ZoomBox待完成，还需要调整

AIStudio.Wpf.DiagramDesigner/ViewModels/BaseViewModel/DiagramViewModel.cs

@@ -400,6 +400,20 @@ namespace AIStudio.Wpf.DiagramDesigner
             }
         }
 
+        private double _delayZoomValue = 1;
+        [Browsable(false)]
+        public double DelayZoomValue
+        {
+            get
+            {
+                return _delayZoomValue;
+            }
+            set
+            {
+                SetProperty(ref _delayZoomValue, value);
+            }
+        }
+
         private string _name;
         [Browsable(false)]
         public string Name
@@ -691,6 +705,8 @@ namespace AIStudio.Wpf.DiagramDesigner
 
         public event DiagramEventHandler Event;
 
+        private IDisposable ZoomValueChangedSubscription;
+
         public DiagramViewModel()
         {
             CreateNewDiagramCommand = new SimpleCommand(ExecuteEnable, ExecuteCreateNewDiagramCommand);
@@ -733,6 +749,14 @@ namespace AIStudio.Wpf.DiagramDesigner
             Mediator.Instance.Register(this);
 
             Items.CollectionChanged += Items_CollectionChanged;
+
+            ZoomValueChangedSubscription = WhenPropertyChanged.Where(o => o.ToString() == nameof(ZoomValue)).Throttle(TimeSpan.FromMilliseconds(100)).Subscribe(OnZoomValueChanged);//Sample
+        }
+
+        //提供给标尺计算，延迟100ms，等布局改变再计算。
+        private void OnZoomValueChanged(string obj)
+        {
+            DelayZoomValue = ZoomValue;
         }
 
         public DiagramViewModel(DiagramItem diagramItem) : this()