Prevent reparenting of foreign window embedding container

A foreign window used to embed a Qt window into it should not end up
with changes to its own parent, as its only job is to give the embedded
Qt window a parent handle.

Pick-to: 6.6
Change-Id: If1bc89658fedf449d266bc0cc750c90b6a841a68
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -150,7 +150,10 @@ QCocoaWindow::~QCocoaWindow()
     QMacAutoReleasePool pool;
     [m_nsWindow makeFirstResponder:nil];
     [m_nsWindow setContentView:nil];
-    if ([m_view superview])
+
+    // Remove from superview only if we have a Qt window parent,
+    // as we don't want to affect window container foreign windows.
+    if (QPlatformWindow::parent())
         [m_view removeFromSuperview];
 
     // Make sure to disconnect observer in all case if view is valid

src/plugins/platforms/ios/qioswindow.mm

@@ -91,7 +91,12 @@ QIOSWindow::~QIOSWindow()
     clearAccessibleCache();
 
     quiview_cast(m_view).platformWindow = 0;
-    [m_view removeFromSuperview];
+
+    // Remove from superview only if we have a Qt window parent,
+    // as we don't want to affect window container foreign windows.
+    if (QPlatformWindow::parent())
+        [m_view removeFromSuperview];
+
     [m_view release];
 }
 

tests/auto/gui/kernel/qwindow/tst_foreignwindow.cpp

@@ -25,6 +25,7 @@ private slots:
     void initialState();
 
     void embedForeignWindow();
+    void embedInForeignWindow();
 };
 
 void tst_ForeignWindow::fromWinId()
@@ -94,5 +95,49 @@ void tst_ForeignWindow::embedForeignWindow()
     QTRY_COMPARE(nativeWindow.parentWinId(), originalParentWinId);
 }
 
+void tst_ForeignWindow::embedInForeignWindow()
+{
+    // When a foreign window is used as a container to embed a Qt UI
+    // in a foreign window hierarchy, the foreign window merely acts
+    // as a parent, and should not be modified.
+
+    {
+        // At a minimum, we must be able to reparent into the window
+        NativeWindow nativeWindow;
+        QVERIFY(nativeWindow);
+
+        std::unique_ptr<QWindow> foreignWindow(QWindow::fromWinId(nativeWindow));
+
+        QWindow embeddedWindow;
+        embeddedWindow.setParent(foreignWindow.get());
+        QTRY_VERIFY(nativeWindow.isParentOf(embeddedWindow.winId()));
+    }
+
+    {
+        // The foreign window's native window should not be reparent as a
+        // result of creating the foreign window, adding and removing children,
+        // or destroying the foreign window.
+
+        NativeWindow topLevelNativeWindow;
+        NativeWindow childNativeWindow;
+        childNativeWindow.setParent(topLevelNativeWindow);
+        QVERIFY(topLevelNativeWindow.isParentOf(childNativeWindow));
+
+        std::unique_ptr<QWindow> foreignWindow(QWindow::fromWinId(childNativeWindow));
+        QVERIFY(topLevelNativeWindow.isParentOf(childNativeWindow));
+
+        QWindow embeddedWindow;
+        embeddedWindow.setParent(foreignWindow.get());
+        QTRY_VERIFY(childNativeWindow.isParentOf(embeddedWindow.winId()));
+        QVERIFY(topLevelNativeWindow.isParentOf(childNativeWindow));
+
+        embeddedWindow.setParent(nullptr);
+        QVERIFY(topLevelNativeWindow.isParentOf(childNativeWindow));
+
+        foreignWindow.reset();
+        QVERIFY(topLevelNativeWindow.isParentOf(childNativeWindow));
+    }
+}
+
 #include <tst_foreignwindow.moc>
 QTEST_MAIN(tst_ForeignWindow)

tests/shared/nativewindow.h

@@ -20,23 +20,29 @@ class NativeWindow
 {
     Q_DISABLE_COPY(NativeWindow)
 public:
+#if defined(Q_OS_MACOS)
+    using Handle = NSView*;
+#elif defined(Q_OS_IOS)
+    using Handle = UIView*;
+#elif defined(Q_OS_WIN)
+    using Handle = HWND;
+#elif QT_CONFIG(xcb)
+    using Handle = xcb_window_t;
+#endif
+
     NativeWindow();
     ~NativeWindow();
 
     operator WId() const;
     WId parentWinId() const;
+    bool isParentOf(WId childWinId);
+    void setParent(WId parent);
 
     void setGeometry(const QRect &rect);
     QRect geometry() const;
 
 private:
-#if defined(Q_OS_MACOS) || defined(Q_OS_IOS)
+    Handle m_handle = {};
-    VIEW_BASE *m_handle = nullptr;
-#elif defined(Q_OS_WIN)
-    HWND m_handle = nullptr;
-#elif QT_CONFIG(xcb)
-    xcb_window_t m_handle = 0;
-#endif
 };
 
 #if defined(Q_OS_MACOS) || defined(Q_OS_IOS)
@@ -92,6 +98,20 @@ WId NativeWindow::parentWinId() const
     return WId(m_handle.superview);
 }
 
+bool NativeWindow::isParentOf(WId childWinId)
+{
+    auto *subview = reinterpret_cast<Handle>(childWinId);
+    return subview.superview == m_handle;
+}
+
+void NativeWindow::setParent(WId parent)
+{
+    if (auto *superview = reinterpret_cast<Handle>(parent))
+        [superview addSubview:m_handle];
+    else
+        [m_handle removeFromSuperview];
+}
+
 #elif defined(Q_OS_WIN)
 
 NativeWindow::NativeWindow()
@@ -141,6 +161,16 @@ WId NativeWindow::parentWinId() const
     return WId(GetAncestor(m_handle, GA_PARENT));
 }
 
+bool NativeWindow::isParentOf(WId childWinId)
+{
+    return GetAncestor(Handle(childWinId), GA_PARENT) == m_handle;
+}
+
+void NativeWindow::setParent(WId parent)
+{
+    SetParent(m_handle, Handle(parent));
+}
+
 #elif QT_CONFIG(xcb)
 
 struct Connection
@@ -203,6 +233,22 @@ WId NativeWindow::parentWinId() const
     return tree->parent;
 }
 
+bool NativeWindow::isParentOf(WId childWinId)
+{
+    xcb_query_tree_reply_t *tree = xcb_query_tree_reply(
+        connection, xcb_query_tree(connection, Handle(childWinId)), nullptr);
+    const auto cleanup = qScopeGuard([&]{ free(tree); });
+    return tree->parent == m_handle;
+}
+
+void NativeWindow::setParent(WId parent)
+{
+    xcb_screen_t *screen = xcb_setup_roots_iterator(xcb_get_setup(connection)).data;
+
+    xcb_reparent_window(connection, m_handle,
+        parent ? Handle(parent) : screen->root, 0, 0);
+}
+
 #endif
 
 #endif // NATIVEWINDOW_H