text: /* Public Domain Curses */
  
  #include <curspriv.h>
  
  RCSID("$Id: overlay.c,v 1.36 2008/07/14 12:35:23 wmcbrine Exp $")
  
  /*man-start**************************************************************
  
    Name:                                                         overlay
  
    Synopsis:
          int overlay(const WINDOW *src_w, WINDOW *dst_w)
          int overwrite(const WINDOW *src_w, WINDOW *dst_w)
          int copywin(const WINDOW *src_w, WINDOW *dst_w, int src_tr,
                      int src_tc, int dst_tr, int dst_tc, int dst_br,
                      int dst_bc, bool overlay)
  
    Description:
          overlay() and overwrite() copy all the text from src_w into
          dst_w. The windows need not be the same size. Those characters
          in the source window that intersect with the destination window
          are copied, so that the characters appear in the same physical
          position on the screen. The difference between the two functions
          is that overlay() is non-destructive (blanks are not copied)
          while overwrite() is destructive (blanks are copied).
  
          copywin() is similar, but doesn't require that the two windows
          overlap. The arguments src_tc and src_tr specify the top left
          corner of the region to be copied. dst_tc, dst_tr, dst_br, and
          dst_bc specify the region within the destination window to copy
          to. The argument "overlay", if TRUE, indicates that the copy is
          done non-destructively (as in overlay()); blanks in the source
          window are not copied to the destination window. When overlay is
          FALSE, blanks are copied.
  
    Return Value:
          All functions return OK on success and ERR on error.
  
    Portability                                X/Open    BSD    SYS V
          overlay                                 Y       Y       Y
          overwrite                               Y       Y       Y
          copywin                                 Y       -      3.0
  
  **man-end****************************************************************/
  
  /* Thanks to Andreas Otte <venn@@uni-paderborn.de> for the
     corrected overlay()/overwrite() behavior. */
  
  static int _copy_win(const WINDOW *src_w, WINDOW *dst_w, int src_tr,
                       int src_tc, int src_br, int src_bc, int dst_tr,
                       int dst_tc, bool overlay)
  {
      int col, line, y1, fc, *minchng, *maxchng;
      chtype *w1ptr, *w2ptr;
  
      int lc = 0;
      int xdiff = src_bc - src_tc;
      int ydiff = src_br - src_tr;
  
      if (!src_w || !dst_w)
          return ERR;
  
      minchng = dst_w->_firstch;
      maxchng = dst_w->_lastch;
  
      for (y1 = 0; y1 < dst_tr; y1++)
      {
          minchng++;
          maxchng++;
      }
  
      for (line = 0; line < ydiff; line++)
      {
          w1ptr = src_w->_y[line + src_tr] + src_tc;
          w2ptr = dst_w->_y[line + dst_tr] + dst_tc;
  
          fc = _NO_CHANGE;
  
          for (col = 0; col < xdiff; col++)
          {
              if ((*w1ptr) != (*w2ptr) &&
                  !((*w1ptr & A_CHARTEXT) == ' ' && overlay))
              {
                  *w2ptr = *w1ptr;
  
                  if (fc == _NO_CHANGE)
                      fc = col + dst_tc;
  
                  lc = col + dst_tc;
              }
  
              w1ptr++;
              w2ptr++;
          }
  
          if (*minchng == _NO_CHANGE)
          {
              *minchng = fc;
              *maxchng = lc;
          }
          else if (fc != _NO_CHANGE)
          {
              if (fc < *minchng)
                  *minchng = fc;
              if (lc > *maxchng)
                  *maxchng = lc;
          }
  
          minchng++;
          maxchng++;
      }
  
      return OK;
  }
  
  int overlay(const WINDOW *src_w, WINDOW *dst_w)
  {
      int first_line, first_col, last_line, last_col;
      int src_start_x, src_start_y, dst_start_x, dst_start_y;
      int xdiff, ydiff;
  
      PDC_LOG(("overlay() - called\n"));
  
      if (!src_w || !dst_w)
          return ERR;
  
      first_col = max(dst_w->_begx, src_w->_begx);
      first_line = max(dst_w->_begy, src_w->_begy);
  
      last_col = min(src_w->_begx + src_w->_maxx, dst_w->_begx + dst_w->_maxx);
      last_line = min(src_w->_begy + src_w->_maxy, dst_w->_begy + dst_w->_maxy);
  
      /* determine the overlapping region of the two windows in real
         coordinates */
  
      /* if no overlapping region, do nothing */
  
      if ((last_col < first_col) || (last_line < first_line))
          return OK;
  
      /* size of overlapping region */
  
      xdiff = last_col - first_col;
      ydiff = last_line - first_line;
  
      if (src_w->_begx <= dst_w->_begx)
      {
          src_start_x = dst_w->_begx - src_w->_begx;
          dst_start_x = 0;
      }
      else
      {
          dst_start_x = src_w->_begx - dst_w->_begx;
          src_start_x = 0;
      }
  
      if (src_w->_begy <= dst_w->_begy)
      {
          src_start_y = dst_w->_begy - src_w->_begy;
          dst_start_y = 0;
      }
      else
      {
          dst_start_y = src_w->_begy - dst_w->_begy;
          src_start_y = 0;
      }
  
      return _copy_win(src_w, dst_w, src_start_y, src_start_x,
                       src_start_y + ydiff, src_start_x + xdiff,
                       dst_start_y, dst_start_x, TRUE);
  }
  
  int overwrite(const WINDOW *src_w, WINDOW *dst_w)
  {
      int first_line, first_col, last_line, last_col;
      int src_start_x, src_start_y, dst_start_x, dst_start_y;
      int xdiff, ydiff;
  
      PDC_LOG(("overwrite() - called\n"));
  
      if (!src_w || !dst_w)
          return ERR;
  
      first_col = max(dst_w->_begx, src_w->_begx);
      first_line = max(dst_w->_begy, src_w->_begy);
  
      last_col = min(src_w->_begx + src_w->_maxx, dst_w->_begx + dst_w->_maxx);
      last_line = min(src_w->_begy + src_w->_maxy, dst_w->_begy + dst_w->_maxy);
  
      /* determine the overlapping region of the two windows in real
         coordinates */
  
      /* if no overlapping region, do nothing */
  
      if ((last_col < first_col) || (last_line < first_line))
          return OK;
  
      /* size of overlapping region */
  
      xdiff = last_col - first_col;
      ydiff = last_line - first_line;
  
      if (src_w->_begx <= dst_w->_begx)
      {
          src_start_x = dst_w->_begx - src_w->_begx;
          dst_start_x = 0;
      }
      else
      {
          dst_start_x = src_w->_begx - dst_w->_begx;
          src_start_x = 0;
      }
  
      if (src_w->_begy <= dst_w->_begy)
      {
          src_start_y = dst_w->_begy - src_w->_begy;
          dst_start_y = 0;
      }
      else
      {
          dst_start_y = src_w->_begy - dst_w->_begy;
          src_start_y = 0;
      }
  
      return _copy_win(src_w, dst_w, src_start_y, src_start_x,
                       src_start_y + ydiff, src_start_x + xdiff,
                       dst_start_y, dst_start_x, FALSE);
  }
  
  int copywin(const WINDOW *src_w, WINDOW *dst_w, int src_tr, int src_tc,
              int dst_tr, int dst_tc, int dst_br, int dst_bc, int overlay)
  {
      int src_end_x, src_end_y;
      int src_rows, src_cols, dst_rows, dst_cols;
      int min_rows, min_cols;
  
      PDC_LOG(("copywin() - called\n"));
  
      if (!src_w || !dst_w || dst_w == curscr || dst_br > dst_w->_maxy
          || dst_bc > dst_w->_maxx || dst_tr < 0 || dst_tc < 0)
          return ERR;
  
      src_rows = src_w->_maxy - src_tr;
      src_cols = src_w->_maxx - src_tc;
      dst_rows = dst_br - dst_tr + 1;
      dst_cols = dst_bc - dst_tc + 1;
  
      min_rows = min(src_rows, dst_rows);
      min_cols = min(src_cols, dst_cols);
  
      src_end_y = src_tr + min_rows;
      src_end_x = src_tc + min_cols;
  
      return _copy_win(src_w, dst_w, src_tr, src_tc, src_end_y, src_end_x,
                       dst_tr, dst_tc, (bool)overlay);   /* BJG */
  }
  