protected VisualElement GetControllerEditor()
 {
     if (controller is VFXCascadedOperatorController)
     {
         var edit = new VFXCascadedOperatorEdit();
         edit.controller = controller as VFXCascadedOperatorController;
         return(edit);
     }
     if (controller is VFXNumericUniformOperatorController)
     {
         var edit = new VFXUniformOperatorEdit <VFXNumericUniformOperatorController, VFXOperatorNumericUniform>();
         edit.controller = controller as VFXNumericUniformOperatorController;
         return(edit);
     }
     if (controller is VFXBranchOperatorController)
     {
         var edit = new VFXUniformOperatorEdit <VFXBranchOperatorController, Branch>();
         edit.controller = controller as VFXBranchOperatorController;
         return(edit);
     }
     if (controller is VFXUnifiedOperatorController)
     {
         var edit = new VFXUnifiedOperatorEdit();
         edit.controller = controller as VFXUnifiedOperatorController;
         return(edit);
     }
     return(null);
 }
            public OperandInfo(VFXCascadedOperatorEdit owner, VFXOperatorNumericCascadedUnified op, int index) : base(owner, op, index)
            {
                field = new TextField();
                field.RegisterCallback <BlurEvent>(OnChangeValue);
                field.RegisterCallback <KeyDownEvent>(OnKeyDown);

                Insert(0, field);
            }