4 files changed, 17 insertions, 12 deletions
diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 7c596d5ae5..c057fccade 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -1124,7 +1124,7 @@ static void init_platform(const QString &pluginArgument, const QString &platform
                 = QStringLiteral("This application failed to start because it could not find or load the Qt platform plugin \"%1\"\nin \"%2\".\n\n").arg(name, QDir::toNativeSeparators(platformPluginPath));
         if (!keys.isEmpty()) {
             fatalMessage += QStringLiteral("Available platform plugins are: %1.\n\n").arg(
-                        keys.join(QStringLiteral(", ")));
+                        keys.join(QLatin1String(", ")));
         }
         fatalMessage += QStringLiteral("Reinstalling the application may fix this problem.");
 #if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)
diff --git a/src/gui/kernel/qplatformintegration.h b/src/gui/kernel/qplatformintegration.h
index 29f7b9b3a6..54904ef60d 100644
--- a/src/gui/kernel/qplatformintegration.h
+++ b/src/gui/kernel/qplatformintegration.h
@@ -109,6 +109,7 @@ public:
 
     virtual QPlatformPixmap *createPlatformPixmap(QPlatformPixmap::PixelType type) const;
     virtual QPlatformWindow *createPlatformWindow(QWindow *window) const = 0;
+    virtual QPlatformWindow *createForeignWindow(QWindow *, WId) const { return 0; }
     virtual QPlatformBackingStore *createPlatformBackingStore(QWindow *window) const = 0;
 #ifndef QT_NO_OPENGL
     virtual QPlatformOpenGLContext *createPlatformOpenGLContext(QOpenGLContext *context) const;
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 9d41a72072..8e98958949 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -424,7 +424,7 @@ void QWindowPrivate::setTopLevelScreen(QScreen *newScreen, bool recreate)
     }
 }
 
-void QWindowPrivate::create(bool recursive)
+void QWindowPrivate::create(bool recursive, WId nativeHandle)
 {
     Q_Q(QWindow);
     if (platformWindow)
@@ -433,8 +433,10 @@ void QWindowPrivate::create(bool recursive)
     if (q->parent())
         q->parent()->create();
 
-    platformWindow = QGuiApplicationPrivate::platformIntegration()->createPlatformWindow(q);
-    Q_ASSERT(platformWindow || q->type() == Qt::ForeignWindow);
+    QPlatformIntegration *platformIntegration = QGuiApplicationPrivate::platformIntegration();
+    platformWindow = nativeHandle ? platformIntegration->createForeignWindow(q, nativeHandle)
+        : platformIntegration->createPlatformWindow(q);
+    Q_ASSERT(platformWindow);
 
     if (!platformWindow) {
         qWarning() << "Failed to create platform window for" << q << "with flags" << q->flags();
@@ -629,9 +631,6 @@ WId QWindow::winId() const
 {
     Q_D(const QWindow);
 
-    if (type() == Qt::ForeignWindow)
-        return WId(property("_q_foreignWinId").value<WId>());
-
     if(!d->platformWindow)
         const_cast<QWindow *>(this)->create();
 
@@ -865,7 +864,12 @@ void QWindow::setFlags(Qt::WindowFlags flags)
 Qt::WindowFlags QWindow::flags() const
 {
     Q_D(const QWindow);
-    return d->windowFlags;
+    Qt::WindowFlags flags = d->windowFlags;
+
+    if (d->platformWindow && d->platformWindow->isForeignWindow())
+        flags |= Qt::ForeignWindow;
+
+    return flags;
 }
 
 /*!
@@ -2584,13 +2588,13 @@ QWindow *QWindow::fromWinId(WId id)
     }
 
     QWindow *window = new QWindow;
-    window->setFlags(Qt::ForeignWindow);
-    window->setProperty("_q_foreignWinId", QVariant::fromValue(id));
-    window->create();
+    qt_window_private(window)->create(false, id);
+
     if (!window->handle()) {
         delete window;
         return nullptr;
     }
+
     return window;
 }
 
diff --git a/src/gui/kernel/qwindow_p.h b/src/gui/kernel/qwindow_p.h
index 272401453a..59016e4551 100644
--- a/src/gui/kernel/qwindow_p.h
+++ b/src/gui/kernel/qwindow_p.h
@@ -136,7 +136,7 @@ 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);