From e09f4d47cdbcf7f139cb37f136b67a0a06169aac Mon Sep 17 00:00:00 2001
From: imonlyfourteen <155100608+imonlyfourteen@users.noreply.github.com>
Date: Tue, 4 Jun 2024 08:35:27 +0000
Subject: [PATCH] Add middle mouse button drag in the GraphView

Handle middle mouse button in `mouseMoveEvent()` (new) and `mousePressEvent()` methods.
---
 src/GUI/graphview.cpp | 25 +++++++++++++++++++++++++
 src/GUI/graphview.h   |  2 ++
 2 files changed, 27 insertions(+)

diff --git a/src/GUI/graphview.cpp b/src/GUI/graphview.cpp
index c2039142..30dc35e2 100644
--- a/src/GUI/graphview.cpp
+++ b/src/GUI/graphview.cpp
@@ -342,10 +342,35 @@ void GraphView::resizeEvent(QResizeEvent *e)
 	QGraphicsView::resizeEvent(e);
 }
 
+void GraphView::mouseMoveEvent(QMouseEvent *e)
+{
+	if (e->buttons() & Qt::MiddleButton) {
+		QScrollBar *sb = horizontalScrollBar();
+#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
+		int x = e->x();
+#else // QT 5.15
+		int x = e->position().toPoint().x();
+#endif // QT 5.15
+		sb->setSliderPosition(sb->sliderPosition() - (x - _xStartDrag));
+		_xStartDrag = x;
+	}
+
+	QGraphicsView::mouseMoveEvent(e);
+}
+
 void GraphView::mousePressEvent(QMouseEvent *e)
 {
+#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
 	if (e->button() == Qt::LeftButton)
 		newSliderPosition(mapToScene(e->pos()));
+	else if (e->button() == Qt::MiddleButton)
+		_xStartDrag = e->x();
+#else // QT 5.15
+	if (e->button() == Qt::LeftButton)
+		newSliderPosition(mapToScene(e->position().toPoint()));
+	else if (e->button() == Qt::MiddleButton)
+		_xStartDrag = e->position().toPoint().x();
+#endif // QT 5.15
 
 	QGraphicsView::mousePressEvent(e);
 }
diff --git a/src/GUI/graphview.h b/src/GUI/graphview.h
index 21ac3ecd..fc08100d 100644
--- a/src/GUI/graphview.h
+++ b/src/GUI/graphview.h
@@ -57,6 +57,7 @@ protected:
 	void setUnits(Units units);
 
 	void resizeEvent(QResizeEvent *e);
+	void mouseMoveEvent(QMouseEvent *e);
 	void mousePressEvent(QMouseEvent *e);
 	void wheelEvent(QWheelEvent *e);
 	void changeEvent(QEvent *e);
@@ -122,6 +123,7 @@ private:
 	qreal _minYRange;
 
 	qreal _zoom;
+	int _xStartDrag;
 };
 
 #endif // GRAPHVIEW_H