#region License
/* 
 * Copyright (C) 1999-2022 John Källén.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Reko.Core;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using Reko.Core.Memory;

namespace Reko.UserInterfaces.WindowsForms.Controls
{
    /// <summary>
    /// Draws a byte map by doing a space-filling curve.
    /// </summary>
    public class ByteMapView : Control
    {
        Graphics g;

        int x_old, y_old;
        int x_new, y_new;
        const int ScaleFactor = 4;
        private IEnumerator<byte> rdr;
        private SegmentMap segmentMap;
        private byte[] data;

        public SegmentMap SegmentMap { get { return this.segmentMap; } set { this.segmentMap = value; OnImageMapChanged(); } }

        void msg(string ss)
        {
            //Debug.Print("{0}", ss);  //use this for debugging
        }

        void DrawSpaceFillingCurve()
        {
            if (segmentMap == null)
                return;
            x_old = 0;
            y_old = 0;

            this.rdr = SegmentMap.Segments.Values
                .Select(seg => seg.MemoryArea as ByteMemoryArea)    //$TODO: ony byte granular memory areas
                .Where(bmem => bmem != null)
                .OrderBy(bmem => bmem.BaseAddress)
                .Distinct()
                .SelectMany(bmeme => bmeme.Bytes).GetEnumerator();
            this.data = new byte[Width * Height * 4];

            SpaceFill(1, 1, Width, Height);

            GCHandle h = default(GCHandle);
            Bitmap bmp = null;
            try {
                h = GCHandle.Alloc(data);
                var ptr = Marshal.UnsafeAddrOfPinnedArrayElement(data, 0);
                bmp = new Bitmap(Width, Height, Width * 4,
                                    PixelFormat.Format32bppRgb, ptr);
                g.DrawImage(bmp, ClientRectangle.Location);
            }
            finally
            {
                if (h != default(GCHandle))
                    h.Free();
                if (bmp != null)
                    bmp.Dispose();
            }
        }

        int abs(int nn)
        {
            return Math.Abs(nn);
        }

        void render(int x0, int y0, char dir)
        { //msg("render: "+x0+","+y0);
            x_new = x0;
            y_new = y0;
            if ((x_old > 0) && (x_new > 0))
            {
#if DEBUGGING_CODE

                g.FillRectangle(Brushes.Blue, ScaleFactor * x_old, ScaleFactor * y_old, ScaleFactor / 2, ScaleFactor / 2);
                g.DrawLine(Pens.Blue, ScaleFactor * x_old+ScaleFactor/4, ScaleFactor * y_old + ScaleFactor / 4, 
                    ScaleFactor * x_new + ScaleFactor / 4, ScaleFactor * y_new + ScaleFactor / 4);
#endif

                byte b;
                if (!rdr.MoveNext())
                    b = 0xFF;
                else
                    b = rdr.Current;

                if (ClientRectangle.Contains(x_old, y_old))
                {
                    int o = (y_old * Width + x_old) * 4;

                    this.data[o+0] = b;
                    this.data[o+1] = b;
                    this.data[o+2] = b;
                    this.data[o+3] = 0;
                }
            }
            else
            {
              //  g.FillRectangle(Brushes.Red, ScaleFactor * x_new, ScaleFactor * y_new, 3 * ScaleFactor / 2, 3 * ScaleFactor / 2);
            }
            x_old = x_new;
            y_old = y_new;
        }

        void SpaceFill(int ll, int tt, int ww, int hh) //left, top, width, height
        {
            if (hh > ww) //go top->down
            {
                if ((hh % 2 == 1) && (ww % 2 == 0)) go(ll, tt, ww, 0, 0, hh, 'm'); //go diagonal
                else go(ll, tt, ww, 0, 0, hh, 'r'); //go top->down
            }
            else //go left->right
            {
                if ((ww % 2 == 1) && (hh % 2 == 0)) go(ll, tt, ww, 0, 0, hh, 'm'); //go diagonal
                else go(ll, tt, ww, 0, 0, hh, 'l'); //go left->right
            }
        }

        //x0, y0: start corner looking to the center of the rectangle
        //dxl, dyl: vector from the start corner to the left corner of the rectangle
        //dxr, dyr: vector from the start corner to the right corner of the rectangle
        //dir: direction to go - 'l'=left, 'm'=middle, 'r'=right
        //msg("go: "+x0+", "+y0+", "+dxl+", "+dyl+", "+dxr+", "+dyr+", "+dir);
        //render if 2x3 or smaller
        void go(int x0, int y0, int dxl, int dyl, int dxr, int dyr, char dir)
        { 
            if (abs((dxl + dyl) * (dxr + dyr)) <= 6)
            {
                int ddx, ddy, ii;
                if (abs(dxl + dyl) == 1)
                {
                    ddx = dxr / abs(dxr + dyr);
                    ddy = dyr / abs(dxr + dyr);
                    for (ii = 0; ii < abs(dxr + dyr); ii++)
                        render(x0 + ii * ddx + (dxl + ddx - 1) / 2, y0 + ii * ddy + (dyl + ddy - 1) / 2, dir);
                    return;
                }
                if (abs(dxr + dyr) == 1)
                {
                    ddx = dxl / abs(dxl + dyl);
                    ddy = dyl / abs(dxl + dyl);
                    for (ii = 0; ii < abs(dxl + dyl); ii++)
                        render(x0 + ii * ddx + (dxr + ddx - 1) / 2, y0 + ii * ddy + (dyr + ddy - 1) / 2, dir);
                    return;
                }
                if (dir == 'l')
                {
                    ddx = dxr / abs(dxr + dyr);
                    ddy = dyr / abs(dxr + dyr);
                    for (ii = 0; ii < abs(dxr + dyr); ii++)
                        render(x0 + ii * ddx + (dxl / 2 + ddx - 1) / 2, y0 + ii * ddy + (dyl / 2 + ddy - 1) / 2, dir);
                    for (ii = abs(dxr + dyr) - 1; ii >= 0; ii--)
                        render(x0 + ii * ddx + (dxl + dxl / 2 + ddx - 1) / 2, y0 + ii * ddy + (dyl + dyl / 2 + ddy - 1) / 2, dir);
                    return;
                }
                if (dir == 'r')
                {
                    ddx = dxl / abs(dxl + dyl);
                    ddy = dyl / abs(dxl + dyl);
                    for (ii = 0; ii < abs(dxl + dyl); ii++)
                        render(x0 + ii * ddx + (dxr / 2 + ddx - 1) / 2, y0 + ii * ddy + (dyr / 2 + ddy - 1) / 2, dir);
                    for (ii = abs(dxl + dyl) - 1; ii >= 0; ii--)
                        render(x0 + ii * ddx + (dxr + dxr / 2 + ddx - 1) / 2, y0 + ii * ddy + (dyr + dyr / 2 + ddy - 1) / 2, dir);
                    return;
                }
                if (dir == 'm')
                {
                    if (abs(dxr + dyr) == 3)
                    {
                        ddx = dxr / abs(dxr + dyr);
                        ddy = dyr / abs(dxr + dyr);
                        render(x0 + (dxl / 2 + ddx - 1) / 2, y0 + (dyl / 2 + ddy - 1) / 2, dir);
                        render(x0 + (dxl + dxl / 2 + ddx - 1) / 2, y0 + (dyl + dyl / 2 + ddy - 1) / 2, dir);
                        render(x0 + ddx + (dxl + dxl / 2 + ddx - 1) / 2, y0 + ddy + (dyl + dyl / 2 + ddy - 1) / 2, dir);
                        render(x0 + ddx + (dxl / 2 + ddx - 1) / 2, y0 + ddy + (dyl / 2 + ddy - 1) / 2, dir);
                        render(x0 + 2 * ddx + (dxl / 2 + ddx - 1) / 2, y0 + 2 * ddy + (dyl / 2 + ddy - 1) / 2, dir);
                        render(x0 + 2 * ddx + (dxl + dxl / 2 + ddx - 1) / 2, y0 + 2 * ddy + (dyl + dyl / 2 + ddy - 1) / 2, dir);
                        return;
                    }
                    if (abs(dxl + dyl) == 3)
                    {
                        ddx = dxl / abs(dxl + dyl);
                        ddy = dyl / abs(dxl + dyl);
                        render(x0 + (dxr / 2 + ddx - 1) / 2, y0 + (dyr / 2 + ddy - 1) / 2, dir);
                        render(x0 + (dxr + dxr / 2 + ddx - 1) / 2, y0 + (dyr + dyr / 2 + ddy - 1) / 2, dir);
                        render(x0 + ddx + (dxr + dxr / 2 + ddx - 1) / 2, y0 + ddy + (dyr + dyr / 2 + ddy - 1) / 2, dir);
                        render(x0 + ddx + (dxr / 2 + ddx - 1) / 2, y0 + ddy + (dyr / 2 + ddy - 1) / 2, dir);
                        render(x0 + 2 * ddx + (dxr / 2 + ddx - 1) / 2, y0 + 2 * ddy + (dyr / 2 + ddy - 1) / 2, dir);
                        render(x0 + 2 * ddx + (dxr + dxr / 2 + ddx - 1) / 2, y0 + 2 * ddy + (dyr + dyr / 2 + ddy - 1) / 2, dir);
                        return;
                    }
                }
                msg("renderError");
                return;
            }
            //divide into 2 parts if necessary
            if (2 * (abs(dxl) + abs(dyl)) > 3 * (abs(dxr) + abs(dyr))) //left side much longer than right side
            {
                var dxl2 = dxl / 2;
                var dyl2 = dyl / 2;
                if ((abs(dxr) + abs(dyr)) % 2 == 0) //right side is even
                {
                    if ((abs(dxl) + abs(dyl)) % 2 == 0) //make 2 parts from even side
                    {
                        if (dir == 'l')
                        {
                            if ((abs(dxl) + abs(dyl)) % 4 == 0) //make 2 parts even-even from even side
                            {
                                go(x0, y0, dxl2, dyl2, dxr, dyr, 'l');
                                go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr, dyr, 'l');
                            }
                            else //make 2 parts odd-odd from even side
                            {
                                go(x0, y0, dxl2, dyl2, dxr, dyr, 'm');
                                go(x0 + dxl2 + dxr, y0 + dyl2 + dyr, -dxr, -dyr, dxl - dxl2, dyl - dyl2, 'm');
                            }
                            return;
                        }
                    }
                    else //make 2 parts from odd side
                    {
                        if (dir == 'm')
                        {
                            if ((abs(dxl2) + abs(dyl2)) % 2 == 0)
                            {
                                go(x0, y0, dxl2, dyl2, dxr, dyr, 'l');
                                go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr, dyr, 'm');
                            }
                            else
                            {
                                go(x0, y0, dxl2, dyl2, dxr, dyr, 'm');
                                go(x0 + dxl2 + dxr, y0 + dyl2 + dyr, -dxr, -dyr, dxl - dxl2, dyl - dyl2, 'r');
                            }
                            return;
                        }
                    }
                }
                else //right side is odd
                {
                    if (dir == 'l')
                    {
                        go(x0, y0, dxl2, dyl2, dxr, dyr, 'l');
                        go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr, dyr, 'l');
                        return;
                    }
                    if (dir == 'm')
                    {
                        go(x0, y0, dxl2, dyl2, dxr, dyr, 'l');
                        go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr, dyr, 'm');
                        return;
                    }
                }
            }
            if (2 * (abs(dxr) + abs(dyr)) > 3 * (abs(dxl) + abs(dyl))) //right side much longer than left side
            {
                var dxr2 = dxr / 2;
                var dyr2 = dyr / 2;
                if ((abs(dxl) + abs(dyl)) % 2 == 0) //left side is even
                {
                    if ((abs(dxr) + abs(dyr)) % 2 == 0) //make 2 parts from even side
                    {
                        if (dir == 'r')
                        {
                            if ((abs(dxr) + abs(dyr)) % 4 == 0) //make 2 parts even-even from even side
                            {
                                go(x0, y0, dxl, dyl, dxr2, dyr2, 'r');
                                go(x0 + dxr2, y0 + dyr2, dxl, dyl, dxr - dxr2, dyr - dyr2, 'r');
                            }
                            else //make 2 parts odd-odd from even side
                            {
                                go(x0, y0, dxl, dyl, dxr2, dyr2, 'm');
                                go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxr - dxr2, dyr - dyr2, -dxl, -dyl, 'm');
                            }
                            return;
                        }
                    }
                    else //make 2 parts from odd side
                    {
                        if (dir == 'm')
                        {
                            if ((abs(dxr2) + abs(dyr2)) % 2 == 0)
                            {
                                go(x0, y0, dxl, dyl, dxr2, dyr2, 'r');
                                go(x0 + dxr2, y0 + dyr2, dxl, dyl, dxr - dxr2, dyr - dyr2, 'm');
                            }
                            else
                            {
                                go(x0, y0, dxl, dyl, dxr2, dyr2, 'm');
                                go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxr - dxr2, dyr - dyr2, -dxl, -dyl, 'l');
                            }
                            return;
                        }
                    }
                }
                else //left side is odd
                {
                    if (dir == 'r')
                    {
                        go(x0, y0, dxl, dyl, dxr2, dyr2, 'r');
                        go(x0 + dxr2, y0 + dyr2, dxl, dyl, dxr - dxr2, dyr - dyr2, 'r');
                        return;
                    }
                    if (dir == 'm')
                    {
                        go(x0, y0, dxl, dyl, dxr2, dyr2, 'r');
                        go(x0 + dxr2, y0 + dyr2, dxl, dyl, dxr - dxr2, dyr - dyr2, 'm');
                        return;
                    }
                }
            }
            //divide into 2x2 parts
            if ((dir == 'l') || (dir == 'r'))
            {
                var dxl2 = dxl / 2;
                var dyl2 = dyl / 2;
                var dxr2 = dxr / 2;
                var dyr2 = dyr / 2;
                if ((abs(dxl + dyl) % 2 == 0) && (abs(dxr + dyr) % 2 == 0)) //even-even
                {
                    if (abs(dxl2 + dyl2 + dxr2 + dyr2) % 2 == 0) //ee-ee or oo-oo
                    {
                        if (dir == 'l')
                        {
                            go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'r');
                            go(x0 + dxr2, y0 + dyr2, dxl2, dyl2, dxr - dxr2, dyr - dyr2, 'l');
                            go(x0 + dxr2 + dxl2, y0 + dyr2 + dyl2, dxl - dxl2, dyl - dyl2, dxr - dxr2, dyr - dyr2, 'l');
                            go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxl2 - dxl, dyl2 - dyl, -dxr2, -dyr2, 'r');
                        }
                        else
                        {
                            go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'l');
                            go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr2, dyr2, 'r');
                            go(x0 + dxr2 + dxl2, y0 + dyr2 + dyl2, dxl - dxl2, dyl - dyl2, dxr - dxr2, dyr - dyr2, 'r');
                            go(x0 + dxr + dxl2, y0 + dyr + dyl2, -dxl2, -dyl2, dxr2 - dxr, dyr2 - dyr, 'l');
                        }
                    }
                    else //ee-oo or oo-ee
                    {
                        if ((dxr2 + dyr2) % 2 == 0) //ee-oo
                        {
                            if (dir == 'l')
                            {
                                go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'r');
                                go(x0 + dxr2, y0 + dyr2, dxl2, dyl2, dxr - dxr2, dyr - dyr2, 'm');
                                go(x0 + dxr + dxl2, y0 + dyr + dyl2, dxr2 - dxr, dyr2 - dyr, dxl - dxl2, dyl - dyl2, 'm');
                                go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxl2 - dxl, dyl2 - dyl, -dxr2, -dyr2, 'r');
                            }
                            else //ee-oo for dir='r' not possible, so transforming into e-1,e+1-oo = oo-oo 
                            {
                                if (dxr2 != 0) dxr2++; else dyr2++;
                                go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'l');
                                go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr2, dyr2, 'm');
                                go(x0 + dxl + dxr2, y0 + dyl + dyr2, dxr - dxr2, dyr - dyr2, dxl2 - dxl, dyl2 - dyl, 'm');
                                go(x0 + dxl2 + dxr, y0 + dyl2 + dyr, -dxl2, -dyl2, dxr2 - dxr, dyr2 - dyr, 'l');
                            }
                        }
                        else //oo-ee
                        {
                            if (dir == 'r')
                            {
                                go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'l');
                                go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr2, dyr2, 'm');
                                go(x0 + dxl + dxr2, y0 + dyl + dyr2, dxr - dxr2, dyr - dyr2, dxl2 - dxl, dyl2 - dyl, 'm');
                                go(x0 + dxl2 + dxr, y0 + dyl2 + dyr, -dxl2, -dyl2, dxr2 - dxr, dyr2 - dyr, 'l');
                            }
                            else //oo-ee for dir='l' not possible, so transforming into oo-e-1,e+1 = oo-oo 
                            {
                                if (dxl2 != 0) dxl2++; else dyl2++;
                                go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'r');
                                go(x0 + dxr2, y0 + dyr2, dxl2, dyl2, dxr - dxr2, dyr - dyr2, 'm');
                                go(x0 + dxr + dxl2, y0 + dyr + dyl2, dxr2 - dxr, dyr2 - dyr, dxl - dxl2, dyl - dyl2, 'm');
                                go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxl2 - dxl, dyl2 - dyl, -dxr2, -dyr2, 'r');
                            }
                        }
                    }
                }
                else //not even-even
                {
                    if ((abs(dxl + dyl) % 2 != 0) && (abs(dxr + dyr) % 2 != 0)) //odd-odd
                    {
                        if (dxl2 % 2 != 0) dxl2 = dxl - dxl2; //get it in a shape eo-eo 
                        if (dyl2 % 2 != 0) dyl2 = dyl - dyl2;
                        if (dxr2 % 2 != 0) dxr2 = dxr - dxr2;
                        if (dyr2 % 2 != 0) dyr2 = dyr - dyr2;
                        if (dir == 'l')
                        {
                            go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'r');
                            go(x0 + dxr2, y0 + dyr2, dxl2, dyl2, dxr - dxr2, dyr - dyr2, 'm');
                            go(x0 + dxr + dxl2, y0 + dyr + dyl2, dxr2 - dxr, dyr2 - dyr, dxl - dxl2, dyl - dyl2, 'm');
                            go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxl2 - dxl, dyl2 - dyl, -dxr2, -dyr2, 'r');
                        }
                        else
                        {
                            go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'l');
                            go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr2, dyr2, 'm');
                            go(x0 + dxl + dxr2, y0 + dyl + dyr2, dxr - dxr2, dyr - dyr2, dxl2 - dxl, dyl2 - dyl, 'm');
                            go(x0 + dxl2 + dxr, y0 + dyl2 + dyr, -dxl2, -dyl2, dxr2 - dxr, dyr2 - dyr, 'l');
                        }
                    }
                    else //even-odd or odd-even
                    {
                        if (abs(dxl + dyl) % 2 == 0) //odd-even
                        {
                            if (dir == 'l')
                            {
                                if (dxr2 % 2 != 0) dxr2 = dxr - dxr2; //get it in a shape eo-xx 
                                if (dyr2 % 2 != 0) dyr2 = dyr - dyr2;
                                if (abs(dxl + dyl) > 2)
                                {
                                    go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'r');
                                    go(x0 + dxr2, y0 + dyr2, dxl2, dyl2, dxr - dxr2, dyr - dyr2, 'l');
                                    go(x0 + dxr2 + dxl2, y0 + dyr2 + dyl2, dxl - dxl2, dyl - dyl2, dxr - dxr2, dyr - dyr2, 'l');
                                    go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxl2 - dxl, dyl2 - dyl, -dxr2, -dyr2, 'r');
                                }
                                else
                                {
                                    go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'r');
                                    go(x0 + dxr2, y0 + dyr2, dxl2, dyl2, dxr - dxr2, dyr - dyr2, 'm');
                                    go(x0 + dxr + dxl2, y0 + dyr + dyl2, dxr2 - dxr, dyr2 - dyr, dxl - dxl2, dyl - dyl2, 'm');
                                    go(x0 + dxr2 + dxl, y0 + dyr2 + dyl, dxl2 - dxl, dyl2 - dyl, -dxr2, -dyr2, 'r');
                                }
                            }
                            else msg("4-part-error1: " + x0 + ", " + y0 + ", " + dxl + ", " + dyl + ", " + dxr + ", " + dyr + ", " + dir);
                        }
                        else //even-odd
                        {
                            if (dir == 'r')
                            {
                                if (dxl2 % 2 != 0) dxl2 = dxl - dxl2; //get it in a shape xx-eo 
                                if (dyl2 % 2 != 0) dyl2 = dyl - dyl2;
                                if (abs(dxr + dyr) > 2)
                                {
                                    go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'l');
                                    go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr2, dyr2, 'r');
                                    go(x0 + dxr2 + dxl2, y0 + dyr2 + dyl2, dxl - dxl2, dyl - dyl2, dxr - dxr2, dyr - dyr2, 'r');
                                    go(x0 + dxr + dxl2, y0 + dyr + dyl2, -dxl2, -dyl2, dxr2 - dxr, dyr2 - dyr, 'l');
                                }
                                else
                                {
                                    go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'l');
                                    go(x0 + dxl2, y0 + dyl2, dxl - dxl2, dyl - dyl2, dxr2, dyr2, 'm');
                                    go(x0 + dxl + dxr2, y0 + dyl + dyr2, dxr - dxr2, dyr - dyr2, dxl2 - dxl, dyl2 - dyl, 'm');
                                    go(x0 + dxl2 + dxr, y0 + dyl2 + dyr, -dxl2, -dyl2, dxr2 - dxr, dyr2 - dyr, 'l');
                                }
                            }
                            else msg("4-part-error2: " + x0 + ", " + y0 + ", " + dxl + ", " + dyl + ", " + dxr + ", " + dyr + ", " + dir);
                        }
                    }
                }
            }
            else //dir=='m' -> divide into 3x3 parts
            {
                int dxl2;
                int dyl2;
                int dxr2;
                int dyr2;
                if ((abs(dxl + dyl) % 2 == 0) && (abs(dxr + dyr) % 2 == 0))
                    msg("9-part-error1: " + x0 + ", " + y0 + ", " + dxl + ", " + dyl + ", " + dxr + ", " + dyr + ", " + dir);
                if (abs(dxr + dyr) % 2 == 0) //even-odd: oeo-ooo
                {
                    dxl2 = dxl / 3;
                    dyl2 = dyl / 3;
                    dxr2 = dxr / 3;
                    dyr2 = dyr / 3;
                    if ((dxl2 + dyl2) % 2 == 0) //make it odd  
                    {
                        dxl2 = dxl - 2 * dxl2;
                        dyl2 = dyl - 2 * dyl2;
                    }
                    if ((dxr2 + dyr2) % 2 == 0) //make it odd (not necessary, however results are better for 12x30, 18x30 etc.) 
                    {
                        if (abs(dxr2 + dyr2) != 2)
                        {
                            if (dxr < 0) dxr2++;
                            if (dxr > 0) dxr2--;  //dont use else here !
                            if (dyr < 0) dyr2++;
                            if (dyr > 0) dyr2--;  //dont use else here !
                        }
                    }
                }
                else //odd-even: ooo-oeo
                {
                    dxl2 = dxl / 3;
                    dyl2 = dyl / 3;
                    dxr2 = dxr / 3;
                    dyr2 = dyr / 3;
                    if ((dxr2 + dyr2) % 2 == 0) //make it odd  
                    {
                        dxr2 = dxr - 2 * dxr2;
                        dyr2 = dyr - 2 * dyr2;
                    }
                    if ((dxl2 + dyl2) % 2 == 0) //make it odd (not necessary, however results are better for 12x30, 18x30 etc.)
                    {
                        if (abs(dxl2 + dyl2) != 2)
                        {
                            if (dxl < 0) dxl2++;
                            if (dxl > 0) dxl2--;  //dont use else here !
                            if (dyl < 0) dyl2++;
                            if (dyl > 0) dyl2--;  //dont use else here !
                        }
                    }
                }
                if (abs(dxl + dyl) < abs(dxr + dyr))
                {
                    go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'm');
                    go(x0 + dxl2 + dxr2, y0 + dyl2 + dyr2, -dxr2, -dyr2, dxl - 2 * dxl2, dyl - 2 * dyl2, 'm');
                    go(x0 + dxl - dxl2, y0 + dyl - dyl2, dxl2, dyl2, dxr2, dyr2, 'm');
                    go(x0 + dxl + dxr2, y0 + dyl + dyr2, dxr - 2 * dxr2, dyr - 2 * dyr2, -dxl2, -dyl2, 'm');
                    go(x0 + dxr - dxr2 + dxl - dxl2, y0 + dyr - dyr2 + dyl - dyl2, 2 * dxl2 - dxl, 2 * dyl2 - dyl, 2 * dxr2 - dxr, 2 * dyr2 - dyr, 'm');
                    go(x0 + dxl2 + dxr2, y0 + dyl2 + dyr2, dxr - 2 * dxr2, dyr - 2 * dyr2, -dxl2, -dyl2, 'm');
                    go(x0 + dxr - dxr2, y0 + dyr - dyr2, dxl2, dyl2, dxr2, dyr2, 'm');
                    go(x0 + dxr + dxl2, y0 + dyr + dyl2, -dxr2, -dyr2, dxl - 2 * dxl2, dyl - 2 * dyl2, 'm');
                    go(x0 + dxr - dxr2 + dxl - dxl2, y0 + dyr - dyr2 + dyl - dyl2, dxl2, dyl2, dxr2, dyr2, 'm');
                }
                else
                {
                    go(x0, y0, dxl2, dyl2, dxr2, dyr2, 'm');
                    go(x0 + dxl2 + dxr2, y0 + dyl2 + dyr2, dxr - 2 * dxr2, dyr - 2 * dyr2, -dxl2, -dyl2, 'm');
                    go(x0 + dxr - dxr2, y0 + dyr - dyr2, dxl2, dyl2, dxr2, dyr2, 'm');
                    go(x0 + dxr + dxl2, y0 + dyr + dyl2, -dxr2, -dyr2, dxl - 2 * dxl2, dyl - 2 * dyl2, 'm');
                    go(x0 + dxr - dxr2 + dxl - dxl2, y0 + dyr - dyr2 + dyl - dyl2, 2 * dxl2 - dxl, 2 * dyl2 - dyl, 2 * dxr2 - dxr, 2 * dyr2 - dyr, 'm');
                    go(x0 + dxl2 + dxr2, y0 + dyl2 + dyr2, -dxr2, -dyr2, dxl - 2 * dxl2, dyl - 2 * dyl2, 'm');
                    go(x0 + dxl - dxl2, y0 + dyl - dyl2, dxl2, dyl2, dxr2, dyr2, 'm');
                    go(x0 + dxl + dxr2, y0 + dyl + dyr2, dxr - 2 * dxr2, dyr - 2 * dyr2, -dxl2, -dyl2, 'm');
                    go(x0 + dxr - dxr2 + dxl - dxl2, y0 + dyr - dyr2 + dyl - dyl2, dxl2, dyl2, dxr2, dyr2, 'm');
                }
            }
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            this.g = e.Graphics;
            DrawSpaceFillingCurve();
        }

        protected virtual void OnImageMapChanged()
        {
            Invalidate();
        }
    }
}
