The linear gauge in FusionWidgets XT suite can also act as an input control, allowing users to visually drag & change the value of pointer. Once the value is updated, it can be retrieved from the chart using client-side JavaScript.

Here, we'll see how to do the same.

We need to tell the chart to switch the edit mode on. This can be done either at the global level using:

Once the user has changed the value of the gauge, the chart automatically calls the FC_ChartUpdated(DOMId) JavaScript function.

You'll have to define this method in your HTML page and then write JavaScript code to retrieve the data using getData(index) or getDataForId(id) method. Let's quickly see an example.

We'll build a simple example to let the user choose his satisfaction % using a linear gauge chart. Once he has selected the value, we'll simply display it within the HTML page.

In your real-life application, you could use the return value to assign to a hidden form field and then submit the form to server-side scripts for processing.

The chart will use the following XML: s

Let's now look at the HTML + JavaScript code required to retrieve data from this pointer when user changes the value. We create an HTML page with the following code.

This page is present in Download Package > Code > LinearGauge > EditMode.html

Here, we've done the following:

1. Initialized an angular gauge with data provided by Data.xml (containing the data listed above). The XML contains editMode='1'.
2. Defined the FC_ChartUpdated(DOMId) JavaScript function and added code to retrieve chart's updated value and display the value in an HTML element.

FC_ChartUpdated is called whenever a pointer's value is updated. In this function we have done the following:

1. Check if the event was raised by our chart. This is done by matching the DOM Id of the chart.
2. Retrieve the new data of the chart using getData(pointerIndex) method. This method returns the numeric value of a particular pointer based on its pointer index. The first pointer on the chart bears an index of 1, second 2 and so on.
3. Change the content of the contentDiv to show this value (for demo purpose).

When the above code is executed, the chart renders in edit mode and the pointer can be dragged to any value. Whenever the pointer value is changed, the chart calls FC_ChartUpdated(DOMId) JavaScript function, which retrieves the new data using the getData(pointerIndex) method and displays this value in a DIV, as shown in the following image:

Instead of getData(index) method, you can also use getDataForId(pointerId) method to retrieve pointer's value as under:

var pointerValue = chartRef.getDataForId("CS");

Here, CS was the pointer ID we had specified in XML.

      FusionCharts("myChartId").addEventListener ("RealtimeUpdateComplete" , 
        function(event, parameter) 
        {
            alert( "Your satisfaction index: " + event.sender.getData(1) + "%" );
        }  
      );

      FusionCharts("myChartId").addEventListener ("RealtimeUpdateError" , 
        function(event, parameter) 
        {
          alert( "Problem occurred while updating real-time data. The error status code is" +  parameter.httpStatus );
        }  
      );

So, you just saw how easy it is to create editable linear gauges using FusionWidgets XT.