/*!
  \file Draw_Ellipse.c
  \author Mario Palomo <mpalomo@ihman.com>
  \author Jose M. de la Huerga Fernández
  \author Pepe González Mora
  \date 05-2002

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Library General Public
  License as published by the Free Software Foundation; either
  version 2 of the License, or (at your option) any later version.

  This library 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
  Library General Public License for more details.

  You should have received a copy of the GNU Library General Public
  License along with this library; if not, write to the Free Foundation,
  Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/

#define SDL_DRAW_PUTPIXEL_BPP(A, B, C)  \
*(A(B(Uint8*)super->pixels + (y0+y)*super->pitch +               \
                                          (x0+x)*SDL_DRAW_BPP)) = C; \
*(A(B(Uint8*)super->pixels + (y0-y)*super->pitch +               \
                                          (x0+x)*SDL_DRAW_BPP)) = C; \
*(A(B(Uint8*)super->pixels + (y0+y)*super->pitch +               \
                                          (x0-x)*SDL_DRAW_BPP)) = C; \
*(A(B(Uint8*)super->pixels + (y0-y)*super->pitch +               \
                                          (x0-x)*SDL_DRAW_BPP)) = C;


#if SDL_DRAW_BPP == 1
#define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP(0+,0+,color)

#elif SDL_DRAW_BPP == 2
#define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP((Uint16*),0+,color)

#elif SDL_DRAW_BPP == 3
#define SDL_DRAW_PUTPIXEL \
  SDL_DRAW_PUTPIXEL_BPP(0+,1+,colorbyte1)   \
  if (SDL_BYTEORDER == SDL_BIG_ENDIAN) {   \
    SDL_DRAW_PUTPIXEL_BPP(0+,0+,colorbyte2)   \
    SDL_DRAW_PUTPIXEL_BPP(0+,2+,colorbyte0) \
  }else{                                   \
    SDL_DRAW_PUTPIXEL_BPP(0+,0+,colorbyte0)   \
    SDL_DRAW_PUTPIXEL_BPP(0+,2+,colorbyte2) \
  }

#elif SDL_DRAW_BPP == 4
#define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP((Uint32*),0+,color)

#endif /*SDL_DRAW_BPP*/


void SDL_DRAWFUNCTION(SDL_Surface *super,
                      Sint16 x0, Sint16 y0,
                      Uint16 Xradius, Uint16 Yradius,
                      Uint32 color)
{
  Sint32 x, y;
  Sint32 Xchange, Ychange;
  Sint32 EllipseError;
  Sint32 TwoASquare, TwoBSquare;
  Sint32 StoppingX, StoppingY;

#if SDL_DRAW_BPP == 3
  Uint8 colorbyte0 = (Uint8) (color & 0xff);
  Uint8 colorbyte1 = (Uint8) ((color >> 8)  & 0xff);
  Uint8 colorbyte2 = (Uint8) ((color >> 16) & 0xff);
#endif

  TwoASquare = 2*Xradius*Xradius;
  TwoBSquare = 2*Yradius*Yradius;

  /*1st set of points*/
  x = Xradius-1;  /*radius zero == draw nothing*/
  y = 0;

  Xchange = Yradius*Yradius*(1-2*Xradius);
  Ychange = Xradius*Xradius;

  EllipseError = 0;

  StoppingX = TwoBSquare*Xradius;
  StoppingY = 0;

  /* Lock surface */
  if (SDL_MUSTLOCK(super)) {
      if (SDL_LockSurface(super) < 0)  { return; }
  }
  
  /*Plot four ellipse points by iteration*/
  while (StoppingX > StoppingY) {

    SDL_DRAW_PUTPIXEL

    ++y;
    StoppingY    += TwoASquare;
    EllipseError += Ychange;
    Ychange      += TwoASquare;
    if (( 2*EllipseError + Xchange) > 0) {
      --x;
      StoppingX    -= TwoBSquare;
      EllipseError += Xchange;
      Xchange      += TwoBSquare;
    }
  }/*while*/

  /*2nd set of points*/
  x = 0;
  y = Yradius-1;  /*radius zero == draw nothing*/
  Xchange = Yradius*Yradius;
  Ychange = Xradius*Xradius*(1-2*Yradius);
  EllipseError = 0;
  StoppingX = 0;
  StoppingY = TwoASquare*Yradius;

  /*Plot four ellipse points by iteration*/
  while (StoppingX < StoppingY) {

    SDL_DRAW_PUTPIXEL

    ++x;
    StoppingX    += TwoBSquare;
    EllipseError += Xchange;
    Xchange      += TwoBSquare;
    if ((2*EllipseError + Ychange) > 0) {
      --y;
      StoppingY    -= TwoASquare;
      EllipseError += Ychange;
      Ychange      += TwoASquare;
    }
  }

  /* Unlock surface */
  if (SDL_MUSTLOCK(super))  { SDL_UnlockSurface(super); }
  
}/*Draw_Ellipse*/


#undef SDL_DRAW_PUTPIXEL
#undef SDL_DRAW_PUTPIXEL_BPP

