccessibleEvent qaEvent(this, QAccessible::ParentChanged);
+        QAccessible::updateAccessibility(&qaEvent);
+    }
+#endif
+
 }
 
 void QWidgetPrivate::setParent_sys(QWidget *newparent, Qt::WindowFlags f)

tests/auto/other/qaccessibility/tst_qaccessibility.cpp

@@ -237,6 +237,8 @@ private slots:
 
     void widgetLocaleTest();
     void noInterfacesBeforeSetActive();
+    void parentChangedEvent();
+
 protected slots:
     void onClicked();
 private:
@@ -4859,5 +4861,27 @@ void tst_QAccessibility::noInterfacesBeforeSetActive()
     }
 }
 
+void tst_QAccessibility::parentChangedEvent()
+{
+    {
+        QMainWindow mainWindow;
+        QWidget w;
+        QTestAccessibility::clearEvents();
+
+        w.setParent(&mainWindow);
+        QAccessibleEvent parentChangedEvent(&w, QAccessible::ParentChanged);
+        QVERIFY(QTestAccessibility::containsEvent(&parentChangedEvent));
+    }
+    {
+        QWindow mainWindow;
+        QWindow w;
+        QTestAccessibility::clearEvents();
+
+        w.setParent(&mainWindow);
+        QAccessibleEvent parentChangedEvent(&w, QAccessible::ParentChanged);
+        QVERIFY(QTestAccessibility::containsEvent(&parentChangedEvent));
+    }
+}
+
 QTEST_MAIN(tst_QAccessibility)
 #include "tst_qaccessibility.moc"