{
    $Id$

    This file is part of the Free Pascal run time library.
    Copyright (c) 1999-2000 by Thomas Schatzl and Carl Eric Codere

    This include implements polygon filling and flood filling.

    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.

 **********************************************************************}

{ simple descriptive name }
function max(a, b : Longint) : Longint;
begin
  max := b;
  if (a > b) then max := a;
end;

{ here too }
function min(a, b : Longint) : Longint;
begin
  min := b;
  if (a < b) then min := a;
end;

procedure fillpoly(numpoints : Word; var polypoints);

type
  pedge = ^tedge;
  tedge = packed record
    yMin, yMax, x, dX, dY, frac : Longint;
  end;

  pedgearray = ^tedgearray;
  tedgearray = array[0..0] of tedge;

  ppedgearray = ^tpedgearray;
  tpedgearray = array[0..0] of pedge;

var
  nActive, nNextEdge : Longint;
  p0, p1 : pointtype;
  endy, i, j, gap, x0, x1, y, nEdges : Longint;
  ET : pedgearray;
  GET, AET : ppedgearray;
  t : pedge;

  ptable : ^pointtype;


begin
{ /********************************************************************
  * Add entries to the global edge table.  The global edge table has a
  * bucket for each scan line in the polygon. Each bucket contains all
  * the edges whose yMin == yScanline.  Each bucket contains the yMax,
  * the x coordinate at yMax, and the denominator of the slope (dX)
*/}
  getmem(et, sizeof(tedge) * numpoints);
  getmem(get, sizeof(pedge) * numpoints);
  getmem(aet, sizeof(pedge) * numpoints);

  ptable := @polypoints;

 { check for getmem success }
  
  nEdges := 0;
  for i := 0 to (numpoints-1) do begin
    p0 := ptable[i];
    if (i+1) >= numpoints then p1 := ptable[0]
    else p1 := ptable[i+1];
   { ignore if this is a horizontal edge}
    if (p0.y = p1.y) then continue;
    {swap ptable if necessary to ensure p0 contains yMin}
    if (p0.y > p1.y) then begin
      p0 := p1;
      p1 := ptable[i];
    end;
   { create the new edge }
    et^[nEdges].ymin := p0.y;
    et^[nEdges].ymax := p1.y;
    et^[nEdges].x := p0.x;
    et^[nEdges].dX := p1.x-p0.x;
    et^[nEdges].dy := p1.y-p0.y;
    et^[nEdges].frac := 0;
    get^[nEdges] :=  @et^[nEdges];
    inc(nEdges);
  end;
 { sort the GET on ymin }
  gap := 1;
  while (gap < nEdges) do gap := 3*gap+1;
  gap := gap div 3;
  while (gap > 0) do begin
    for i := gap to (nEdges-1) do begin
      j := i - gap;
      while (j >= 0) do begin
        if (GET^[j]^.ymin <= GET^[j+gap]^.yMin) then break;
        t := GET^[j];
        GET^[j] := GET^[j+gap];
        GET^[j+gap] := t;
        dec(j, gap);
      end;
    end;
    gap := gap div 3;
  end;
  { initialize the active edge table, and set y to first entering edge}
  nActive := 0;
  nNextEdge := 0;

  y := GET^[nNextEdge]^.ymin;
  { Now process the edges using the scan line algorithm.  Active edges
  will be added to the Active Edge Table (AET), and inactive edges will
  be deleted.  X coordinates will be updated with incremental integer
  arithmetic using the slope (dY / dX) of the edges. }
  while (nNextEdge < nEdges) or (nActive <> 0) do begin
    {Move from the ET bucket y to the AET those edges whose yMin == y
    (entering edges) }
    while (nNextEdge < nEdges) and (GET^[nNextEdge]^.ymin = y) do begin
      AET^[nActive] := GET^[nNextEdge];
      inc(nActive);
      inc(nNextEdge);
    end;
    { Remove from the AET those entries for which yMax == y (leaving
    edges) }
    i := 0;
    while (i < nActive) do begin
      if (AET^[i]^.yMax = y) then begin
        dec(nActive);
        move(AET^[i+1], AET^[i], (nActive-i)*sizeof(pedge));
      end else
        inc(i);
    end;

    if (y >= 0) then begin
    {Now sort the AET on x.  Since the list is usually quite small,
    the sort is implemented as a simple non-recursive shell sort }

    gap := 1;
    while (gap < nActive) do gap := 3*gap+1;

    gap := gap div 3;
    while (gap > 0) do begin
      for i := gap to (nActive-1) do begin
        j := i - gap;
        while (j >= 0) do begin
          if (AET^[j]^.x <= AET^[j+gap]^.x) then break;
          t := AET^[j];
          AET^[j] := AET^[j+gap];
          AET^[j+gap] := t;
          dec(j, gap);
        end;
      end;
      gap := gap div 3;
    end;

    { Fill in desired pixels values on scan line y by using pairs of x
    coordinates from the AET }
    i := 0;
    while (i < nActive) do begin
      x0 := AET^[i]^.x;
      x1 := AET^[i+1]^.x;
      {Left edge adjustment for positive fraction.  0 is interior. }
      if (AET^[i]^.frac > 0) then inc(x0);
      {Right edge adjustment for negative fraction.  0 is exterior. }
      if (AET^[i+1]^.frac <= 0) then dec(x1);

      x0 := max(x0, 0);
      x1 := min(x1, viewWidth);
      { Draw interior spans}
      if (x1 >= x0) then begin
        PatternLine(x0, x1, y);
      end;

      inc(i, 2);
    end;

    end;

    { Update all the x coordinates.  Edges are scan converted using a
    modified midpoint algorithm (Bresenham's algorithm reduces to the
    midpoint algorithm for two dimensional lines) }
    for i := 0 to (nActive-1) do begin
      t := AET^[i];
      { update the fraction by dX}
      inc(t^.frac, t^.dX);

      if (t^.dX < 0) then
        while ( -(t^.frac) >= t^.dY) do begin
          inc(t^.frac, t^.dY);
          dec(t^.x);
        end
      else
        while (t^.frac >= t^.dY) do begin
          dec(t^.frac, t^.dY);
          inc(t^.x);
        end;
    end;
    inc(y);
    if (y >= ViewHeight) then break;
  end;
  freemem(et, sizeof(tedge) * numpoints);
  freemem(get, sizeof(pedge) * numpoints);
  freemem(aet, sizeof(pedge) * numpoints);
end;


{ maximum supported Y resultion }
const
  MaxYRes = 2048;
  { changing this to 1 or 2 doesn't improve performance noticably }
  YResDiv = 4;

type
  PFloodLine = ^TFloodLine;
  TFloodLine = record
    next: PFloodLine;
    x1 : smallint;
    x2 : smallint;
    y  : smallint;
  end;

  TDrawnList  = Array[0..(MaxYRes - 1) div YResDiv] of PFloodLine;

var
   DrawnList : TDrawnList;
   Buffer : Record                         { Union for byte and word addressing of buffer }
     ByteIndex : Word;
     WordIndex : Word;
     Case Boolean Of
        False : (Bytes : Array [0..StdBufferSize-1] Of Byte);
        True  : (Words : Array [0..(StdBufferSize DIV 2)-1] Of Word);
     End;

  s1, s2, s3 : PWordArray;                { Three buffers for scanlines                 }


  Procedure PushPoint (x, y : smallint);
  {********************************************************}
  { Adds a  point to the list of points to check if we     }
  { need to draw. Doesn't add the point if there is a      }
  { buffer overflow.                                       }
  {********************************************************}
  Begin
    If Buffer.WordIndex<(StdBufferSize DIV 2)-3 then
     Begin
       Buffer.Words[Buffer.WordIndex]:=x;
       Buffer.Words[Buffer.WordIndex+1]:=y;
       Inc (Buffer.WordIndex,2);
     End
  End;

  Procedure PopPoint (Var x, y : smallint);
  {********************************************************}
  { Removes a point from the list of points to check, if   }
  { we try to access an illegal point, then the routine    }
  { returns -1,-1 as a coordinate pair.                    }
  {********************************************************}
  Begin
   If Buffer.WordIndex>1 then
    Begin
      x:=Buffer.Words[Buffer.WordIndex-2];
      y:=Buffer.Words[Buffer.WordIndex-1];
      Dec (Buffer.WordIndex,2);
    End
   Else
    Begin
      x:=-1;
      y:=-1;
    End;
  End;






  {********************************************************}
  { Procedure AddLinePoints()                              }
  {--------------------------------------------------------}
  { Adds a line segment to the list of lines which will be }
  { drawn to the screen. The line added is on the specified}
  { Y axis, from the x1 to x2 coordinates.                 }
  {********************************************************}
  Procedure AddLinePoints(x1,x2,y: smallint);
   var temp: PFloodLine;
   begin
     new(temp);
     temp^.x1 := x1;
     temp^.x2 := x2;
     temp^.y := y;
     temp^.next := DrawnList[y div YResDiv];
     DrawnList[y div YResDiv] := temp;
   end;

  {********************************************************}
  { Procedure AlreadyDrawn()                               }
  {--------------------------------------------------------}
  { This routine searches through the list of segments     }
  { which will be drawn to the screen, and determines  if  }
  { the specified point (x,y) will already be drawn.       }
  { i.e : Checks if the x,y point lies within a known      }
  { segment which will be drawn to the screen. This makes  }
  { sure that we don't draw some segments two times.       }
  { Return TRUE if the point is already in the segment list}
  { to draw, otherwise returns FALSE.                      }
  {********************************************************}
  Function AlreadyDrawn(x, y: smallint): boolean;
  var
    temp : PFloodLine;
   begin
    AlreadyDrawn := false;
    temp := DrawnList[y div YResDiv];
    while assigned(temp) do
      begin
        if (temp^.y = y) and
           (temp^.x1 <= x) and
           (temp^.x2 >= x) then
          begin
            AlreadyDrawn := true;
            exit;
          end;
        temp := temp^.next;
      end;
   end;

  {********************************************************}
  { Procedure CleanUpDrawnList                             }
  {--------------------------------------------------------}
  { removes all elements from the DrawnList. Doesn't init  }
  { elements of it with NILL                               }
  {********************************************************}
  Procedure CleanUpDrawnList;
  var
    l: longint;
    temp1, temp2: PFloodLine;
  begin
    for l := 0 to high(DrawnList) do
      begin
        temp1 := DrawnList[l];
        while assigned(temp1) do
          begin
            temp2 := temp1;
            temp1 := temp1^.next;
            dispose(temp2);
          end;
      end;
  end;


  Procedure FloodFill (x, y : smallint; Border: word);
  {********************************************************}
  { Procedure FloodFill()                                  }
  {--------------------------------------------------------}
  { This routine fills a region of the screen bounded by   }
  { the <Border> color. It uses the current fillsettings   }
  { for the flood filling. Clipping is supported, and      }
  { coordinates are local/viewport relative.               }
  {********************************************************}
  Var
   stemp: PWordArray;
   Beginx : smallint;
   d, e : Byte;
   Cont : Boolean;
   BackupColor : Word;
   x1, x2, prevy: smallint;
   Index : smallint;
  Begin
    FillChar(DrawnList,sizeof(DrawnList),0);
    { init prevy }
    prevy := 32767;
    { Save current drawing color }
    BackupColor := CurrentColor;
    CurrentColor := FillSettings.Color;
    { MaxX is based on zero index }
    GetMem (s1,(ViewWidth+1)*2);  { A pixel color represents a word }
    GetMem (s2,(ViewWidth+1)*2);  { A pixel color represents a word }
    GetMem (s3,(ViewWidth+1)*2);  { A pixel color represents a word }
    if (not assigned(s1)) or (not assigned(s2)) or (not assigned(s3)) then
      begin
        _GraphResult := grNoFloodMem;
        exit;
      end;
    If (x<0) Or (y<0) Or
       (x>ViewWidth) Or (y>ViewHeight) then Exit;
    { Some internal variables }
    Index := 0;
    { Index of points to check  }
    Buffer.WordIndex:=0;
    PushPoint (x,y);
    While Buffer.WordIndex>0 Do
     Begin
       PopPoint (x,y);
       { Get the complete lines for the following }
       If y <> prevy then
         begin
           If (prevy - y = 1) then
             { previous line was one below the new one, so the previous s2 }
             { = new s1                                                    }
             Begin
               stemp := s3;
               s3 := s1;
               s1 := s2;
               s2 := stemp;
               GetScanline(0,ViewWidth,y-1,s2^);
             End
           Else If (y - prevy = 1) then
             { previous line was one above the new one, so the previous s3 }
             { = new s1                                                    }
             Begin
               stemp := s2;
               s2 := s1;
               s1 := s3;
               s3 := stemp;
               GetScanline(0,ViewWidth,y+1,s3^);
             End
           Else
             begin
               GetScanline(0,ViewWidth,y-1,s2^);
               GetScanline(0,ViewWidth,y,s1^);
               GetScanline(0,ViewWidth,y+1,s3^);
             end;
         end;
       prevy := y;
       { check the current scan line }
       While (s1^[x]<>Border) And (x<=ViewWidth) Do Inc (x);
       d:=0;
       e:=0;
       dec(x);
       Beginx:=x;
       REPEAT
         { check the above line }
         If y<ViewHeight then
           Begin
              Cont:=(s3^[x]<>Border) and (not AlreadyDrawn(x,y+1));
              If (e=0) And Cont then
                Begin
                  PushPoint (x,y+1);
                  e:=1;
                End
              Else
                If (e=1) And Not Cont then e:=0;
           End;
        { check the line below }
        If (y>0) then
          Begin
            Cont:=(s2^[x]<>Border) and (not AlreadyDrawn(x,y-1));
            If (d=0) And Cont then
              Begin
                PushPoint (x,y-1);
                d:=1;
              End
            Else
              If (d=1) And Not Cont then d:=0;
          End;
        Dec (x);
       Until (x<0) Or (s1^[x]=Border);
       { swap the values }
       x1:=x+1;
       x2:=BeginX;
       if x1 > x2 then
         Begin
           x:=x1;
           x1:=x2;
           x2:=x;
         end;
       { Add to the list of drawn lines }
       AddLinePoints(x1,x2,y);
       PatternLine (x1,x2,y);
     End; { end while }

    FreeMem (s1,(ViewWidth+1)*2);
    FreeMem (s2,(ViewWidth+1)*2);
    FreeMem (s3,(ViewWidth+1)*2);
    CleanUpDrawnList;
    CurrentColor := BackUpColor;
  End;

{
$Log$
Revision 1.17  2000-02-12 13:39:19  jonas
  + new, faster fillpoly from Thomas Schatzl
  * some logging commands in vesa.inc disabled

Revision 1.16  2000/01/07 16:41:37  daniel
  * copyright 2000

Revision 1.15  2000/01/07 16:32:25  daniel
  * copyright 2000 added

Revision 1.14  2000/01/02 19:01:32  jonas
  * made floodfill a *LOT* faster (better DrawnPoints management)

Revision 1.13  1999/12/20 11:22:36  peter
  * integer -> smallint to overcome -S2 switch needed for ggi version

Revision 1.12  1999/12/11 23:41:38  jonas
  * changed definition of getscanlineproc to "getscanline(x1,x2,y:
    smallint; var data);" so it can be used by getimage too
  * changed getimage so it uses getscanline
  * changed floodfill, getscanline16 and definitions in Linux
    include files so they use this new format
  + getscanlineVESA256 for 256 color VESA modes (banked)

Revision 1.11  1999/09/27 23:34:40  peter
  * new graph unit is default for go32v2
  * removed warnings/notes

Revision 1.10  1999/09/24 22:52:38  jonas
  * optimized patternline a bit (always use hline when possible)
  * isgraphmode stuff cleanup
  * vesainfo.modelist now gets disposed in cleanmode instead of in
    closegraph (required moving of some declarations from vesa.inc to
    new vesah.inc)
  * queryadapter gets no longer called from initgraph (is called from
    initialization of graph unit)
  * bugfix for notput in 32k and 64k vesa modes
  * a div replaced by / in fillpoly

Revision 1.9  1999/09/24 14:23:08  jonas
  * floodfill uses scanline data from previous loop if line is adjacent

Revision 1.8  1999/09/18 22:21:09  jonas
  + hlinevesa256 and vlinevesa256
  + support for not/xor/or/andput in vesamodes with 32k/64k colors
  * lots of changes to avoid warnings under FPC

Revision 1.7  1999/09/17 13:58:31  jonas
* another fix for a case where internalellipsedefault went haywire
* sector() and pieslice() fully implemented!
* small change to prevent buffer overflow with floodfill

Revision 1.6  1999/09/12 17:28:59  jonas
  * several changes to internalellipse to make it faster
    and to make sure it updates the ArcCall correctly
    (not yet done for width = 3)
  * Arc mostly works now, only sometimes an endless loop, don't know
    why

Revision 1.5  1999/09/11 19:43:00  jonas
  * FloodFill: did not take into account current viewport settings
  * GetScanLine: only get line inside viewport, data outside of it
    is not used anyway
  * InternalEllipseDefault: fix for when xradius or yradius = 0 and
    increase xradius and yradius always by one (TP does this too)
  * fixed conlict in vesa.inc from last update
  * some conditionals to avoid range check and overflow errors in
    places where it doesn't matter

Revision 1.4  1999/07/12 14:52:52  jonas
  * fixed procvar syntax error and ceil and floor functions

Revision 1.3  1999/07/12 13:27:11  jonas
  + added Log and Id tags
  * added first FPC support, only VGA works to some extend for now
  * use -dasmgraph to use assembler routines, otherwise Pascal
    equivalents are used
  * use -dsupportVESA to support VESA (crashes under FPC for now)
  * only dispose vesainfo at closegrph if a vesa card was detected
  * changed int32 to longint (int32 is not declared under FPC)
  * changed the declaration of almost every procedure in graph.inc to
    "far;" becquse otherwise you can't assign them to procvars under TP
    real mode (but unexplainable "data segnment too large" errors prevent
    it from working under real mode anyway)

}