Applies to: Nevron Chart for .NET
How to implement custom cursor snapping?
In many cases you may need to snap the axis cursors to nearest data point value or some other value which has some user defined meaning (for example an important value or threshold in data).
In such cases you need to implement custom snapping for the axis cursor. The following code example will snap a vertical axis cursor to randomly generated values of a line series:
[C#]
using System;
using System.Windows.Forms;
using Nevron.Chart;
using Nevron.Chart.WinForm;
using Nevron.GraphicsCore;
...
private void Form1_Load(object sender, EventArgs e)
{
m_Chart = (NChart)nChartControl1.Charts[0];
m_Chart.BoundsMode = BoundsMode.Stretch;
Random random = new Random();
// create a 2D line chart
NLineSeries line = new NLineSeries();
m_Chart.Series.Add(line);
line.DataLabelStyle.Format = "<value>";
line.MarkerStyle.PointShape = PointShape.Cylinder;
line.MarkerStyle.Visible = true;
line.MarkerStyle.PointShape = PointShape.Cross;
line.Values.FillRandom(random, 17);
// confiure the axis cursor tool
ConfigureAxisCursorTool();
}
private void ConfigureAxisCursorTool()
{
m_HorizontalAxisCursor = new NAxisCursor();
m_HorizontalAxisCursor.BeginEndAxis = (int)StandardAxis.PrimaryY;
m_HorizontalAxisCursor.ValueSnapper = null;
m_HorizontalAxisCursor.ValueChanged += new EventHandler(OnValueChanged);
m_HorizontalAxisCursor.SynchronizeOnMouseAction = MouseAction.Move;
m_VerticalAxisCursor = new NAxisCursor();
m_VerticalAxisCursor.BeginEndAxis = (int)StandardAxis.PrimaryX;
m_VerticalAxisCursor.ValueSnapper = null;
m_VerticalAxisCursor.ValueChanged += new EventHandler(OnValueChanged);
m_VerticalAxisCursor.SynchronizeOnMouseAction = MouseAction.Move;
m_Chart.Axis(StandardAxis.PrimaryX).Cursors.Add(m_HorizontalAxisCursor);
m_Chart.Axis(StandardAxis.PrimaryY).Cursors.Add(m_VerticalAxisCursor);
nChartControl1.Controller.Tools.Clear();
nChartControl1.Controller.Selection.Clear();
nChartControl1.Controller.Selection.Add(m_Chart);
nChartControl1.Controller.Tools.Add(new NDataCursorTool());
}
private double SnapToValue(NDataSeriesDouble series, double value)
{
if (series.Count == 0)
return value;
double snapValue = (double)series[0];
double minDistance = Math.Abs(snapValue - value);
for (int i = 1; i < series.Count; i++)
{
double currentSnapValue = (double)series[i];
double currentDistance = Math.Abs(currentSnapValue - value);
if (currentDistance < minDistance)
{
snapValue = currentSnapValue;
minDistance = currentDistance;
}
}
return snapValue;
}
private void OnValueChanged(object sender, EventArgs e)
{
NLineSeries line = (NLineSeries)m_Chart.Series[0];
m_VerticalAxisCursor.Value = SnapToValue(line.Values, m_VerticalAxisCursor.Value);
}
NChart m_Chart;
NAxisCursor m_HorizontalAxisCursor;
NAxisCursor m_VerticalAxisCursor;
[VB.NET]
Imports System
Imports System.Windows.Forms
Imports Nevron.Chart
Imports Nevron.Chart.WinForm
Imports Nevron.GraphicsCore
...
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
m_Chart = DirectCast(NChartControl1.Charts(0), NChart)
m_Chart.BoundsMode = BoundsMode.Stretch
Dim random As New Random()
' create a 2D line chart
Dim line As New NLineSeries()
m_Chart.Series.Add(line)
line.DataLabelStyle.Format = "<value>"
line.MarkerStyle.PointShape = PointShape.Cylinder
line.MarkerStyle.Visible = True
line.MarkerStyle.PointShape = PointShape.Cross
line.Values.FillRandom(random, 17)
' confiure the axis cursor tool
ConfigureAxisCursorTool()
End Sub
Private Sub ConfigureAxisCursorTool()
m_HorizontalAxisCursor = New NAxisCursor()
m_HorizontalAxisCursor.BeginEndAxis = CInt(StandardAxis.PrimaryY)
m_HorizontalAxisCursor.ValueSnapper = Nothing
AddHandler m_HorizontalAxisCursor.ValueChanged, AddressOf OnValueChanged
m_HorizontalAxisCursor.SynchronizeOnMouseAction = MouseAction.Move
m_VerticalAxisCursor = New NAxisCursor()
m_VerticalAxisCursor.BeginEndAxis = CInt(StandardAxis.PrimaryX)
m_VerticalAxisCursor.ValueSnapper = Nothing
AddHandler m_VerticalAxisCursor.ValueChanged, AddressOf OnValueChanged
m_VerticalAxisCursor.SynchronizeOnMouseAction = MouseAction.Move
m_Chart.Axis(StandardAxis.PrimaryX).Cursors.Add(m_HorizontalAxisCursor)
m_Chart.Axis(StandardAxis.PrimaryY).Cursors.Add(m_VerticalAxisCursor)
nChartControl1.Controller.Tools.Clear()
nChartControl1.Controller.Selection.Clear()
nChartControl1.Controller.Selection.Add(m_Chart)
nChartControl1.Controller.Tools.Add(New NDataCursorTool())
End Sub
Private Function SnapToValue(series As NDataSeriesDouble, value As Double) As Double
If series.Count = 0 Then
Return value
End If
Dim snapValue As Double = CDbl(series(0))
Dim minDistance As Double = Math.Abs(snapValue - value)
For i As Integer = 1 To series.Count - 1
Dim currentSnapValue As Double = CDbl(series(i))
Dim currentDistance As Double = Math.Abs(currentSnapValue - value)
If currentDistance < minDistance Then
snapValue = currentSnapValue
minDistance = currentDistance
End If
Next
Return snapValue
End Function
Private Sub OnValueChanged(sender As Object, e As EventArgs)
Dim line As NLineSeries = DirectCast(m_Chart.Series(0), NLineSeries)
m_VerticalAxisCursor.Value = SnapToValue(line.Values, m_VerticalAxisCursor.Value)
End Sub
Dim m_Chart As NChart
Dim m_HorizontalAxisCursor As NAxisCursor
Dim m_VerticalAxisCursor As NAxisCursor
Note that the SnapToValue function accepts as a parameter a NDataSeries object – this allows you use to the same function to snap to any value series (for example X values in a line series).
Article ID: 57, Created On: 10/6/2010, Modified: 6/20/2011