How to Customize Viewport Zoom (include annotations in ZoomExtents)

Update: There’s an updated code sample for SciChart v5 here:

Text Annotations and the Zoom Extents Modifier

Hi Jose,

Sorry to interrupt Yuriy’s excellent support handling! There is a little known (and not documented) feature which we included to provide users with a workaround in cases like this.

There is a property called SciChartSurface.ViewportManager (expects IViewportManager) which is queried on render to get the X and Y axis VisibleRange.

See below the implementation of DefaultViewportManager:

using System.Diagnostics;

   /// <summary>
    /// The DefaultViewportManager performs a naive calculation for X and Y Axis VisibleRange. 
    /// On each render of the parent SciChartSurface, either autorange to fit the data (depending on the Axis.AutoRange property value), 
    /// or return the original axis range (no change)
    /// </summary>
    public class DefaultViewportManager : ViewportManagerBase
    {
        /// <summary>
        /// Called when the <see cref="IAxis.VisibleRange"/> changes for an axis. Override in derived types to get a notification of this occurring
        /// </summary>
        /// <param name="axis">The <see cref="IAxis"/>instance</param>
        public override void OnVisibleRangeChanged(IAxis axis)
        {
        }

        /// <summary>
        /// Called when the <see cref="ISciChartSurface" /> is rendered.
        /// </summary>
        /// <param name="sciChartSurface">The SciChartSurface instance</param>
        public override void OnParentSurfaceRendered(ISciChartSurface sciChartSurface)
        {            
        }

        /// <summary>
        /// Overridden by derived types, called when the parent <see cref="SciChartSurface" /> requests the XAxis VisibleRange.
        /// The Range returned by this method will be applied to the chart on render
        /// </summary>
        /// <param name="xAxis">The XAxis</param>
        /// <returns>
        /// The new VisibleRange for the XAxis
        /// </returns>
        protected override IRange OnCalculateNewXRange(IAxis xAxis)
        {
            // Calculate the VisibleRange of X Axis, depending on AutoRange property
            if (xAxis.AutoRange)
            {
                var newXRange = xAxis.GetMaximumRange();
                if (newXRange != null && newXRange.IsDefined)
                    return newXRange;
            }

            return xAxis.VisibleRange;
        }

        /// <summary>
        /// Overridden by derived types, called when the parent <see cref="SciChartSurface" /> requests a YAxis VisibleRange.
        /// The Range returned by this method will be applied to the chart on render
        /// </summary>
        /// <param name="yAxis">The YAxis</param>
        /// <param name="renderPassInfo"></param>
        /// <returns>
        /// The new VisibleRange for the YAxis
        /// </returns>
        protected override IRange OnCalculateNewYRange(IAxis yAxis, RenderPassInfo renderPassInfo)
        {
            if (yAxis.AutoRange && renderPassInfo.PointSeries != null && renderPassInfo.RenderableSeries != null)
            {
                var newYRange = yAxis.CalculateYRange(renderPassInfo);
                if (newYRange != null && newYRange.IsDefined)
                {
                    return newYRange;
                }
            }

            return yAxis.VisibleRange;
        }
    }

If you create a class like the above and change the behaviour of OnCalculateNewYRange to return a VisibleRange including your threshold level then you can effectively override the AutoRanging of the chart.

Try this method and let me know how it works

Best regards,
Andrew