ScrollXTo does not scroll to date

amusleh
10 Mar 2022, 10:00 ( Updated at: 10 Mar 2022, 10:05 )

Hi,

First of all this is great idea! we might develop an indicator for this.

The issue with your code is you take the mouse up event time value and you use it as target for another chart.

The time value of mouse up event is not related to scrolling at all, it's the time point where the mouse cursor was.

To solve the issue you can use the chart scroll changed event instead, ex:

using System;
using cAlgo.API;
using cAlgo.API.Internals;
using cAlgo.API.Indicators;
using cAlgo.Indicators;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Threading;

namespace cAlgo
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.IsraelStandardTime, AccessRights = AccessRights.FileSystem)]
    public class SyncObjectsInstance : Indicator
    {
        protected override void Initialize()
        {
            Synchronizer.Instance.Register(this);
            Timer.Start(Synchronizer.HeartbeatRate);
        }

        protected override void OnTimer()
        {
            Synchronizer.Instance.Heartbeat(this);
        }

        public override void Calculate(int index)
        {
            // do nothing
        }
    }

    public class Synchronizer
    {
        public static readonly TimeSpan HeartbeatTimeout = TimeSpan.FromSeconds(5);
        public static readonly TimeSpan HeartbeatRate = TimeSpan.FromSeconds(4);

        private static readonly object _sync = new object();
        private static Synchronizer _instance = null;

        public static Synchronizer Instance
        {
            get
            {
                if (_instance != null)
                    return _instance;

                lock (_sync)
                {
                    if (_instance != null)
                        return _instance;

                    _instance = new Synchronizer();
                }

                return _instance;
            }
        }

        private readonly Dictionary<string, HashSet<SyncObjectsInstance>> _instances;
        private readonly Dictionary<SyncObjectsInstance, DateTime> _instanceHeartbeats;

        public Synchronizer()
        {
            _instances = new Dictionary<string, HashSet<SyncObjectsInstance>>(StringComparer.OrdinalIgnoreCase);
            _instanceHeartbeats = new Dictionary<SyncObjectsInstance, DateTime>();
        }

        public void Register(SyncObjectsInstance instance)
        {
            // instance.Print("Register");

            lock (_sync)
            {
                Restore(instance);
            }
        }

        public void Heartbeat(SyncObjectsInstance instance)
        {
            //   instance.Print("Heartbeat");

            lock (_sync)
            {
                var now = DateTime.Now;

                _instanceHeartbeats[instance] = now;

                var expiredInstances = _instanceHeartbeats.Where(hb => now - hb.Value > HeartbeatTimeout).Select(hb => hb.Key).ToArray();

                foreach (var expiredInstance in expiredInstances)
                {
                    expiredInstance.Chart.ScrollChanged -= Chart_ScrollChanged;
                    _instanceHeartbeats.Remove(expiredInstance);
                    _instances[expiredInstance.SymbolName].Remove(expiredInstance);
                }
            }
        }

        private void Chart_ScrollChanged(ChartScrollEventArgs obj)
        {
            lock (_sync)
            {
                HashSet<SyncObjectsInstance> symbolInstances;

                if (!_instances.TryGetValue(obj.Chart.SymbolName, out symbolInstances))
                    return;

                foreach (var instance in symbolInstances)
                {
                    if (instance.Chart == obj.Chart)
                        continue;

                    instance.BeginInvokeOnMainThread(() => ScrollChart(instance, obj.Chart.Bars.OpenTimes[obj.Chart.FirstVisibleBarIndex]));
                }
            }
        }

        private void ScrollChart(SyncObjectsInstance targetInstance, DateTime targetTime)
        {
            //p("ScrollChart " + targetTime);

            targetInstance.Print("ScrollChart | ", targetInstance.TimeFrame);

            targetInstance.Chart.ScrollXTo(targetTime);

            //int middleBar = targetInstance.Chart.FirstVisibleBarIndex + ((targetInstance.Chart.LastVisibleBarIndex - targetInstance.Chart.FirstVisibleBarIndex) / 2);
            //DateTime midDate = targetInstance.Bars.OpenTimes[middleBar];
            //bool crossDate = false;
            //int crossDir = midDate < targetTime ? 1 : -1;

            //while (midDate != targetTime && !crossDate)
            //{
            //    p("midDate= " + midDate + " targetTime= " + targetTime + " middleBar= " + middleBar + " midDate= " + midDate);
            //    p("FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);
            //    targetInstance.Chart.ScrollXBy(crossDir);
            //    middleBar = targetInstance.Chart.FirstVisibleBarIndex + ((targetInstance.Chart.LastVisibleBarIndex - targetInstance.Chart.FirstVisibleBarIndex) / 2);
            //    midDate = targetInstance.Bars.OpenTimes[middleBar];
            //    crossDate = crossDir == 1 ? midDate > targetTime : midDate < targetTime;
            //}
        }

        private void p(string text)
        {
            File.AppendAllText("d:\\temp\\a.log", text + Environment.NewLine);
        }

        //p("a targetTime= " + targetTime +
        // " targetInstance.Chart.TimeFrame.ToString()= " + targetInstance.Chart.TimeFrame.ToString() +
        // " FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex +
        // );

        //targetInstance.Chart.ScrollXBy(100);
        //targetInstance.Chart.ScrollXTo(targetTime);
        //Thread.Sleep(300);
        //targetInstance.Chart.ScrollXBy((targetInstance.Chart.FirstVisibleBarIndex - targetInstance.Chart.LastVisibleBarIndex) / 2);

        //p("diff= " + ((targetInstance.Chart.FirstVisibleBarIndex - targetInstance.Chart.LastVisibleBarIndex) / 2));

        //p("f" + " TimeFrame= " + targetInstance.Chart.TimeFrame + " args.targetTime= " + targetTime + " LastVisibleBarIndex= " +
        //  targetInstance.Chart.LastVisibleBarIndex + " lastTime= " + targetInstance.Bars.OpenTimes[targetInstance.Chart.LastVisibleBarIndex] +
        //  " FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " firstTime= " +
        //  targetInstance.Bars.OpenTimes[targetInstance.Chart.FirstVisibleBarIndex] +
        //  " middleIdx= " + middleBar +
        //  " middleDate= " + targetInstance.Bars.OpenTimes[middleBar] +
        //  "-2Bars= " + ((targetInstance.Chart.LastVisibleBarIndex - targetInstance.Chart.FirstVisibleBarIndex) / -2).ToString()
        //  );

        //p("crossDir= " + crossDir);
        //p("a FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);

        //for (int i = 0; i < 100; i++)
        //{
        //    //p("FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);
        //    targetInstance.Chart.ScrollXBy(-1);
        //    targetInstance.Chart.
        //    //Thread.Sleep(300);
        //}

        //p("b FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);

        private void Restore(SyncObjectsInstance sender)
        {
            HashSet<SyncObjectsInstance> symbolInstances;

            if (!_instances.TryGetValue(sender.SymbolName, out symbolInstances))
            {
                symbolInstances = new HashSet<SyncObjectsInstance>();
                _instances.Add(sender.SymbolName, symbolInstances);
            }

            sender.Chart.ScrollChanged += Chart_ScrollChanged; ;

            symbolInstances.Add(sender);
            _instanceHeartbeats[sender] = DateTime.Now;
        }
    }
}

You can improve it by using Bars delta of scroll changed event args instead of first visible bar on the chart.

Also there is the issue of simultaneous scrolling which can be solved if you work little bit on it.

eynt
10 Mar 2022, 16:10

RE:

Hello and thank you for your reply.

I was able to solve the issue by making a few small changes in the ScrollChart method. I tried to apply it to your version of the indicator however there were sync issues when 2 charts are changed at the same time so I let it go. I am uploading my fixed version of the indicator, feel free to use/improve/share it with the community. If there are any updates or improvements on the subject please let me know.

using System;
using cAlgo.API;
using cAlgo.API.Internals;
using cAlgo.API.Indicators;
using cAlgo.Indicators;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Threading;

namespace cAlgo
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.IsraelStandardTime, AccessRights = AccessRights.FileSystem)]
    public class SyncObjectsInstance : Indicator
    {
        protected override void Initialize()
        {
            Synchronizer.Instance.Register(this);
            Timer.Start(Synchronizer.HeartbeatRate);
        }

        protected override void OnTimer()
        {
            Synchronizer.Instance.Heartbeat(this);
        }

        public override void Calculate(int index)
        {
            // do nothing
        }
    }

    public class Synchronizer
    {
        public static readonly TimeSpan HeartbeatTimeout = TimeSpan.FromSeconds(5);
        public static readonly TimeSpan HeartbeatRate = TimeSpan.FromSeconds(4);

        private static readonly object _sync = new object();
        private static Synchronizer _instance = null;

        public static Synchronizer Instance
        {
            get
            {
                if (_instance != null)
                    return _instance;

                lock (_sync)
                {
                    if (_instance != null)
                        return _instance;

                    _instance = new Synchronizer();
                }

                return _instance;
            }
        }

        private readonly Dictionary<string, HashSet<SyncObjectsInstance>> _instances;
        private readonly Dictionary<SyncObjectsInstance, DateTime> _instanceHeartbeats;

        public Synchronizer()
        {
            _instances = new Dictionary<string, HashSet<SyncObjectsInstance>>(StringComparer.OrdinalIgnoreCase);
            _instanceHeartbeats = new Dictionary<SyncObjectsInstance, DateTime>();
        }

        public void Register(SyncObjectsInstance instance)
        {
            // instance.Print("Register");

            lock (_sync)
            {
                Restore(instance);
            }
        }

        public void Heartbeat(SyncObjectsInstance instance)
        {
            //   instance.Print("Heartbeat");

            lock (_sync)
            {
                var now = DateTime.Now;

                _instanceHeartbeats[instance] = now;

                var expiredInstances = _instanceHeartbeats.Where(hb => now - hb.Value > HeartbeatTimeout).Select(hb => hb.Key).ToArray();

                foreach (var expiredInstance in expiredInstances)
                {
                    expiredInstance.Chart.MouseUp -= OnMouseUp;
                    _instanceHeartbeats.Remove(expiredInstance);
                    _instances[expiredInstance.SymbolName].Remove(expiredInstance);
                }
            }
        }
        private void OnMouseUp(ChartMouseEventArgs args)
        {
            lock (_sync)
            {
                HashSet<SyncObjectsInstance> symbolInstances;

                if (!_instances.TryGetValue(args.Chart.SymbolName, out symbolInstances))
                    return;

                foreach (var instance in symbolInstances)
                {
                    if (instance.Chart == args.Chart)
                        continue;

                    instance.BeginInvokeOnMainThread(() => ScrollChart(instance, args.TimeValue));
                }
            }
        }

        private void ScrollChart(SyncObjectsInstance targetInstance, DateTime targetTime)
        {
            //p("ScrollChart " + targetTime);
            //targetInstance.Chart.ScrollXTo(targetTime);

            int leftBar = targetInstance.Chart.FirstVisibleBarIndex;
            int rightBar = targetInstance.Chart.LastVisibleBarIndex;
            int middleBar = leftBar + ((rightBar - leftBar) / 2);
            DateTime midDate = targetInstance.Bars.OpenTimes[middleBar];
            bool crossDate = false;
            int crossDir = midDate < targetTime ? 1 : -1;
            int scrolledBars = 0;

            while (midDate != targetTime && !crossDate)
            {
                //p("midDate= " + midDate + " targetTime= " + targetTime + " middleBar= " + middleBar + " midDate= " + midDate);
                //p("FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);
                //targetInstance.Chart.ScrollXBy(crossDir);
                leftBar += crossDir;
                rightBar += crossDir;
                scrolledBars += crossDir;
                //middleBar = targetInstance.Chart.FirstVisibleBarIndex + ((targetInstance.Chart.LastVisibleBarIndex - targetInstance.Chart.FirstVisibleBarIndex) / 2);
                middleBar = leftBar + ((rightBar - leftBar) / 2);
                midDate = targetInstance.Bars.OpenTimes[middleBar];
                crossDate = crossDir == 1 ? midDate > targetTime : midDate < targetTime;
            }

            targetInstance.Chart.ScrollXBy(scrolledBars);
        }

        private void p(string text)
        {
            File.AppendAllText("d:\\temp\\a.log", text + Environment.NewLine);
        }

        //p("a targetTime= " + targetTime + 
        // " targetInstance.Chart.TimeFrame.ToString()= " + targetInstance.Chart.TimeFrame.ToString() +
        // " FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex +
        // );

        //targetInstance.Chart.ScrollXBy(100);
        //targetInstance.Chart.ScrollXTo(targetTime);
        //Thread.Sleep(300);
        //targetInstance.Chart.ScrollXBy((targetInstance.Chart.FirstVisibleBarIndex - targetInstance.Chart.LastVisibleBarIndex) / 2);

        //p("diff= " + ((targetInstance.Chart.FirstVisibleBarIndex - targetInstance.Chart.LastVisibleBarIndex) / 2));

        //p("f" + " TimeFrame= " + targetInstance.Chart.TimeFrame + " args.targetTime= " + targetTime + " LastVisibleBarIndex= " +
        //  targetInstance.Chart.LastVisibleBarIndex + " lastTime= " + targetInstance.Bars.OpenTimes[targetInstance.Chart.LastVisibleBarIndex] +
        //  " FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " firstTime= " +
        //  targetInstance.Bars.OpenTimes[targetInstance.Chart.FirstVisibleBarIndex] +
        //  " middleIdx= " + middleBar +
        //  " middleDate= " + targetInstance.Bars.OpenTimes[middleBar] +
        //  "-2Bars= " + ((targetInstance.Chart.LastVisibleBarIndex - targetInstance.Chart.FirstVisibleBarIndex) / -2).ToString()
        //  );

        //p("crossDir= " + crossDir);
        //p("a FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);

        //for (int i = 0; i < 100; i++)
        //{
        //    //p("FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);
        //    targetInstance.Chart.ScrollXBy(-1);
        //    targetInstance.Chart.
        //    //Thread.Sleep(300);
        //}

        //p("b FirstVisibleBarIndex= " + targetInstance.Chart.FirstVisibleBarIndex + " LastVisibleBarIndex= " + targetInstance.Chart.LastVisibleBarIndex);

        private void Restore(SyncObjectsInstance sender)
        {
            HashSet<SyncObjectsInstance> symbolInstances;

            if (!_instances.TryGetValue(sender.SymbolName, out symbolInstances))
            {
                symbolInstances = new HashSet<SyncObjectsInstance>();
                _instances.Add(sender.SymbolName, symbolInstances);
            }

            sender.Chart.MouseUp += OnMouseUp;

            symbolInstances.Add(sender);
            _instanceHeartbeats[sender] = DateTime.Now;
        }
    }
}