fixed automatic fov_max when using shift+wheel

openglcanvas.cpp

@@ -722,7 +722,17 @@ void OpenGLCanvas::wheelEvent(QWheelEvent *event){
         if(event->modifiers()==Qt::ShiftModifier){
             change_fov_max(fov_max+((double)event->delta())/30);
         }else{
-            change_fov(fov+((double)event->delta())/30);
+            int new_fov=fov+event->delta()/30;
+            change_fov((double)new_fov);
+            if(auto_fov_max){
+                if(new_fov<60)
+                    change_fov_max(60);
+                else
+                    if(new_fov>180)
+                        change_fov_max(1);
+                    else
+                        change_fov_max(90-new_fov/2);
+            }
         }
     }
 }