freepascal.compiler/rtl/inc/graph/fills.inc

{
    This file is part of the Free Pascal run time library.
    Copyright (c) 1993,99 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.

 **********************************************************************}
{$R-}   { No range checking here, because we do some special typecasts }

type
{$IFDEF FPC}
	graph_int = int32;  	{ platform specific integer used for indexes;
							  should be 16 bits on TP/BP and 32 bits on every-
							  thing else for speed reasons }
	graph_float = double;	{ the platform's preferred floating point size }
{$ELSE}
	graph_int = integer;	{ platform specific integer used for indexes;
							  should be 16 bits on TP/BP and 32 bits on every-
							  thing else for speed reasons }
	graph_float = real;  	{ the platform's preferred floating point size }
{$ENDIF}

	pedge = ^edge;
	edge = packed record	{ an edge structure }
		x,					{ current x-coordinate on the edge }
		dx : graph_float;	{ deltax of the edge }
		i : graph_int;		{ index to which points this edge belongs to
							  always [i] and [i+1] }
	end;

	{ used for typecasting because TP/BP is more strict here than FPC }
	pedgearray = ^edgearray;
    { 0..0 }
	edgearray = array[0..0] of edge;

	pint = ^graph_int;

	pintarray = ^intarray;
    { 0..0 }
	intarray = array[0..0] of graph_int;

	ppointtype = ^pointtype;
	ppointarray = ^pointarray;
	pointarray = array[0..0] of pointtype;

{ definition of the called compare routine for the sort process. Returns -1 if
 the two parameters should be swapped }
type
	compareproc = function (a, b : pointer) : graph_int;

{ simple bubblesort, since it is expected that the edges themselves are not
  too mixed, it is fastest (?). Rather than sorting the active edge table
  this way, it is recommened to implement this using a linked list (not
  nearly as much memory is transfered then) }
   procedure bsort(p : pointer; number : integer; sizeelem :
      integer; c : compareproc);
   var    i : graph_int;
	   swap : boolean;
       temp : pointer;

	   curp, nextp : pointer;
   begin
     getmem(temp, sizeelem);
	 repeat
	    curp := p;
		nextp := pointer(longint(p) + sizeelem);
		swap := false;
		for i := 0 to (number-2) do begin
			if (c(curp, nextp)=1) then begin
				{ swap elements, you can't do it slower ;( }
				move(curp^, temp^, sizeelem);
				move(nextp^, curp^, sizeelem);
				move(temp^, nextp^, sizeelem);
				swap := true;
			end;
			inc(longint(curp), sizeelem);
			inc(longint(nextp), sizeelem);
		end;
	 until swap = false;
	 freemem(temp, sizeelem);
   end;

  { guess what this does }
  function ceil(x : graph_float) : graph_int;
    var t : graph_int;
  begin
	t:=Trunc(x);
	If frac(x)>0 then inc(t);
	ceil := t;
  end;

  { guess what this does too }
  function floor(x : graph_float) : graph_int;
   var t : graph_int;
  begin
	t:=Trunc(x);
	If frac(x)<0 then dec(t);
	floor := t;
  end;

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

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

  { needed for the compare functions; should NOT be used for anything else }
var
	ptable : ppointarray; { pointer to points list }

function compare_ind(u, v : pointer) : graph_int; far;
begin
	if (ptable^[pint(u)^].y <= ptable^[pint(v)^].y) then compare_ind := -1
	else compare_ind := 1;
end;

function compare_active(u, v : pointer) : graph_int; far;
begin
	if (pedge(u)^.x <= pedge(v)^.x) then compare_active := -1
	else compare_active := 1;
end;

procedure fillpoly(numpoints : word; var PolyPoints);
{ variables needed within the helper procedures too }
var
	activetable : pedgearray; { active edge table, e.g. edges crossing current scanline }
	activepoints : graph_int; { number of points in active edge table }

{ remove edge i from active edge table }
procedure cdelete(index : graph_int);
var
	j : graph_int;
begin
	j := 0;
	while (j < activepoints) and (pedgearray(activetable)^[j].i <> index) do inc(j);
	if (j >= activepoints) then exit;
	dec(activepoints);
	move(pedgearray(activetable)^[j+1], pedgearray(activetable)^[j],
		(activepoints-j) * sizeof(edge));
end;

{ insert edge index into active edge table (at the last position) }
procedure cinsert(index, y : graph_int);
var
	j : graph_int;
	deltax : graph_float;
	p, q : ppointtype;
begin
	if (index < (numpoints-1)) then j := index + 1 else j := 0;

	if (ptable^[index].y < ptable^[j].y) then begin
		p := @ptable^[index];
		q := @ptable^[j];
	end else begin
		p := @ptable^[j];
		q := @ptable^[index];
	end;
	deltax := (q^.x-p^.x)/(q^.y-p^.y);
	with activetable^[activepoints] do begin
		dx := deltax;
		x := dx * (y { + 0.5} - p^.y) + p^.x;
		i := index;
	end;
	inc(activepoints);
end;

{ variables for the main procedure }
var
	k, i, j : graph_int;
	starty, endy, y, xl, xr : graph_int;
    oldcolor : word;
var
	indextable : pintarray; { list of vertex indices, sorted by y }

begin
    oldcolor := CurrentColor;
    CurrentColor := FillSettings.Color;
	ptable := @PolyPoints;
	if (numpoints<=0) then exit;

	getmem(indextable, sizeof(graph_int) * numpoints);
	getmem(activetable, sizeof(edge) * numpoints);
    if (not assigned(activetable)) or (not assigned(indextable)) then
      begin
        _GraphResult := grNoScanMem;
        exit;
      end;
{$R-}
	{ create y-sorted array of indices indextable[k] into vertex list }
	for k := 0 to (numpoints-1) do
		indextable^[k] := k;
	{ sort the indextable by points[indextable[k]].y }
	bsort(indextable, numpoints, sizeof(graph_int), compare_ind);
	{ start with empty active edge table }
	activepoints := 0;
	{ indextable[k] is the next vertex to process }
	k := 0;
	{ ymin of polygon }
	starty := ceil(pointarray(polypoints)[indextable^[0]].y-0.5);
	{ ymax of polygon }
	endy := floor(pointarray(polypoints)[indextable^[numpoints-1]].y-0.5);

	{ step through scanlines }
	for y := starty to endy do begin
		{ check vertices between previous scanline and current one, if any }
		while (k < numpoints) and
           (pointarray(polypoints)[indextable^[k]].y<=(y+0.5)) do begin
			i := indextable^[k];
			{ insert or delete edges before and after points[i] ((i-1) to i and
			  i to (i+1)) from active edge table if they cross scanline y }
			{ point previous to i }
			if (i > 0) then j := i-1 else j := numpoints-1;
			{ old edge, remove from list }
			if (pointarray(polypoints)[j].y <= (y-0.5)) then cdelete(j)
			{ new edge, add to active edges }
			else if (pointarray(polypoints)[j].y > (y + 0.5)) then cinsert(j, y);

			{ point next after i }
			if (i < (numpoints-1)) then j := i+1 else j := 0;
			{ old edge, remove from active edge table }
			if (pointarray(polypoints)[j].y <= (y - 0.5)) then cdelete(i)
			{ new edge, add to active edges }
			else if (pointarray(polypoints)[j].y > (y + 0.5)) then cinsert(i, y);
			inc(k);
		end;
		{ sort active edges list by active[j].x }
		bsort(activetable, activepoints, sizeof(edge), compare_active);
		j := 0;
		{ draw horizontal segments for scanline y }
		while (j < activepoints) do begin
			{xl := ceil(activetable^[j].x-0.5);}
			xl := trunc(activetable^[j].x-0.5);
			if frac(activetable^[j].x-0.5)>0 then inc(xl);

			xr := trunc(activetable^[j+1].x-0.5);
			if frac(activetable^[j+1].x-0.5)<0 then dec(xr);

			if (xl <= xr) then
                PatternLine(xl,xr,y);
{				line(xl, y, xr+1, y);}
			{ increment both edges' coordinates }
			with activetable^[j] do begin
				x := x + dx;
			end;
			with activetable^[j+1] do begin
				x := x + dx;
			end;
			inc(j, 2);
		end;
	end;
{$R+}
	freemem(activetable, sizeof(edge) * numpoints);
	freemem(indextable, sizeof(graph_int) * numpoints);
    { restore the old color }
    CurrentColor := OldColor;
    { now let's draw the outline of this polygon }
    DrawPoly(NumPoints, PolyPoints);
end;



type
  TFloodLine = record
    x1 : Integer;
    x2 : Integer;
    y  : Integer;
  end;

  TDrawnList  = Array[0..StdBuffersize] of TFloodLine;

var
   DrawnIndex : Word;
   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 : Integer);
  {********************************************************}
  { 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.                                       }
  {********************************************************}
   var
    i: integer;
  Begin
    If Buffer.WordIndex<(StdBufferSize DIV 2) then
     Begin
       Buffer.Words[Buffer.WordIndex]:=x;
       Buffer.Words[Buffer.WordIndex+1]:=y;
       Inc (Buffer.WordIndex,2);
     End
  End;

  Procedure PopPoint (Var x, y : Integer);
  {********************************************************}
  { 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: integer);
   begin
     DrawnList[DrawnIndex].x1 := x1;
     DrawnList[DrawnIndex].x2 := x2;
     DrawnList[DrawnIndex].y := y;
     Inc(DrawnIndex);
   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: integer): boolean;
   var
    LocalIndex : integer;
   begin
    AlreadyDrawn := FALSE;
    LocalIndex := 0;
    while LocalIndex < DrawnIndex do
     Begin
       { if vertical val is equal to our y point ... }
       if DrawnList[LocalIndex].y = y then
         Begin
           { then check if x >< ... }
           if (x >= DrawnList[LocalIndex].x1) and
               (x <= DrawnList[LocalIndex].x2) then
                 Begin
                   AlreadyDrawn := TRUE;
                   exit;
                 end;
         end;
       Inc(LocalIndex);
     end;
   end;


  Procedure FloodFill (x, y : Integer; 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
   Beginx : Integer;
   d, e, a : Byte;
   Cont : Boolean;
   BackupColor : Word;
   x1, x2: integer;
   Index : Integer;
  Begin
    { Save current drawing color }
    BackupColor := CurrentColor;
    CurrentColor := FillSettings.Color;
    { MaxX is based on zero index }
    GetMem (s1,(MaxX+1)*2);  { A pixel color represents a word }
    GetMem (s2,(MaxX+1)*2);  { A pixel color represents a word }
    GetMem (s3,(MaxX+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>MaxX) Or (y>MaxY) then Exit;
    { Some internal variables }
    Index := 0;
    { Index of segments to draw }
    DrawnIndex := 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 }
       GetScanline (y-1,s2^);
       GetScanline (y,s1^);
       GetScanline (y+1,s3^);

       { check the current scan line }
       While (s1^[x]<>Border) And (x<=MaxX) Do Inc (x);
       d:=0;
       e:=0;
       Dec (x);
       Beginx:=x;
       REPEAT
         { check the above line }
         If y<MaxY 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,(MaxX+1)*2);
    FreeMem (s2,(MaxX+1)*2);
    FreeMem (s3,(MaxX+1)*2);
    CurrentColor := BackUpColor;
  End;