MSChart Polar chart with selection

// This code shows how to implement mouse-drag selection of points in a Polar chart using mschart.
//
// Features:
//  - points inside the selection are highlighted
//  - after the selection, the points coordinates are shown in a textbox
//
// To test it follow these steps:
//  - open VS and create a new Windows Forms Application project called "PolarChartSelectionTest"
//  - remove the automatically generated Form1.cs class
//  - then add a new class called Form1 (yes, the same name of the just-deleted class)
//  - open Form1.cs and replace the code with the following
//  - add a reference to the assembly System.Windows.Forms.DataVisualization.dll
//
//
// Requirements:
//  - .net framework 4 (or .net framework 3.5 with mschart.exe installed)


using System;
using System.Drawing;
using System.Windows.Forms;
using System.Windows.Forms.DataVisualization.Charting;

namespace PolarChartSelectionTest
{
    public partial class Form1: Form
    {
        #region Nested Classes

        internal class PolarPoint
        {
            public double Angle { get; private set; }
            public double Y { get; private set; }
            public PolarPoint(double angle, double y)
            {
                this.Angle = angle;
                this.Y = y;
            }
        }

        internal class RectangleInPolarPoints
        {
            public PolarPoint TopLeft { get; private set; }
            public PolarPoint TopRight { get; private set; }
            public PolarPoint BottomLeft { get; private set; }
            public PolarPoint BottonRight { get; private set; }
            public RectangleInPolarPoints(PolarPoint topLeft, PolarPoint bottomLeft, PolarPoint topRight, PolarPoint bottomRight)
            {
                this.TopLeft = topLeft;
                this.TopRight = topRight;
                this.BottomLeft = bottomLeft;
                this.BottonRight = bottomRight;
            }
        }

        internal struct PointD
        {
            public double X { get; private set; }
            public double Y { get; private set; }
            public PointD(double x, double y)
                : this()
            {
                this.X = x;
                this.Y = y;
            }
        }

        #endregion

        #region Designer code

        private System.Windows.Forms.DataVisualization.Charting.Chart chart1;
        private System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.SplitContainer splitContainer1;

        private void InitializeComponent()
        {
            System.Windows.Forms.DataVisualization.Charting.ChartArea chartArea1 = new System.Windows.Forms.DataVisualization.Charting.ChartArea();
            System.Windows.Forms.DataVisualization.Charting.Legend legend1 = new System.Windows.Forms.DataVisualization.Charting.Legend();
            System.Windows.Forms.DataVisualization.Charting.Series series1 = new System.Windows.Forms.DataVisualization.Charting.Series();
            this.chart1 = new System.Windows.Forms.DataVisualization.Charting.Chart();
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.splitContainer1 = new System.Windows.Forms.SplitContainer();
            ((System.ComponentModel.ISupportInitialize)(this.chart1)).BeginInit();
            this.splitContainer1.Panel1.SuspendLayout();
            this.splitContainer1.Panel2.SuspendLayout();
            this.splitContainer1.SuspendLayout();
            this.SuspendLayout();
            //
            // chart1
            //
            chartArea1.Name = "ChartArea1";
            this.chart1.ChartAreas.Add(chartArea1);
            this.chart1.Dock = System.Windows.Forms.DockStyle.Fill;
            legend1.Name = "Legend1";
            this.chart1.Legends.Add(legend1);
            this.chart1.Location = new System.Drawing.Point(0, 0);
            this.chart1.Name = "chart1";
            series1.ChartArea = "ChartArea1";
            series1.Legend = "Legend1";
            series1.Name = "Series1";
            this.chart1.Series.Add(series1);
            this.chart1.Size = new System.Drawing.Size(644, 339);
            this.chart1.TabIndex = 0;
            this.chart1.Text = "chart1";
            //
            // textBox1
            //
            this.textBox1.Dock = System.Windows.Forms.DockStyle.Fill;
            this.textBox1.Font = new System.Drawing.Font("Courier New", 9.75F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.textBox1.Location = new System.Drawing.Point(0, 0);
            this.textBox1.Multiline = true;
            this.textBox1.Name = "textBox1";
            this.textBox1.ScrollBars = System.Windows.Forms.ScrollBars.Vertical;
            this.textBox1.Size = new System.Drawing.Size(644, 79);
            this.textBox1.TabIndex = 1;
            //
            // splitContainer1
            //
            this.splitContainer1.Dock = System.Windows.Forms.DockStyle.Fill;
            this.splitContainer1.Location = new System.Drawing.Point(0, 0);
            this.splitContainer1.Name = "splitContainer1";
            this.splitContainer1.Orientation = System.Windows.Forms.Orientation.Horizontal;
            //
            // splitContainer1.Panel1
            //
            this.splitContainer1.Panel1.Controls.Add(this.chart1);
            //
            // splitContainer1.Panel2
            //
            this.splitContainer1.Panel2.Controls.Add(this.textBox1);
            this.splitContainer1.Size = new System.Drawing.Size(644, 422);
            this.splitContainer1.SplitterDistance = 339;
            this.splitContainer1.TabIndex = 2;
            //
            // Form1
            //
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(644, 422);
            this.Controls.Add(this.splitContainer1);
            this.Name = "MyForm";
            this.Text = "Polar chart with selection";
            ((System.ComponentModel.ISupportInitialize)(this.chart1)).EndInit();
            this.splitContainer1.Panel1.ResumeLayout(false);
            this.splitContainer1.Panel2.ResumeLayout(false);
            this.splitContainer1.Panel2.PerformLayout();
            this.splitContainer1.ResumeLayout(false);
            this.ResumeLayout(false);

        }
        #endregion

        #region Constructor

        public Form1()
        {
            InitializeComponent();

            this.chart1.MouseDown += new MouseEventHandler(chart1_MouseDown);
            this.chart1.MouseMove += new MouseEventHandler(chart1_MouseMove);
            this.chart1.MouseUp += new MouseEventHandler(chart1_MouseUp);
            this.chart1.PostPaint += new EventHandler<ChartPaintEventArgs>(chart1_PostPaint);
        }
        #endregion

        #region Chart Data Initialization

        protected override void OnLoad(EventArgs e)
        {
            this.FillChart();
        }

        private void FillChart()
        {
            var items = new[] { new PolarPoint(0, 10), new PolarPoint(30, 4), new PolarPoint(120, 2), new PolarPoint(185, 9), new PolarPoint(240, 7) };

            this.chart1.Series.Clear();
            var seriesLines = this.chart1.Series.Add("Values");
            seriesLines.XValueMember = "Angle";
            seriesLines.YValueMembers = "Y";
            seriesLines.ChartType = SeriesChartType.Polar;

            this.chart1.DataSource = items;
        }
        #endregion

        #region Selection Management

        Point? clickPoint;
        RectangleF? highlightRectAbs;
        RectangleInPolarPoints highlightRect;

        void chart1_MouseDown(object sender, MouseEventArgs e)
        {
            this.highlightRectAbs = null;
            this.highlightRect = null;

            // deselect all points
            var s = this.chart1.Series[0];
            for (int i = 0; i < s.Points.Count; i++)
                s.Points[i].Tag = false;

            this.clickPoint = e.Location;
        }

        void chart1_MouseMove(object sender, MouseEventArgs e)
        {
            if (this.clickPoint.HasValue && this.clickPoint != e.Location)
            {
                int width = Math.Abs(e.X - this.clickPoint.Value.X);
                int height = Math.Abs(e.Y - this.clickPoint.Value.Y);
                int x = Math.Min(e.X, this.clickPoint.Value.X);
                int y = Math.Min(e.Y, this.clickPoint.Value.Y);

                this.highlightRectAbs = new RectangleF(x, y, width, height);
                this.highlightRect = null;
                if (this.highlightRectAbs.Value.Width != 0 && this.highlightRectAbs.Value.Height != 0)
                {
                    this.chart1.Invalidate();
                }
            }
        }

        void chart1_MouseUp(object sender, MouseEventArgs e)
        {
            this.clickPoint = null;
            this.chart1.Invalidate();

            // here we have finished our selection
            this.SelectionFinished();
        }

        void chart1_PostPaint(object sender, ChartPaintEventArgs e)
        {
            var area = e.ChartElement as ChartArea;
            if (area == null)
                return;

            if (!this.highlightRectAbs.HasValue)
                return;

            // get center and radius
            var minY = area.AxisY.ValueToPixelPosition(area.AxisY.Minimum);
            var maxX = area.AxisX.ValueToPixelPosition(area.AxisX.Maximum);
            var maxY = area.AxisY.ValueToPixelPosition(area.AxisY.Maximum);
            var radius = Math.Abs(maxY - minY);
            var centerX = maxX;
            var centerY = minY;

            if (this.highlightRect == null)
                this.highlightRect = GetRectangleInPolarPoints(this.highlightRectAbs.Value, area, centerX, centerY, radius);
            this.highlightRectAbs = GetRectangleF(this.highlightRect, area, centerX, centerY, radius);

            using (var brush = new SolidBrush(Color.FromArgb(15, Color.Black)))
            {
                var cg = e.ChartGraphics;
                cg.Graphics.FillRectangle(brush, this.highlightRectAbs.Value);
                cg.Graphics.DrawRectangle(Pens.Red, this.highlightRectAbs.Value.X, this.highlightRectAbs.Value.Y,
                                          this.highlightRectAbs.Value.Width, this.highlightRectAbs.Value.Height);

                var s = e.Chart.Series[0];
                for (int i = 0; i < s.Points.Count; i++)
                {
                    var point = s.Points[i];

                    var pt = GetCoordsOfPoint(point.XValue, point.YValues[0], area, centerX, centerY, radius);

                    // highlights the points if they're into the selection
                    if (this.highlightRectAbs.Value.Contains(pt))
                    {
                        cg.Graphics.FillEllipse(Brushes.GreenYellow, pt.X - 5, pt.Y - 5, 10, 10);
                        point.Tag = true;
                    }
                    else
                    {
                        point.Tag = false;
                    }
                }
            }

        }

        private void SelectionFinished()
        {
            this.textBox1.Text = "Selection:" + Environment.NewLine;
            var s = this.chart1.Series[0];
            for (int i = 0; i < s.Points.Count; i++)
            {
                var point = s.Points[i];
                if (point.Tag is bool && (bool)point.Tag == true)
                    this.textBox1.AppendText(string.Format("Angle = {0,6:N2}, Y = {1,6:N2}\r\n", point.XValue, point.YValues[0]));
            }
        }

        #endregion

        #region Helper Methods

        static PointF GetCoordsOfPoint(PolarPoint polPt, ChartArea area, double centerX, double centerY, double radius)
        {
            return GetCoordsOfPoint(polPt.Angle, polPt.Y, area, centerX, centerY, radius);
        }

        static PointF GetCoordsOfPoint(double angle, double yVal, ChartArea area, double centerX, double centerY, double radius)
        {
            double xRatio = 360.0 / Math.Abs(area.AxisX.Maximum - area.AxisX.Minimum);
            double radAngle = (-(angle * xRatio + area.AxisX.Crossing) - 270) * Math.PI / 180;
            double yRadius = Scale(yVal, area.AxisY.Minimum, area.AxisY.Maximum, 0, radius);

            double h = Math.Sin(radAngle);
            double w = Math.Cos(radAngle);

            return new PointF((float)(centerX + w * yRadius), (float)(centerY - h * yRadius));
        }

        static PolarPoint GetPolarPointFromCoords(double x, double y, ChartArea area, double centerX, double centerY, double radius)
        {
            double xRatio = 360.0 / Math.Abs(area.AxisX.Maximum - area.AxisX.Minimum);

            var xComp = x - centerX;
            var yComp = centerY - y;

            var hypotenuseLength = Math.Sqrt(xComp * xComp + yComp * yComp);
            var angle = GetZero360Angle(-(Math.Atan2(yComp, xComp) * 180 / Math.PI) - 270);

            //angle = Scale(angle, 0, 360, area.AxisX.Minimum, area.AxisX.Maximum);
            angle = (angle - area.AxisX.Crossing) / xRatio;

            return new PolarPoint(angle , Scale(hypotenuseLength, 0, radius, area.AxisY.Minimum, area.AxisY.Maximum));
        }

        static RectangleInPolarPoints GetRectangleInPolarPoints(RectangleF rect, ChartArea area, double centerX, double centerY, double radius)
        {
            var topLeft = GetPolarPointFromCoords(rect.Left, rect.Top, area, centerX, centerY, radius);
            var bottomLeft = GetPolarPointFromCoords(rect.Left, rect.Bottom, area, centerX, centerY, radius);
            var topRight = GetPolarPointFromCoords(rect.Right, rect.Top, area, centerX, centerY, radius);
            var bottomRight = GetPolarPointFromCoords(rect.Right, rect.Bottom, area, centerX, centerY, radius);
            return new RectangleInPolarPoints(topLeft, bottomLeft, topRight, bottomRight);
        }

        static RectangleF GetRectangleF(RectangleInPolarPoints recPolar, ChartArea area, double centerX, double centerY, double radius)
        {
            var topLeftPt = GetCoordsOfPoint(recPolar.TopLeft, area, centerX, centerY, radius);
            var bottomLeftPt = GetCoordsOfPoint(recPolar.BottomLeft, area, centerX, centerY, radius);
            var topRightPt = GetCoordsOfPoint(recPolar.TopRight, area, centerX, centerY, radius);

            var width = (float)(topRightPt.X - topLeftPt.X);
            var height = (float)(bottomLeftPt.Y - topLeftPt.Y);

            return new RectangleF(topLeftPt, new SizeF(width, height));
        }

        static double GetZero360Angle(double angle)
        {
            while (angle < 0)
                angle += 360;
            while (angle > 360)
                angle -= 360;
            return angle;
        }


        static double Scale(double oldScaleVal, double oldScaleMin, double oldScaleMax, double newScaleMin, double newScaleMax)
        {
            return newScaleMin + (oldScaleVal - oldScaleMin) / (oldScaleMax - oldScaleMin) * (newScaleMax - newScaleMin);
        }

        #endregion
    }
}