Using Generic X-Axis

For an example of how to create a generic x-axis plugin, create a Visual Studio project using the ‘Generic X-Axis Project Template’.

To use the generic x-axis in a display, there are two distinct tasks which need fulfilling.  Firstly, the main view model for the display has to manage the generic x-axis instance and any changes to it.  You then need to read the generic x-axis data correctly in order to use it.

The generic x-axis system consists of the following parts:

• IXAxisMappingSelector – used for cycling though available generic x-axis mappings. A display will need to register and unregister with this class.
• IXAxisMappingInstanceSupported – every display main view model will need to implement this interface.
• IXAxisMappingsController – provides access to all system registered generic x-axis mappings. Also provides quick access to the system wide default generic x-axis mapping (which happens to be Time).
• IXAxisMappingInstance – a system wide instance of a generic x-axis mapping, specific to am ICompositeSessionContainerController. This instance provides methods for converting timestamps to mapped data values and vice versa.
• IXAxisMappingAdapter – a system wide representation of a generic x-axis mapping, individual instances are created from this when required.

The following code is to be considered the minimum required implementation for a display’s main view model for managing the generic x-axis: 

internal class MyDisplayViewModel :
    DisplayViewModelBase,
    IXAxisMappingInstanceSupported
{
    private IXAxisMappingsController xAxisMappingsController;
    private IXAxisMappingSelector xAxisMappingSelector;

    public MyDisplayViewModel(
        IXAxisMappingsController xAxisMappingsController,
        IXAxisMappingSelector xAxisMappingSelector,
        IDefaultXAxisMappingProvider defaultXAxisMappingProvider)
    {
        this.xAxisMappingsController = xAxisMappingsController;
        this.xAxisMappingSelector = xAxisMappingSelector;

        this.XAxisMappingAdapter = this.xAxisMappingsController.DefaultXAxisMapping;

        this.ParameterSetProvider.SetXAxisMappingInstance(
            defaultXAxisMappingProvider.DefaultXAxisMappingInstance);
    }

    public IXAxisMappingAdapter XAxisMappingAdapter { get; private set; }

    public IXAxisMappingInstance XAxisMappingInstance { get; private set; }

    public void SetXAxisMapping(IXAxisMappingAdapter xAxisMappingAdapter)
    {
        this.XAxisMappingAdapter = xAxisMappingAdapter;

        this.RefreshXAxisMappingInstance();
        this.RefreshData();
    }

    protected override void OnInitialised()
    {
        base.OnInitialised();

        this.xAxisMappingSelector.RegisterDisplay(this.ScopeIdentity, this);
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            this.xAxisMappingSelector.UnregisterDisplay(this.ScopeIdentity);
        }

        base.Dispose(disposing);
    }

    protected override void OnCompositeSessionContainerChanged()
    {
        base.OnCompositeSessionContainerChanged();

        this.RefreshXAxisMappingInstance();
    }

    protected override void OnContainerCompositeSessionAdded()
    {
        base.OnContainerCompositeSessionAdded();

        this.RefreshXAxisMappingInstance();
    }

    protected override void OnParameterAdded(
        IParameterController parameterController,
        IParameterSetController parameterSetController)
    {
        parameterController.AxisMappingInstance = this.XAxisMappingInstance;
    }

    protected override void OnPrimarySessionChanged()
    {
        base.OnPrimarySessionChanged();

        this.RefreshXAxisMappingInstance();
    }

    private void CycleXAxisMappings()
    {
        this.SetXAxisMapping(
            this.xAxisMappingsController.GetNextXAxisMapping(
                this.XAxisMappingAdapter));
    }

    private void OnXAxisMappingInstanceMappingFailed(object sender, EventArgs e)
    {
        this.SetXAxisMapping(this.xAxisMappingsController.DefaultXAxisMapping);
    }

    private void RefreshXAxisMappingInstance()
    {
        if (this.XAxisMappingInstance != null)
        {
            this.XAxisMappingInstance.MappingFailed -= 
                this.OnXAxisMappingInstanceMappingFailed;
        }

        this.XAxisMappingInstance = 
            this.xAxisMappingsController.GetXAxisMappingInstanceFor(
                this.XAxisMappingAdapter,
                this.CompositeSessionContainerController);

        this.XAxisMappingInstance.MappingFailed += 
            this.OnXAxisMappingInstanceMappingFailed;

        this.ParameterSetProvider
            .SetXAxisMappingInstance(this.XAxisMappingInstance);
        this.ClearCachedData = true;
    }
}

Data is returned for a parameter in an IDataResult, which in turn contains an IMappedTimestamps object, which is where the timestamps and generic x-axis values are returned.  You should be aware that the values mapped to the timestamps will only be the delta generic x-axis value from the last value.  To convert timestamps to actual values you can use the IXAxisMappingInstance.GetMappedTimestampsAndValuesInRange() method.

If your particular display needs to work with an axis, whether in time or generic x-axis mode, you can get an axis object from IXAxisMappingInstance.GetAxis().