Checks if the JsChartViewer.ViewPortChanged event has occurred.
When mouse actions (such as drag to scroll, drag to select region to zoom into, click to zoom in/out, etc) occurs on the browser side, the JsChartViewer.ViewPortChanged event will occur. Typically, the event handler will send either a partial chart update request (AJAX request) or a full page update request to the server.
However, in a typical web page, there may be other causes of a partial chart update request or full page update request. For example, for a time based chart, the web page may have a FORM to allow the user to enter the start date and end date used, and then press the submit button.
This property determines if the JsChartViewer.ViewPortChanged event has occurred, so as to identify if it is the cause of the HTTP request.