moving the window do not jump to the mouse anymore

ChannelListWidget.cpp

@@ -35,7 +35,10 @@ ChannelTree::~ChannelTree()
 void ChannelTree::mousePressEvent(QMouseEvent * event)
 {
 	if (event->button() == Qt::LeftButton)
+	{
+		m_oldPosition = event->globalPos();
 		doMove = true;
+	}
 	else if (event->button() == Qt::RightButton)
 		m_parent->hide();
 
@@ -52,7 +55,10 @@ void ChannelTree::mouseReleaseEvent(QMouseEvent * event)
 void ChannelTree::mouseMoveEvent(QMouseEvent * event)
 {
 	if (doMove)
-		m_parent->move(event->globalPos());
+	{
+		m_parent->move(m_parent->pos() + (event->globalPos() - m_oldPosition));
+		m_oldPosition = event->globalPos();
+	}
 
 	QTreeWidget::mouseMoveEvent(event);
 }
@@ -79,7 +85,10 @@ Background::~Background()
 void Background::mousePressEvent(QMouseEvent * event)
 {
 	if (event->button() == Qt::LeftButton)
+	{
+		m_oldPosition = event->globalPos();
 		doMove = true;
+	}
 	else if (event->button() == Qt::RightButton)
 		m_parent->hide();
 
@@ -96,7 +105,10 @@ void Background::mouseReleaseEvent(QMouseEvent * event)
 void Background::mouseMoveEvent(QMouseEvent * event)
 {
 	if (doMove)
-		m_parent->move(event->globalPos());
+	{
+		m_parent->move(m_parent->pos() + (event->globalPos() - m_oldPosition));
+		m_oldPosition = event->globalPos();
+	}
 
 	QLabel::mouseMoveEvent(event);
 }