{
    $Id$
    This file is part of the Free Pascal run time library.
    Copyright (c) 1993-98 by Gernot Tenchio

    Mandelbrot Example using the Graph unit

    See the file COPYING.FPC, included in this distribution,
    for details about the copyright.

    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.

 **********************************************************************}
program mandel;

{
  Mandelbrot example using the graph unit.

  Note: For linux you need to run this program as root !!
}

uses
  Graph;

const
  shift:byte=12;

var
  SerchPoint,ActualPoint,NextPoint       : PointType;
  LastColor                              : longint;
  Gd,Gm,
  Max_Color,Max_X_Width,
  Max_Y_Width,Y_Width                    : integer;
  Y1,Y2,X1,X2,Dy,Dx                      : Real;
  Zm                                     : Integer;
  Flag                                   : boolean;
  LineY                                  : array [0..600] OF BYTE;
  LineX                                  : array [0..100,0..600] OF INTEGER;
const
    SX : array [0..7] OF SHORTINT=(-1, 0, 1, 1, 1, 0,-1,-1);
    SY : array [0..7] OF SHORTINT=(-1,-1,-1, 0, 1, 1, 1, 0);
type
    arrayType = array[1..50] of integer;

{------------------------------------------------------------------------------}
function CalcMandel(Point:PointType; z:integer) : Longint ;
var
  x,y,xq,yq,Cx,Cy : real ;
begin
  Cy:=y2 + dy*Point.y ;
  Cx:=x2 + dx*Point.x ;
  X:=-Cx ; Y:=-Cy ;
  repeat
    xq:=x * x;
    yq:=y * y  ;
    y :=x * y;
    y :=y + y - cy;
    x :=xq - yq - cx ;
    z :=z -1;
  until (Z=0) or (Xq + Yq > 4 );
  if Z=0 Then
    CalcMandel:=1
  else
    CalcMandel:=(z mod Max_Color) + 1 ;
end;

{-----------------------------------------------------------------------------}
procedure Partition(var A : arrayType; First, Last : Byte);
var
  Right,Left : byte ;
  V,Temp     : integer;
begin
    V := A[(First + Last) SHR 1];
    Right := First;
    Left := Last;
    repeat
      while (A[Right] < V) do
        inc(Right);
      while (A[Left] > V) do
        Dec(Left);
      if (Right <= Left) then
        begin
          Temp:=A[Left];
          A[Left]:=A[Right];
          A[Right]:=Temp;
          Right:=Right+1;
          Left:=Left-1;
        end;
    until Right > Left;
    if (First < Left) then
      Partition(A, First, Left);
    if (Right < Last) then
      Partition(A, Right, Last)
end;

{-----------------------------------------------------------------------------}
function BlackScan(var NextPoint:PointType) : boolean;
begin
  BlackScan:=true;
  repeat
    if NextPoint.X=Max_X_Width then
      begin
        if NextPoint.Y < Y_Width then
          begin
            NextPoint.X:=0 ;
            NextPoint.Y:=NextPoint.Y+1;
          end
        else
          begin
            BlackScan:=false;
            exit;
          end ; { IF }
      end ; { IF }
    NextPoint.X:=NextPoint.X+1;
  until GetPixel(NextPoint.X,NextPoint.Y)=0;
end ;

{------------------------------------------------------------------------------}
procedure Fill(Ymin,Ymax,LastColor:integer);
var
 P1,P3,P4,P    : integer ;
 Len,P2        : byte ;
 Darray        : arraytype;
begin
  SetColor(LastColor);
  for P1:=Ymin+1 to Ymax-1 do
   begin
     Len:=LineY[P1] ;
     if Len >= 2 then
      begin
        for P2:=1 to Len do
          Darray[P2]:=LineX[P2,P1] ;
        if Len > 2 then
          Partition(Darray,1,len);
        P2:=1;
        repeat
          P3:= Darray[P2] ; P4:= Darray[P2 + 1];
          if P3 <> P4 then
           begin
             line ( P3 , P1 , P4 , P1) ;
             if Flag then
              begin
                P:=Max_Y_Width-P1;
                line ( P3 , P , P4 , P ) ;
              end;
           end; { IF }
          P2:=P2+2;
        until P2 >= Len ;
      end; { IF }
   end; { FOR }
end;

{-----------------------------------------------------------------------------}
Function NewPosition(Last:Byte):Byte;
begin
  newposition:=(((last+1) and 254)+6) and 7;
end;

{-----------------------------------------------------------------------------}
procedure CalcBounds;
var
  lastOperation,KK,
  Position                     : Byte ;
  foundcolor                   : longint;
  Start,Found,NotFound         : boolean ;
  MerkY,Ymax                   : Integer ;
label
  L;
begin
  repeat
    FillChar(LineY,SizeOf(LineY),0) ;
    ActualPoint:=NextPoint;
    LastColor:=CalcMandel(NextPoint,Zm) ;
    putpixel (ActualPoint.X,ActualPoint.Y,LastColor);
    if Flag then
      putpixel (ActualPoint.X,Max_Y_Width-ActualPoint.Y,LastColor) ;
    Ymax:=NextPoint.Y ;
    MerkY:=NextPoint.Y ;
    NotFound:=false ;
    Start:=false ;
    LastOperation:=4 ;
    repeat
      Found:=false ;
      KK:=0 ;
      Position:=NewPosition(LastOperation);
      repeat
        LastOperation:=(Position+KK) and 7 ;
        SerchPoint.X:=ActualPoint.X+Sx[LastOperation];
        SerchPoint.Y:=ActualPoint.Y+Sy[LastOperation];
        if ((SerchPoint.X < 0) or
            (SerchPoint.X > Max_X_Width) or
            (SerchPoint.Y < NextPoint.Y) or
            (SerchPoint.Y > Y_Width)) then
          goto L;
        if (SerchPoint.X=NextPoint.X) and (SerchPoint.Y=NextPoint.Y) then
          begin
            Start:=true ;
            Found:=true ;
          end
        else
          begin
            FoundColor:=GetPixel(SerchPoint.X,SerchPoint.Y) ;
            if FoundColor = 0 then
              begin
                FoundColor:= CalcMandel (SerchPoint,Zm) ;
                Putpixel (SerchPoint.X,SerchPoint.Y,FoundColor) ;
                if Flag then
                  PutPixel (SerchPoint.X,Max_Y_Width-SerchPoint.Y,FoundColor) ;
              end ;
            if FoundColor=LastColor then
              begin
                if ActualPoint.Y <> SerchPoint.Y then
                  begin
                    if SerchPoint.Y = MerkY then
                      LineY[ActualPoint.Y]:=LineY[ActualPoint.Y]-1;
                    MerkY:= ActualPoint.Y ;
                    LineY[SerchPoint.Y]:=LineY[SerchPoint.Y]+1;
                  end ;
                LineX[LineY[SerchPoint.Y],SerchPoint.Y]:=SerchPoint.X ;
                if SerchPoint.Y > Ymax then Ymax:= SerchPoint.Y ;
                  Found:=true ;
                ActualPoint:=SerchPoint ;
              end;
L:
            KK:=KK+1;
            if KK > 8 then
              begin
                Start:=true ;
                NotFound:=true ;
              end;
          end;
      until Found or (KK > 8);
    until Start ;
    if not NotFound then
      Fill(NextPoint.Y,Ymax,LastColor) ;
  until not BlackScan(NextPoint);
end ;


{------------------------------------------------------------------------------
                              MAINROUTINE
------------------------------------------------------------------------------}

begin
{$ifdef Linux}
  gm:=0;
  gd:=0;
{$else}
  gm:=$103;
  gd:=$ff;
  {$ifDEF TURBO}
    gd:=detect;
  {$endif}
{$endif}
  InitGraph(gd,gm,'D:\bp\bgi');
  if GraphResult <> grOk then Halt(1);
  Max_X_Width:=GetMaxX;
  Max_y_Width:=GetMaxY;
  Max_Color:=GetMaxColor-1;
  ClearViewPort;

  x1:=-0.9;
  x2:= 2.2;
  y1:= 1.25;
  y2:=-1.25;
  zm:=90;
  dx:=(x1 - x2) / Max_X_Width ;
  dy:=(y1 - y2) / Max_Y_Width ;
  if abs(y1) = abs(y2) then
   begin
     flag:=true;
     Y_Width:=Max_Y_Width shr 1
   end
  else
   begin
     flag:=false;
     Y_Width:=Max_Y_Width;
   end;
  NextPoint.X:=0;
  NextPoint.Y:=0;
  LastColor:=CalcMandel(SerchPoint,zm);
  CalcBounds ;
  readln;
  CloseGraph;
end.
{
  $Log$
  Revision 1.3  1998-09-11 10:55:25  peter
    + header+log

}