From 6f2c3b90ce29a20e14cc769841056d4b36c42d50 Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Sat, 29 Dec 2018 21:30:28 +0100
Subject: Implement drag'n'move.

---
 src/outputwindow.cc | 32 +++++++++++++++++++++++++++++++-
 src/outputwindow.h  |  8 ++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/src/outputwindow.cc b/src/outputwindow.cc
index 8c4cb7b..95c3c7b 100644
--- a/src/outputwindow.cc
+++ b/src/outputwindow.cc
@@ -164,6 +164,34 @@ void OutputWindow::reset()
 	}
 }
 
+void OutputWindow::mouseMoveEvent(QMouseEvent* event)
+{
+	if(dragging)
+	{
+		dragOffset = event->pos() - dragOffsetOrigo;
+	}
+}
+
+void OutputWindow::mousePressEvent(QMouseEvent* event)
+{
+	if(event->buttons() & Qt::MiddleButton)
+	{
+		dragging = true;
+		dragOffsetOrigo = event->pos();
+		dragOffset = {};
+	}
+}
+
+void OutputWindow::mouseReleaseEvent(QMouseEvent* event)
+{
+	if(event->buttons() & Qt::MiddleButton)
+	{
+		dragging = false;
+		offset = dragOffsetOrigo - event->pos();
+		dragOffset = dragOffsetOrigo = {};
+	}
+}
+
 void OutputWindow::wheelEvent(QWheelEvent* event)
 {
 	double delta = event->delta() / 120.0 * scale;
@@ -178,7 +206,9 @@ void OutputWindow::paintEvent(QPaintEvent *)
 {
 	//sem.acquire();
 	QPainter painter(this);
-	paint(painter, {width() / 2.0, height() / 2.0}, true, scale);
+	paint(painter,
+	      { width() / 2.0 + offset.x() + dragOffset.x(),
+	        height() / 2.0 + offset.y() + dragOffset.y() }, true, scale);
 	sem.release();
 }
 
diff --git a/src/outputwindow.h b/src/outputwindow.h
index bb7ef7b..182499a 100644
--- a/src/outputwindow.h
+++ b/src/outputwindow.h
@@ -65,6 +65,9 @@ public slots:
 	void reset();
 
 protected:
+	void mouseMoveEvent(QMouseEvent* event);
+	void mousePressEvent(QMouseEvent* event);
+	void mouseReleaseEvent(QMouseEvent* event);
 	void wheelEvent(QWheelEvent* event);
 	void paintEvent(QPaintEvent* event);
 
@@ -92,4 +95,9 @@ private:
 	QString penfile;
 
 	volatile float scale{2.0f};
+
+	bool dragging{false};
+	QPoint dragOffsetOrigo{0, 0};
+	QPoint dragOffset{0, 0};
+	QPoint offset{0, 0};
 };
-- 
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