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3
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Zoom History

Ok, so as I had not had a reply,I have managed to slog this out and I have created a customRubberBandXyZoomModifier.

In this I keep a copy of all the VisibleRanges on the mouse down and on the mouse up ( if it was dragging) I copy these ranges into a list of ranges in my ViewModel (parent) see below.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Abt.Controls.SciChart;
using AVR_HMI.ViewModels;

namespace AVR_HMI.Charting
{
    public class customRubberBandXyZoomModifier : RubberBandXyZoomModifier
    {
        AnalogueChartViewModel _parent;

        IRange _tempOldXRange;

        List<IRange> _tempOldYRange = new List<IRange>();

        public customRubberBandXyZoomModifier(AnalogueChartViewModel parent)
        {
            _parent = parent;
        }

        public override void OnModifierMouseDown(ModifierMouseArgs e)
        {
            _tempOldXRange = XAxis.VisibleRange;

            _tempOldYRange.Clear();
            foreach (NumericAxis na in YAxes)
            {
                _tempOldYRange.Add(na.VisibleRange);
            }
            base.OnModifierMouseDown(e);
        }


        public override void OnModifierMouseUp(ModifierMouseArgs e)
        {
            if (IsDragging)
            {
                if (_tempOldXRange != null)
                {
                    _parent.OldXRange = _tempOldXRange;
                    _parent.XRangeHistory.Add(_tempOldXRange);
                    _tempOldXRange = null;
                }

                if (_tempOldYRange.Count != 0)
                {
                    int n = 0;
                    foreach (IRange ra in _tempOldYRange)
                    {
                        if (_parent.YRangeHistories[n] != null)
                        {
                            _parent.YRangeHistories[n].RangeHistory.Add(_tempOldYRange[n]);
                        }
                        else
                        {
                            break;
                        }
                        n++;
                    }
                }
                _parent.ZoomBack.RaiseCanExecuteChanged();
                _parent.AutoRangeEnable = false;
            }
            base.OnModifierMouseUp(e);
        }
    }
}

Then in the view model, I have an unzoom button which takes the last set of Ranges off the list and restores these ranges as below

       List<IRange> _xRangeHistory = new List<IRange>();

        public List<IRange> XRangeHistory
        {
            get { return _xRangeHistory; }
            set { _xRangeHistory = value; }
        }

        List<YRangeHistory> _yRangeHistories = new List<YRangeHistory>();

        public List<YRangeHistory> YRangeHistories
        {
            get { return _yRangeHistories; }
            set { _yRangeHistories = value; }
        }


        DelegateCommand _zoomBack;
        public DelegateCommand ZoomBack
        {
            get
            {
                if (_zoomBack == null)
                {
                    _zoomBack = new DelegateCommand(
                        this.OnZoomBackCommandExecute,
                        this.OnZoomBackChangedCommandCanExecute);
                }

                return _zoomBack;
            }
        }

        private bool OnZoomBackChangedCommandCanExecute(object obj)
        {
            if (YRangeHistories.Count == 0 || YRangeHistories[0].RangeHistory.Count == 0)
            {
               return false;
            }
            return true;
        }

        private void OnZoomBackCommandExecute(object obj)
        {
            if (XRangeHistory.Count != 0)
            {
                XAxis.VisibleRange = XRangeHistory[XRangeHistory.Count-1];
                XRangeHistory.Remove(XAxis.VisibleRange);
            }

            if (YRangeHistories.Count != 0)
            {
                int n=0;
                foreach (NumericAxis na in YAxes)
                {
                    int offset =  YRangeHistories[n].RangeHistory.Count;
                    if(offset > 0)
                    {
                        na.VisibleRange = YRangeHistories[n].RangeHistory[offset - 1];
                        YRangeHistories[n].RangeHistory.Remove(na.VisibleRange);
                    }
                    n++;
                }
 
            }
            if (YRangeHistories.Count == 0 || YRangeHistories[0].RangeHistory.Count == 0)
            {
                AutoRangeEnable = true;
            }
            ZoomBack.RaiseCanExecuteChanged();

            VPManager.InvalidateParentSurface(RangeMode.None);
        }

On adding a new YAxis, I add a new YRangeHistory


                       YAxes.Add(numericAxis);
                       YRangeHistories.Add(new YRangeHistory());

YRangeHistory Class


using System.Collections.Generic;
using System.Linq;
using System.Text;
using Abt.Controls.SciChart;

namespace AVR_HMI.Charting
{
    public class YRangeHistory
    {
        List<IRange> _RangeHistory;

        public List<IRange> RangeHistory
        {
            get { return _RangeHistory; }
            set { _RangeHistory = value; }
        }

        public YRangeHistory()
        {
             _RangeHistory = new List<IRange>();
        }
    }
}

Hope this helps others, and if there is a better/easier way of doing this, please get back to me, I know I am on the demo version of SciChart at the moment, but we are intending to buy it and I worry about the lack of good documentation/support. I don't want to start looking elsewhere.

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