Added initial support for transparent undocking

demo/MainWindow.cpp

@@ -50,6 +50,7 @@
 #include <QWidgetAction>
 #include <QComboBox>
 #include <QInputDialog>
+#include <QRubberBand>
 
 #include <QMap>
 #include <QElapsedTimer>
@@ -321,7 +322,7 @@ CMainWindow::CMainWindow(QWidget *parent) :
 
 	// uncomment the following line if you wand a fixed tab width that does
 	// not change if the visibility of the close button changes
-	// CDockManager::setConfigFlag(CDockManager::RetainTabSizeWhenCloseButtonHidden, true);
+	CDockManager::setConfigFlag(CDockManager::OpaqueUndocking, false);
 
 	// Now create the dock manager and its content
 	d->DockManager = new CDockManager(this);

src/DockAreaTabBar.cpp

@@ -36,6 +36,7 @@
 #include <QApplication>
 
 #include "FloatingDockContainer.h"
+#include "FloatingOverlay.h"
 #include "DockAreaWidget.h"
 #include "DockOverlay.h"
 #include "DockManager.h"
@@ -55,7 +56,7 @@ struct DockAreaTabBarPrivate
 	CDockAreaTabBar* _this;
 	QPoint DragStartMousePos;
 	CDockAreaWidget* DockArea;
-	CFloatingDockContainer* FloatingWidget = nullptr;
+	IFloatingWidget* FloatingWidget = nullptr;
 	QWidget* TabsContainerWidget;
 	QBoxLayout* TabsLayout;
 	int CurrentIndex = -1;
@@ -245,17 +246,31 @@ void CDockAreaTabBar::mouseDoubleClickEvent(QMouseEvent *event)
 
 
 //============================================================================
-CFloatingDockContainer* CDockAreaTabBar::makeAreaFloating(const QPoint& Offset,
-	eDragState DragState)
+IFloatingWidget* CDockAreaTabBar::makeAreaFloating(const QPoint& Offset, eDragState DragState)
 {
 	QSize Size = d->DockArea->size();
-	CFloatingDockContainer* FloatingWidget = new CFloatingDockContainer(d->DockArea);
-    FloatingWidget->startFloating(Offset, Size, DragState, nullptr);
-	auto TopLevelDockWidget = FloatingWidget->topLevelDockWidget();
-	if (TopLevelDockWidget)
+	bool OpaqueUndocking = CDockManager::configFlags().testFlag(CDockManager::OpaqueUndocking) ||
+		(DraggingFloatingWidget != DragState);
+	CFloatingDockContainer* FloatingDockContainer = nullptr;
+	IFloatingWidget* FloatingWidget;
+	if (OpaqueUndocking)
 	{
-		TopLevelDockWidget->emitTopLevelChanged(true);
+		FloatingWidget = FloatingDockContainer = new CFloatingDockContainer(d->DockArea);
 	}
+	else
+	{
+		FloatingWidget = new CFloatingOverlay(d->DockArea);
+	}
+
+    FloatingWidget->startFloating(Offset, Size, DragState, nullptr);
+    if (FloatingDockContainer)
+    {
+		auto TopLevelDockWidget = FloatingDockContainer->topLevelDockWidget();
+		if (TopLevelDockWidget)
+		{
+			TopLevelDockWidget->emitTopLevelChanged(true);
+		}
+    }
 
 	return FloatingWidget;
 }

src/DockAreaTabBar.h

@@ -39,6 +39,7 @@ class CDockWidgetTab;
 struct DockAreaTabBarPrivate;
 class CDockAreaTitleBar;
 class CFloatingDockContainer;
+class IFloatingWidget;
 
 /**
  * Custom tabbar implementation for tab area that is shown on top of a
@@ -95,8 +96,7 @@ protected:
 	/**
 	 * Makes the dock area floating
 	 */
-	CFloatingDockContainer* makeAreaFloating(const QPoint& Offset,
-		eDragState DragState);
+	IFloatingWidget* makeAreaFloating(const QPoint& Offset, eDragState DragState);
 
 
 public:

src/DockAreaWidget.h

@@ -131,7 +131,6 @@ protected:
 	 */
 	void internalSetCurrentDockWidget(CDockWidget* DockWidget);
 
-
 	/**
 	 * Marks tabs menu to update
 	 */

src/DockContainerWidget.cpp

@@ -164,12 +164,24 @@ public:
 	void dropIntoSection(CFloatingDockContainer* FloatingWidget,
 		CDockAreaWidget* TargetArea, DockWidgetArea area);
 
+	/**
+	 * Moves the dock widget or dock area given in Widget parameter to a
+	 * new dock widget area
+	 */
+	void moveToNewSection(QWidget* Widget, CDockAreaWidget* TargetArea, DockWidgetArea area);
+
 	/**
 	 * Creates a new tab for a widget dropped into the center of a section
 	 */
 	void dropIntoCenterOfSection(CFloatingDockContainer* FloatingWidget,
 		CDockAreaWidget* TargetArea);
 
+	/**
+	 * Creates a new tab for a widget dropped into the center of a section
+	 */
+	void moveIntoCenterOfSection(QWidget* Widget, CDockAreaWidget* TargetArea);
+
+
 	/**
 	 * Adds new dock areas to the internal dock area list
 	 */
@@ -503,6 +515,53 @@ void DockContainerWidgetPrivate::dropIntoSection(CFloatingDockContainer* Floatin
 }
 
 
+//============================================================================
+void DockContainerWidgetPrivate::moveIntoCenterOfSection(QWidget* Widget, CDockAreaWidget* TargetArea)
+{
+	auto DroppedDockWidget = qobject_cast<CDockWidget*>(Widget);
+	auto DroppedArea = qobject_cast<CDockAreaWidget*>(Widget);
+
+	if (DroppedDockWidget)
+	{
+		CDockAreaWidget* OldDockArea = DroppedDockWidget->dockAreaWidget();
+		if (OldDockArea)
+		{
+			OldDockArea->removeDockWidget(DroppedDockWidget);
+		}
+		TargetArea->insertDockWidget(0, DroppedDockWidget, false);
+	}
+	else
+	{
+		QList<CDockWidget*> NewDockWidgets = DroppedArea->dockWidgets();
+		int NewCurrentIndex = DroppedArea->currentIndex();
+		for (int i = 0; i < NewDockWidgets.count(); ++i)
+		{
+			CDockWidget* DockWidget = NewDockWidgets[i];
+			TargetArea->insertDockWidget(i, DockWidget, false);
+		}
+		TargetArea->setCurrentIndex(NewCurrentIndex);
+		DroppedArea->dockContainer()->removeDockArea(DroppedArea);
+		DroppedArea->deleteLater();
+	}
+
+	TargetArea->updateTitleBarVisibility();
+	return;
+}
+
+
+//============================================================================
+void DockContainerWidgetPrivate::moveToNewSection(QWidget* Widget, CDockAreaWidget* TargetArea, DockWidgetArea area)
+{
+	// Dropping into center means all dock widgets in the dropped floating
+	// widget will become tabs of the drop area
+	if (CenterDockWidgetArea == area)
+	{
+		moveIntoCenterOfSection(Widget, TargetArea);
+		return;
+	}
+}
+
+
 //============================================================================
 void DockContainerWidgetPrivate::addDockAreasToList(const QList<CDockAreaWidget*> NewDockAreas)
 {
@@ -1245,6 +1304,53 @@ void CDockContainerWidget::dropFloatingWidget(CFloatingDockContainer* FloatingWi
 }
 
 
+//============================================================================
+void CDockContainerWidget::dropWidget(QWidget* DockWidget, const QPoint& TargetPos)
+{
+    ADS_PRINT("CDockContainerWidget::dropFloatingWidget");
+	CDockAreaWidget* DockArea = dockAreaAt(TargetPos);
+	auto dropArea = InvalidDockWidgetArea;
+	auto ContainerDropArea = d->DockManager->containerOverlay()->dropAreaUnderCursor();
+	CDockWidget* TopLevelDockWidget = topLevelDockWidget();
+
+	if (DockArea)
+	{
+		auto dropOverlay = d->DockManager->dockAreaOverlay();
+		dropOverlay->setAllowedAreas(AllDockAreas);
+		dropArea = dropOverlay->showOverlay(DockArea);
+		if (ContainerDropArea != InvalidDockWidgetArea &&
+			ContainerDropArea != dropArea)
+		{
+			dropArea = InvalidDockWidgetArea;
+		}
+
+		if (dropArea != InvalidDockWidgetArea)
+		{
+            ADS_PRINT("Dock Area Drop Content: " << dropArea);
+            d->moveToNewSection(DockWidget, DockArea, dropArea);
+		}
+	}
+
+	// mouse is over container
+	if (InvalidDockWidgetArea == dropArea)
+	{
+		dropArea = ContainerDropArea;
+        ADS_PRINT("Container Drop Content: " << dropArea);
+		if (dropArea != InvalidDockWidgetArea)
+		{
+			//d->dropIntoContainer(FloatingWidget, dropArea);
+		}
+	}
+
+	// If there was a top level widget before the drop, then it is not top
+	// level widget anymore
+	if (TopLevelDockWidget)
+	{
+		TopLevelDockWidget->emitTopLevelChanged(false);
+	}
+}
+
+
 //============================================================================
 QList<CDockAreaWidget*> CDockContainerWidget::openedDockAreas() const
 {

src/DockContainerWidget.h

@@ -47,6 +47,8 @@ class CDockManager;
 struct DockManagerPrivate;
 class CFloatingDockContainer;
 struct FloatingDockContainerPrivate;
+class CFloatingOverlay;
+struct FloatingOverlayPrivate;
 
 /**
  * Container that manages a number of dock areas with single dock widgets
@@ -68,6 +70,9 @@ private:
 	friend class CFloatingDockContainer;
 	friend struct FloatingDockContainerPrivate;
 	friend class CDockWidget;
+	friend class CFloatingOverlay;
+	friend struct FloatingOverlayPrivate;
+
 protected:
 	/**
 	 * Handles activation events to update zOrderIndex
@@ -89,6 +94,11 @@ protected:
 	 */
 	void dropFloatingWidget(CFloatingDockContainer* FloatingWidget, const QPoint& TargetPos);
 
+	/**
+	 * Drop a dock area or a dock widget given in widget parameter
+	 */
+	void dropWidget(QWidget* Widget, const QPoint& TargetPos);
+
 	/**
 	 * Adds the given dock area to this container widget
 	 */

src/DockManager.h

@@ -30,10 +30,18 @@
 //============================================================================
 //                                   INCLUDES
 //============================================================================
-#include "DockContainerWidget.h"
-#include <QIcon>
-
-#include "ads_globals.h"
+#include <ads_globals.h>
+#include <DockContainerWidget.h>
+#include <DockWidget.h>
+#include <FloatingDockContainer.h>
+#include <qbytearray.h>
+#include <qflags.h>
+#include <qlist.h>
+#include <qmap.h>
+#include <qobjectdefs.h>
+#include <qstring.h>
+#include <qstringlist.h>
+#include <QtGui/qicon.h>
 
 class QSettings;
 class QMenu;
@@ -76,6 +84,8 @@ private:
 	friend class CDockWidgetTab;
 	friend struct DockAreaWidgetPrivate;
 	friend struct DockWidgetTabPrivate;
+	friend class CFloatingOverlay;
+	friend struct FloatingOverlayPrivate;
 
 protected:
 	/**
@@ -140,7 +150,12 @@ public:
 		TabCloseButtonIsToolButton = 0x0040,//! If enabled the tab close buttons will be QToolButtons instead of QPushButtons - disabled by default
 		AllTabsHaveCloseButton = 0x0080, //!< if this flag is set, then all tabs that are closable show a close button
 		RetainTabSizeWhenCloseButtonHidden = 0x0100, //!< if this flag is set, the space for the close button is reserved even if the close button is not visible
-		DefaultConfig = ActiveTabHasCloseButton | DockAreaHasCloseButton | OpaqueSplitterResize | XmlCompressionEnabled, ///< the default configuration
+		OpaqueUndocking = 0x0200,
+		DefaultConfig = ActiveTabHasCloseButton
+		              | DockAreaHasCloseButton
+		              | OpaqueSplitterResize
+		              | XmlCompressionEnabled
+		              | OpaqueUndocking, ///< the default configuration
 	};
 	Q_DECLARE_FLAGS(ConfigFlags, eConfigFlag)
 

src/DockOverlay.cpp

@@ -52,7 +52,6 @@ struct DockOverlayPrivate
 	DockWidgetAreas AllowedAreas = InvalidDockWidgetArea;
 	CDockOverlayCross* Cross;
 	QPointer<QWidget> TargetWidget;
-	QRect TargetRect;
 	DockWidgetArea LastLocation = InvalidDockWidgetArea;
 	bool DropPreviewEnabled = true;
 	CDockOverlay::eMode Mode = CDockOverlay::ModeDockAreaOverlay;
@@ -408,7 +407,6 @@ DockWidgetArea CDockOverlay::showOverlay(QWidget* target)
 	}
 
 	d->TargetWidget = target;
-	d->TargetRect = QRect();
 	d->LastLocation = InvalidDockWidgetArea;
 
 	// Move it over the target.
@@ -427,8 +425,8 @@ void CDockOverlay::hideOverlay()
 {
 	hide();
 	d->TargetWidget.clear();
-	d->TargetRect = QRect();
 	d->LastLocation = InvalidDockWidgetArea;
+	d->DropAreaRect = QRect();
 }
 
 
@@ -440,6 +438,13 @@ void CDockOverlay::enableDropPreview(bool Enable)
 }
 
 
+//============================================================================
+bool CDockOverlay::dropPreviewEnabled() const
+{
+	return d->DropPreviewEnabled;
+}
+
+
 //============================================================================
 void CDockOverlay::paintEvent(QPaintEvent* event)
 {

src/DockOverlay.h

@@ -97,6 +97,11 @@ public:
 	 */
 	void enableDropPreview(bool Enable);
 
+	/**
+	 * Returns true if drop preview is enabled
+	 */
+	bool dropPreviewEnabled() const;
+
 	/**
 	 * The drop overlay rectangle for the target area
 	 */

src/DockWidgetTab.cpp

@@ -46,6 +46,7 @@
 #include "DockWidget.h"
 #include "DockAreaWidget.h"
 #include "FloatingDockContainer.h"
+#include "FloatingOverlay.h"
 #include "DockOverlay.h"
 #include "DockManager.h"
 #include "IconProvider.h"
@@ -70,7 +71,7 @@ struct DockWidgetTabPrivate
 	bool IsActiveTab = false;
 	CDockAreaWidget* DockArea = nullptr;
 	eDragState DragState = DraggingInactive;
-	CFloatingDockContainer* FloatingWidget = nullptr;
+	IFloatingWidget* FloatingWidget = nullptr;
 	QIcon Icon;
 	QAbstractButton* CloseButton = nullptr;
 	QSpacerItem* IconTextSpacer;
@@ -228,29 +229,46 @@ bool DockWidgetTabPrivate::startFloating(eDragState DraggingState)
     ADS_PRINT("startFloating");
 	DragState = DraggingState;
 	QSize Size = DockArea->size();
-	CFloatingDockContainer* FloatingWidget = nullptr;
+	IFloatingWidget* FloatingWidget = nullptr;
+	bool OpaqueUndocking = CDockManager::configFlags().testFlag(CDockManager::OpaqueUndocking) ||
+		(DraggingFloatingWidget != DraggingState);
+	std::cout << "OpaqueUndocking " << OpaqueUndocking << std::endl;
 	if (DockArea->dockWidgetsCount() > 1)
 	{
 		// If section widget has multiple tabs, we take only one tab
-		FloatingWidget = new CFloatingDockContainer(DockWidget);
+		if (OpaqueUndocking)
+		{
+			FloatingWidget = new CFloatingDockContainer(DockWidget);
+		}
+		else
+		{
+			FloatingWidget = new CFloatingOverlay(DockWidget);
+		}
 	}
 	else
 	{
 		// If section widget has only one content widget, we can move the complete
 		// dock area into floating widget
-		FloatingWidget = new CFloatingDockContainer(DockArea);
+		if (OpaqueUndocking)
+		{
+			FloatingWidget = new CFloatingDockContainer(DockArea);
+		}
+		else
+		{
+			FloatingWidget = new CFloatingOverlay(DockArea);
+		}
 	}
 
     if (DraggingFloatingWidget == DraggingState)
     {
-        FloatingWidget->startDragging(DragStartMousePosition, Size, _this);
+        FloatingWidget->startFloating(DragStartMousePosition, Size, DraggingFloatingWidget, _this);
     	auto Overlay = DockWidget->dockManager()->containerOverlay();
     	Overlay->setAllowedAreas(OuterDockAreas);
     	this->FloatingWidget = FloatingWidget;
     }
     else
     {
-     	FloatingWidget->initFloatingGeometry(DragStartMousePosition, Size);
+     	FloatingWidget->startFloating(DragStartMousePosition, Size, DraggingInactive, nullptr);
     }
     DockWidget->emitTopLevelChanged(true);
 	return true;

src/FloatingDockContainer.h

@@ -31,6 +31,8 @@
 //============================================================================
 #include "ads_globals.h"
 
+#include <QRubberBand>
+
 #ifdef Q_OS_LINUX
 #include <QDockWidget>
 #define tFloatingWidgetBase QDockWidget
@@ -57,13 +59,30 @@ class CDockAreaTitleBar;
 struct DockAreaTitleBarPrivate;
 class CFloatingWidgetTitleBar;
 
+/**
+ * Pure virtual interface for floating widgets
+ */
+class IFloatingWidget
+{
+public:
+	virtual void startFloating(const QPoint& DragStartMousePos, const QSize& Size,
+        eDragState DragState, QWidget* MouseEventHandler) = 0;
+
+	/**
+	 * Moves the widget to a new position relative to the position given when
+	 * startFloating() was called
+	 */
+	virtual void moveFloating() = 0;
+};
+
+
 /**
  * This implements a floating widget that is a dock container that accepts
  * docking of dock widgets like the main window and that can be docked into
  * another dock container.
  * Every floating window of the docking system is a FloatingDockContainer.
  */
-class ADS_EXPORT CFloatingDockContainer : public tFloatingWidgetBase
+class ADS_EXPORT CFloatingDockContainer : public tFloatingWidgetBase, public IFloatingWidget
 {
 	Q_OBJECT
 private:
@@ -103,7 +122,7 @@ protected:
 	}
 
 	/**
-	 * Call this function if you explecitely want to signal that dragging has
+	 * Call this function if you explicitly want to signal that dragging has
 	 * finished
 	 */
 	void finishDragging();
@@ -150,7 +169,7 @@ public:
 	using Super = QWidget;
 
 	/**
-	 * Create empty flatingb widget - required for restore state
+	 * Create empty floating widget - required for restore state
 	 */
 	CFloatingDockContainer(CDockManager* DockManager);
 

src/FloatingOverlay.cpp

@@ -0,0 +1,277 @@
+//============================================================================
+/// \file   FloatingOverlay.cpp
+/// \author Uwe Kindler
+/// \date   26.11.2019
+/// \brief  Implementation of CFloatingOverlay
+//============================================================================
+
+//============================================================================
+//                                   INCLUDES
+//============================================================================
+#include "FloatingOverlay.h"
+
+#include <iostream>
+
+#include <QEvent>
+#include <QApplication>
+#include <QPainter>
+
+#include "DockWidget.h"
+#include "DockAreaWidget.h"
+#include "DockManager.h"
+#include "DockContainerWidget.h"
+#include "DockOverlay.h"
+
+namespace ads
+{
+
+/**
+ * Private data class (pimpl)
+ */
+struct FloatingOverlayPrivate
+{
+	CFloatingOverlay *_this;
+	QWidget* Content;
+	QPoint DragStartMousePosition;
+	CDockManager* DockManager;
+	CDockContainerWidget *DropContainer = nullptr;
+	qreal WindowOpacity;
+	bool Hidden = false;
+
+
+	/**
+	 * Private data constructor
+	 */
+	FloatingOverlayPrivate(CFloatingOverlay *_public);
+	void updateDropOverlays(const QPoint &GlobalPos);
+
+	void setHidden(bool Value)
+	{
+		Hidden = Value;
+		_this->update();
+	}
+};
+// struct LedArrayPanelPrivate
+
+
+//============================================================================
+void FloatingOverlayPrivate::updateDropOverlays(const QPoint &GlobalPos)
+{
+	if (!_this->isVisible() || !DockManager)
+	{
+		return;
+	}
+
+	auto Containers = DockManager->dockContainers();
+	CDockContainerWidget *TopContainer = nullptr;
+	for (auto ContainerWidget : Containers)
+	{
+		if (!ContainerWidget->isVisible())
+		{
+			continue;
+		}
+
+		/*if (DockContainer == ContainerWidget)
+		{
+			continue;
+		}*/
+
+		QPoint MappedPos = ContainerWidget->mapFromGlobal(GlobalPos);
+		if (ContainerWidget->rect().contains(MappedPos))
+		{
+			if (!TopContainer || ContainerWidget->isInFrontOf(TopContainer))
+			{
+				TopContainer = ContainerWidget;
+			}
+		}
+	}
+
+	DropContainer = TopContainer;
+	auto ContainerOverlay = DockManager->containerOverlay();
+	auto DockAreaOverlay = DockManager->dockAreaOverlay();
+
+	if (!TopContainer)
+	{
+		ContainerOverlay->hideOverlay();
+		DockAreaOverlay->hideOverlay();
+		setHidden(false);
+		return;
+	}
+
+	int VisibleDockAreas = TopContainer->visibleDockAreaCount();
+	ContainerOverlay->setAllowedAreas(
+	    VisibleDockAreas > 1 ? OuterDockAreas : AllDockAreas);
+	DockWidgetArea ContainerArea = ContainerOverlay->showOverlay(TopContainer);
+	ContainerOverlay->enableDropPreview(ContainerArea != InvalidDockWidgetArea);
+	auto DockArea = TopContainer->dockAreaAt(GlobalPos);
+	if (DockArea && DockArea->isVisible() && VisibleDockAreas > 0)
+	{
+		DockAreaOverlay->enableDropPreview(true);
+		DockAreaOverlay->setAllowedAreas(
+		    (VisibleDockAreas == 1) ? NoDockWidgetArea : AllDockAreas);
+		DockWidgetArea Area = DockAreaOverlay->showOverlay(DockArea);
+
+		// A CenterDockWidgetArea for the dockAreaOverlay() indicates that
+		// the mouse is in the title bar. If the ContainerArea is valid
+		// then we ignore the dock area of the dockAreaOverlay() and disable
+		// the drop preview
+		if ((Area == CenterDockWidgetArea)
+		    && (ContainerArea != InvalidDockWidgetArea))
+		{
+			DockAreaOverlay->enableDropPreview(false);
+			ContainerOverlay->enableDropPreview(true);
+		}
+		else
+		{
+			ContainerOverlay->enableDropPreview(InvalidDockWidgetArea == Area);
+		}
+	}
+	else
+	{
+		DockAreaOverlay->hideOverlay();
+	}
+
+	auto DockDropArea = DockAreaOverlay->dropAreaUnderCursor();
+	auto ContainerDropArea = ContainerOverlay->dropAreaUnderCursor();
+	setHidden(DockDropArea != InvalidDockWidgetArea || ContainerDropArea != InvalidDockWidgetArea);
+}
+
+
+//============================================================================
+FloatingOverlayPrivate::FloatingOverlayPrivate(CFloatingOverlay *_public) :
+	_this(_public)
+{
+
+}
+
+//============================================================================
+CFloatingOverlay::CFloatingOverlay(QWidget* Content, QWidget* parent) :
+	QFrame(parent),
+	d(new FloatingOverlayPrivate(this))
+{
+	d->Content = Content;
+	setAttribute(Qt::WA_DeleteOnClose);
+
+	setWindowFlags(Qt::Tool | Qt::FramelessWindowHint);
+	setWindowOpacity(1);
+	setWindowTitle("FloatingOverlay");
+	setAttribute(Qt::WA_NoSystemBackground);
+	setAttribute(Qt::WA_TranslucentBackground);
+	// We install an event filter to detect mouse release events because we
+	// do not receive mouse release event if the floating widget is behind
+	// the drop overlay cross
+	qApp->installEventFilter(this);
+}
+
+
+//============================================================================
+CFloatingOverlay::CFloatingOverlay(CDockWidget* Content, QWidget* parent)
+	: CFloatingOverlay((QWidget*)Content, Content->dockManager())
+{
+	d->DockManager = Content->dockManager();
+}
+
+
+//============================================================================
+CFloatingOverlay::CFloatingOverlay(CDockAreaWidget* Content, QWidget* parent)
+	: CFloatingOverlay((QWidget*)Content, Content->dockManager())
+{
+	d->DockManager = Content->dockManager();
+}
+
+
+//============================================================================
+CFloatingOverlay::~CFloatingOverlay()
+{
+	delete d;
+}
+
+
+//============================================================================
+void CFloatingOverlay::moveFloating()
+{
+	int BorderSize = (frameSize().width() - size().width()) / 2;
+	const QPoint moveToPos = QCursor::pos() - d->DragStartMousePosition
+	    - QPoint(BorderSize, 0);
+	move(moveToPos);
+}
+
+
+//============================================================================
+void CFloatingOverlay::startFloating(const QPoint &DragStartMousePos,
+    const QSize &Size, eDragState DragState, QWidget *MouseEventHandler)
+{
+	Q_UNUSED(MouseEventHandler)
+	Q_UNUSED(DragState)
+	resize(Size);
+	d->DragStartMousePosition = DragStartMousePos;
+	moveFloating();
+	show();
+
+}
+
+
+//============================================================================
+void CFloatingOverlay::moveEvent(QMoveEvent *event)
+{
+	std::cout << "CFloatingOverlay::moveEvent" << std::endl;
+	QWidget::moveEvent(event);
+	d->updateDropOverlays(QCursor::pos());
+}
+
+
+//============================================================================
+bool CFloatingOverlay::eventFilter(QObject *watched, QEvent *event)
+{
+	Q_UNUSED(watched);
+	if (event->type() == QEvent::MouseButtonRelease)
+	{
+		ADS_PRINT("FloatingWidget::eventFilter QEvent::MouseButtonRelease");
+		std::cout << "CFloatingOverlay::eventFilter QEvent::MouseButtonRelease" << std::endl;
+
+		if (d->DropContainer)
+		{
+			d->DropContainer->dropWidget(d->Content, QCursor::pos());
+			d->DropContainer = nullptr;
+		}
+
+		this->close();
+		d->DockManager->containerOverlay()->hideOverlay();
+		d->DockManager->dockAreaOverlay()->hideOverlay();
+	}
+
+	return false;
+}
+
+
+//============================================================================
+void CFloatingOverlay::paintEvent(QPaintEvent* event)
+{
+	Q_UNUSED(event);
+
+	if (d->Hidden)
+	{
+		return;
+	}
+
+	QRect r = rect();
+	QPainter painter(this);
+    QColor Color = palette().color(QPalette::Active, QPalette::Highlight);
+    QPen Pen = painter.pen();
+    Pen.setColor(Color.darker(120));
+    Pen.setStyle(Qt::SolidLine);
+    Pen.setWidth(1);
+    Pen.setCosmetic(true);
+    painter.setPen(Pen);
+    Color = Color.lighter(130);
+    Color.setAlpha(64);
+    painter.setBrush(Color);
+	painter.drawRect(r.adjusted(0, 0, -1, -1));
+}
+
+
+
+} // namespace ads
+
+//---------------------------------------------------------------------------
+// EOF FloatingOverlay.cpp

src/FloatingOverlay.h

@@ -0,0 +1,67 @@
+#ifndef FloatingOverlayH
+#define FloatingOverlayH
+//============================================================================
+/// \file   FloatingOverlay.h
+/// \author Uwe Kindler
+/// \date   26.11.2019
+/// \brief  Declaration of CFloatingOverlay
+//============================================================================
+
+//============================================================================
+//                                   INCLUDES
+//============================================================================
+#include <QFrame>
+#include "FloatingDockContainer.h"
+
+namespace ads
+{
+class CDockWidget;
+class CDockAreaWidget;
+struct FloatingOverlayPrivate;
+
+/**
+ * A floating overlay is a temporary floating widget that is just used to
+ * indicate the floating widget movement
+ */
+class CFloatingOverlay : public QFrame, public IFloatingWidget
+{
+private:
+	FloatingOverlayPrivate* d;
+	friend class FloatingOverlayPrivate;
+
+protected:
+	virtual void moveEvent(QMoveEvent *event) override;
+	virtual bool eventFilter(QObject *watched, QEvent *event) override;
+	virtual void paintEvent(QPaintEvent *e) override;
+
+	/**
+	 * The content is a DockArea or a DockWidget
+	 */
+	CFloatingOverlay(QWidget* Content, QWidget* parent);
+
+public:
+	using Super = QRubberBand;
+	CFloatingOverlay(CDockWidget* Content, QWidget* parent = nullptr);
+	CFloatingOverlay(CDockAreaWidget* Content, QWidget* parent = nullptr);
+
+	/**
+	 * Delete private data
+	 */
+	~CFloatingOverlay();
+
+	virtual void startFloating(const QPoint& DragStartMousePos, const QSize& Size,
+        eDragState DragState, QWidget* MouseEventHandler) override;
+
+	/**
+	 * Moves the widget to a new position relative to the position given when
+	 * startFloating() was called
+	 */
+	virtual void moveFloating() override;
+};
+
+
+} // namespace ads
+
+//---------------------------------------------------------------------------
+#endif // FloatingOverlayH
+

src/ads_globals.h

@@ -34,6 +34,7 @@
 #include <QtCore/QtGlobal>
 #include <QPixmap>
 #include <QWidget>
+#include <QDebug>
 
 #ifndef ADS_STATIC
 #ifdef ADS_SHARED_EXPORT
@@ -46,6 +47,7 @@
 #endif
 
 // Define ADS_DEBUG_PRINT to enable a lot of debug output
+#define ADS_DEBUG_PRINT
 #ifdef ADS_DEBUG_PRINT
 #define ADS_PRINT(s) qDebug() << s
 #else

src/src.pro

@@ -37,6 +37,7 @@ HEADERS += \
     DockWidget.h \
     DockWidgetTab.h \
     FloatingDockContainer.h \
+    FloatingOverlay.h \
     DockOverlay.h \
     DockSplitter.h \
     DockAreaTitleBar.h \
@@ -53,6 +54,7 @@ SOURCES += \
     DockWidget.cpp \
     DockWidgetTab.cpp \
     FloatingDockContainer.cpp \
+    FloatingOverlay.cpp \
     DockOverlay.cpp \
     DockSplitter.cpp \
     DockAreaTitleBar.cpp \