增加双击中键缩放到全部的特性.

src/CameraControls.ts

@@ -141,6 +141,9 @@ export class CameraControls
         this.m_State = CameraControlState.Rotate;
         this.m_Viewer.UpdateLockTarget();
     }
+
+    //最后一次按中键的时间
+    lastMiddleClickTime = 0;
     //鼠标    
     onMouseDown = (event: MouseEvent) =>
     {
@@ -161,6 +164,14 @@ export class CameraControls
                 }
             case MouseKey.Middle:
                 {
+                    let curTime = Date.now();
+                    let t = curTime - this.lastMiddleClickTime;
+                    this.lastMiddleClickTime = curTime;
+                    if (t < 350)
+                    {
+                        this.m_Viewer.ZoomAll();
+                        return;
+                    }
                     if (this.m_KeyDown.get(KeyBoard.Control))
                     {
                         this.beginRotate();