Revert "QWindow: Persist foreign winId to support destroy/create cycles"

This reverts commit 4d5aedac1de02ec21bc6f4ae8c66e1e7bfc665a4.

It broke window activation on iOS somehow.

Change-Id: I01fc476d23a65f39aa33d9abd06417ffcd13b5aa
Task-number: QTBUG-125142
Reviewed-by: Jani Heikkinen <jani.heikkinen@qt.io>

src/gui/kernel/qwindow.cpp

@@ -521,9 +521,7 @@ void QWindowPrivate::setTopLevelScreen(QScreen *newScreen, bool recreate)
     }
 }
 
-static constexpr auto kForeignWindowId = "_q_foreignWinId";
+void QWindowPrivate::create(bool recursive, WId nativeHandle)
-
-void QWindowPrivate::create(bool recursive)
 {
     Q_Q(QWindow);
     if (platformWindow)
@@ -551,8 +549,6 @@ void QWindowPrivate::create(bool recursive)
             setTopLevelScreen(screen, false);
     }
 
-    const WId nativeHandle = q->property(kForeignWindowId).value<WId>();
-
     QPlatformIntegration *platformIntegration = QGuiApplicationPrivate::platformIntegration();
     platformWindow = nativeHandle ? platformIntegration->createForeignWindow(q, nativeHandle)
         : platformIntegration->createPlatformWindow(q);
@@ -2063,16 +2059,6 @@ void QWindowPrivate::destroy()
         QObject *object = childrenWindows.at(i);
         if (object->isWindowType()) {
             QWindow *w = static_cast<QWindow*>(object);
-            auto *childPlatformWindow = w->handle();
-            if (!childPlatformWindow)
-                continue;
-
-            // Decouple the foreign window from this window,
-            // so that destroying our native handle doesn't
-            // bring down the foreign window as well.
-            if (childPlatformWindow->isForeignWindow())
-                childPlatformWindow->setParent(nullptr);
-
             qt_window_private(w)->destroy();
         }
     }
@@ -3000,11 +2986,7 @@ QWindow *QWindow::fromWinId(WId id)
     }
 
     QWindow *window = new QWindow;
-
+    qt_window_private(window)->create(false, id);
-    // Persist the winId in a private property so that we
-    // can recreate the window after being destroyed.
-    window->setProperty(kForeignWindowId, id);
-    window->create();
 
     if (!window->handle()) {
         delete window;

src/gui/kernel/qwindow_p.h

@@ -66,7 +66,7 @@ public:
     void updateSiblingPosition(SiblingPosition);
 
     bool windowRecreationRequired(QScreen *newScreen) const;
-    void create(bool recursive);
+    void create(bool recursive, WId nativeHandle = 0);
     void destroy();
     void setTopLevelScreen(QScreen *newScreen, bool recreate);
     void connectToScreen(QScreen *topLevelScreen);

src/plugins/platforms/ios/qioswindow.mm

@@ -55,7 +55,6 @@ QIOSWindow::QIOSWindow(QWindow *window, WId nativeHandle)
 
     connect(qGuiApp, &QGuiApplication::applicationStateChanged, this, &QIOSWindow::applicationStateChanged);
 
-    if (QPlatformWindow::parent())
     setParent(QPlatformWindow::parent());
 
     if (!isForeignWindow()) {

src/plugins/platforms/windows/qwindowswindow.cpp

@@ -1357,8 +1357,6 @@ QWindowsForeignWindow::QWindowsForeignWindow(QWindow *window, HWND hwnd)
     , m_hwnd(hwnd)
     , m_topLevelStyle(0)
 {
-    if (QPlatformWindow::parent())
-        setParent(QPlatformWindow::parent());
 }
 
 void QWindowsForeignWindow::setParent(const QPlatformWindow *newParentWindow)

src/plugins/platforms/xcb/qxcbwindow.cpp

@@ -522,10 +522,6 @@ QXcbForeignWindow::QXcbForeignWindow(QWindow *window, WId nativeHandle)
         QRect nativeGeometry(geometry->x, geometry->y, geometry->width, geometry->height);
         QPlatformWindow::setGeometry(nativeGeometry);
     }
-
-    // And reparent, if we have a parent already
-    if (QPlatformWindow::parent())
-        setParent(QPlatformWindow::parent());
 }
 
 QXcbForeignWindow::~QXcbForeignWindow()

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

@@ -26,9 +26,6 @@ private slots:
 
     void embedForeignWindow();
     void embedInForeignWindow();
-
-    void destroyExplicitly();
-    void destroyWhenParentIsDestroyed();
 };
 
 void tst_ForeignWindow::fromWinId()
@@ -141,50 +138,5 @@ void tst_ForeignWindow::embedInForeignWindow()
     }
 }
 
-void tst_ForeignWindow::destroyExplicitly()
-{
-    NativeWindow nativeWindow;
-    QVERIFY(nativeWindow);
-
-    std::unique_ptr<QWindow> foreignWindow(QWindow::fromWinId(nativeWindow));
-    QVERIFY(foreignWindow->handle());
-
-    // Explicitly destroying a foreign window is a no-op, as
-    // the documentation claims that it "releases the native
-    // platform resources associated with this window.", which
-    // is not technically true for foreign windows.
-    auto *windowHandleBeforeDestroy = foreignWindow->handle();
-    foreignWindow->destroy();
-    QCOMPARE(foreignWindow->handle(), windowHandleBeforeDestroy);
-}
-
-void tst_ForeignWindow::destroyWhenParentIsDestroyed()
-{
-    QWindow parentWindow;
-
-    NativeWindow nativeWindow;
-    QVERIFY(nativeWindow);
-
-    std::unique_ptr<QWindow> foreignWindow(QWindow::fromWinId(nativeWindow));
-    foreignWindow->setParent(&parentWindow);
-    QTRY_COMPARE(nativeWindow.parentWinId(), parentWindow.winId());
-
-    // Reparenting into a window will result in creating it
-    QVERIFY(parentWindow.handle());
-
-    // Destroying the parent window of the foreign window results
-    // in destroying the foreign window as well, as the foreign
-    // window no longer has a parent it can be embedded in.
-    QVERIFY(foreignWindow->handle());
-    parentWindow.destroy();
-    QVERIFY(!foreignWindow->handle());
-
-    // But the foreign window can be recreated again, and will
-    // continue to be a native child of the parent window.
-    foreignWindow->create();
-    QVERIFY(foreignWindow->handle());
-    QTRY_COMPARE(nativeWindow.parentWinId(), parentWindow.winId());
-}
-
 #include <tst_foreignwindow.moc>
 QTEST_MAIN(tst_ForeignWindow)

tests/shared/nativewindow.h

@@ -238,7 +238,7 @@ WId NativeWindow::parentWinId() const
     xcb_query_tree_reply_t *tree = xcb_query_tree_reply(
         connection, xcb_query_tree(connection, m_handle), nullptr);
     const auto cleanup = qScopeGuard([&]{ free(tree); });
-    return tree ? tree->parent : 0;
+    return tree->parent;
 }
 
 bool NativeWindow::isParentOf(WId childWinId)