mesh widget casting

modules/viz/include/opencv2/viz/widgets.hpp

@@ -185,6 +185,7 @@ namespace cv
         template<> CV_EXPORTS TextWidget Widget::cast<TextWidget>();
         template<> CV_EXPORTS CloudWidget Widget::cast<CloudWidget>();
         template<> CV_EXPORTS CloudNormalsWidget Widget::cast<CloudNormalsWidget>();
+        template<> CV_EXPORTS MeshWidget Widget::cast<MeshWidget>();
 
     } /* namespace viz */
 } /* namespace cv */

modules/viz/src/cloud_widgets.cpp

@@ -464,3 +464,9 @@ cv::viz::MeshWidget::MeshWidget(const Mesh3d &mesh)
     
     WidgetAccessor::setProp(*this, actor);
 }
+
+template<> CV_EXPORTS cv::viz::MeshWidget cv::viz::Widget::cast<cv::viz::MeshWidget>()
+{
+    Widget3D widget = this->cast<Widget3D>();
+    return static_cast<MeshWidget&>(widget);
+}