From 3303e07056f258322982feac20ede3cd2f46e8b6 Mon Sep 17 00:00:00 2001
From: Tats <info@sofianaudry.com>
Date: Mon, 13 Jul 2015 16:45:03 -0600
Subject: [PATCH] Added support for scrolling in source+destination canvases by
 mid-button clicking.

---
 MapperGLCanvas.cpp | 18 ++++++++++++++++++
 MapperGLCanvas.h   |  1 +
 2 files changed, 19 insertions(+)

diff --git a/MapperGLCanvas.cpp b/MapperGLCanvas.cpp
index c198e11..5b6fdd3 100644
--- a/MapperGLCanvas.cpp
+++ b/MapperGLCanvas.cpp
@@ -391,6 +391,24 @@ void MapperGLCanvas::wheelEvent(QWheelEvent *event)
   event->accept();
 }
 
+void MapperGLCanvas::mouseMoveEvent(QMouseEvent *event)
+{
+  static QPoint lastPos;
+
+  // Click-and-drag translate view.
+  if (event->buttons() & Qt::MiddleButton)
+  {
+    QPoint pos = event->pos();
+    QPointF diff = mapToScene(pos) - mapToScene(lastPos);
+    QGraphicsView* view = scene()->views().first();
+    view->translate(diff.x(), diff.y());
+    view->update();
+    lastPos = pos;
+  }
+
+  QGraphicsView::mouseMoveEvent(event);
+}
+
 bool MapperGLCanvas::eventFilter(QObject *target, QEvent *event)
 {
   if (event->type() == QEvent::KeyPress)
diff --git a/MapperGLCanvas.h b/MapperGLCanvas.h
index 7b537eb..ed6e16e 100644
--- a/MapperGLCanvas.h
+++ b/MapperGLCanvas.h
@@ -142,6 +142,7 @@ public slots:
   void deselectAll();
 
   void wheelEvent(QWheelEvent *event);
+  void mouseMoveEvent(QMouseEvent *event);
 
   // Event Filter
   bool eventFilter(QObject *target, QEvent *event);