text: /****************************************************************************
   * Copyright (c) 1998-2008,2009 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>                         *
   *     and: Thomas E. Dickey                        1996-on                 *
   *     and: Juergen Pfeifer                         2009                    *
   ****************************************************************************/
  
  /*-----------------------------------------------------------------
   *
   *	lib_doupdate.c
   *
   * 	The routine doupdate() and its dependents.
   * 	All physical output is concentrated here (except _nc_outch()
    *	in lib_tputs.c).
   *
   *-----------------------------------------------------------------*/
  
  #include <curses.priv.h>
  
  #if defined __HAIKU__ && defined __BEOS__
  #undef __BEOS__
  #endif
  
  #ifdef __BEOS__
  #undef false
  #undef true
  #include <OS.h>
  #endif
  
  #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
  #elif HAVE_SELECT
  #if HAVE_SYS_SELECT_H
  #include <sys/select.h>
  #endif
  #endif
  
  #include <ctype.h>
  #include <term.h>
  
  MODULE_ID("$Id: tty_update.c,v 1.248 2009/02/15 00:51:22 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
  
  #define FILL_BCE() (SP->_coloron && !SP->_default_color && !back_color_erase)
  
  static const NCURSES_CH_T blankchar = NewChar(BLANK_TEXT);
  static NCURSES_CH_T normal = NewChar(BLANK_TEXT);
  
  /*
   * 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 NCURSES_INLINE NCURSES_CH_T ClrBlank(WINDOW *win);
  static int ClrBottom(int total);
  static void ClearScreen(NCURSES_CH_T blank);
  static void ClrUpdate(void);
  static void DelChar(int count);
  static void InsStr(NCURSES_CH_T * line, int count);
  static void TransformLine(int const lineno);
  
  #ifdef POSITION_DEBUG
  /****************************************************************************
   *
   * Debugging code.  Only works on ANSI-standard terminals.
   *
   ****************************************************************************/
  
  static void
  position_check(int expected_y, int expected_x, char *legend)
  /* check to see if the real cursor position matches the virtual */
  {
      char buf[20];
      char *s;
      int y, x;
  
      if (!_nc_tracing || (expected_y < 0 && expected_x < 0))
  	return;
  
      _nc_flush();
      memset(buf, '\0', sizeof(buf));
      putp("\033[6n");		/* only works on ANSI-compatibles */
      _nc_flush();
      *(s = buf) = 0;
      do {
  	int ask = sizeof(buf) - 1 - (s - buf);
  	int got = read(0, s, ask);
  	if (got == 0)
  	    break;
  	s += got;
      } while (strchr(buf, 'R') == 0);
      _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 (expected_x < 0)
  	    expected_x = x - 1;
  	if (expected_y < 0)
  	    expected_y = y - 1;
  	if (y - 1 != expected_y || x - 1 != expected_x) {
  	    beep();
  	    tputs(tparm("\033[%d;%dH", expected_y + 1, expected_x + 1), 1, _nc_outch);
  	    _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);
  	}
      }
  }
  #else
  #define position_check(expected_y, expected_x, legend)	/* nothing */
  #endif /* POSITION_DEBUG */
  
  /****************************************************************************
   *
   * Optimized update code
   *
   ****************************************************************************/
  
  static NCURSES_INLINE void
  GoTo(int const row, int const col)
  {
      TR(TRACE_MOVE, ("GoTo(%d, %d) from (%d, %d)",
  		    row, col, SP->_cursrow, SP->_curscol));
  
      position_check(SP->_cursrow, SP->_curscol, "GoTo");
  
      mvcur(SP->_cursrow, SP->_curscol, row, col);
      position_check(SP->_cursrow, SP->_curscol, "GoTo2");
  }
  
  static NCURSES_INLINE void
  PutAttrChar(CARG_CH_T ch)
  {
      int chlen = 1;
      NCURSES_CH_T my_ch;
      PUTC_DATA;
      NCURSES_CH_T tilde;
      NCURSES_CH_T attr = CHDEREF(ch);
  
      TR(TRACE_CHARPUT, ("PutAttrChar(%s) at (%d, %d)",
  		       _tracech_t(ch),
  		       SP->_cursrow, SP->_curscol));
  #if USE_WIDEC_SUPPORT
      /*
       * If this is not a valid character, there is nothing more to do.
       */
      if (isWidecExt(CHDEREF(ch))) {
  	TR(TRACE_CHARPUT, ("...skip"));
  	return;
      }
      /*
       * Determine the number of character cells which the 'ch' value will use
       * on the screen.  It should be at least one.
       */
      if ((chlen = wcwidth(CharOf(CHDEREF(ch)))) <= 0) {
  	static const NCURSES_CH_T blank = NewChar(BLANK_TEXT);
  
  	/*
  	 * If the character falls into any of these special cases, do
  	 * not force the result to a blank:
  	 *
  	 * a) it is printable (this works around a bug in wcwidth()).
  	 * b) use_legacy_coding() has been called to modify the treatment
  	 *    of codes 128-255.
  	 * c) the acs_map[] has been initialized to allow codes 0-31
  	 *    to be rendered.  This supports Linux console's "PC"
  	 *    characters.  Codes 128-255 are allowed though this is
  	 *    not checked.
  	 */
  	if (is8bits(CharOf(CHDEREF(ch)))
  	    && (isprint(CharOf(CHDEREF(ch)))
  		|| (SP->_legacy_coding > 0 && CharOf(CHDEREF(ch)) >= 160)
  		|| (SP->_legacy_coding > 1 && CharOf(CHDEREF(ch)) >= 128)
  		|| (AttrOf(attr) & A_ALTCHARSET
  		    && ((CharOfD(ch) < ACS_LEN
  			 && SP->_acs_map != 0
  			 && SP->_acs_map[CharOfD(ch)] != 0)
  			|| (CharOfD(ch) >= 128))))) {
  	    ;
  	} else {
  	    ch = CHREF(blank);
  	    TR(TRACE_CHARPUT, ("forced to blank"));
  	}
  	chlen = 1;
      }
  #endif
  
      if ((AttrOf(attr) & A_ALTCHARSET)
  	&& SP->_acs_map != 0
  	&& CharOfD(ch) < ACS_LEN) {
  	my_ch = CHDEREF(ch);	/* work around const param */
  #if USE_WIDEC_SUPPORT
  	/*
  	 * This is crude & ugly, but works most of the time.  It checks if the
  	 * acs_chars string specified that we have a mapping for this
  	 * character, and uses the wide-character mapping when we expect the
  	 * normal one to be broken (by mis-design ;-).
  	 */
  	if (SP->_screen_acs_fix
  	    && SP->_screen_acs_map[CharOf(my_ch)]) {
  	    RemAttr(attr, A_ALTCHARSET);
  	    my_ch = _nc_wacs[CharOf(my_ch)];
  	}
  #endif
  	/*
  	 * If we (still) have alternate character set, it is the normal 8bit
  	 * flavor.  The _screen_acs_map[] array tells if the character was
  	 * really in acs_chars, needed because of the way wide/normal line
  	 * drawing flavors are integrated.
  	 */
  	if (AttrOf(attr) & A_ALTCHARSET) {
  	    int j = CharOfD(ch);
  	    chtype temp = UChar(SP->_acs_map[j]);
  
  	    if (!(SP->_screen_acs_map[j])) {
  		RemAttr(attr, A_ALTCHARSET);
  		if (temp == 0)
  		    temp = ' ';
  	    }
  	    if (temp != 0)
  		SetChar(my_ch, temp, AttrOf(attr));
  	}
  	ch = CHREF(my_ch);
      }
      if (tilde_glitch && (CharOfD(ch) == L('~'))) {
  	SetChar(tilde, L('`'), AttrOf(attr));
  	ch = CHREF(tilde);
      }
  
      UpdateAttrs(attr);
  #if !USE_WIDEC_SUPPORT
      /* FIXME - we do this special case for signal handling, should see how to
       * make it work for wide characters.
       */
      if (SP->_outch != 0) {
  	SP->_outch(UChar(ch));
      } else
  #endif
      {
  	PUTC(CHDEREF(ch), SP->_ofp);	/* macro's fastest... */
  	COUNT_OUTCHARS(1);
      }
      SP->_curscol += chlen;
      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 defined(__BEOS__)
  	/*
  	 * BeOS's select() is declared in socket.h, so the configure script does
  	 * not see it.  That's just as well, since that function works only for
  	 * sockets.  This (using snooze and ioctl) was distilled from Be's patch
  	 * for ncurses which uses a separate thread to simulate select().
  	 *
  	 * FIXME: the return values from the ioctl aren't very clear if we get
  	 * interrupted.
  	 */
  	int n = 0;
  	int howmany = ioctl(0, 'ichr', &n);
  	if (howmany >= 0 && n > 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;
  	_nc_flush();
      }
      return FALSE;
  }
  
  /* put char at lower right corner */
  static void
  PutCharLR(const ARG_CH_T 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);
  	SP->_curscol--;
  	position_check(SP->_cursrow, SP->_curscol, "exit_am_mode");
  
  	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);
  	PutAttrChar(ch);
  	GoTo(screen_lines - 1, screen_columns - 2);
  	InsStr(newscr->_line[screen_lines - 1].text + screen_columns - 2, 1);
      }
  }
  
  /*
   * Wrap the cursor position, i.e., advance to the beginning of the next line.
   */
  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++;
  	/*
  	 * We've actually moved - but may have to work around problems with
  	 * video attributes not working.
  	 */
  	if (!move_standout_mode && AttrOf(SCREEN_ATTRS(SP))) {
  	    TR(TRACE_CHARPUT, ("turning off (%#lx) %s before wrapping",
  			       (unsigned long) AttrOf(SCREEN_ATTRS(SP)),
  			       _traceattr(AttrOf(SCREEN_ATTRS(SP)))));
  	    (void) VIDATTR(A_NORMAL, 0);
  	}
      } else {
  	SP->_curscol--;
      }
      position_check(SP->_cursrow, SP->_curscol, "wrap_cursor");
  }
  
  static NCURSES_INLINE void
  PutChar(const ARG_CH_T 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();
  
      position_check(SP->_cursrow, SP->_curscol, "PutChar");
  }
  
  /*
   * Check whether the given character can be output by clearing commands.  This
   * includes test for being a space and not including any 'bad' attributes, such
   * as A_REVERSE.  All attribute flags which don't affect appearance of a space
   * or can be output by clearing (A_COLOR in case of bce-terminal) are excluded.
   */
  static NCURSES_INLINE bool
  can_clear_with(ARG_CH_T ch)
  {
      if (!back_color_erase && SP->_coloron) {
  #if NCURSES_EXT_FUNCS
  	int pair;
  
  	if (!SP->_default_color)
  	    return FALSE;
  	if (SP->_default_fg != C_MASK || SP->_default_bg != C_MASK)
  	    return FALSE;
  	if ((pair = GetPair(CHDEREF(ch))) != 0) {
  	    short fg, bg;
  	    pair_content(pair, &fg, &bg);
  	    if (fg != C_MASK || bg != C_MASK)
  		return FALSE;
  	}
  #else
  	if (AttrOfD(ch) & A_COLOR)
  	    return FALSE;
  #endif
      }
      return (ISBLANK(CHDEREF(ch)) &&
  	    (AttrOfD(ch) & ~(NONBLANK_ATTR | A_COLOR)) == BLANK_ATTR);
  }
  
  /*
   * 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 NCURSES_CH_T * ntext, int num)
  {
      int i;
  
      TR(TRACE_CHARPUT, ("EmitRange %d:%s", num, _nc_viscbuf(ntext, num)));
  
      if (erase_chars || repeat_char) {
  	while (num > 0) {
  	    int runcount;
  	    NCURSES_CH_T ntext0;
  
  	    while (num > 1 && !CharEq(ntext[0], ntext[1])) {
  		PutChar(CHREF(ntext[0]));
  		ntext++;
  		num--;
  	    }
  	    ntext0 = ntext[0];
  	    if (num == 1) {
  		PutChar(CHREF(ntext0));
  		return 0;
  	    }
  	    runcount = 2;
  
  	    while (runcount < num && CharEq(ntext[runcount], ntext0))
  		runcount++;
  
  	    /*
  	     * The cost expression in the middle isn't exactly right.
  	     * _cup_ch_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_ch_cost
  		&& can_clear_with(CHREF(ntext0))) {
  		UpdateAttrs(ntext0);
  		putp(TPARM_1(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);
  		tputs(TPARM_2(repeat_char, CharOf(ntext0), rep_count),
  		      rep_count, _nc_outch);
  		SP->_curscol += rep_count;
  
  		if (wrap_possible)
  		    PutChar(CHREF(ntext0));
  	    } else {
  		for (i = 0; i < runcount; i++)
  		    PutChar(CHREF(ntext[i]));
  	    }
  	    ntext += runcount;
  	    num -= runcount;
  	}
  	return 0;
      }
  
      for (i = 0; i < num; i++)
  	PutChar(CHREF(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 NCURSES_CH_T * otext,
  	 const NCURSES_CH_T * ntext,
  	 int row,
  	 int first, int last)
  {
      int i, j, same;
  
      TR(TRACE_CHARPUT, ("PutRange(%p, %p, %d, %d, %d)",
  		       otext, ntext, row, first, last));
  
      if (otext != ntext
  	&& (last - first + 1) > SP->_inline_cost) {
  	for (j = first, same = 0; j <= last; j++) {
  	    if (!same && isWidecExt(otext[j]))
  		continue;
  	    if (CharEq(otext[j], ntext[j])) {
  		same++;
  	    } else {
  		if (same > SP->_inline_cost) {
  		    EmitRange(ntext + first, j - same - first);
  		    GoTo(row, first = j);
  		}
  		same = 0;
  	    }
  	}
  	i = EmitRange(ntext + first, j - same - first);
  	/*
  	 * Always return 1 for the next GoTo() after a PutRange() if we found
  	 * identical characters at end of interval
  	 */
  	return (same == 0 ? i : 1);
      }
      return EmitRange(ntext + first, last - first + 1);
  }
  
  /* leave unbracketed here so 'indent' works */
  #define MARK_NOCHANGE(win,row) \
  		win->_line[row].firstchar = _NOCHANGE; \
  		win->_line[row].lastchar = _NOCHANGE; \
  		if_USE_SCROLL_HINTS(win->_line[row].oldindex = row)
  
  NCURSES_EXPORT(int)
  NCURSES_SP_NAME(doupdate) (NCURSES_SP_DCL0)
  {
      int i;
      int nonempty;
  #if USE_TRACE_TIMES
      struct tms before, after;
  #endif /* USE_TRACE_TIMES */
  
      T((T_CALLED("doupdate()")));
  
      if (curscr == 0
  	|| newscr == 0)
  	returnCode(ERR);
  
  #ifdef TRACE
      if (USE_TRACEF(TRACE_UPDATE)) {
  	if (curscr->_clear)
  	    _tracef("curscr is clear");
  	else
  	    _tracedump("curscr", curscr);
  	_tracedump("newscr", newscr);
  	_nc_unlock_global(tracef);
      }
  #endif /* TRACE */
  
      _nc_signal_handler(FALSE);
  
      if (SP_PARM->_fifohold)
  	SP_PARM->_fifohold--;
  
  #if USE_SIZECHANGE
      if (SP_PARM->_endwin || _nc_handle_sigwinch(SP_PARM)) {
  	/*
  	 * 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(SP_PARM);
      }
  #endif
  
      if (SP_PARM->_endwin) {
  
  	T(("coming back from shell mode"));
  	reset_prog_mode();
  
  	_nc_mvcur_resume();
  	_nc_screen_resume();
  	SP_PARM->_mouse_resume(SP_PARM);
  
  	SP_PARM->_endwin = FALSE;
      }
  #if USE_TRACE_TIMES
      /* zero the metering machinery */
      RESET_OUTCHARS();
      (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;
  		NCURSES_CH_T *thisline = newscr->_line[i].text;
  		attr_t thisattr = AttrOf(thisline[j]) & SP_PARM->_xmc_triggers;
  		attr_t turnon = thisattr & ~rattr;
  
  		/* is an attribute turned on here? */
  		if (turnon == 0) {
  		    rattr = thisattr;
  		    continue;
  		}
  
  		TR(TRACE_ATTRS, ("At (%d, %d): from %s...", i, j, _traceattr(rattr)));
  		TR(TRACE_ATTRS, ("...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) & SP_PARM->_xmc_triggers))
  		if (ISBLANK(thisline[j]) && SAFE(turnon)) {
  		    RemAttr(thisline[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
  			|| !ISBLANK(thisline[j - k])
  			|| !SAFE(AttrOf(thisline[j - k]))) {
  			failed = TRUE;
  			TR(TRACE_ATTRS, ("No room at start in %d,%d%s%s",
  					 i, j - k,
  					 (ISBLANK(thisline[j - k])
  					  ? ""
  					  : ":nonblank"),
  					 (SAFE(AttrOf(thisline[j - k]))
  					  ? ""
  					  : ":unsafe")));
  			break;
  		    }
  		}
  		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++) {
  			    attr_t testattr = AttrOf(newscr->_line[m].text[n]);
  			    if ((testattr & SP_PARM->_xmc_triggers) == rattr) {
  				end_onscreen = TRUE;
  				TR(TRACE_ATTRS,
  				   ("Range attributed with %s ends at (%d, %d)",
  				    _traceattr(turnon), m, n));
  				goto foundit;
  			    }
  			}
  			n = 0;
  		    }
  		    TR(TRACE_ATTRS,
  		       ("Range attributed with %s ends offscreen",
  			_traceattr(turnon)));
  		  foundit:;
  
  		    if (end_onscreen) {
  			NCURSES_CH_T *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
  			       && ISBLANK(lastline[n])
  			       && SAFE(AttrOf(lastline[n]))) {
  			    RemAttr(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
  				|| !ISBLANK(lastline[n + k])
  				|| !SAFE(AttrOf(lastline[n + k]))) {
  				failed = TRUE;
  				TR(TRACE_ATTRS,
  				   ("No room at end in %d,%d%s%s",
  				    i, j - k,
  				    (ISBLANK(lastline[n + k])
  				     ? ""
  				     : ":nonblank"),
  				    (SAFE(AttrOf(lastline[n + k]))
  				     ? ""
  				     : ":unsafe")));
  				break;
  			    }
  			}
  		    }
  		}
  
  		if (failed) {
  		    int p, q = j;
  
  		    TR(TRACE_ATTRS,
  		       ("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++) {
  			    attr_t testattr = AttrOf(newscr->_line[p].text[q]);
  			    if ((testattr & SP_PARM->_xmc_triggers) == rattr)
  				goto foundend;
  			    RemAttr(newscr->_line[p].text[q], turnon);
  			}
  			q = 0;
  		    }
  		  foundend:;
  		} else {
  		    TR(TRACE_ATTRS,
  		       ("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++)
  			AddAttr(thisline[j - k], turnon);
  		}
  
  		rattr = thisattr;
  	    }
  	}
  
  #ifdef TRACE
  	/* show altered highlights after magic-cookie check */
  	if (USE_TRACEF(TRACE_UPDATE)) {
  	    _tracef("After magic-cookie check...");
  	    _tracedump("newscr", newscr);
  	    _nc_unlock_global(tracef);
  	}
  #endif /* TRACE */
      }
  #endif /* USE_XMC_SUPPORT */
  
      nonempty = 0;
      if (curscr->_clear || newscr->_clear) {	/* force refresh ? */
  	ClrUpdate();
  	curscr->_clear = FALSE;	/* reset flag */
  	newscr->_clear = FALSE;	/* reset flag */
      } else {
  	int changedlines = CHECK_INTERVAL;
  
  	if (check_pending())
  	    goto cleanup;
  
  	nonempty = min(screen_lines, newscr->_maxy + 1);
  
  	if (SP_PARM->_scrolling) {
  	    _nc_scroll_optimize();
  	}
  
  	nonempty = ClrBottom(nonempty);
  
  	TR(TRACE_UPDATE, ("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);
      }
  
      if (!newscr->_leaveok) {
  	curscr->_curx = newscr->_curx;
  	curscr->_cury = newscr->_cury;
  
  	GoTo(curscr->_cury, curscr->_curx);
      }
  
    cleanup:
      /*
       * We would like to keep the physical screen in normal mode in case we get
       * other processes writing to the screen.  This goal cannot be met for
       * magic cookies since it interferes with attributes that may propagate
       * past the current position.
       */
  #if USE_XMC_SUPPORT
      if (magic_cookie_glitch != 0)
  #endif
  	UpdateAttrs(normal);
  
      _nc_flush();
      WINDOW_ATTRS(curscr) = WINDOW_ATTRS(newscr);
  
  #if USE_TRACE_TIMES
      (void) times(&after);
      TR(TRACE_TIMES,
         ("Update cost: %ld chars, %ld clocks system time, %ld clocks user time",
  	_nc_outchars,
  	(long) (after.tms_stime - before.tms_stime),
  	(long) (after.tms_utime - before.tms_utime)));
  #endif /* USE_TRACE_TIMES */
  
      _nc_signal_handler(TRUE);
  
      returnCode(OK);
  }
  
  #if NCURSES_SP_FUNCS
  NCURSES_EXPORT(int)
  doupdate(void)
  {
      return NCURSES_SP_NAME(doupdate) (CURRENT_SCREEN);
  }
  #endif
  
  /*
   *	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))->_nc_bkgd)
  
  static NCURSES_INLINE NCURSES_CH_T
  ClrBlank(WINDOW *win)
  {
      NCURSES_CH_T blank = blankchar;
      if (back_color_erase)
  	AddAttr(blank, (AttrOf(BCE_BKGD(win)) & BCE_ATTRS));
      return blank;
  }
  
  /*
  **	ClrUpdate()
  **
  **	Update by clearing and redrawing the entire screen.
  **
  */
  
  static void
  ClrUpdate(void)
  {
      int i;
      NCURSES_CH_T blank = ClrBlank(stdscr);
      int nonempty = min(screen_lines, newscr->_maxy + 1);
  
      TR(TRACE_UPDATE, (T_CALLED("ClrUpdate")));
  
      ClearScreen(blank);
  
      TR(TRACE_UPDATE, ("updating screen from scratch"));
  
      nonempty = ClrBottom(nonempty);
  
      for (i = 0; i < nonempty; i++)
  	TransformLine(i);
  
      TR(TRACE_UPDATE, (T_RETURN("")));
  }
  
  /*
  **	ClrToEOL(blank)
  **
  **	Clear to end of current line, starting at the cursor position
  */
  
  static void
  ClrToEOL(NCURSES_CH_T blank, bool needclear)
  {
      int j;
  
      if (curscr != 0
  	&& SP->_cursrow >= 0) {
  	for (j = SP->_curscol; j < screen_columns; j++) {
  	    if (j >= 0) {
  		NCURSES_CH_T *cp = &(curscr->_line[SP->_cursrow].text[j]);
  
  		if (!CharEq(*cp, blank)) {
  		    *cp = blank;
  		    needclear = TRUE;
  		}
  	    }
  	}
      } else {
  	needclear = TRUE;
      }
  
      if (needclear) {
  	UpdateAttrs(blank);
  	TPUTS_TRACE("clr_eol");
  	if (clr_eol && SP->_el_cost <= (screen_columns - SP->_curscol)) {
  	    putp(clr_eol);
  	} else {
  	    int count = (screen_columns - SP->_curscol);
  	    while (count-- > 0)
  		PutChar(CHREF(blank));
  	}
      }
  }
  
  /*
  **	ClrToEOS(blank)
  **
  **	Clear to end of screen, starting at the cursor position
  */
  
  static void
  ClrToEOS(NCURSES_CH_T blank)
  {
      int row, col;
  
      row = SP->_cursrow;
      col = SP->_curscol;
  
      UpdateAttrs(blank);
      TPUTS_TRACE("clr_eos");
      tputs(clr_eos, screen_lines - row, _nc_outch);
  
      while (col < screen_columns)
  	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)
  {
      int row;
      int col;
      int top = total;
      int last = min(screen_columns, newscr->_maxx + 1);
      NCURSES_CH_T blank = newscr->_line[total - 1].text[last - 1];
      bool ok;
  
      if (clr_eos && can_clear_with(CHREF(blank))) {
  
  	for (row = total - 1; row >= 0; row--) {
  	    for (col = 0, ok = TRUE; ok && col < last; col++) {
  		ok = (CharEq(newscr->_line[row].text[col], blank));
  	    }
  	    if (!ok)
  		break;
  
  	    for (col = 0; ok && col < last; col++) {
  		ok = (CharEq(curscr->_line[row].text[col], blank));
  	    }
  	    if (!ok)
  		top = row;
  	}
  
  	/* don't use clr_eos for just one line if clr_eol available */
  	if (top < total) {
  	    GoTo(top, 0);
  	    ClrToEOS(blank);
  	    if (SP->oldhash && SP->newhash) {
  		for (row = top; row < screen_lines; row++)
  		    SP->oldhash[row] = SP->newhash[row];
  	    }
  	}
      }
      return top;
  }
  
  #if USE_XMC_SUPPORT
  #if USE_WIDEC_SUPPORT
  #define check_xmc_transition(a, b) \
      ((((a)->attr ^ (b)->attr) & ~((a)->attr) & SP->_xmc_triggers) != 0)
  #define xmc_turn_on(a,b) check_xmc_transition(&(a), &(b))
  #else
  #define xmc_turn_on(a,b) ((((a)^(b)) & ~(a) & SP->_xmc_triggers) != 0)
  #endif
  
  #define xmc_new(r,c) newscr->_line[r].text[c]
  #define xmc_turn_off(a,b) xmc_turn_on(b,a)
  #endif /* USE_XMC_SUPPORT */
  
  /*
  **	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;
      NCURSES_CH_T *newLine = newscr->_line[lineno].text;
      NCURSES_CH_T *oldLine = curscr->_line[lineno].text;
      int n;
      bool attrchanged = FALSE;
  
      TR(TRACE_UPDATE, (T_CALLED("TransformLine(%d)"), lineno));
  
      /* copy new hash value to old one */
      if (SP->oldhash && SP->newhash)
  	SP->oldhash[lineno] = SP->newhash[lineno];
  
      /*
       * If we have colors, there is the possibility of having two color pairs
       * that display as the same colors.  For instance, Lynx does this.  Check
       * for this case, and update the old line with the new line's colors when
       * they are equivalent.
       */
      if (SP->_coloron) {
  	int oldPair;
  	int newPair;
  
  	for (n = 0; n < screen_columns; n++) {
  	    if (!CharEq(newLine[n], oldLine[n])) {
  		oldPair = GetPair(oldLine[n]);
  		newPair = GetPair(newLine[n]);
  		if (oldPair != newPair
  		    && unColor(oldLine[n]) == unColor(newLine[n])) {
  		    if (oldPair < SP->_pair_limit
  			&& newPair < SP->_pair_limit
  			&& SP->_color_pairs[oldPair] == SP->_color_pairs[newPair]) {
  			SetPair(oldLine[n], GetPair(newLine[n]));
  		    }
  		}
  	    }
  	}
      }
  
      if (ceol_standout_glitch && clr_eol) {
  	firstChar = 0;
  	while (firstChar < screen_columns) {
  	    if (!SameAttrOf(newLine[firstChar], oldLine[firstChar])) {
  		attrchanged = TRUE;
  		break;
  	    }
  	    firstChar++;
  	}
      }
  
      firstChar = 0;
  
      if (attrchanged) {		/* we may have to disregard the whole line */
  	GoTo(lineno, firstChar);
  	ClrToEOL(ClrBlank(curscr), FALSE);
  	PutRange(oldLine, newLine, lineno, 0, (screen_columns - 1));
  #if USE_XMC_SUPPORT
  
  	/*
  	 * 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 (ISBLANK(newLine[n])
  		&& ((n > 0
  		     && xmc_turn_on(newLine[n - 1], newLine[n]))
  		    || (n == 0
  			&& lineno > 0
  			&& xmc_turn_on(xmc_new(lineno - 1, screen_columns - 1),
  				       newLine[n])))) {
  		n = m;
  	    }
  
  	    PutChar(CHREF(newLine[n]));
  
  	    /* check for turn-off:
  	     * If we are writing an attributed non-blank, where the
  	     * next cell is blank, and not attributed.
  	     */
  	    if (!ISBLANK(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], xmc_new(lineno + 1, 0))))) {
  		n = m;
  	    }
  
  	}
  #endif
      } else {
  	NCURSES_CH_T blank;
  
  	/* it may be cheap to clear leading whitespace with clr_bol */
  	blank = newLine[0];
  	if (clr_bol && can_clear_with(CHREF(blank))) {
  	    int oFirstChar, nFirstChar;
  
  	    for (oFirstChar = 0; oFirstChar < screen_columns; oFirstChar++)
  		if (!CharEq(oldLine[oFirstChar], blank))
  		    break;
  	    for (nFirstChar = 0; nFirstChar < screen_columns; nFirstChar++)
  		if (!CharEq(newLine[nFirstChar], blank))
  		    break;
  
  	    if (nFirstChar == oFirstChar) {
  		firstChar = nFirstChar;
  		/* find the first differing character */
  		while (firstChar < screen_columns
  		       && CharEq(newLine[firstChar], oldLine[firstChar]))
  		    firstChar++;
  	    } else if (oFirstChar > nFirstChar) {
  		firstChar = nFirstChar;
  	    } else {		/* oFirstChar < nFirstChar */
  		firstChar = oFirstChar;
  		if (SP->_el1_cost < nFirstChar - oFirstChar) {
  		    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;
  		}
  	    }
  	} else {
  	    /* find the first differing character */
  	    while (firstChar < screen_columns
  		   && CharEq(newLine[firstChar], oldLine[firstChar]))
  		firstChar++;
  	}
  	/* if there wasn't one, we're done */
  	if (firstChar >= screen_columns) {
  	    TR(TRACE_UPDATE, (T_RETURN("")));
  	    return;
  	}
  
  	blank = newLine[screen_columns - 1];
  
  	if (!can_clear_with(CHREF(blank))) {
  	    /* find the last differing character */
  	    nLastChar = screen_columns - 1;
  
  	    while (nLastChar > firstChar
  		   && CharEq(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(NCURSES_CH_T));
  	    }
  	    TR(TRACE_UPDATE, (T_RETURN("")));
  	    return;
  	}
  
  	/* find last non-blank character on old line */
  	oLastChar = screen_columns - 1;
  	while (oLastChar > firstChar && CharEq(oldLine[oLastChar], blank))
  	    oLastChar--;
  
  	/* find last non-blank character on new line */
  	nLastChar = screen_columns - 1;
  	while (nLastChar > firstChar && CharEq(newLine[nLastChar], blank))
  	    nLastChar--;
  
  	if ((nLastChar == firstChar)
  	    && (SP->_el_cost < (oLastChar - nLastChar))) {
  	    GoTo(lineno, firstChar);
  	    if (!CharEq(newLine[firstChar], blank))
  		PutChar(CHREF(newLine[firstChar]));
  	    ClrToEOL(blank, FALSE);
  	} else if ((nLastChar != oLastChar)
  		   && (!CharEq(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, FALSE);
  	    } 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 */
  	    /* can be -1 if no characters differ */
  	    while (CharEq(newLine[nLastChar], oldLine[oLastChar])) {
  		/* don't split a wide char */
  		if (isWidecExt(newLine[nLastChar]) &&
  		    !CharEq(newLine[nLastChar - 1], oldLine[oLastChar - 1]))
  		    break;
  		nLastChar--;
  		oLastChar--;
  		if (nLastChar == -1 || oLastChar == -1)
  		    break;
  	    }
  
  	    n = min(oLastChar, nLastChar);
  	    if (n >= firstChar) {
  		GoTo(lineno, firstChar);
  		PutRange(oldLine, newLine, lineno, firstChar, n);
  	    }
  
  	    if (oLastChar < nLastChar) {
  		int m = max(nLastNonblank, oLastNonblank);
  #if USE_WIDEC_SUPPORT
  		while (isWidecExt(newLine[n + 1]) && n) {
  		    --n;
  		    --oLastChar;
  		}
  #endif
  		GoTo(lineno, n + 1);
  		if ((nLastChar < nLastNonblank)
  		    || InsCharCost(nLastChar - oLastChar) > (m - n)) {
  		    PutRange(oldLine, newLine, lineno, n + 1, m);
  		} else {
  		    InsStr(&newLine[n + 1], nLastChar - oLastChar);
  		}
  	    } else if (oLastChar > nLastChar) {
  		GoTo(lineno, n + 1);
  		if (DelCharCost(oLastChar - nLastChar)
  		    > SP->_el_cost + nLastNonblank - (n + 1)) {
  		    if (PutRange(oldLine, newLine, lineno,
  				 n + 1, nLastNonblank))
  			GoTo(lineno, nLastNonblank + 1);
  		    ClrToEOL(blank, FALSE);
  		} 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(NCURSES_CH_T));
      TR(TRACE_UPDATE, (T_RETURN("")));
      return;
  }
  
  /*
  **	ClearScreen(blank)
  **
  **	Clear the physical screen and put cursor at home
  **
  */
  
  static void
  ClearScreen(NCURSES_CH_T blank)
  {
      int i, j;
      bool fast_clear = (clear_screen || clr_eos || clr_eol);
  
      TR(TRACE_UPDATE, ("ClearScreen() called"));
  
  #if NCURSES_EXT_FUNCS
      if (SP->_coloron
  	&& !SP->_default_color) {
  	_nc_do_color(GET_SCREEN_PAIR(SP), 0, FALSE, _nc_outch);
  	if (!back_color_erase) {
  	    fast_clear = FALSE;
  	}
      }
  #endif
  
      if (fast_clear) {
  	if (clear_screen) {
  	    UpdateAttrs(blank);
  	    TPUTS_TRACE("clear_screen");
  	    putp(clear_screen);
  	    SP->_cursrow = SP->_curscol = 0;
  	    position_check(SP->_cursrow, SP->_curscol, "ClearScreen");
  	} else if (clr_eos) {
  	    SP->_cursrow = SP->_curscol = -1;
  	    GoTo(0, 0);
  
  	    UpdateAttrs(blank);
  	    TPUTS_TRACE("clr_eos");
  	    tputs(clr_eos, screen_lines, _nc_outch);
  	} else if (clr_eol) {
  	    SP->_cursrow = SP->_curscol = -1;
  
  	    UpdateAttrs(blank);
  	    for (i = 0; i < screen_lines; i++) {
  		GoTo(i, 0);
  		TPUTS_TRACE("clr_eol");
  		putp(clr_eol);
  	    }
  	    GoTo(0, 0);
  	}
      } else {
  	UpdateAttrs(blank);
  	for (i = 0; i < screen_lines; i++) {
  	    GoTo(i, 0);
  	    for (j = 0; j < screen_columns; j++)
  		PutChar(CHREF(blank));
  	}
  	GoTo(0, 0);
      }
  
      for (i = 0; i < screen_lines; i++) {
  	for (j = 0; j < screen_columns; j++)
  	    curscr->_line[i].text[j] = blank;
      }
  
      TR(TRACE_UPDATE, ("screen cleared"));
  }
  
  /*
  **	InsStr(line, count)
  **
  **	Insert the count characters pointed to by line.
  **
  */
  
  static void
  InsStr(NCURSES_CH_T * line, int count)
  {
      TR(TRACE_UPDATE, ("InsStr(%p,%d) called", line, count));
  
      /* Prefer parm_ich as it has the smallest cost - no need to shift
       * the whole line on each character. */
      /* The order must match that of InsCharCost. */
      if (parm_ich) {
  	TPUTS_TRACE("parm_ich");
  	tputs(TPARM_1(parm_ich, count), count, _nc_outch);
  	while (count) {
  	    PutAttrChar(CHREF(*line));
  	    line++;
  	    count--;
  	}
      } else if (enter_insert_mode && exit_insert_mode) {
  	TPUTS_TRACE("enter_insert_mode");
  	putp(enter_insert_mode);
  	while (count) {
  	    PutAttrChar(CHREF(*line));
  	    if (insert_padding) {
  		TPUTS_TRACE("insert_padding");
  		putp(insert_padding);
  	    }
  	    line++;
  	    count--;
  	}
  	TPUTS_TRACE("exit_insert_mode");
  	putp(exit_insert_mode);
      } else {
  	while (count) {
  	    TPUTS_TRACE("insert_character");
  	    putp(insert_character);
  	    PutAttrChar(CHREF(*line));
  	    if (insert_padding) {
  		TPUTS_TRACE("insert_padding");
  		putp(insert_padding);
  	    }
  	    line++;
  	    count--;
  	}
      }
      position_check(SP->_cursrow, SP->_curscol, "InsStr");
  }
  
  /*
  **	DelChar(count)
  **
  **	Delete count characters at current position
  **
  */
  
  static void
  DelChar(int count)
  {
      int n;
  
      TR(TRACE_UPDATE, ("DelChar(%d) called, position = (%ld,%ld)",
  		      count,
  		      (long) newscr->_cury,
  		      (long) newscr->_curx));
  
      if (parm_dch) {
  	TPUTS_TRACE("parm_dch");
  	tputs(TPARM_1(parm_dch, count), count, _nc_outch);
      } else {
  	for (n = 0; n < count; n++) {
  	    TPUTS_TRACE("delete_character");
  	    putp(delete_character);
  	}
      }
  }
  
  /*
   * 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, NCURSES_CH_T blank)
  {
      int i;
  
      if (n == 1 && scroll_forward && top == miny && bot == maxy) {
  	GoTo(bot, 0);
  	UpdateAttrs(blank);
  	TPUTS_TRACE("scroll_forward");
  	putp(scroll_forward);
      } else if (n == 1 && delete_line && bot == maxy) {
  	GoTo(top, 0);
  	UpdateAttrs(blank);
  	TPUTS_TRACE("delete_line");
  	putp(delete_line);
      } else if (parm_index && top == miny && bot == maxy) {
  	GoTo(bot, 0);
  	UpdateAttrs(blank);
  	TPUTS_TRACE("parm_index");
  	tputs(TPARM_2(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_2(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");
  	    putp(scroll_forward);
  	}
      } else if (delete_line && bot == maxy) {
  	GoTo(top, 0);
  	UpdateAttrs(blank);
  	for (i = 0; i < n; i++) {
  	    TPUTS_TRACE("delete_line");
  	    putp(delete_line);
  	}
      } else
  	return ERR;
  
  #if NCURSES_EXT_FUNCS
      if (FILL_BCE()) {
  	int j;
  	for (i = 0; i < n; i++) {
  	    GoTo(bot - i, 0);
  	    for (j = 0; j < screen_columns; j++)
  		PutChar(CHREF(blank));
  	}
      }
  #endif
      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,
  		    NCURSES_CH_T blank)
  {
      int i;
  
      if (n == 1 && scroll_reverse && top == miny && bot == maxy) {
  	GoTo(top, 0);
  	UpdateAttrs(blank);
  	TPUTS_TRACE("scroll_reverse");
  	putp(scroll_reverse);
      } else if (n == 1 && insert_line && bot == maxy) {
  	GoTo(top, 0);
  	UpdateAttrs(blank);
  	TPUTS_TRACE("insert_line");
  	putp(insert_line);
      } else if (parm_rindex && top == miny && bot == maxy) {
  	GoTo(top, 0);
  	UpdateAttrs(blank);
  	TPUTS_TRACE("parm_rindex");
  	tputs(TPARM_2(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_2(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");
  	    putp(scroll_reverse);
  	}
      } else if (insert_line && bot == maxy) {
  	GoTo(top, 0);
  	UpdateAttrs(blank);
  	for (i = 0; i < n; i++) {
  	    TPUTS_TRACE("insert_line");
  	    putp(insert_line);
  	}
      } else
  	return ERR;
  
  #if NCURSES_EXT_FUNCS
      if (FILL_BCE()) {
  	int j;
  	for (i = 0; i < n; i++) {
  	    GoTo(top + i, 0);
  	    for (j = 0; j < screen_columns; j++)
  		PutChar(CHREF(blank));
  	}
      }
  #endif
      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, NCURSES_CH_T 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");
  	putp(delete_line);
      } else if (parm_delete_line) {
  	TPUTS_TRACE("parm_delete_line");
  	tputs(TPARM_2(parm_delete_line, n, 0), n, _nc_outch);
      } else {			/* if (delete_line) */
  	for (i = 0; i < n; i++) {
  	    TPUTS_TRACE("delete_line");
  	    putp(delete_line);
  	}
      }
  
      GoTo(ins, 0);
      UpdateAttrs(blank);
      if (n == 1 && insert_line) {
  	TPUTS_TRACE("insert_line");
  	putp(insert_line);
      } else if (parm_insert_line) {
  	TPUTS_TRACE("parm_insert_line");
  	tputs(TPARM_2(parm_insert_line, n, 0), n, _nc_outch);
      } else {			/* if (insert_line) */
  	for (i = 0; i < n; i++) {
  	    TPUTS_TRACE("insert_line");
  	    putp(insert_line);
  	}
      }
  
      return OK;
  }
  
  /*
   * Note:  some terminals require the cursor to be within the scrolling margins
   * before setting them.  Generally, the cursor must be at the appropriate end
   * of the scrolling margins when issuing an indexing operation (it is not
   * apparent whether it must also be at the left margin; we do this just to be
   * safe).  To make the related cursor movement a little faster, we use the
   * save/restore cursor capabilities if the terminal has them.
   */
  NCURSES_EXPORT(int)
  _nc_scrolln(int n, int top, int bot, int maxy)
  /* scroll region from top to bot by n lines */
  {
      NCURSES_CH_T 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.
  	 */
  	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");
  		putp(save_cursor);
  	    }
  	    TPUTS_TRACE("change_scroll_region");
  	    putp(TPARM_2(change_scroll_region, top, bot));
  	    if (cursor_saved) {
  		TPUTS_TRACE("restore_cursor");
  		putp(restore_cursor);
  	    } else {
  		SP->_cursrow = SP->_curscol = -1;
  	    }
  
  	    res = scroll_csr_forward(n, top, bot, top, bot, blank);
  
  	    TPUTS_TRACE("change_scroll_region");
  	    putp(TPARM_2(change_scroll_region, 0, maxy));
  	    SP->_cursrow = SP->_curscol = -1;
  	}
  
  	if (res == ERR && _nc_idlok)
  	    res = scroll_idl(n, top, bot - n + 1, blank);
  
  	/*
  	 * Clear the newly shifted-in text.
  	 */
  	if (res != ERR
  	    && (non_dest_scroll_region || (memory_below && bot == maxy))) {
  	    static const NCURSES_CH_T blank2 = NewChar(BLANK_TEXT);
  	    if (bot == maxy && clr_eos) {
  		GoTo(bot - n + 1, 0);
  		ClrToEOS(blank2);
  	    } else {
  		for (i = 0; i < n; i++) {
  		    GoTo(bot - i, 0);
  		    ClrToEOL(blank2, FALSE);
  		}
  	    }
  	}
  
      } else {			/* (n < 0) - scroll down (backward) */
  	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");
  		putp(save_cursor);
  	    }
  	    TPUTS_TRACE("change_scroll_region");
  	    putp(TPARM_2(change_scroll_region, top, bot));
  	    if (cursor_saved) {
  		TPUTS_TRACE("restore_cursor");
  		putp(restore_cursor);
  	    } else {
  		SP->_cursrow = SP->_curscol = -1;
  	    }
  
  	    res = scroll_csr_backward(-n, top, bot, top, bot, blank);
  
  	    TPUTS_TRACE("change_scroll_region");
  	    putp(TPARM_2(change_scroll_region, 0, maxy));
  	    SP->_cursrow = SP->_curscol = -1;
  	}
  
  	if (res == ERR && _nc_idlok)
  	    res = scroll_idl(-n, bot + n + 1, top, blank);
  
  	/*
  	 * Clear the newly shifted-in text.
  	 */
  	if (res != ERR
  	    && (non_dest_scroll_region || (memory_above && top == 0))) {
  	    static const NCURSES_CH_T blank2 = NewChar(BLANK_TEXT);
  	    for (i = 0; i < -n; i++) {
  		GoTo(i + top, 0);
  		ClrToEOL(blank2, FALSE);
  	    }
  	}
      }
  
      if (res == ERR)
  	return (ERR);
  
      _nc_scroll_window(curscr, n, top, bot, blank);
  
      /* shift hash values too - they can be reused */
      _nc_scroll_oldhash(n, top, bot);
  
      return (OK);
  }
  
  NCURSES_EXPORT(void)
  _nc_screen_resume(void)
  {
      /* make sure terminal is in a sane known state */
      SetAttr(SCREEN_ATTRS(SP), A_NORMAL);
      newscr->_clear = TRUE;
  
      /* reset color pairs and definitions */
      if (SP->_coloron || SP->_color_defs)
  	_nc_reset_colors();
  
      /* restore user-defined colors, if any */
      if (SP->_color_defs < 0) {
  	int n;
  	SP->_color_defs = -(SP->_color_defs);
  	for (n = 0; n < SP->_color_defs; ++n) {
  	    if (SP->_color_table[n].init) {
  		init_color(n,
  			   SP->_color_table[n].r,
  			   SP->_color_table[n].g,
  			   SP->_color_table[n].b);
  	    }
  	}
      }
  
      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);
  }
  
  NCURSES_EXPORT(void)
  _nc_screen_init(void)
  {
      _nc_screen_resume();
  }
  
  /* wrap up screen handling */
  NCURSES_EXPORT(void)
  _nc_screen_wrap(void)
  {
      UpdateAttrs(normal);
  #if NCURSES_EXT_FUNCS
      if (SP->_coloron
  	&& !SP->_default_color) {
  	static const NCURSES_CH_T blank = NewChar(BLANK_TEXT);
  	SP->_default_color = TRUE;
  	_nc_do_color(-1, 0, FALSE, _nc_outch);
  	SP->_default_color = FALSE;
  
  	mvcur(SP->_cursrow, SP->_curscol, screen_lines - 1, 0);
  
  	ClrToEOL(blank, TRUE);
      }
  #endif
      if (SP->_color_defs) {
  	_nc_reset_colors();
      }
  }
  
  #if USE_XMC_SUPPORT
  NCURSES_EXPORT(void)
  _nc_do_xmc_glitch(attr_t previous)
  {
      attr_t chg = XMC_CHANGES(previous ^ AttrOf(SCREEN_ATTRS(SP)));
  
      while (chg != 0) {
  	if (chg & 1) {
  	    SP->_curscol += magic_cookie_glitch;
  	    if (SP->_curscol >= SP->_columns)
  		wrap_cursor();
  	    TR(TRACE_UPDATE, ("bumped to %d,%d after cookie", SP->_cursrow, SP->_curscol));
  	}
  	chg >>= 1;
      }
  }
  #endif /* USE_XMC_SUPPORT */
  