message: arnaud commentary
diff: @@ -1615,12 +1615,19 @@ namespace RINGMesh
  if( ImGui::Button( "home [H]", ImVec2( -1, 0 ) ) )
  {
  glup_viewer_home();
  - if( geomodels2d_.empty() ) {
  + bool geomodel_2d_displayed { false };
  + for( auto& geomodel2d: geomodels2d_ ) {
  + if( geomodel2d->is_visible_ ) {
  + geomodel_2d_displayed = true ;
  + }
  + }
  + if( !geomodel_2d_displayed ) {
  float axis[3] = { 1, 0.5, 1 };
  - float angle = 80;
  + float angle { 80 };
  glup_viewer_set_scene_rotation( axis, angle );
  }
  }
  +
  ImGui::Separator();
  ImGui::Checkbox( "Lighting [L]", &lighting_ );
  if( lighting_ )
  