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tty_update.c

/****************************************************************************
 * Copyright (c) 1998-2003,2004 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 1996-2004                                      *
 ****************************************************************************/

/*-----------------------------------------------------------------
 *
 *    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>

#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 1.205 2004/02/07 18:02:42 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)

/*
 * 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 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 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 inline void
PutAttrChar(CARG_CH_T ch)
{
    int chlen = 1;
    NCURSES_CH_T my_ch;
    PUTC_DATA;
    NCURSES_CH_T tilde;
    NCURSES_ATTR_T attr = AttrOfD(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 (isnac(CHDEREF(ch)))
      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 NCURSES_CH_T blank = NewChar(BLANK_TEXT);

      if (isprint(CharOf(CHDEREF(ch)))
          || (SP->_posix_locale && CharOf(CHDEREF(ch)) >= 160)) {
          ;
      } else {
          ch = CHREF(blank);
          TR(TRACE_CHARPUT, ("forced to blank"));
      }
      chlen = 1;
    }
#endif

    if ((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->_acs_map[CharOf(my_ch)] & A_ALTCHARSET) {
          attr &= ~(A_ALTCHARSET);
          my_ch = _nc_wacs[CharOf(my_ch)];
      }
#endif
      if (attr & A_ALTCHARSET) {
          chtype temp = UChar(SP->_acs_map[CharOfD(ch)]);
          if (temp != 0)
            SetChar(my_ch, temp, attr);
          RemAttr(my_ch, A_ALTCHARSET);
      }
      ch = CHREF(my_ch);
    }
    if (tilde_glitch && (CharOfD(ch) == L('~'))) {
      SetChar(tilde, L('`'), 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... */
      TRACE_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);
    }
}

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--;
    }
    position_check(SP->_cursrow, SP->_curscol, "wrap_cursor");
}

static 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 inline bool
can_clear_with(ARG_CH_T ch)
{
    if (!back_color_erase && SP->_coloron) {
#if NCURSES_EXT_FUNCS
      if (!SP->_default_color)
          return FALSE;
      if (SP->_default_fg != C_MASK || SP->_default_bg != C_MASK)
          return FALSE;
      if (AttrOfD(ch) & A_COLOR) {
          short fg, bg;
          pair_content(PAIR_NUMBER(AttrOfD(ch)), &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;

    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(AttrOf(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(AttrOf(ntext0));
            tputs(tparm(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 && isnac(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)
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;
            attr_t 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;
            }

            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) & (attr_t)~NONBLANK_ATTR))
            if (ISBLANK(newscr->_line[i].text[j]) && SAFE(turnon)) {
                RemAttr(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
                  || !ISBLANK(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;
                        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;
                }
            }

            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++) {
                      if (AttrOf(newscr->_line[p].text[q]) == 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(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 || newscr->_clear) {     /* force refresh ? */
      TR(TRACE_UPDATE, ("clearing and updating from scratch"));
      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->_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:
    /*
     * Keep the physical screen in normal mode in case we get other
     * processes writing to the screen.
     */
    UpdateAttrs(A_NORMAL);

    _nc_flush();
    curscr->_attrs = newscr->_attrs;

#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);
}

/*
 *    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 inline NCURSES_CH_T
ClrBlank(WINDOW *win)
{
    NCURSES_CH_T blank = NewChar(BLANK_TEXT);
    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, ("ClrUpdate() called"));

    ClearScreen(blank);

    TR(TRACE_UPDATE, ("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(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(AttrOf(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(AttrOf(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
static inline bool
check_xmc_transition(NCURSES_CH_T * a, NCURSES_CH_T * b)
{
    if (((a->attr ^ b->attr) & ~(a->attr) & SP->_xmc_triggers) != 0) {
      return TRUE;
    }
    return FALSE;
}
#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, ("TransformLine(%d) called", lineno));

    /* copy new hash value to old one */
    if (SP->oldhash && SP->newhash)
      SP->oldhash[lineno] = SP->newhash[lineno];

#define ColorOf(n) (AttrOf(n) & A_COLOR)
#define unColor(n) (AttrOf(n) & ALL_BUT_COLOR)
    /*
     * 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) {
      attr_t oldColor;
      attr_t newColor;
      int oldPair;
      int newPair;

      for (n = 0; n < screen_columns; n++) {
          if (!CharEq(newLine[n], oldLine[n])) {
            oldColor = ColorOf(oldLine[n]);
            newColor = ColorOf(newLine[n]);
            if (oldColor != newColor
                && unColor(oldLine[n]) == unColor(newLine[n])) {
                oldPair = PAIR_NUMBER(oldColor);
                newPair = PAIR_NUMBER(newColor);
                if (oldPair < COLOR_PAIRS
                  && newPair < COLOR_PAIRS
                  && SP->_color_pairs[oldPair] == SP->_color_pairs[newPair]) {
                  RemAttr(oldLine[n], A_COLOR);
                  AddAttr(oldLine[n], ColorOf(newLine[n]));
                }
            }
          }
      }
    }

    if (ceol_standout_glitch && clr_eol) {
      firstChar = 0;
      while (firstChar < screen_columns) {
          if (AttrOf(newLine[firstChar]) != AttrOf(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(AttrOf(blank));
                  TPUTS_TRACE("clr_eol");
                  putp(clr_eol);
                } else {
                  GoTo(lineno, nFirstChar - 1);
                  UpdateAttrs(AttrOf(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)
          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));
          }
          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 (isnac(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);
            GoTo(lineno, n + 1);
            if (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(AttrOf(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));
}

/*
**    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((int) COLOR_PAIR(SP->_current_attr), 0, FALSE, _nc_outch);
      if (!back_color_erase) {
          fast_clear = FALSE;
      }
    }
#endif

    if (fast_clear) {
      if (clear_screen) {
          UpdateAttrs(AttrOf(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(AttrOf(blank));
          TPUTS_TRACE("clr_eos");
          tputs(clr_eos, screen_lines, _nc_outch);
      } else if (clr_eol) {
          SP->_cursrow = SP->_curscol = -1;

          UpdateAttrs(AttrOf(blank));
          for (i = 0; i < screen_lines; i++) {
            GoTo(i, 0);
            TPUTS_TRACE("clr_eol");
            putp(clr_eol);
          }
          GoTo(0, 0);
      }
    } else {
      UpdateAttrs(AttrOf(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(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 = (%d,%d)", count,
                  newscr->_cury, newscr->_curx));

    if (parm_dch) {
      TPUTS_TRACE("parm_dch");
      tputs(tparm(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(AttrOf(blank));
      TPUTS_TRACE("scroll_forward");
      putp(scroll_forward);
    } else if (n == 1 && delete_line && bot == maxy) {
      GoTo(top, 0);
      UpdateAttrs(AttrOf(blank));
      TPUTS_TRACE("delete_line");
      putp(delete_line);
    } else if (parm_index && top == miny && bot == maxy) {
      GoTo(bot, 0);
      UpdateAttrs(AttrOf(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(AttrOf(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(AttrOf(blank));
      for (i = 0; i < n; i++) {
          TPUTS_TRACE("scroll_forward");
          putp(scroll_forward);
      }
    } else if (delete_line && bot == maxy) {
      GoTo(top, 0);
      UpdateAttrs(AttrOf(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(AttrOf(blank));
      TPUTS_TRACE("scroll_reverse");
      putp(scroll_reverse);
    } else if (n == 1 && insert_line && bot == maxy) {
      GoTo(top, 0);
      UpdateAttrs(AttrOf(blank));
      TPUTS_TRACE("insert_line");
      putp(insert_line);
    } else if (parm_rindex && top == miny && bot == maxy) {
      GoTo(top, 0);
      UpdateAttrs(AttrOf(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(AttrOf(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(AttrOf(blank));
      for (i = 0; i < n; i++) {
          TPUTS_TRACE("scroll_reverse");
          putp(scroll_reverse);
      }
    } else if (insert_line && bot == maxy) {
      GoTo(top, 0);
      UpdateAttrs(AttrOf(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(AttrOf(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(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(AttrOf(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(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(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(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))) {
          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(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(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))) {
          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 */
    SP->_current_attr = 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(A_NORMAL);
#if NCURSES_EXT_FUNCS
    if (SP->_coloron
      && !SP->_default_color) {
      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 ^ SP->_current_attr);

    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 */

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