# viewerPerformanceWatchdogMixin

#### viewerPerformanceWatchdogMixin(viewer)
Widgets/Viewer/viewerPerformanceWatchdogMixin.js 35

  A mixin which adds the `PerformanceWatchdog` widget to the `Viewer` widget. Rather than being called directly, this function is normally passed as a parameter to `Viewer#extend`, as shown in the example below.

  Name | Type | Default | Description
  --- | --- | --- | ---
  `viewer` | Viewer |  | The viewer instance.
  `options.lowFrameRateMessage` | String | `'This application appears to be performing poorly on your system. Please try using a different web browser or updating your video drivers.'` | optional The message to display when a low frame rate is detected. The message is interpeted as HTML, so make sure it comes from a trusted source so that your application is not vulnerable to cross-site scripting attacks.

  ##### Throws:

  - DeveloperError : viewer is required.

  ##### Example:

      var viewer = new Cesium.Viewer('cesiumContainer');
      viewer.extend(Cesium.viewerPerformanceWatchdogMixin, {
          lowFrameRateMessage : 'Why is this going so <em>slowly</em>?'
      });