# viewerPerformanceWatchdogMixin

widgets/Source/Viewer/viewerPerformanceWatchdogMixin.js 24
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.

##### Example:

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

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