curveview: set padding on top and bottom

app/widget/curvewidget/curveview.cpp

@@ -318,6 +318,12 @@ void CurveView::ContextMenuEvent(Menu &m)
   connect(reset_zoom_action, &QAction::triggered, this, &CurveView::ResetZoom);
 }
 
+void CurveView::SceneRectUpdateEvent(QRectF &r)
+{
+  r.setTop(r.top() - this->height());
+  r.setBottom(r.bottom() + this->height());
+}
+
 void CurveView::ZoomToFitInternal(const QList<NodeKeyframe *> &keys)
 {
   if (keys.isEmpty()) {

app/widget/curvewidget/curveview.h

@@ -68,6 +68,8 @@ protected:
 
   virtual void ContextMenuEvent(Menu &m) override;
 
+  virtual void SceneRectUpdateEvent(QRectF &r) override;
+
 private:
   void ZoomToFitInternal(const QList<NodeKeyframe *> &keys);