Add horizontal scrolling to MainWindow QMdiArea

include/MainWindow.h

@@ -29,20 +29,32 @@
 #include <QtCore/QTimer>
 #include <QtCore/QList>
 #include <QMainWindow>
+#include <QMdiArea>
 
 #include "ConfigManager.h"
 #include "SubWindow.h"
 
 class QAction;
 class QDomElement;
 class QGridLayout;
-class QMdiArea;
 
 class ConfigManager;
 class PluginView;
 class ToolButton;
 
 
+class ScrollFixMdiArea : public QMdiArea
+{
+	Q_OBJECT
+protected:
+	virtual void wheelEvent(QWheelEvent * we);
+public:
+	ScrollFixMdiArea(QWidget* parent = nullptr) :
+		QMdiArea(parent)
+	{ /* only need to init QMdiArea */ }
+};
+
+
 class MainWindow : public QMainWindow
 {
 	Q_OBJECT
@@ -191,7 +203,7 @@ private slots:
 	bool guiSaveProject();
 	bool guiSaveProjectAs( const QString & filename );
 
-	QMdiArea * m_workspace;
+	ScrollFixMdiArea * m_workspace;
 
 	QWidget * m_toolBar;
 	QGridLayout * m_toolBarLayout;

src/gui/MainWindow.cpp

@@ -181,7 +181,7 @@ MainWindow::MainWindow() :
 					embed::getIconPixmap( "computer" ).transformed( QTransform().rotate( 90 ) ),
 							splitter, dirs_as_items) );
 
-	m_workspace = new QMdiArea(splitter);
+	m_workspace = new ScrollFixMdiArea(splitter);
 
 	// Load background
 	emit initProgress(tr("Loading background picture"));
@@ -1702,3 +1702,24 @@ void MainWindow::onProjectFileNameChanged()
 {
 	this->resetWindowTitle();
 }
+
+
+
+
+void ScrollFixMdiArea::wheelEvent(QWheelEvent * we)
+{
+	QPoint deg = we->angleDelta();
+	QScrollBar* bar = we->modifiers() & Qt::ShiftModifier
+		? horizontalScrollBar()
+		: verticalScrollBar();
+	int multiplier = we->modifiers() & Qt::ControlModifier
+		? 2
+		: 1;
+	if (!bar->isVisible())
+	{
+		we->ignore();
+		return;
+	}
+	bar->setValue(bar->value() - (deg.y() * multiplier));
+	we->accept();
+}

src/gui/TrackContainerView.cpp

@@ -469,7 +469,28 @@ void TrackContainerView::scrollArea::wheelEvent( QWheelEvent * _we )
 	m_trackContainerView->wheelEvent( _we );
 	if( !_we->isAccepted() )
 	{
-		QScrollArea::wheelEvent( _we );
+		// Handle Shift+Wheel orientation of QWheelEvent
+		if (_we->modifiers() & Qt::ShiftModifier
+			&& _we->orientation() == Qt::Vertical)
+		{
+			// copy QWheelEvent but change orientation to Horizontal
+			QWheelEvent we(
+				_we->posF(), _we->globalPosF(), _we->pixelDelta(),
+				_we->angleDelta(), _we->delta(), Qt::Horizontal,
+				_we->buttons(), _we->modifiers(), _we->phase(),
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 7, 0))
+				_we->source(), _we->inverted()
+#else
+				_we->source()
+#endif
+			);
+			QScrollArea::wheelEvent(&we);
+		}
+		else
+		{
+			// Normal scroll event
+			QScrollArea::wheelEvent(_we);
+		}
 	}
 }
 

src/gui/editors/AutomationEditor.cpp

@@ -1738,13 +1738,35 @@ void AutomationEditor::wheelEvent(QWheelEvent * we )
 	}
 	else if(we->modifiers() & Qt::ShiftModifier)
 	{
-		m_leftRightScroll->setValue(m_leftRightScroll->value() -
-							we->angleDelta().y() * 2 / 15);
+		auto cur_pos = m_leftRightScroll->value();
+		auto new_pos = cur_pos - we->angleDelta().y() * 2 / 15;
+		// If we are already at the limits of scrolling value, check if the new
+		// position is less/greater than min/max in order to allow the parent
+		// to process the wheelEvent
+		if (
+			(cur_pos == m_leftRightScroll->minimum() && new_pos < m_leftRightScroll->minimum())
+			|| (cur_pos == m_leftRightScroll->maximum() && new_pos > m_leftRightScroll->maximum())
+		)
+		{
+			we->ignore();
+			return;
+		}
+		m_leftRightScroll->setValue(new_pos);
 	}
 	else
 	{
-		m_topBottomScroll->setValue(m_topBottomScroll->value() -
-							(we->angleDelta().x() + we->angleDelta().y()) / 30);
+		auto cur_pos = m_topBottomScroll->value();
+		auto new_pos = cur_pos - ((we->angleDelta().x() + we->angleDelta().y()) / 30);
+		// same as above comment for m_leftRightScroll
+		if (
+			(cur_pos == m_topBottomScroll->minimum() && new_pos < m_topBottomScroll->minimum())
+			|| (cur_pos == m_topBottomScroll->maximum() && new_pos > m_topBottomScroll->maximum())
+		)
+		{
+			we->ignore();
+			return;
+		}
+		m_topBottomScroll->setValue(new_pos);
 	}
 }
 

src/gui/editors/PianoRoll.cpp

@@ -3537,13 +3537,35 @@ void PianoRoll::wheelEvent(QWheelEvent * we )
 	}
 	else if(we->modifiers() & Qt::ShiftModifier)
 	{
-		m_leftRightScroll->setValue(m_leftRightScroll->value() -
-							we->angleDelta().y() * 2 / 15);
+		auto cur_pos = m_leftRightScroll->value();
+		auto new_pos = cur_pos - we->angleDelta().y() * 2 / 15;
+		// If we are already at the limits of scrolling value, check if the new
+		// position is less/greater than min/max in order to allow the parent
+		// to process the wheelEvent
+		if (
+			(cur_pos == m_leftRightScroll->minimum() && new_pos < m_leftRightScroll->minimum())
+			|| (cur_pos == m_leftRightScroll->maximum() && new_pos > m_leftRightScroll->maximum())
+		)
+		{
+			we->ignore();
+			return;
+		}
+		m_leftRightScroll->setValue(new_pos);
 	}
 	else
 	{
-		m_topBottomScroll->setValue(m_topBottomScroll->value() -
-							we->angleDelta().y() / 30);
+		auto cur_pos = m_topBottomScroll->value();
+		auto new_pos = cur_pos - we->angleDelta().y() / 30;
+		// same as above comment for m_leftRightScroll
+		if (
+			(cur_pos == m_topBottomScroll->minimum() && new_pos < m_topBottomScroll->minimum())
+			|| (cur_pos == m_topBottomScroll->maximum() && new_pos > m_topBottomScroll->maximum())
+		)
+		{
+			we->ignore();
+			return;
+		}
+		m_topBottomScroll->setValue(new_pos);
 	}
 }
 

src/gui/editors/SongEditor.cpp

@@ -566,8 +566,20 @@ void SongEditor::wheelEvent( QWheelEvent * we )
 	}
 	else if(we->modifiers() & Qt::ShiftModifier)
 	{
-		m_leftRightScroll->setValue(m_leftRightScroll->value() -
-							we->angleDelta().y() / 30);
+		auto cur_pos = m_leftRightScroll->value();
+		auto new_pos = cur_pos - we->angleDelta().y() / 30;
+		// If we are already at the limits of scrolling value, check if the new
+		// position is less/greater than min/max in order to allow the parent
+		// to process the wheelEvent
+		if (
+			(cur_pos == m_leftRightScroll->minimum() && new_pos < m_leftRightScroll->minimum())
+			|| (cur_pos == m_leftRightScroll->maximum() && new_pos > m_leftRightScroll->maximum())
+		)
+		{
+			we->ignore();
+			return;
+		}
+		m_leftRightScroll->setValue(new_pos);
 	}
 	else
 	{