"Paint.exe" in CsGL

using System;
using System.Drawing;
using CsGL.OpenGL;
using System.Diagnostics;

namespace _2D_draw
{
	/// <summary>
	/// 
	/// </summary>
	public class DrawingObjectOval : DrawingObject
	{
		Point start = new Point();
		Point end   = new Point();
		Rectangle bounds = new Rectangle();
		Curves ellipse = new Curves();

		public DrawingObjectOval()
		{
			strType = "Oval";
			comment = "Oval";
		}

		private void calcRectangle()
		{
			int w = Math.Abs( end.X  - start.X );
			int h = Math.Abs(end.Y  - start.Y );
			bounds = new Rectangle( start , new Size( w , h) ) ;
		}

		public void Draw()
		{
			Draw( GL.GL_RENDER , 0);
		}

		// ******************************************************************
		// draw the ellipse
		public override void Draw( uint mode , uint highlight)
		{
			GL.glLoadName( ID );  // used to select an object
			//System.Console.WriteLine("Draw: " + ID.ToString() + " " + this.strType);
			if ( highlight == ID )
			{
				GL.glColor3ub( 100 , 0 , 200);
			}
			else
			{
				GL.glColor3ub( 0 , 0 , 0);
			}

			calcRectangle();

			// if it's for selection, draw only the rectangle
			if (mode == GL.GL_SELECT)
			{
				GL.glRectd( (double)start.X , (double)start.Y , (double)end.X, (double)end.Y );
			}
			else
			{
				ellipse.DrawEllipse( bounds );
			}
			GL.glFlush();
			//DrawEllipse();
		}

		private void DrawEllipse()
		{
			double  h , k;
			double a , b;

			a = (start.X - end.X)/2.0;
			b = (start.Y - end.Y)/2.0;
			h = (double)start.X + a;
			k = (double)start.Y + b;

			double x , ytop , ybot , delx;
			double X = (double) start.X;

			double s;
			GL.glBegin( GL.GL_LINES );

			int num = 25;
			delx = a/(double)num;

			double xPrev , yTprev , yBprev;
			xPrev = X;
			yTprev = (double)start.Y;
			yBprev = (double)start.Y;

			for ( int i = 1;i<=num;i++)
			{
				x = X + (double)i * delx;
				s = 1 - (x-h)*(x-h) / a * a;
				s = Math.Sqrt(s);
				ytop = k + s;
				ybot = k - s;
				
				GL.glVertex2d( xPrev , yTprev );
				GL.glVertex2d( x , ytop );

				//GL.glVertex2d( xPrev , yBprev );
				//GL.glVertex2d( x , ybot );

				xPrev = x;
				yBprev = ybot;
				yTprev = ytop;

			}

			GL.glEnd();
		}

		public  override void HandleMouseDown(System.Windows.Forms.MouseEventArgs e)
		{
			start = transform( e.X , e.Y );
		}

		public override void HandleMouseUp(System.Windows.Forms.MouseEventArgs e)
		{
			end = transform( e.X , e.Y );
			Draw();
		}

		public override  void HandleMouseMove(System.Windows.Forms.MouseEventArgs e)
		{
			end = transform( e.X , e.Y );
			Draw();
		}



	}
}