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lib_doupdate.c

/****************************************************************************
 * Copyright (c) 1998 Free Software Foundation, Inc.                        *
 *                                                                          *
 * Permission is hereby granted, free of charge, to any person obtaining a  *
 * copy of this software and associated documentation files (the            *
 * "Software"), to deal in the Software without restriction, including      *
 * without limitation the rights to use, copy, modify, merge, publish,      *
 * distribute, distribute with modifications, sublicense, and/or sell       *
 * copies of the Software, and to permit persons to whom the Software is    *
 * furnished to do so, subject to the following conditions:                 *
 *                                                                          *
 * The above copyright notice and this permission notice shall be included  *
 * in all copies or substantial portions of the Software.                   *
 *                                                                          *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
 * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
 * THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
 *                                                                          *
 * Except as contained in this notice, the name(s) of the above copyright   *
 * holders shall not be used in advertising or otherwise to promote the     *
 * sale, use or other dealings in this Software without prior written       *
 * authorization.                                                           *
 ****************************************************************************/

/****************************************************************************
 *  Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
 *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
 ****************************************************************************/


/*-----------------------------------------------------------------
 *
 *    lib_doupdate.c
 *
 *    The routine doupdate() and its dependents.  Also _nc_outstr(),
 *    so all physical output is concentrated here (except _nc_outch()
 *    in lib_tputs.c).
 *
 *-----------------------------------------------------------------*/

#include <curses.priv.h>

#if defined(TRACE) && HAVE_SYS_TIMES_H && HAVE_TIMES
#define USE_TRACE_TIMES 1
#else
#define USE_TRACE_TIMES 0
#endif

#if HAVE_SYS_TIME_H && HAVE_SYS_TIME_SELECT
#include <sys/time.h>
#endif

#if USE_TRACE_TIMES
#include <sys/times.h>
#endif

#if USE_FUNC_POLL
#include <stropts.h>
#include <poll.h>
#elif HAVE_SELECT
#if HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#endif

#ifdef __BEOS__
/* BeOS select() only works on sockets.  Use the tty hack instead */
#include <socket.h>
#define select check_select
#endif

#include <term.h>

MODULE_ID("$Id: lib_doupdate.c,v 1.98 1998/02/11 12:14:00 tom Exp $")

/*
 * This define controls the line-breakout optimization.  Every once in a
 * while during screen refresh, we want to check for input and abort the
 * update if there's some waiting.  CHECK_INTERVAL controls the number of
 * changed lines to be emitted between input checks.
 *
 * Note: Input-check-and-abort is no longer done if the screen is being
 * updated from scratch.  This is a feature, not a bug.
 */
#define CHECK_INTERVAL  5

/*
 * Enable checking to see if doupdate and friends are tracking the true
 * cursor position correctly.  NOTE: this is a debugging hack which will
 * work ONLY on ANSI-compatible terminals!
 */
/* #define POSITION_DEBUG */

static inline chtype ClrBlank ( WINDOW *win );
static int ClrBottom(int total);
static int InsStr( chtype *line, int count );
static void ClearScreen( chtype blank );
static void ClrUpdate( WINDOW *win );
static void DelChar( int count );
static void TransformLine( int const lineno );

#ifdef POSITION_DEBUG
/****************************************************************************
 *
 * Debugging code.  Only works on ANSI-standard terminals.
 *
 ****************************************************************************/

void position_check(int expected_y, int expected_x, char *legend)
/* check to see if the real cursor position matches the virtual */
{
    static char  buf[9];
    int y, x;

    if (_nc_tracing)
      return;

    memset(buf, '\0', sizeof(buf));
    (void) write(1, "\033[6n", 4);  /* only works on ANSI-compatibles */
    (void) read(0, (void *)buf, 8);
    _tracef("probe returned %s", _nc_visbuf(buf));

    /* try to interpret as a position report */
    if (sscanf(buf, "\033[%d;%dR", &y, &x) != 2)
      _tracef("position probe failed in %s", legend);
    else if (y - 1 != expected_y || x - 1 != expected_x)
      _tracef("position seen (%d, %d) doesn't match expected one (%d, %d) in %s",
            y-1, x-1, expected_y, expected_x, legend);
    else
      _tracef("position matches OK in %s", legend);
}
#endif /* POSITION_DEBUG */

/****************************************************************************
 *
 * Optimized update code
 *
 ****************************************************************************/

static inline void GoTo(int const row, int const col)
{
      chtype      oldattr = SP->_current_attr;

      TR(TRACE_MOVE, ("GoTo(%d, %d) from (%d, %d)",
                  row, col, SP->_cursrow, SP->_curscol));

#ifdef POSITION_DEBUG
      position_check(SP->_cursrow, SP->_curscol, "GoTo");
#endif /* POSITION_DEBUG */

      /*
       * Force restore even if msgr is on when we're in an alternate
       * character set -- these have a strong tendency to screw up the
       * CR & LF used for local character motions!
       */
      if ((oldattr & A_ALTCHARSET)
          || (oldattr && !move_standout_mode))
      {
            TR(TRACE_CHARPUT, ("turning off (%#lx) %s before move",
               oldattr, _traceattr(oldattr)));
            vidattr(A_NORMAL);
      }

      mvcur(SP->_cursrow, SP->_curscol, row, col);
      SP->_cursrow = row;
      SP->_curscol = col;
}

static inline void PutAttrChar(chtype ch)
{
      if (tilde_glitch && (TextOf(ch) == '~'))
            ch = ('`' | AttrOf(ch));

      TR(TRACE_CHARPUT, ("PutAttrChar(%s) at (%d, %d)",
                    _tracechtype(ch),
                     SP->_cursrow, SP->_curscol));
      UpdateAttrs(ch);
      putc((int)TextOf(ch), SP->_ofp);
#ifdef TRACE
      _nc_outchars++;
#endif /* TRACE */
      SP->_curscol++;
      if (char_padding) {
            TPUTS_TRACE("char_padding");
            putp(char_padding);
      }
}

static bool check_pending(void)
/* check for pending input */
{
      bool have_pending = FALSE;

      /*
       * Only carry out this check when the flag is zero, otherwise we'll
       * have the refreshing slow down drastically (or stop) if there's an
       * unread character available.
       */
      if(SP->_fifohold != 0)
            return FALSE;

      if (SP->_checkfd >= 0) {
#if USE_FUNC_POLL
            struct pollfd fds[1];
            fds[0].fd = SP->_checkfd;
            fds[0].events = POLLIN;
            if (poll(fds, 1, 0) > 0)
            {
                  have_pending = TRUE;
            }
#elif HAVE_SELECT
            fd_set fdset;
            struct timeval ktimeout;

            ktimeout.tv_sec =
            ktimeout.tv_usec = 0;

            FD_ZERO(&fdset);
            FD_SET(SP->_checkfd, &fdset);
            if (select(SP->_checkfd+1, &fdset, NULL, NULL, &ktimeout) > 0)
            {
                  have_pending = TRUE;
            }
#endif
      }
      if (have_pending) {
            SP->_fifohold = 5;
            fflush(SP->_ofp);
      }
      return FALSE;
}

/*
 * No one supports recursive inline functions.  However, gcc is quieter if we
 * instantiate the recursive part separately.
 */
#if CC_HAS_INLINE_FUNCS
static void callPutChar(chtype const);
#else
#define callPutChar(ch) PutChar(ch)
#endif

static inline void PutChar(chtype const ch);    /* forward declaration */

/* put char at lower right corner */
static void PutCharLR(chtype const ch)
{
    if (!auto_right_margin)
    {
      /* we can put the char directly */
      PutAttrChar(ch);
    }
    else if (enter_am_mode && exit_am_mode)
    {
      /* we can suppress automargin */
      TPUTS_TRACE("exit_am_mode");
      putp(exit_am_mode);

      PutAttrChar(ch);

      TPUTS_TRACE("enter_am_mode");
      putp(enter_am_mode);
    }
    else if ((enter_insert_mode && exit_insert_mode)
           || insert_character || parm_ich)
    {
      GoTo(screen_lines-1,screen_columns-2);
      callPutChar(ch);
      GoTo(screen_lines-1,screen_columns-2);
      InsStr(newscr->_line[screen_lines-1].text+screen_columns-2,1);
    }
}

static void wrap_cursor(void)
{
    if (eat_newline_glitch)
    {
      /*
       * xenl can manifest two different ways.  The vt100
       * way is that, when you'd expect the cursor to wrap,
       * it stays hung at the right margin (on top of the
       * character just emitted) and doesn't wrap until the
       * *next* graphic char is emitted.  The c100 way is
       * to ignore LF received just after an am wrap.
       *
       * An aggressive way to handle this would be to
       * emit CR/LF after the char and then assume the wrap
       * is done, you're on the first position of the next
       * line, and the terminal out of its weird state.
       * Here it's safe to just tell the code that the
       * cursor is in hyperspace and let the next mvcur()
       * call straighten things out.
       */
      SP->_curscol = -1;
      SP->_cursrow = -1;
    }
    else if (auto_right_margin)
    {
      SP->_curscol = 0;
      SP->_cursrow++;
    }
    else
    {
      SP->_curscol--;
    }
}

static inline void PutChar(chtype const ch)
/* insert character, handling automargin stuff */
{
    if (SP->_cursrow == screen_lines-1 && SP->_curscol == screen_columns-1)
      PutCharLR(ch);
    else
      PutAttrChar(ch);

    if (SP->_curscol >= screen_columns)
      wrap_cursor();

#ifdef POSITION_DEBUG
    position_check(SP->_cursrow, SP->_curscol, "PutChar");
#endif /* POSITION_DEBUG */
}

/*
 * Issue a given span of characters from an array.
 * Must be functionally equivalent to:
 *    for (i = 0; i < num; i++)
 *        PutChar(ntext[i]);
 * but can leave the cursor positioned at the middle of the interval.
 *
 * Returns: 0 - cursor is at the end of interval
 *        1 - cursor is somewhere in the middle
 *
 * This code is optimized using ech and rep.
 */
static int EmitRange(const chtype *ntext, int num)
{
    int     i;

    if (erase_chars || repeat_char)
    {
      while (num > 0)
      {
          int     runcount;
          chtype ntext0;

          while (num>1 && ntext[0]!=ntext[1])
          {
            PutChar(ntext[0]);
            ntext++;
            num--;
          }
          ntext0 = ntext[0];
          if (num==1)
          {
            PutChar(ntext0);
            return 0;
          }
          runcount = 2;

          while (runcount < num && ntext[runcount] == ntext0)
            runcount++;

          /*
           * The cost expression in the middle isn't exactly right.
           * _cup_cost is an upper bound on the cost for moving to the
           * end of the erased area, but not the cost itself (which we
           * can't compute without emitting the move).  This may result
           * in erase_chars not getting used in some situations for
           * which it would be marginally advantageous.
           */
          if (erase_chars
            && runcount > SP->_ech_cost + SP->_cup_cost
            && can_clear_with(ntext0))
          {
            UpdateAttrs(ntext0);
            putp(tparm(erase_chars, runcount));

            /*
             * If this is the last part of the given interval,
             * don't bother moving cursor, since it can be the
             * last update on the line.
             */
            if (runcount < num)
                GoTo(SP->_cursrow, SP->_curscol + runcount);
            else
                return 1;     /* cursor stays in the middle */
          }
          else if (repeat_char && runcount > SP->_rep_cost)
          {
            bool wrap_possible = (SP->_curscol + runcount >= screen_columns);
            int rep_count = runcount;

            if (wrap_possible)
                rep_count--;

            UpdateAttrs(ntext0);
            putp(tparm(repeat_char, TextOf(ntext0), rep_count));
            SP->_curscol += rep_count;

            if (wrap_possible)
                PutChar(ntext0);
          }
          else
          {
            for (i = 0; i < runcount; i++)
                PutChar(ntext[i]);
          }
          ntext += runcount;
          num -= runcount;
      }
      return 0;
    }

    for (i = 0; i < num; i++)
      PutChar(ntext[i]);
    return 0;
}

/*
 * Output the line in the given range [first .. last]
 *
 * If there's a run of identical characters that's long enough to justify
 * cursor movement, use that also.
 *
 * Returns: same as EmitRange
 */
static int PutRange(
      const chtype *otext,
      const chtype *ntext,
      int row,
      int first, int last)
{
      int j, run;
      int cost = min(SP->_cup_ch_cost, SP->_hpa_ch_cost);

      TR(TRACE_CHARPUT, ("PutRange(%p, %p, %d, %d, %d)",
                   otext, ntext, row, first, last));

      if (otext != ntext
       && (last-first+1) > cost) {
            for (j = first, run = 0; j <= last; j++) {
                  if (otext[j] == ntext[j]) {
                        run++;
                  } else {
                        if (run > cost) {
                              int before_run = (j - run);
                              EmitRange(ntext+first, before_run-first);
                              GoTo(row, first = j);
                        }
                        run = 0;
                  }
            }
      }
      return EmitRange(ntext + first, last-first+1);
}

#if CC_HAS_INLINE_FUNCS
static void callPutChar(chtype const ch)
{
      PutChar(ch);
}
#endif

#define MARK_NOCHANGE(win,row) \
      { \
            win->_line[row].firstchar = _NOCHANGE; \
            win->_line[row].lastchar = _NOCHANGE; \
            if_USE_SCROLL_HINTS(win->_line[row].oldindex = row); \
      }

int doupdate(void)
{
int   i;
int   nonempty;
#if USE_TRACE_TIMES
struct tms before, after;
#endif /* USE_TRACE_TIMES */

      T((T_CALLED("doupdate()")));

#ifdef TRACE
      if (_nc_tracing & TRACE_UPDATE)
      {
          if (curscr->_clear)
            _tracef("curscr is clear");
          else
            _tracedump("curscr", curscr);
          _tracedump("newscr", newscr);
      }
#endif /* TRACE */

      _nc_signal_handler(FALSE);

      if (SP->_fifohold)
            SP->_fifohold--;

#if USE_SIZECHANGE
      if (SP->_endwin || SP->_sig_winch)
      {
            /*
             * This is a transparent extension:  XSI does not address it,
             * and applications need not know that ncurses can do it.
             *
             * Check if the terminal size has changed while curses was off
             * (this can happen in an xterm, for example), and resize the
             * ncurses data structures accordingly.
             */
            _nc_update_screensize();
      }
#endif

      if (SP->_endwin) {

            T(("coming back from shell mode"));
            reset_prog_mode();

            _nc_mvcur_resume();
            _nc_screen_resume();
            SP->_mouse_resume(SP);

            SP->_endwin = FALSE;
      }

#if USE_TRACE_TIMES
      /* zero the metering machinery */
      _nc_outchars = 0;
      (void) times(&before);
#endif /* USE_TRACE_TIMES */

      /*
       * This is the support for magic-cookie terminals.  The
       * theory: we scan the virtual screen looking for attribute
       * turnons.  Where we find one, check to make sure it's
       * realizable by seeing if the required number of
       * un-attributed blanks are present before and after the
       * attributed range; try to shift the range boundaries over
       * blanks (not changing the screen display) so this becomes
       * true.  If it is, shift the beginning attribute change
       * appropriately (the end one, if we've gotten this far, is
       * guaranteed room for its cookie). If not, nuke the added
       * attributes out of the span.
       */
#if USE_XMC_SUPPORT
      if (magic_cookie_glitch > 0) {
          int     j, k;
          attr_t rattr = A_NORMAL;

          for (i = 0; i < screen_lines; i++)
            for (j = 0; j < screen_columns; j++)
            {
                bool failed = FALSE;
                chtype turnon = AttrOf(newscr->_line[i].text[j]) & ~rattr;

                /* is an attribute turned on here? */
                if (turnon == 0) {
                  rattr = AttrOf(newscr->_line[i].text[j]);
                  continue;
                }

                T(("At (%d, %d): from %s...", i, j, _traceattr(rattr)));
                T(("...to %s",_traceattr(turnon)));

                /*
                 * If the attribute change location is a blank with a
                 * "safe" attribute, undo the attribute turnon.  This may
                 * ensure there's enough room to set the attribute before
                 * the first non-blank in the run.
                 */
#define SAFE(a)   !((a) & (chtype)~NONBLANK_ATTR)
                if (TextOf(newscr->_line[i].text[j])==' ' && SAFE(turnon))
                {
                  newscr->_line[i].text[j] &= ~turnon;
                  continue;
                }

                /* check that there's enough room at start of span */
                for (k = 1; k <= magic_cookie_glitch; k++)
                  if (j-k < 0
                        || TextOf(newscr->_line[i].text[j-k]) != ' '
                        || !SAFE(AttrOf(newscr->_line[i].text[j-k])))
                      failed = TRUE;
                if (!failed)
                {
                  bool  end_onscreen = FALSE;
                  int   m, n = j;

                  /* find end of span, if it's onscreen */
                  for (m = i; m < screen_lines; m++)
                  {
                      for ( ; n < screen_columns; n++)
                      {
                        if (AttrOf(newscr->_line[m].text[n]) == rattr)
                        {
                            end_onscreen = TRUE;
                            T(("Range attributed with %s ends at (%d, %d)",
                               _traceattr(turnon),m,n));
                            goto foundit;
                        }
                      }
                      n = 0;
                  }
                  T(("Range attributed with %s ends offscreen",
                      _traceattr(turnon)));
                foundit:;

                  if (end_onscreen)
                  {
                      chtype  *lastline = newscr->_line[m].text;

                      /*
                       * If there are safely-attributed blanks at the
                       * end of the range, shorten the range.  This will
                       * help ensure that there is enough room at end
                       * of span.
                       */
                      while (n >= 0
                           && TextOf(lastline[n]) == ' '
                           && SAFE(AttrOf(lastline[n])))
                        lastline[n--] &= ~turnon;

                      /* check that there's enough room at end of span */
                      for (k = 1; k <= magic_cookie_glitch; k++)
                        if (n + k >= screen_columns
                              || TextOf(lastline[n + k]) != ' '
                              || !SAFE(AttrOf(lastline[n+k])))
                            failed = TRUE;
                  }
                }

                if (failed)
                {
                  int p, q = j;

                  T(("Clearing %s beginning at (%d, %d)",
                                    _traceattr(turnon), i, j));

                  /* turn off new attributes over span */
                  for (p = i; p < screen_lines; p++)
                  {
                      for ( ; q < screen_columns; q++)
                      {
                        if (AttrOf(newscr->_line[p].text[q]) == rattr)
                            goto foundend;
                        newscr->_line[p].text[q] &= ~turnon;
                      }
                      q = 0;
                  }
                foundend:;
                }
                else
                {
                  T(("Cookie space for %s found before (%d, %d)",
                                    _traceattr(turnon), i, j));

                  /*
                   * back up the start of range so there's room
                   * for cookies before the first nonblank character
                   */
                  for (k = 1; k <= magic_cookie_glitch; k++)
                      newscr->_line[i].text[j-k] |= turnon;
                }

                rattr = AttrOf(newscr->_line[i].text[j]);
            }

#ifdef TRACE
          /* show altered highlights after magic-cookie check */
          if (_nc_tracing & TRACE_UPDATE)
          {
            _tracef("After magic-cookie check...");
            _tracedump("newscr", newscr);
          }
#endif /* TRACE */
      }
#endif      /* USE_XMC_SUPPORT */

      nonempty = 0;
      if (curscr->_clear) {         /* force refresh ? */
            /* yes, clear all & update */
            T(("clearing and updating curscr"));
            if (is_wintouched(newscr))
                  ClrUpdate(newscr);
            else
                  ClrUpdate(curscr);
            curscr->_clear = FALSE; /* reset flag */
            newscr->_clear = FALSE; /* reset flag */
      } else if (newscr->_clear) {
            T(("clearing and updating newscr"));
            ClrUpdate(newscr);
            newscr->_clear = FALSE;
      } else {
            int changedlines = CHECK_INTERVAL;

            if(check_pending())
                goto cleanup;

            nonempty = min(screen_lines, newscr->_maxy+1);

            if (SP->_scrolling) {
#if USE_HASHMAP
#if defined(TRACE) || defined(NCURSES_TEST)
            if (_nc_optimize_enable & OPTIMIZE_HASHMAP)
#endif /*TRACE */
                  _nc_hash_map();
#elif !USE_SCROLL_HINTS
            _nc_setup_scroll();
#endif
#if defined(TRACE) || defined(NCURSES_TEST)
            if (_nc_optimize_enable & OPTIMIZE_SCROLL)
#endif /*TRACE */
#if USE_SCROLL_HINTS || USE_HASHMAP
                  _nc_scroll_optimize();
#else
                  _nc_perform_scroll();
#endif
            }

            nonempty = ClrBottom(nonempty);

            T(("Transforming lines, nonempty %d", nonempty));
            for (i = 0; i < nonempty; i++) {
                  /*
                   * Here is our line-breakout optimization.
                   */
                  if (changedlines == CHECK_INTERVAL)
                  {
                      if (check_pending())
                        goto cleanup;
                      changedlines = 0;
                  }

                  /*
                   * newscr->line[i].firstchar is normally set
                   * by wnoutrefresh.  curscr->line[i].firstchar
                   * is normally set by _nc_scroll_window in the
                   * vertical-movement optimization code,
                   */
                  if (newscr->_line[i].firstchar != _NOCHANGE
                   || curscr->_line[i].firstchar != _NOCHANGE)
                  {
                        TransformLine(i);
                        changedlines++;
                  }

                  /* mark line changed successfully */
                  if (i <= newscr->_maxy)
                        MARK_NOCHANGE(newscr,i)
                  if (i <= curscr->_maxy)
                        MARK_NOCHANGE(curscr,i)
            }
      }

      /* put everything back in sync */
      for (i = nonempty; i <= newscr->_maxy; i++)
            MARK_NOCHANGE(newscr,i)
      for (i = nonempty; i <= curscr->_maxy; i++)
            MARK_NOCHANGE(curscr,i)

      curscr->_curx = newscr->_curx;
      curscr->_cury = newscr->_cury;

      GoTo(curscr->_cury, curscr->_curx);

    cleanup:
      /*
       * Keep the physical screen in normal mode in case we get other
       * processes writing to the screen.
       */
      UpdateAttrs(A_NORMAL);

      fflush(SP->_ofp);
      curscr->_attrs = newscr->_attrs;
/*    curscr->_bkgd  = newscr->_bkgd; */

#if USE_TRACE_TIMES
      (void) times(&after);
      TR(TRACE_TIMES, ("Update cost: %ld chars, %ld clocks system time, %ld clocks user time",
          _nc_outchars,
          after.tms_stime-before.tms_stime,
          after.tms_utime-before.tms_utime));
#endif /* USE_TRACE_TIMES */

      _nc_signal_handler(TRUE);

      returnCode(OK);
}

/*
 *    ClrBlank(win)
 *
 *    Returns the attributed character that corresponds to the "cleared"
 *    screen.  If the terminal has the back-color-erase feature, this will be
 *    colored according to the wbkgd() call.
 *
 *    We treat 'curscr' specially because it isn't supposed to be set directly
 *    in the wbkgd() call.  Assume 'stdscr' for this case.
 */
#define BCE_ATTRS (A_NORMAL|A_COLOR)
#define BCE_BKGD(win) (((win) == curscr ? stdscr : (win))->_bkgd)

static inline chtype ClrBlank (WINDOW *win)
{
chtype      blank = BLANK;
      if (back_color_erase)
            blank |= (BCE_BKGD(win) & BCE_ATTRS);
      return blank;
}

/*
**    ClrUpdate(win)
**
**    Update by clearing and redrawing the entire screen.
**
*/

static void ClrUpdate(WINDOW *win)
{
      int i;
      chtype blank = ClrBlank(win);
      int nonempty = min(screen_lines, newscr->_maxy+1);

      T(("ClrUpdate() called"));

      if (win == curscr) {
            /* discard updates */
            for (i = 0; i < screen_lines ; i++) {
                  memcpy( newscr->_line[i].text,
                        curscr->_line[i].text,
                        screen_columns * sizeof(chtype));
            }
      }

      ClearScreen(blank);

      T(("updating screen from scratch"));

      nonempty = ClrBottom(nonempty);

      for (i = 0; i < nonempty; i++)
            TransformLine(i);
}

/*
**    ClrToEOL(blank)
**
**    Clear to end of current line, starting at the cursor position
*/

static void ClrToEOL(chtype blank)
{
int   j;
bool  needclear = FALSE;

      for (j = SP->_curscol; j < screen_columns; j++)
      {
          chtype *cp = &(curscr->_line[SP->_cursrow].text[j]);

          if (*cp != blank)
          {
            *cp = blank;
            needclear = TRUE;
          }
      }

      if (needclear)
      {
          UpdateAttrs(blank);
          TPUTS_TRACE("clr_eol");
          if (SP->_el_cost > (screen_columns - SP->_curscol))
          {
            int count = (screen_columns - SP->_curscol);
            while (count-- > 0)
                  PutChar(blank);
          }
          else
            putp(clr_eol);
      }
}

/*
**    ClrToEOS(blank)
**
**    Clear to end of screen, starting at the cursor position
*/

static void ClrToEOS(chtype blank)
{
int row, col;

      UpdateAttrs(blank);
      TPUTS_TRACE("clr_eos");
      row = SP->_cursrow;
      tputs(clr_eos, screen_lines-row, _nc_outch);

      for (col = SP->_curscol; col < screen_columns; col++)
            curscr->_line[row].text[col] = blank;

      for (row++; row < screen_lines; row++)
      {
            for (col = 0; col < screen_columns; col++)
                  curscr->_line[row].text[col] = blank;
      }
}

/*
 *    ClrBottom(total)
 *
 *    Test if clearing the end of the screen would satisfy part of the
 *    screen-update.  Do this by scanning backwards through the lines in the
 *    screen, checking if each is blank, and one or more are changed.
 */
static int ClrBottom(int total)
{
static      chtype      *tstLine;
static      size_t      lenLine;

int   row, col;
int   top    = total;
int   last   = min(screen_columns, newscr->_maxx+1);
size_t      length = sizeof(chtype) * last;
chtype      blank  = newscr->_line[total-1].text[last-1]; /* lower right char */

      if(!clr_eos || !can_clear_with(blank))
            return total;

      if (tstLine == 0)
            tstLine = (chtype *)malloc(length);
      else if (length > lenLine)
            tstLine = (chtype *)realloc(tstLine, length);

      if (tstLine != 0) {
            lenLine = length;
            for (col = 0; col < last; col++)
                  tstLine[col] = blank;

            for (row = total-1; row >= 0; row--) {
                  if (memcmp(tstLine, newscr->_line[row].text, length))
                        break;
                  if (memcmp(tstLine, curscr->_line[row].text, length))
                        top = row;
            }

            /* don't use clr_eos for just one line if clr_eol available */
            if (top < total-1 || (top < total && !clr_eol && !clr_bol)) {
                  GoTo(top,0);
                  ClrToEOS(blank);
                  total = top;
            }
      }
#if NO_LEAKS
      FreeAndNull(tstLine);
#endif
      return total;
}


/*
**    TransformLine(lineno)
**
**    Transform the given line in curscr to the one in newscr, using
**    Insert/Delete Character if _nc_idcok && has_ic().
**
**          firstChar = position of first different character in line
**          oLastChar = position of last different character in old line
**          nLastChar = position of last different character in new line
**
**          move to firstChar
**          overwrite chars up to min(oLastChar, nLastChar)
**          if oLastChar < nLastChar
**                insert newLine[oLastChar+1..nLastChar]
**          else
**                delete oLastChar - nLastChar spaces
*/

static void TransformLine(int const lineno)
{
int   firstChar, oLastChar, nLastChar;
chtype      *newLine = newscr->_line[lineno].text;
chtype      *oldLine = curscr->_line[lineno].text;
int   n;
bool  attrchanged = FALSE;

      T(("TransformLine(%d) called", lineno));

      if(ceol_standout_glitch && clr_eol) {
            firstChar = 0;
            while(firstChar < screen_columns) {
                  if(AttrOf(newLine[firstChar]) != AttrOf(oldLine[firstChar]))
                        attrchanged = TRUE;
                  firstChar++;
            }
      }

      firstChar = 0;

      if (attrchanged) {      /* we may have to disregard the whole line */
            GoTo(lineno, firstChar);
            ClrToEOL(ClrBlank(curscr));
            PutRange(oldLine, newLine, lineno, 0, (screen_columns-1));
#if USE_XMC_SUPPORT

#define NEW(r,c) newscr->_line[r].text[c]
#define xmc_turn_on(a,b) ((((a)^(b)) & ~(a) & SP->_xmc_triggers) != 0)
#define xmc_turn_off(a,b) xmc_turn_on(b,a)

      /*
       * This is a very simple loop to paint characters which may have the
       * magic cookie glitch embedded.  It doesn't know much about video
       * attributes which are continued from one line to the next.  It
       * assumes that we have filtered out requests for attribute changes
       * that do not get mapped to blank positions.
       *
       * FIXME: we are not keeping track of where we put the cookies, so this
       * will work properly only once, since we may overwrite a cookie in a
       * following operation.
       */
      } else if (magic_cookie_glitch > 0) {
            GoTo(lineno, firstChar);
            for (n = 0; n < screen_columns; n++) {
                  int m = n + magic_cookie_glitch;

                  /* check for turn-on:
                   * If we are writing an attributed blank, where the
                   * previous cell is not attributed.
                   */
                  if (TextOf(newLine[n]) == ' '
                   && ((n > 0
                     && xmc_turn_on(newLine[n-1], newLine[n]))
                    || (n == 0
                     && lineno > 0
                     && xmc_turn_on(NEW(lineno-1,screen_columns-1), newLine[n])))) {
                        n = m;
                  }

                  PutChar(newLine[n]);

                  /* check for turn-off:
                   * If we are writing an attributed non-blank, where the
                   * next cell is blank, and not attributed.
                   */
                  if (TextOf(newLine[n]) != ' '
                   && ((n+1 < screen_columns
                     && xmc_turn_off(newLine[n], newLine[n+1]))
                    || (n+1 >= screen_columns
                     && lineno+1 < screen_lines
                     && xmc_turn_off(newLine[n], NEW(lineno+1,0))))) {
                        n = m;
                  }

            }
#undef NEW
#endif
      } else {
            chtype blank;

            /* find the first differing character */
            while (firstChar < screen_columns  &&
                        newLine[firstChar] == oldLine[firstChar])
                  firstChar++;

            /* if there wasn't one, we're done */
            if (firstChar >= screen_columns)
                  return;

            /* it may be cheap to clear leading whitespace with clr_bol */
            if (clr_bol && can_clear_with(blank=newLine[0]))
            {
                  int oFirstChar, nFirstChar;

                  for (oFirstChar = 0; oFirstChar < screen_columns; oFirstChar++)
                        if (oldLine[oFirstChar] != blank)
                              break;
                  for (nFirstChar = 0; nFirstChar < screen_columns; nFirstChar++)
                        if (newLine[nFirstChar] != blank)
                              break;

                  if (nFirstChar > oFirstChar + SP->_el1_cost)
                  {
                      if (nFirstChar >= screen_columns && SP->_el_cost <= SP->_el1_cost)
                      {
                        GoTo(lineno, 0);
                        UpdateAttrs(blank);
                        TPUTS_TRACE("clr_eol");
                        putp(clr_eol);
                      }
                      else
                      {
                        GoTo(lineno, nFirstChar - 1);
                        UpdateAttrs(blank);
                        TPUTS_TRACE("clr_bol");
                        putp(clr_bol);
                      }

                      while (firstChar < nFirstChar)
                        oldLine[firstChar++] = blank;

                      if (firstChar >= screen_columns)
                        return;
                  }
            }

            blank = newLine[screen_columns-1];

            if(!can_clear_with(blank))
            {
                  /* find the last differing character */
                  nLastChar = screen_columns - 1;

                  while (nLastChar > firstChar
                   && newLine[nLastChar] == oldLine[nLastChar])
                        nLastChar--;

                  if (nLastChar >= firstChar) {
                        GoTo(lineno, firstChar);
                        PutRange(oldLine, newLine, lineno, firstChar, nLastChar);
                        memcpy( oldLine + firstChar,
                              newLine + firstChar,
                              (nLastChar - firstChar + 1) * sizeof(chtype));
                  }
                  return;
            }

            /* find last non-blank character on old line */
            oLastChar = screen_columns - 1;
            while (oLastChar > firstChar  &&  oldLine[oLastChar] == blank)
                  oLastChar--;

            /* find last non-blank character on new line */
            nLastChar = screen_columns - 1;
            while (nLastChar > firstChar  &&  newLine[nLastChar] == blank)
                  nLastChar--;

            if((nLastChar == firstChar)
             && (SP->_el_cost < (oLastChar - nLastChar))) {
                  GoTo(lineno, firstChar);
                  if(newLine[firstChar] != blank )
                        PutChar(newLine[firstChar]);
                  ClrToEOL(blank);
            } else if( newLine[nLastChar] != oldLine[oLastChar]
                        || !(_nc_idcok && has_ic()) ) {
                  GoTo(lineno, firstChar);
                  if ((oLastChar - nLastChar) > SP->_el_cost) {
                        if(PutRange(oldLine, newLine, lineno, firstChar, nLastChar))
                            GoTo(lineno, nLastChar+1);
                        ClrToEOL(blank);
                  } else {
                        n = max( nLastChar , oLastChar );
                        PutRange(oldLine, newLine, lineno, firstChar, n);
                  }
            } else {
                  int nLastNonblank = nLastChar;
                  int oLastNonblank = oLastChar;

                  /* find the last characters that really differ */
                  while (newLine[nLastChar] == oldLine[oLastChar]) {
                        if (nLastChar != 0
                         && oLastChar != 0) {
                              nLastChar--;
                              oLastChar--;
                         } else {
                              break;
                         }
                  }

                  n = min(oLastChar, nLastChar);
                  if (n >= firstChar) {
                        GoTo(lineno, firstChar);
                        PutRange(oldLine, newLine, lineno, firstChar, n);
                  }
                  GoTo(lineno, n+1);

                  if (oLastChar < nLastChar) {
                        int m = max(nLastNonblank, oLastNonblank);
                        if (InsCharCost(nLastChar - oLastChar)
                         > (m - n)) {
                              PutRange(oldLine, newLine, lineno, n+1, m);
                        } else {
                              InsStr(&newLine[n+1], nLastChar - oLastChar);
                        }
                  } else if (oLastChar > nLastChar ) {
                        if (DelCharCost(oLastChar - nLastChar)
                            > SP->_el_cost + nLastNonblank - (n+1)) {
                              if(PutRange(oldLine, newLine, lineno,
                                          n+1, nLastNonblank))
                                    GoTo(lineno, nLastNonblank+1);
                              ClrToEOL(blank);
                        } else {
                              /*
                               * The delete-char sequence will
                               * effectively shift in blanks from the
                               * right margin of the screen.  Ensure
                               * that they are the right color by
                               * setting the video attributes from
                               * the last character on the row.
                               */
                              UpdateAttrs(blank);
                              DelChar(oLastChar - nLastChar);
                        }
                  }
            }
      }

      /* update the code's internal representation */
      if (screen_columns > firstChar)
            memcpy( oldLine + firstChar,
                  newLine + firstChar,
                  (screen_columns - firstChar) * sizeof(chtype));
}

/*
**    ClearScreen(blank)
**
**    Clear the physical screen and put cursor at home
**
*/

static void ClearScreen(chtype blank)
{
      int   i, j;

      T(("ClearScreen() called"));

      if (clear_screen) {
            UpdateAttrs(blank);
            TPUTS_TRACE("clear_screen");
            putp(clear_screen);
            SP->_cursrow = SP->_curscol = 0;
#ifdef POSITION_DEBUG
            position_check(SP->_cursrow, SP->_curscol, "ClearScreen");
#endif /* POSITION_DEBUG */
      } else if (clr_eos) {
            SP->_cursrow = SP->_curscol = -1;
            GoTo(0,0);

            UpdateAttrs(blank);
            TPUTS_TRACE("clr_eos");
            putp(clr_eos);
      } else if (clr_eol) {
            SP->_cursrow = SP->_curscol = -1;

            for (i = 0; i < screen_lines; i++) {
                  GoTo(i, 0);
                  UpdateAttrs(blank);
                  TPUTS_TRACE("clr_eol");
                  putp(clr_eol);
            }
            GoTo(0,0);
      } else {
            T(("cannot clear screen"));
            return;
      }

      for (i = 0; i < screen_lines; i++) {
            for (j = 0; j < screen_columns; j++)
                  curscr->_line[i].text[j] = blank;
      }

      T(("screen cleared"));
}

/*
**    InsStr(line, count)
**
**    Insert the count characters pointed to by line.
**
*/

static int InsStr(chtype *line, int count)
{
      T(("InsStr(%p,%d) called", line, count));

      if (enter_insert_mode  &&  exit_insert_mode) {
            TPUTS_TRACE("enter_insert_mode");
            putp(enter_insert_mode);
            while (count) {
                  PutAttrChar(*line);
                  line++;
                  count--;
            }
            TPUTS_TRACE("exit_insert_mode");
            putp(exit_insert_mode);
            return(OK);
      } else if (parm_ich) {
            TPUTS_TRACE("parm_ich");
            tputs(tparm(parm_ich, count), count, _nc_outch);
            while (count) {
                  PutAttrChar(*line);
                  line++;
                  count--;
            }
            return(OK);
      } else {
            while (count) {
                  TPUTS_TRACE("insert_character");
                  putp(insert_character);
                  PutAttrChar(*line);
                  if (insert_padding)
                  {
                        TPUTS_TRACE("insert_padding");
                        putp(insert_padding);
                  }
                  line++;
                  count--;
            }
            return(OK);
      }
}

/*
**    DelChar(count)
**
**    Delete count characters at current position
**
*/

static void DelChar(int count)
{
      T(("DelChar(%d) called, position = (%d,%d)", count, newscr->_cury, newscr->_curx));

      if (parm_dch) {
            TPUTS_TRACE("parm_dch");
            tputs(tparm(parm_dch, count), count, _nc_outch);
      } else {
            while (count--)
            {
                  TPUTS_TRACE("delete_character");
                  putp(delete_character);
            }
      }
}

/*
**    _nc_outstr(char *str)
**
**    Emit a string without waiting for update.
*/

void _nc_outstr(const char *str)
{
    FILE *ofp = SP ? SP->_ofp : stdout;

    (void) fputs(str, ofp);
    (void) fflush(ofp);

#ifdef TRACE
    _nc_outchars += strlen(str);
#endif /* TRACE */
}

/*
 * Physical-scrolling support
 *
 * This code was adapted from Keith Bostic's hardware scrolling
 * support for 4.4BSD curses.  I (esr) translated it to use terminfo
 * capabilities, narrowed the call interface slightly, and cleaned
 * up some convoluted tests.  I also added support for the memory_above
 * memory_below, and non_dest_scroll_region capabilities.
 *
 * For this code to work, we must have either
 * change_scroll_region and scroll forward/reverse commands, or
 * insert and delete line capabilities.
 * When the scrolling region has been set, the cursor has to
 * be at the last line of the region to make the scroll up
 * happen, or on the first line of region to scroll down.
 *
 * This code makes one aesthetic decision in the opposite way from
 * BSD curses.  BSD curses preferred pairs of il/dl operations
 * over scrolls, allegedly because il/dl looked faster.  We, on
 * the other hand, prefer scrolls because (a) they're just as fast
 * on many terminals and (b) using them avoids bouncing an
 * unchanged bottom section of the screen up and down, which is
 * visually nasty.
 *
 * (lav): added more cases, used dl/il when bot==maxy and in csr case.
 *
 * I used assumption that capabilities il/il1/dl/dl1 work inside
 * changed scroll region not shifting screen contents outside of it.
 * If there are any terminals behaving different way, it would be
 * necessary to add some conditions to scroll_csr_forward/backward.
 */

/* Try to scroll up assuming given csr (miny, maxy). Returns ERR on failure */
static int scroll_csr_forward(int n, int top, int bot, int miny, int maxy, chtype blank)
{
    int i;

    if (n == 1 && scroll_forward && top == miny && bot == maxy)
    {
      GoTo(bot, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("scroll_forward");
      tputs(scroll_forward, 0, _nc_outch);
    }
    else if (n == 1 && delete_line && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("delete_line");
      tputs(delete_line, 0, _nc_outch);
    }
    else if (parm_index && top == miny && bot == maxy)
    {
      GoTo(bot, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("parm_index");
      tputs(tparm(parm_index, n, 0), n, _nc_outch);
    }
    else if (parm_delete_line && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("parm_delete_line");
      tputs(tparm(parm_delete_line, n, 0), n, _nc_outch);
    }
    else if (scroll_forward && top == miny && bot == maxy)
    {
      GoTo(bot, 0);
      UpdateAttrs(blank);
      for (i = 0; i < n; i++)
      {
          TPUTS_TRACE("scroll_forward");
          tputs(scroll_forward, 0, _nc_outch);
      }
    }
    else if (delete_line && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      for (i = 0; i < n; i++)
      {
          TPUTS_TRACE("delete_line");
          tputs(delete_line, 0, _nc_outch);
      }
    }
    else
      return ERR;

    return OK;
}

/* Try to scroll down assuming given csr (miny, maxy). Returns ERR on failure */
/* n > 0 */
static int scroll_csr_backward(int n, int top, int bot, int miny, int maxy, chtype blank)
{
    int i;

    if (n == 1 && scroll_reverse && top == miny && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("scroll_reverse");
      tputs(scroll_reverse, 0, _nc_outch);
    }
    else if (n == 1 && insert_line && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("insert_line");
      tputs(insert_line, 0, _nc_outch);
    }
    else if (parm_rindex && top == miny && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("parm_rindex");
      tputs(tparm(parm_rindex, n, 0), n, _nc_outch);
    }
    else if (parm_insert_line && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      TPUTS_TRACE("parm_insert_line");
      tputs(tparm(parm_insert_line, n, 0), n, _nc_outch);
    }
    else if (scroll_reverse && top == miny && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      for (i = 0; i < n; i++)
      {
          TPUTS_TRACE("scroll_reverse");
          tputs(scroll_reverse, 0, _nc_outch);
      }
    }
    else if (insert_line && bot == maxy)
    {
      GoTo(top, 0);
      UpdateAttrs(blank);
      for (i = 0; i < n; i++)
      {
          TPUTS_TRACE("insert_line");
          tputs(insert_line, 0, _nc_outch);
      }
    }
    else
      return ERR;

    return OK;
}

/* scroll by using delete_line at del and insert_line at ins */
/* n > 0 */
static int scroll_idl(int n, int del, int ins, chtype blank)
{
    int i;

    if(!((parm_delete_line || delete_line) && (parm_insert_line || insert_line)))
      return ERR;

    GoTo(del, 0);
    UpdateAttrs(blank);
    if (n == 1 && delete_line)
    {
      TPUTS_TRACE("delete_line");
      tputs(delete_line, 0, _nc_outch);
    }
    else if (parm_delete_line)
    {
      TPUTS_TRACE("parm_delete_line");
      tputs(tparm(parm_delete_line, n, 0), n, _nc_outch);
    }
    else /* if (delete_line) */
    {
      for (i = 0; i < n; i++)
      {
          TPUTS_TRACE("delete_line");
          tputs(delete_line, 0, _nc_outch);
      }
    }

    GoTo(ins, 0);
    UpdateAttrs(blank);
    if (n == 1 && insert_line)
    {
      TPUTS_TRACE("insert_line");
      tputs(insert_line, 0, _nc_outch);
    }
    else if (parm_insert_line)
    {
      TPUTS_TRACE("parm_insert_line");
      tputs(tparm(parm_insert_line, n, 0), n, _nc_outch);
    }
    else /* if (insert_line) */
    {
      for (i = 0; i < n; i++)
      {
          TPUTS_TRACE("insert_line");
          tputs(insert_line, 0, _nc_outch);
      }
    }

    return OK;
}

int _nc_scrolln(int n, int top, int bot, int maxy)
/* scroll region from top to bot by n lines */
{
    chtype blank=ClrBlank(stdscr);
    int i;
    bool cursor_saved=FALSE;
    int res;

    TR(TRACE_MOVE, ("mvcur_scrolln(%d, %d, %d, %d)", n, top, bot, maxy));

#if USE_XMC_SUPPORT
    /*
     * If we scroll, we might remove a cookie.
     */
    if (magic_cookie_glitch > 0) {
      return (ERR);
    }
#endif

    if (n > 0) /* scroll up (forward) */
    {
      /*
       * Explicitly clear if stuff pushed off top of region might
       * be saved by the terminal.
       */
      if (non_dest_scroll_region || (memory_above && top == 0)) {
          for (i = 0; i < n; i++)
          {
            GoTo(i, 0);
            ClrToEOL(BLANK);
          }
      }

      res = scroll_csr_forward(n, top, bot, 0, maxy, blank);

      if (res == ERR && change_scroll_region)
      {
          if ((((n==1 && scroll_forward) || parm_index)
             && (SP->_cursrow == bot || SP->_cursrow == bot-1))
            && save_cursor && restore_cursor)
          {
            cursor_saved=TRUE;
            TPUTS_TRACE("save_cursor");
            tputs(save_cursor, 0, _nc_outch);
          }
          TPUTS_TRACE("change_scroll_region");
          tputs(tparm(change_scroll_region, top, bot), 0, _nc_outch);
          if (cursor_saved)
          {
            TPUTS_TRACE("restore_cursor");
            tputs(restore_cursor, 0, _nc_outch);
          }
          else
          {
            SP->_cursrow = SP->_curscol = -1;
          }

          res = scroll_csr_forward(n, top, bot, top, bot, blank);

          TPUTS_TRACE("change_scroll_region");
          tputs(tparm(change_scroll_region, 0, maxy), 0, _nc_outch);
          SP->_cursrow = SP->_curscol = -1;
      }

      if (res == ERR && _nc_idlok)
          res = scroll_idl(n, top, bot-n+1, blank);
    }
    else /* (n < 0) - scroll down (backward) */
    {
      /*
       * Do explicit clear to end of region if it's possible that the
       * terminal might hold on to stuff we push off the end.
       */
      if (non_dest_scroll_region || (memory_below && bot == maxy))
      {
          if (bot == maxy && clr_eos)
          {
            GoTo(maxy + n, 0);
            ClrToEOS(BLANK);
          }
          else if (clr_eol)
          {
            for (i = 0; i < -n; i++)
            {
                GoTo(maxy + n + i, 0);
                ClrToEOL(BLANK);
            }
          }
      }

      res = scroll_csr_backward(-n, top, bot, 0, maxy, blank);

      if (res == ERR && change_scroll_region)
      {
          if (top != 0 && (SP->_cursrow == top || SP->_cursrow == top-1)
              && save_cursor && restore_cursor)
          {
            cursor_saved=TRUE;
            TPUTS_TRACE("save_cursor");
            tputs(save_cursor, 0, _nc_outch);
          }
          TPUTS_TRACE("change_scroll_region");
          tputs(tparm(change_scroll_region, top, bot), 0, _nc_outch);
          if (cursor_saved)
          {
            TPUTS_TRACE("restore_cursor");
            tputs(restore_cursor, 0, _nc_outch);
          }
          else
          {
            SP->_cursrow = SP->_curscol = -1;
          }

          res = scroll_csr_backward(-n, top, bot, top, bot, blank);

          TPUTS_TRACE("change_scroll_region");
          tputs(tparm(change_scroll_region, 0, maxy), 0, _nc_outch);
          SP->_cursrow = SP->_curscol = -1;
      }

      if (res == ERR && _nc_idlok)
          res = scroll_idl(-n, bot+n+1, top, blank);
    }

    if (res == ERR)
      return(ERR);

    _nc_scroll_window(curscr, n, top, bot, blank);

    return(OK);
}


void _nc_screen_resume()
{
    /* make sure terminal is in a sane known state */
    SP->_current_attr = A_NORMAL;
    newscr->_clear = TRUE;

    if (SP->_coloron == TRUE && orig_pair)
      putp(orig_pair);
    if (exit_attribute_mode)
      putp(exit_attribute_mode);
    else
    {
      /* turn off attributes */
      if (exit_alt_charset_mode)
          putp(exit_alt_charset_mode);
      if (exit_standout_mode)
          putp(exit_standout_mode);
      if (exit_underline_mode)
          putp(exit_underline_mode);
    }
    if (exit_insert_mode)
      putp(exit_insert_mode);
    if (enter_am_mode && exit_am_mode)
      putp(auto_right_margin ? enter_am_mode : exit_am_mode);
}

void _nc_screen_init()
{
    _nc_screen_resume();
}

/* wrap up screen handling */
void _nc_screen_wrap()
{
    UpdateAttrs(A_NORMAL);
}

#if USE_XMC_SUPPORT
void _nc_do_xmc_glitch(attr_t previous)
{
      attr_t chg = XMC_CHANGES(previous ^ SP->_current_attr);

      while (chg != 0) {
            if (chg & 1) {
                  SP->_curscol += magic_cookie_glitch;
                  if (SP->_curscol >= SP->_columns)
                        wrap_cursor();
                  T(("bumped to %d,%d after cookie", SP->_cursrow, SP->_curscol));
            }
            chg >>= 1;
      }
}
#endif /* USE_XMC_SUPPORT */

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