compute max_fov when auto_max_fov button pressed

openglcanvas.cpp

@@ -85,6 +85,7 @@ void OpenGLCanvas::change_fov(double f){
 
 void OpenGLCanvas::automaxbutton(bool autovalue){
     auto_fov_max=autovalue;
+    change_fov_max(compute_auto_fov_max(fov));
 }
 
 void OpenGLCanvas::change_fov(int new_fov){