text: /* Indentation functions.
     Copyright (C) 1985 Richard M. Stallman.
  
  This file is part of GNU Emacs.
  
  GNU Emacs is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY.  No author or distributor
  accepts responsibility to anyone for the consequences of using it
  or for whether it serves any particular purpose or works at all,
  unless he says so in writing.  Refer to the GNU Emacs General Public
  License for full details.
  
  Everyone is granted permission to copy, modify and redistribute
  GNU Emacs, but only under the conditions described in the
  GNU Emacs General Public License.   A copy of this license is
  supposed to have been given to you along with GNU Emacs so you
  can know your rights and responsibilities.  It should be in a
  file named COPYING.  Among other things, the copyright notice
  and this notice must be preserved on all copies.  */
  
  
  #include "config.h"
  #include "lisp.h"
  #include "buffer.h"
  #include "indent.h"
  #include "window.h"
  #include "termchar.h"
  #include "termopts.h"
  
  #define CR '\015'
  
  int indent_tabs_mode;
  
  #define min(a, b) ((a) < (b) ? (a) : (b))
  #define max(a, b) ((a) > (b) ? (a) : (b))
  
  /* These three values memoize the current column to avoid recalculation */
  /* Some things in buflow.c set last_known_column_point to -1
    to mark the memoized value as invalid */
  
  /* Last value returned by current_column */
  int last_known_column;
  /* Value of point when current_column was called */
  int last_known_column_point;
  /* Value of bf_modified when current_column was called */
  int last_known_column_modified;
  
  extern int minibuf_prompt_width;
  
  DEFSIMPLE ("current-column", Fcurrent_column, Scurrent_column,
    "Return the horizontal position of point.  The left margin is column 0.\n\
  Ignores finite width of screen,",
    Lisp_Int, XSETINT, current_column ())
  
  current_column ()
  {
    register int col;
    register unsigned char *ptr, *stop, c;
    register int tab_seen;
    register int post_tab;
    register int tab_width = XINT (bf_cur->tab_width);
    int ctl_arrow = !NULL (bf_cur->ctl_arrow);
  
    if (point == last_known_column_point
        && bf_modified == last_known_column_modified)
      return last_known_column;
  
    ptr = &CharAt (point - 1) + 1;
    stop = point <= bf_s1 + 1 ? bf_p1 + 1 : bf_p2 + bf_s1 + 1;
    if (tab_width <= 0) tab_width = 1;
  
    col = 0, tab_seen = 0, post_tab = 0;
  
    while (1)
      {
        if (ptr == stop)
  	{
  	  if (ptr == bf_p1 + 1)
  	    break;
  	  stop = bf_p1 + 1;
  	  ptr = stop + bf_s1;
  	  if (!bf_s1) break;
  	}
  
        c = *--ptr;
        if (c >= 040 && c < 0177)
  	{
  	  col++;
  	}
        else if (c == '\n')
  	break;
        else if (c == '\t')
  	{
  	  if (tab_seen)
  	    col = ((col + tab_width) / tab_width) * tab_width;
  
  	  post_tab += col;
  	  col = 0;
  	  tab_seen = 1;
  	}
        else
  	col += (ctl_arrow && c < 0200) ? 2 : 4;
      }
  
    if (tab_seen)
      {
        col = ((col + tab_width) / tab_width) * tab_width;
        col += post_tab;
      }
  
    last_known_column = col;
    last_known_column_point = point;
    last_known_column_modified = bf_modified;
  
    return col;
  }
  
  ToCol (col)
       int col;
  {
    register int fromcol = current_column ();
    register int n;
    register int tab_width = XINT (bf_cur->tab_width);
  
    if (fromcol > col)
      return;
  
    if (tab_width <= 0) tab_width = 1;
  
    if (indent_tabs_mode)
      {
        n = col / tab_width - fromcol / tab_width;
        if (n)
  	{
  	  while (n-- > 0)
  	    InsCStr ("\t", 1);
  
  	  fromcol = (col / tab_width) * tab_width;
  	}
      }
  
    while (fromcol < col)
      {
        InsCStr ("        ", min (8, col - fromcol));
        fromcol += min (8, col - fromcol);
      }
  
    last_known_column = col;
    last_known_column_point = point;
    last_known_column_modified = bf_modified;
  }
  
  DEFUN ("indent-to", Findent_to, Sindent_to, 1, 2, "nIndent to column: ",
    "Indent from point with tabs and spaces until COLUMN is reached.\n\
  Always do at least MIN spaces even if that goes past COLUMN;\n\
  by default, MIN is zero.")
    (col, minimum)
       Lisp_Object col, minimum;
  {
    int mincol;
  
    CHECK_NUMBER (col, 0);
    if (NULL (minimum))
      XFASTINT (minimum) = 0;
    CHECK_NUMBER (minimum, 1);
  
    mincol = current_column () + XINT (minimum);
    if (mincol < XINT (col)) mincol = XINT (col);
  
    ToCol (mincol);
  
    XSETINT (col, mincol);
    return col;
  }
  
  DEFUN ("current-indentation", Fcurrent_indentation, Scurrent_indentation,
    0, 0, 0,
    "Return the indentation of the current line.\n\
  This is the horizontal position of the character\n\
  following any initial whitespace.")
    ()
  {
    Lisp_Object val;
  
    XFASTINT (val) = position_indentation (ScanBf ('\n', point, -1));
    return val;
  }
  
  position_indentation (pos)
       register int pos;
  {
    register int col = 0;
    register int c;
    register int end = NumCharacters + 1;
    register int tab_width = XINT (bf_cur->tab_width);
  
    if (tab_width <= 0) tab_width = 1;
  
    while (pos < end &&
  	 (c = CharAt (pos),
  	  c == '\t' ? (col += tab_width - col % tab_width)
  	    : (c == ' ' ? ++col : 0)))
      pos++;
  
    return col;
  }
  
  DEFUN ("move-to-column", Fmove_to_column, Smove_to_column, 1, 1, 0,
    "Move point to column COLUMN in the current line.\n\
  Does not change the text, only point.\n\
  Ignores finite width of screen.")
    (column)
       Lisp_Object column;
  {
    register int pos = point;
    register int col = current_column ();
    register int goal;
    register int end = NumCharacters;
    register int tab_width = XINT (bf_cur->tab_width);
    register int ctl_arrow = !NULL (bf_cur->ctl_arrow);
  
    Lisp_Object val;
  
    if (tab_width <= 0) tab_width = 1;
    CHECK_NUMBER (column, 0);
    goal = XINT (column);
    if (col > goal)
      {
        pos = ScanBf ('\n', pos, -1);
        col = 0;
      }
  
    while (col < goal && pos <= end)
      {
        char c = CharAt (pos);
        if (c == '\n')
  	break;
        pos++;
        col++;
        if (c == '\t')
  	{
  	  col += tab_width - 1;
  	  col = col / tab_width * tab_width;
  	}
        else if (ctl_arrow && (c < 040 || c == 0177))
          col++;
        else if (c < 040 || c >= 0177)
          col += 3;
      }
  
    SetPoint (pos);
  
    last_known_column = col;
    last_known_column_point = point;
    last_known_column_modified = bf_modified;
  
    XFASTINT (val) = col;
    return val;
  }
  
  struct position val_compute_motion;
  
  struct position *
  compute_motion (from, fromvpos, fromhpos, to, tovpos, tohpos, width, hscroll, tab_offset)
       int from, fromvpos, fromhpos, to, tovpos, tohpos;
       register int width;
       int hscroll, tab_offset;
  {
    /* Note that cpos is CURRENT_VPOS << SHORTBITS + CURRENT_HPOS,
       and the CURRENT_HPOS may be negative.  Use these macros
       to extract the hpos or the vpos from cpos or anything like it.  */
  #ifdef celerity
  /* On the Celerity, the usual definition fails to work.
     This definition (which ought to be equivalent) does work.  */
  #define HPOS(VAR) (((VAR) & 0x8000 ? 0xffff0000 : 0) | ((VAR) & 0xffff))
  #else
  #define HPOS(VAR) (short) (VAR)
  #endif
  
  #define VPOS(VAR) (((VAR) >> SHORTBITS) + (HPOS (VAR) < 0))
  
  #ifndef TAHOE_REGISTER_BUG
    register
  #endif /* TAHOE_REGISTER_BUG */
      int cpos = fromhpos + (fromvpos << SHORTBITS);
    register int target = tohpos + (tovpos << SHORTBITS);
    register int pos;
    register int c;
    register int tab_width = XFASTINT (bf_cur->tab_width);
    register int ctl_arrow = !NULL (bf_cur->ctl_arrow);
    int selective
      = XTYPE (bf_cur->selective_display) == Lisp_Int
        ? XINT (bf_cur->selective_display)
  	: !NULL (bf_cur->selective_display) ? -1 : 0;
    int prevpos;
    struct position val;
  
    if (tab_width <= 0) tab_width = 1;
    for (pos = from; pos < to && cpos < target; pos++)
      {
        prevpos = cpos;
        c = CharAt (pos);
        if (c >= 040 && c < 0177)
  	cpos++;
        else if (c == '\t')
  	{
  	  cpos += tab_width
  	    - HPOS (cpos + tab_offset + hscroll - (hscroll > 0)
  		    /* Add tab_width here to make sure positive.
  		       cpos can be negative after continuation
  		       but can't be less than -tab_width.  */
  		    + tab_width)
  	      % tab_width;
  	}
        else if (c == '\n')
  	{
  	  if (selective > 0 && position_indentation (pos + 1) >= selective)
  	    {
  	      /* Skip any number of invisible lines all at once */
  	      do
  		{
  		  while (++pos < to && CharAt(pos) != '\n');
  		}
  	      while (selective > 0 && position_indentation (pos + 1) >= selective);
  	      pos--;
  	      /* Allow for the " ..." that is displayed for them. */
  	      cpos += 4;
  	      if (HPOS (cpos) >= width)
  		cpos -= HPOS (cpos) - width;
  	    }
  	  else
  	    cpos += (1 << SHORTBITS) - HPOS (cpos);
  	  cpos -= hscroll;
  	  if (hscroll > 0) cpos++; /* Count the ! on column 0 */
  	  tab_offset = 0;
  	}
        else if (c == CR && selective < 0)
  	{
  	  /* In selective display mode,
  	     everything from a ^M to the end of the line is invisible */
  	  while (pos < to && CharAt(pos) != '\n') pos++;
  	  pos--;
  	}
        else
  	cpos += (ctl_arrow && c < 0200) ? 2 : 4;
  
        if (HPOS (cpos) >= width
  	  && (HPOS (cpos) > width
  	      || (pos < NumCharacters
  		  && CharAt (pos + 1) != '\n')))
  	{
  	  if (cpos >= target)
  	    break;
  	  if (hscroll
  	      || (truncate_partial_width_windows
  		  && width + 1 < screen_width)
  	      || !NULL (bf_cur->truncate_lines))
  	    {
  	      while (pos < to && CharAt(pos) != '\n') pos++;
  	      pos--;
  	    }
  	  else
  	    {
  	      cpos += (1 << SHORTBITS) - width;
  	      tab_offset += width;
  	    }
  
  	}
      }
  
    val_compute_motion.bufpos = pos;
    val_compute_motion.hpos = HPOS (cpos);
    val_compute_motion.vpos = VPOS (cpos);
    val_compute_motion.prevhpos = HPOS (prevpos);
  
    /* Nonzero if have just continued a line */
    val_compute_motion.contin
      = pos != from
        && (val_compute_motion.vpos != VPOS (prevpos))
        && c != '\n';
  
    return &val_compute_motion;
  }
  
  pos_tab_offset (w, pos)
       struct window *w;
       register int pos;
  {
    int opoint = point;
    int col;
  
    if (pos == FirstCharacter || CharAt (pos - 1) == '\n')
      return 0;
    SetPoint (pos);
    col = current_column ();
    SetPoint (opoint);
    return col - (col % (XFASTINT (w->width) - 1));
  }
  
  /* start_hpos is the hpos of the first character of the buffer:
     zero except for the minibuffer window,
     where it is the width of the prompt.  */
  
  struct position val_vmotion;
  
  struct position *
  vmotion (from, vtarget, width, hscroll, window)
       register int from, vtarget, width;
       int hscroll;
       Lisp_Object window;
  {
    struct position pos;
    /* vpos is cumulative vertical position, changed as from is changed */
    register int vpos = 0;
    register int prevline;
    register int first;
    int lmargin = hscroll > 0 ? 1 - hscroll : 0;
    int selective
      = XTYPE (bf_cur->selective_display) == Lisp_Int
        ? XINT (bf_cur->selective_display)
  	: !NULL (bf_cur->selective_display) ? -1 : 0;
    int start_hpos = (EQ (window, minibuf_window) ? minibuf_prompt_width : 0);
  
   retry:
    if (vtarget > vpos)
      {
        /* Moving downward is simple, but must calculate from beg of line 
  	 to determine hpos of starting point */
        if (from > FirstCharacter && CharAt (from - 1) != '\n')
  	{
  	  prevline = ScanBf ('\n', from, -1);
  	  while (selective > 0
  		 && prevline > FirstCharacter
  		 && position_indentation (prevline) >= selective)
  	    prevline = ScanBf ('\n', prevline - 1, -1);
  	  pos = *compute_motion (prevline, 0,
  				 lmargin + (prevline == 1 ? start_hpos : 0),
  				 from, 10000, 10000,
  				 width, hscroll, 0);
  	}
        else
  	{
  	  pos.hpos = lmargin + (from == 1 ? start_hpos : 0);
  	  pos.vpos = 0;
  	}
        return compute_motion (from, vpos, pos.hpos,
  			     1 + NumCharacters, vtarget, - (1 << (SHORTBITS - 1)),
  			     width, hscroll, pos.vpos * width);
      }
  
    /* To move upward, go a line at a time until
       we have gone at least far enough */
  
    first = 1;
  
    while ((vpos > vtarget || first) && from > FirstCharacter)
      {
        prevline = from;
        while (1)
  	{
  	  prevline = ScanBf ('\n', prevline - 1, -1);
  	  if (prevline == FirstCharacter
  	      || selective <= 0
  	      || position_indentation (prevline) < selective)
  	    break;
  	}
        pos = *compute_motion (prevline, 0,
  			     lmargin + (prevline == 1 ? start_hpos : 0),
  			     from, 10000, 10000,
  			     width, hscroll, 0);
        vpos -= pos.vpos;
        first = 0;
        from = prevline;
      }
  
    /* If we made exactly the desired vertical distance,
       or if we hit beginning of buffer,
       return point found */
    if (vpos >= vtarget)
      {
        val_vmotion.bufpos = from;
        val_vmotion.vpos = vpos;
        val_vmotion.hpos = lmargin;
        val_vmotion.contin = 0;
        val_vmotion.prevhpos = 0;
        return &val_vmotion;
      }
    
    /* Otherwise find the correct spot by moving down */
    goto retry;
  }
  
  DEFUN ("vertical-motion", Fvertical_motion, Svertical_motion, 1, 1, 0,
    "Move to start of screen line LINES lines down.\n\
  If LINES is negative, this is moving up.\n\
  Sets point to position found; this may be start of line\n\
   or just the start of a continuation line.\n\
  Returns number of lines moved; may be closer to zero than LINES\n\
   if end of buffer was reached.")
    (lines)
       Lisp_Object lines;
  {
    struct position pos;
    register struct window *w = XWINDOW (selected_window);
  
    CHECK_NUMBER (lines, 0);
  
    pos = *vmotion (point, XINT (lines),
  		  XFASTINT (w->width) - 1
  		  - (XFASTINT (w->width) + XFASTINT (w->left)
  		     != XFASTINT (XWINDOW (minibuf_window)->width)),
  		  /* Not XFASTINT since perhaps could be negative */
  		  XINT (w->hscroll), selected_window);
  
    SetPoint (pos.bufpos);
    return make_number (pos.vpos);
  }
  
  syms_of_indent ()
  {
    DefBoolVar ("indent-tabs-mode", &indent_tabs_mode,
      "*Indentation can insert tabs if this is non-nil.");
    indent_tabs_mode = 1;
  
    defsubr (&Scurrent_indentation);
    defsubr (&Sindent_to);
    defsubr (&Scurrent_column);
    defsubr (&Smove_to_column);
    defsubr (&Svertical_motion);
  }
  