Improving movement inside workspace

include/MainWindow.h

@@ -29,6 +29,7 @@
 #include <QTimer>
 #include <QList>
 #include <QMainWindow>
+#include <QMdiArea>
 
 #include "ConfigManager.h"
 
@@ -45,6 +46,7 @@ class ConfigManager;
 namespace gui
 {
 
+class CustomQMdiArea;
 class PluginView;
 class SubWindow;
 class ToolButton;
@@ -57,7 +59,7 @@ class MainWindow : public QMainWindow
 public:
 	QMdiArea* workspace()
 	{
-		return m_workspace;
+		return reinterpret_cast<QMdiArea*>(m_workspace);
 	}
 
 	QWidget* toolBar()
@@ -203,7 +205,7 @@ private slots:
 	bool guiSaveProject();
 	bool guiSaveProjectAs( const QString & filename );
 
-	QMdiArea * m_workspace;
+	CustomQMdiArea * m_workspace;
 
 	QWidget * m_toolBar;
 	QGridLayout * m_toolBarLayout;
@@ -258,6 +260,20 @@ private slots:
 
 } ;
 
+class CustomQMdiArea : public QMdiArea
+{
+public:
+	CustomQMdiArea(QWidget* parent = nullptr);
+	~CustomQMdiArea() {}
+protected:
+	void mousePressEvent(QMouseEvent* event) override;
+	void mouseMoveEvent(QMouseEvent* event) override;
+	void mouseReleaseEvent(QMouseEvent* event) override;
+private:
+	bool m_isBeingMoved;
+	int m_lastX;
+	int m_lastY;
+};
 
 } // namespace gui
 

src/gui/MainWindow.cpp

@@ -159,7 +159,7 @@ MainWindow::MainWindow() :
 	sideBar->appendTab(new FileBrowser(root_paths.join("*"), FileItem::defaultFilters(), title,
 		embed::getIconPixmap("computer").transformed(QTransform().rotate(90)), splitter, dirs_as_items));
 
-	m_workspace = new QMdiArea(splitter);
+	m_workspace = new CustomQMdiArea(splitter);
 
 	// Load background
 	emit initProgress(tr("Loading background picture"));
@@ -1611,5 +1611,36 @@ void MainWindow::onProjectFileNameChanged()
 	this->resetWindowTitle();
 }
 
+CustomQMdiArea::CustomQMdiArea(QWidget* parent) :
+	QMdiArea(parent),
+	m_isBeingMoved(false)
+{}
+
+void CustomQMdiArea::mousePressEvent(QMouseEvent* event)
+{
+	m_lastX = event->x();
+	m_lastY = event->y();
+	m_isBeingMoved = true;
+}
+
+void CustomQMdiArea::mouseMoveEvent(QMouseEvent* event)
+{
+	if (m_isBeingMoved == false) { return; }
+	if (m_lastX != event->x())
+	{
+		horizontalScrollBar()->setValue(horizontalScrollBar()->value() + m_lastX - event->x());
+		m_lastX = event->x();
+	}
+	if (m_lastY != event->y())
+	{
+		verticalScrollBar()->setValue(verticalScrollBar()->value() + m_lastY - event->y());
+		m_lastY = event->y();
+	}
+}
+
+void CustomQMdiArea::mouseReleaseEvent(QMouseEvent* event)
+{
+	m_isBeingMoved = false;
+}
 
 } // namespace lmms::gui