Printing a polar worksheet

using System;
using System.Collections.Generic;
using System.Drawing;

namespace ComplexNumberWorksheet
{
    class Plot
    {    
    /// <summary>
    /// class to plot x and y 2D carthesian coordinates on a Form or Panel or printer!
    /// 
    /// Because on the form coordinates start at the upper left corner with 0,0
    /// with the y coordinate going down, a little transformation is done here
    /// so that x,y coordinates act as normal carthesian coordinates, with 0,0
    /// in the center of the Form or Panel.
    /// There is Some support for polar coordinates also.
    /// DM 18 dec 2014
    /// </summary>
    
        struct PlotPort
        {
            public int minX;
            public int maxX;
            public int minY;
            public int maxY;
        };

        private PlotPort _PlotW;    //"window" of carthesian coordinates
        private Size _ClientArea;   //keeps the pixels info
        private float _Xspan;
        private float _Yspan;
        private Graphics _G;

        public Plot() { }

        public Plot(Size Plotarea, Graphics G)
        {
            _ClientArea = Plotarea;
            _G = G;
        }

        public Size ClientArea { set { _ClientArea = value; } }

        public Pen PlotPen { get; set; }

        public int AxisUnits { get; set; }

        /// <summary>
        /// Set the bounderies of the form(screen) to real(world) coordinates.
        /// </summary>
        /// <param name="minx">lowest x value</param>
        /// <param name="maxx">highest x value</param>
        /// <param name="miny">lowest y value</param>
        /// <param name="maxy">highest y value</param>
        public void SetPlotPort(int minx, int maxx, int miny, int maxy)
        {
            _PlotW.minX = minx;
            _PlotW.maxX = maxx;
            _PlotW.minY = miny;
            _PlotW.maxY = maxy;
            _Xspan = _PlotW.maxX - _PlotW.minX;
            _Yspan = _PlotW.maxY - _PlotW.minY;
        }

        public void PlotPixel(PointF P, Color C)
        {
            //workhorse of this class
            Bitmap bm = new Bitmap(1, 1);
            bm.SetPixel(0, 0, C);
            P = ToScreen(P);
            _G.DrawImageUnscaled(bm, (int)P.X, (int)P.Y);
        }

        public void PlotLine(PointF from, PointF to)
        {
            _G.DrawLine(PlotPen, ToScreen(from), ToScreen(to));
        }

        public void PlotCircle(PointF midPnt, float radius)
        {
            PointF pt = ToScreen(midPnt);
            _G.DrawEllipse(PlotPen, pt.X - radius * _ClientArea.Width / _Xspan,
                pt.Y - radius * _ClientArea.Height / _Yspan,
                2 * radius * _ClientArea.Width / _Xspan, 2 * radius * _ClientArea.Height / _Yspan);
        }

        public void PlotXGrid()
        {
            for (int i = 1; i < _PlotW.maxY - _PlotW.minY; i ++)
            {
                PlotLine(new PointF(_PlotW.minX, _PlotW.maxY - i), new PointF(_PlotW.maxX, _PlotW.maxY - i)); 
            }
        }

        public void PlotYGrid()
        {
            for (int i = 1; i < _PlotW.maxX - _PlotW.minX; i++)
            {
                PlotLine(new PointF(_PlotW.maxX - i, _PlotW.minY), new PointF(_PlotW.maxX - i, _PlotW.maxY));
            }
        }

        public void PlotGrid()
        {
            PlotXGrid();
            PlotYGrid();
        }

        public void PlotXAxis()
        {
            PlotPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;
            PlotPen.Width = 4;
            PointF X0 = new PointF(_PlotW.minX, _PlotW.minY + _Yspan / 2f);
            PointF X1 = new PointF(_PlotW.maxX, _PlotW.minY + _Yspan / 2f);
            _G.DrawLine(PlotPen, ToScreen(X0), ToScreen(X1));
            PlotPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Solid;
        }

        public void PlotYAxis()
        {
            PlotPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;
            PlotPen.Width = 2;
            PointF Y0 = new PointF(_PlotW.minX + _Xspan / 2f, _PlotW.maxY);
            PointF Y1 = new PointF(_PlotW.minX + _Xspan / 2f, _PlotW.minY);
            _G.DrawLine(PlotPen, ToScreen(Y0), ToScreen(Y1));
            PlotPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Solid;
        }

        public void PlotAxes()
        {
            PlotXAxis();
            PlotYAxis();
        }

        public void PlotPolarLines(int angle, int lenght)
        {
            const double toRad = Math.PI / 180.0;

            float x = 0f;
            float y = 0f;

            for (int i = 0; i < 360; i+=angle)
            {
                x = (float)(lenght * Math.Cos(toRad * i));
                y = (float)(lenght * Math.Sin(toRad * i));
                PlotLine(new PointF(0f, 0f), new PointF(x, y));
            }
        }

        public PointF ToCarthesian(double Theta, double r)
        {          
            return new PointF((float)(r * Math.Cos(Theta)), (float)(r * Math.Sin(Theta)));          
        }

        /// <summary>
        /// Plot a list of carthesian points on the screen
        /// </summary>
        /// <param name="thePts"></param>
        /// <param name="G"></param>
        public void PlotPoints(List<PointF> thePts,Pen P)
        {
            PointF[] PtAr = thePts.ToArray();
            for (int k = 0; k < PtAr.Length; k++)
            {
                PtAr[k] = ToScreen(PtAr[k]);
            }
            _G.DrawLines(P, PtAr);
        }

        /// <summary>
        /// Transform a point in carthesian coordinates to a point on the screen
        /// </summary>
        /// <param name="ptC">The point in carthesian(world) coordinates</param>
        /// <returns>Transformed point to be plotted on the screen</returns>
        private PointF ToScreen(PointF ptC)
        {
            //PointF aP = new PointF();
            ptC.X = _ClientArea.Width / _Xspan * ptC.X + _ClientArea.Width / 2f;
            ptC.Y = -_ClientArea.Height / _Yspan * ptC.Y + _ClientArea.Height / 2f;
            return ptC;
        }
    }
}

//*******************FORM CLASS LISTING STARTS HERE****************

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Drawing.Printing;

namespace ComplexNumberWorksheet
{
    public partial class Form1 : Form
    {
        private PrintDocument PrintDoc; 
        private int axDivisions = 1;
        private int polarAngle = 360;
        private bool showAxes = false;
        private bool showGrids = false;

        public Form1()
        {
            InitializeComponent();
            //Create a PrintDocument object
            PrintDoc = new PrintDocument();
            //Add PrintPage event handler
            PrintDoc.PrintPage += new PrintPageEventHandler(printAPage);
        }

        /// <summary>
        /// Routine to draw, be it on a Panel or PrintPreview or whatever
        /// </summary>
        /// <param name="S">Gives the rectangle size in pixels to draw in</param>
        /// <param name="g">Drawing needs a Graphics object</param>
        private void DrawStuff(Size S, Graphics g)
        {          
            Plot pos = new Plot(S, g);    
            pos.SetPlotPort(-axDivisions, axDivisions, -axDivisions, axDivisions);
            if (showAxes)
            {
                pos.PlotPen = new Pen(Color.Green, 2.5f);
                pos.PlotXAxis();
                pos.PlotYAxis();
            }
            if (showGrids)
            {
                pos.PlotPen = new Pen(Color.Blue);
                pos.PlotXGrid();
                pos.PlotYGrid();
            }

            pos.PlotPen = new Pen(Color.Red);
            pos.PlotPen.Width = 2;
            for (int radius = 1; radius <= axDivisions; radius++)
            {
                pos.PlotCircle(new Point(0, 0), radius);
            }
            pos.PlotPolarLines(polarAngle, axDivisions);
        }

        private void DrawPnl_Paint(object sender, PaintEventArgs e)
        {
            DrawStuff(this.DrawPnl.ClientSize, e.Graphics);
        }

        private void PreviewBtn_Click(object sender, EventArgs e)
        {         
            PrintPreviewDialog printPreviewDlg = new PrintPreviewDialog();
            ((Form)printPreviewDlg).WindowState = FormWindowState.Maximized;
            printPreviewDlg.Document = PrintDoc; //give the PrintDoc to the preview dialog
            printPreviewDlg.Show();            
        }

        private void PrintBtn_Click(object sender, EventArgs e)
        {           
            //Print the document, also fires the PrintPage eventhandler
            PrintDoc.Print();
        }

        private void printAPage(object sender, PrintPageEventArgs PE)
        {
            int sideLength = 0;
            if (PE.PageBounds.Width < PE.PageBounds.Height)
            {
                sideLength = PE.PageBounds.Width;
            }
            else
            {
                sideLength = PE.PageBounds.Height;
            }
            DrawStuff(new Size(sideLength, sideLength), PE.Graphics);
        }

        private void axDivisionsUpDwn_ValueChanged(object sender, EventArgs e)
        {
            this.axDivisions = (int)this.axDivisionsUpDwn.Value;
            this.Refresh();
        }

        private void polarAngleCmbBx_SelectedIndexChanged(object sender, EventArgs e)
        {
            string comboItem = this.polarAngleCmbBx.SelectedItem.ToString();
            comboItem = comboItem.Substring(0, comboItem.Length - 1);
            this.polarAngle = int.Parse(comboItem);
            this.Refresh();
        }

        private void plotAxesChkBx_CheckedChanged(object sender, EventArgs e)
        {
            showAxes = !showAxes;
            this.Refresh();
        }

        private void showGridsChBx_CheckedChanged(object sender, EventArgs e)
        {
            showGrids = !showGrids;
            this.Refresh();
        }             
    }
}