From e8332575f8a6a912ce10d36d09b3a33ba0240f70 Mon Sep 17 00:00:00 2001
From: Uwe Kindler <uwe_kindler@web.de>
Date: Wed, 19 Feb 2020 22:07:17 +0100
Subject: [PATCH] Improved tab dragging, added support for undocking if mouse
 leaves tabbar during tb dragging

---
 demo/MainWindow.cpp    |  2 +-
 src/DockAreaTabBar.cpp | 44 ++++++++++++++++++++----------------------
 src/DockWidgetTab.cpp  |  8 ++++++--
 3 files changed, 28 insertions(+), 26 deletions(-)

diff --git a/demo/MainWindow.cpp b/demo/MainWindow.cpp
index 300fd1c..f8835a7 100644
--- a/demo/MainWindow.cpp
+++ b/demo/MainWindow.cpp
@@ -488,7 +488,7 @@ CMainWindow::CMainWindow(QWidget *parent) :
 
     // uncomment the following line if you want to use opaque undocking and
 	// opaque splitter resizing
-    // CDockManager::setConfigFlags(CDockManager::DefaultOpaqueConfig);
+    //CDockManager::setConfigFlags(CDockManager::DefaultOpaqueConfig);
 
     // uncomment the following line if you want a fixed tab width that does
 	// not change if the visibility of the close button changes
diff --git a/src/DockAreaTabBar.cpp b/src/DockAreaTabBar.cpp
index 1666283..53096b7 100644
--- a/src/DockAreaTabBar.cpp
+++ b/src/DockAreaTabBar.cpp
@@ -35,6 +35,7 @@
 #include <QDebug>
 #include <QBoxLayout>
 #include <QApplication>
+#include <QtGlobal>
 
 #include "FloatingDockContainer.h"
 #include "DockAreaWidget.h"
@@ -69,6 +70,16 @@ struct DockAreaTabBarPrivate
 	 * The function reassigns the stylesheet to update the tabs
 	 */
 	void updateTabs();
+
+	/**
+	 * Convenience function to access first tab
+	 */
+	CDockWidgetTab* firstTab() const {return _this->tab(0);}
+
+	/**
+	 * Convenience function to access last tab
+	 */
+	CDockWidgetTab* lastTab() const {return _this->tab(_this->count() - 1);}
 };
 // struct DockAreaTabBarPrivate
 
@@ -366,6 +377,8 @@ void CDockAreaTabBar::onTabWidgetMoved(const QPoint& GlobalPos)
 
 	int fromIndex = d->TabsLayout->indexOf(MovingTab);
 	auto MousePos = mapFromGlobal(GlobalPos);
+	MousePos.rx() = qMax(d->firstTab()->geometry().left(), MousePos.x());
+	MousePos.rx() = qMin(d->lastTab()->geometry().right(), MousePos.x());
 	int toIndex = -1;
 	// Find tab under mouse
 	for (int i = 0; i < count(); ++i)
@@ -381,38 +394,23 @@ void CDockAreaTabBar::onTabWidgetMoved(const QPoint& GlobalPos)
 		if (toIndex == fromIndex)
 		{
 			toIndex = -1;
-			continue;
-		}
-
-		if (toIndex < 0)
-		{
-			toIndex = 0;
 		}
 		break;
 	}
 
-	// Now check if the mouse is behind the last tab
-	if (toIndex < 0)
-	{
-		if (MousePos.x() > tab(count() - 1)->geometry().right())
-		{
-            ADS_PRINT("after all tabs");
-			toIndex = count() - 1;
-		}
-		else
-		{
-			toIndex = fromIndex;
-		}
-	}
-
-	d->TabsLayout->removeWidget(MovingTab);
-	d->TabsLayout->insertWidget(toIndex, MovingTab);
-	if (toIndex >= 0)
+	if (toIndex > -1)
 	{
+		d->TabsLayout->removeWidget(MovingTab);
+		d->TabsLayout->insertWidget(toIndex, MovingTab);
         ADS_PRINT("tabMoved from " << fromIndex << " to " << toIndex);
 		emit tabMoved(fromIndex, toIndex);
 		setCurrentIndex(toIndex);
 	}
+	else
+	{
+		// Ensure that the moved tab is reset to its start position
+		d->TabsLayout->update();
+	}
 }
 
 //===========================================================================
diff --git a/src/DockWidgetTab.cpp b/src/DockWidgetTab.cpp
index d979c8a..b568556 100644
--- a/src/DockWidgetTab.cpp
+++ b/src/DockWidgetTab.cpp
@@ -215,6 +215,8 @@ void DockWidgetTabPrivate::moveTab(QMouseEvent* ev)
     QPoint Distance = ev->globalPos() - GlobalDragStartMousePosition;
     Distance.setY(0);
     auto TargetPos = Distance + TabDragStartPosition;
+    TargetPos.rx() = qMax(TargetPos.x(), 0);
+    TargetPos.rx() = qMin(_this->parentWidget()->rect().right() - _this->width() + 1, TargetPos.rx());
     _this->move(TargetPos);
     _this->raise();
 }
@@ -364,9 +366,11 @@ void CDockWidgetTab::mouseMoveEvent(QMouseEvent* ev)
     	d->moveTab(ev);
     }
 
+    auto MappedPos = mapToParent(ev->pos());
+    bool MouseOutsideBar = (MappedPos.x() < 0) || (MappedPos.x() > parentWidget()->rect().right());
     // Maybe a fixed drag distance is better here ?
     int DragDistanceY = qAbs(d->GlobalDragStartMousePosition.y() - ev->globalPos().y());
-    if (DragDistanceY >= CDockManager::startDragDistance())
+    if (DragDistanceY >= CDockManager::startDragDistance() || MouseOutsideBar)
 	{
 		// If this is the last dock area in a dock container with only
     	// one single dock widget it does not make  sense to move it to a new
@@ -390,7 +394,7 @@ void CDockWidgetTab::mouseMoveEvent(QMouseEvent* ev)
         	// tab because it looks strange if it remains on its dragged position
         	if (d->isDraggingState(DraggingTab) && !CDockManager::configFlags().testFlag(CDockManager::OpaqueUndocking))
 			{
-				this->move(d->TabDragStartPosition);
+        		parentWidget()->layout()->update();
 			}
             d->startFloating();
         }