viewer: respond to wheel events for moving and zooming

app/widget/handmovableview/handmovableview.cpp

@@ -150,16 +150,21 @@ const HandMovableView::DragMode &HandMovableView::GetDefaultDragMode() const
   return default_drag_mode_;
 }
 
-bool HandMovableView::WheelEventIsAZoomEvent(QWheelEvent *event) const
+bool HandMovableView::WheelEventIsAZoomEvent(QWheelEvent *event)
 {
   return (static_cast<bool>(event->modifiers() & Qt::ControlModifier) == !OLIVE_CONFIG("ScrollZooms").toBool());
 }
 
+qreal HandMovableView::GetScrollZoomMultiplier(QWheelEvent *event)
+{
+  return 1.0 + (static_cast<qreal>(event->angleDelta().x() + event->angleDelta().y()) * 0.001);
+}
+
 void HandMovableView::wheelEvent(QWheelEvent *event)
 {
   if (WheelEventIsAZoomEvent(event)) {
     if (!event->angleDelta().isNull()) {
-      qreal multiplier = 1.0 + (static_cast<qreal>(event->angleDelta().x() + event->angleDelta().y()) * 0.001);
+      qreal multiplier = GetScrollZoomMultiplier(event);
 
       QPointF cursor_pos;
 #if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)

app/widget/handmovableview/handmovableview.h

@@ -34,6 +34,10 @@ class HandMovableView : public QGraphicsView
 public:
   HandMovableView(QWidget* parent = nullptr);
 
+  static bool WheelEventIsAZoomEvent(QWheelEvent* event);
+
+  static qreal GetScrollZoomMultiplier(QWheelEvent* event);
+
 protected:
   virtual void ToolChangedEvent(Tool::Item tool){Q_UNUSED(tool)}
 
@@ -44,8 +48,6 @@ protected:
   void SetDefaultDragMode(DragMode mode);
   const DragMode& GetDefaultDragMode() const;
 
-  bool WheelEventIsAZoomEvent(QWheelEvent* event) const;
-
   virtual void wheelEvent(QWheelEvent* event) override;
 
   virtual void ZoomIntoCursorPosition(QWheelEvent* event, double multiplier, const QPointF &cursor_pos);