Use Native Windows (#797)

* Avoid changing to a top-level window when moving a native window.

* Support using native windows for the dock/area widgets.

src/DockAreaWidget.cpp

@@ -460,6 +460,12 @@ CDockAreaWidget::CDockAreaWidget(CDockManager* DockManager, CDockContainerWidget
 
 	d->createTitleBar();
 	d->ContentsLayout = new DockAreaLayout(d->Layout);
+
+	if (CDockManager::testConfigFlag(CDockManager::UseNativeWindows))
+	{
+		winId();
+	}
+
 	if (d->DockManager)
 	{
 		Q_EMIT d->DockManager->dockAreaCreated(this);

src/DockContainerWidget.cpp

@@ -1574,7 +1574,10 @@ void CDockContainerWidget::removeDockArea(CDockAreaWidget* area)
 
 	// Remove are from parent splitter and recursively hide tree of parent
 	// splitters if it has no visible content
-	area->setParent(nullptr);
+	if (area->testAttribute(Qt::WA_NativeWindow))
+		area->setParent(d->DockManager);
+	else
+		area->setParent(nullptr);
 	internal::hideEmptyParentSplitters(Splitter);
 
 	// Remove this area from cached areas

src/DockManager.h

@@ -217,6 +217,7 @@ public:
 		ShowTabTextOnlyForActiveTab =0x8000000, //! Set this flag to show label texts in dock area tabs only for active tabs
 		DoubleClickUndocksWidget = 0x10000000, //!< If the flag is set, a double click on a tab undocks the widget
 		TabsAtBottom = 0x20000000, //!< If the flag is set, tabs will be shown at the bottom instead of in the title bar.
+		UseNativeWindows = 0x40000000, //!< If the flag is set, windows for the dock and area widgets will be native.
 
 
         DefaultDockAreaButtons = DockAreaHasCloseButton

src/DockWidget.cpp

@@ -396,6 +396,11 @@ CDockWidget::CDockWidget(CDockManager *manager, const QString &title, QWidget* p
 	{
 		setFocusPolicy(Qt::ClickFocus);
 	}
+
+	if (CDockManager::testConfigFlag(CDockManager::UseNativeWindows))
+	{
+		winId();
+	}
 }
 
 

src/FloatingDockContainer.cpp

@@ -728,6 +728,11 @@ CFloatingDockContainer::CFloatingDockContainer(CDockManager *DockManager) :
 	l->addWidget(d->DockContainer);
 #endif
 
+	if (CDockManager::testConfigFlag(CDockManager::UseNativeWindows))
+	{
+		winId();
+	}
+
 	DockManager->registerFloatingWidget(this);
 }