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/****************************************************************************
 * Copyright (c) 1998,1999,2000,2001 Free Software Foundation, Inc.         *
 *                                                                          *
 * Permission is hereby granted, free of charge, to any person obtaining a  *
 * copy of this software and associated documentation files (the            *
 * "Software"), to deal in the Software without restriction, including      *
 * without limitation the rights to use, copy, modify, merge, publish,      *
 * distribute, distribute with modifications, sublicense, and/or sell       *
 * copies of the Software, and to permit persons to whom the Software is    *
 * furnished to do so, subject to the following conditions:                 *
 *                                                                          *
 * The above copyright notice and this permission notice shall be included  *
 * in all copies or substantial portions of the Software.                   *
 *                                                                          *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS  *
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF               *
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.   *
 * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,   *
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR    *
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR    *
 * THE USE OR OTHER DEALINGS IN THE SOFTWARE.                               *
 *                                                                          *
 * Except as contained in this notice, the name(s) of the above copyright   *
 * holders shall not be used in advertising or otherwise to promote the     *
 * sale, use or other dealings in this Software without prior written       *
 * authorization.                                                           *
 ****************************************************************************/

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

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

#ifdef __BEOS__
#include <OS.h>
#endif

#include <curses.priv.h>

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

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

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

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

#include <term.h>

MODULE_ID("$Id: tty_update.c,v 1.151 2001/02/03 23:41:55 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 chtype ClrBlank(WINDOW *win);
static int ClrBottom(int total);
static void ClearScreen(chtype blank);
static void ClrUpdate(void);
static void DelChar(int count);
static void InsStr(chtype * 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)
{
    chtype oldattr = SP->_current_attr;

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

    position_check(SP->_cursrow, SP->_curscol, "GoTo");

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

    mvcur(SP->_cursrow, SP->_curscol, row, col);
    SP->_cursrow = row;
    SP->_curscol = col;
    position_check(SP->_cursrow, SP->_curscol, "GoTo2");
}

static inline void
PutAttrChar(chtype ch)
{
    int data;

    if (tilde_glitch && (TextOf(ch) == '~'))
	ch = ('`' | AttrOf(ch));

    TR(TRACE_CHARPUT, ("PutAttrChar(%s) at (%d, %d)",
		       _tracechtype(ch),
		       SP->_cursrow, SP->_curscol));
    UpdateAttrs(ch);
    data = TextOf(ch);
    if (SP->_outch != 0) {
	SP->_outch(data);
    } else {
	putc(data, SP->_ofp);	/* macro's fastest... */
#ifdef TRACE
	_nc_outchars++;
#endif /* TRACE */
    }
    SP->_curscol++;
    if (char_padding) {
	TPUTS_TRACE("char_padding");
	putp(char_padding);
    }
}

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

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

    if (SP->_checkfd >= 0) {
#if USE_FUNC_POLL
	struct pollfd fds[1];
	fds[0].fd = SP->_checkfd;
	fds[0].events = POLLIN;
	if (poll(fds, 1, 0) > 0) {
	    have_pending = TRUE;
	}
#elif 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(chtype const ch)
{
    if (!auto_right_margin) {
	/* we can put the char directly */
	PutAttrChar(ch);
    } else if (enter_am_mode && exit_am_mode) {
	/* we can suppress automargin */
	TPUTS_TRACE("exit_am_mode");
	putp(exit_am_mode);

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

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

    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(chtype ch)
{
    if (!back_color_erase && SP->_coloron) {
	if (ch & A_COLOR)
	    return FALSE;
#if NCURSES_EXT_FUNCS
	if (!SP->_default_color)
	    return FALSE;
	if (SP->_default_fg != C_MASK || SP->_default_bg != C_MASK)
	    return FALSE;
#endif
    }
    return ((ch & ~(NONBLANK_ATTR | A_COLOR)) == BLANK);
}

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

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

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

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

	    /*
	     * The cost expression in the middle isn't exactly right.
	     * _cup_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(ntext0)) {
		UpdateAttrs(ntext0);
		putp(tparm(erase_chars, runcount));

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

		if (wrap_possible)
		    rep_count--;

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

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

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

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

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

/* 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;
		chtype turnon = AttrOf(newscr->_line[i].text[j]) & ~rattr;

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

		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) & (chtype)~NONBLANK_ATTR))
		if (TextOf(newscr->_line[i].text[j]) == ' ' && SAFE(turnon)) {
		    newscr->_line[i].text[j] &= ~turnon;
		    continue;
		}

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

		    /* find end of span, if it's onscreen */
		    for (m = i; m < screen_lines; m++) {
			for (; n < screen_columns; n++) {
			    if (AttrOf(newscr->_line[m].text[n]) == rattr) {
				end_onscreen = TRUE;
				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) {
			chtype *lastline = newscr->_line[m].text;

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

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

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

		    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;
			    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++)
			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,
	after.tms_stime - before.tms_stime,
	after.tms_utime - before.tms_utime));
#endif /* USE_TRACE_TIMES */

    _nc_signal_handler(TRUE);

    returnCode(OK);
}

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

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

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

static void
ClrUpdate(void)
{
    int i;
    chtype 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(chtype blank, bool needclear)
{
    int j;

    if (curscr != 0
	&& SP->_cursrow >= 0) {
	for (j = SP->_curscol; j < screen_columns; j++) {
	    if (j >= 0) {
		chtype *cp = &(curscr->_line[SP->_cursrow].text[j]);

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

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

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

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

    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);
    chtype blank = ClrBlank(stdscr);
    bool ok;

    if (clr_eos && can_clear_with(blank)) {

	for (row = total - 1; row >= 0; row--) {
	    for (col = 0, ok = TRUE; ok && col < last; col++) {
		ok = (newscr->_line[row].text[col] == blank);
	    }
	    if (!ok)
		break;

	    for (col = 0; ok && col < last; col++) {
		ok = (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 - 1 || (top < total && !clr_eol && !clr_bol)) {
	    GoTo(top, 0);
	    ClrToEOS(blank);
	    total = top;
	    if (SP->oldhash && SP->newhash) {
		for (row = top; row < screen_lines; row++)
		    SP->oldhash[row] = SP->newhash[row];
	    }
	}
    }
    return total;
}

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

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

    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) ((n) & A_COLOR)
#define unColor(n) ((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) {
	chtype oldColor;
	chtype newColor;
	int oldPair;
	int newPair;

	for (n = 0; n < screen_columns; n++) {
	    if (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]) {
			oldLine[n] &= ~A_COLOR;
			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;
	    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

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

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

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

	    PutChar(newLine[n]);

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

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

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

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

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

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

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

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

		if (firstChar >= screen_columns)
		    return;
	    }
	}

	blank = newLine[screen_columns - 1];

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

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

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

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

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

	if ((nLastChar == firstChar)
	    && (SP->_el_cost < (oLastChar - nLastChar))) {
	    GoTo(lineno, firstChar);
	    if (newLine[firstChar] != blank)
		PutChar(newLine[firstChar]);
	    ClrToEOL(blank, FALSE);
	} else if ((nLastChar != oLastChar)
		   && (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 */
	    while (newLine[nLastChar] == oldLine[oLastChar]) {
		if (nLastChar != 0
		    && oLastChar != 0) {
		    nLastChar--;
		    oLastChar--;
		} else {
		    break;
		}
	    }

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

	    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(blank);
		    DelChar(oLastChar - nLastChar);
		}
	    }
	}
    }

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

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

static void
ClearScreen(chtype blank)
{
    int i, j;
    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(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");
	    putp(clr_eos);
	} 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(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(chtype * 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(*line);
	    line++;
	    count--;
	}
    } else if (enter_insert_mode && exit_insert_mode) {
	TPUTS_TRACE("enter_insert_mode");
	putp(enter_insert_mode);
	while (count) {
	    PutAttrChar(*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(*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);
	}
    }
}

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

NCURSES_EXPORT(void)
_nc_outstr(const char *str)
{
    (void) putp(str);
    _nc_flush();
}

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

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

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

#if NCURSES_EXT_FUNCS
    if (FILL_BCE()) {
	for (i = 0; i < n; i++) {
	    GoTo(bot - i, 0);
	    for (j = 0; j < screen_columns; j++)
		PutChar(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, chtype blank)
{
    int i, j;

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

#if NCURSES_EXT_FUNCS
    if (FILL_BCE()) {
	for (i = 0; i < n; i++) {
	    GoTo(top + i, 0);
	    for (j = 0; j < screen_columns; j++)
		PutChar(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, chtype blank)
{
    int i;

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

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

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

    return OK;
}

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

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

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

    if (n > 0) {		/* scroll up (forward) */
	/*
	 * Explicitly clear if stuff pushed off top of region might
	 * be saved by the terminal.
	 */
	res = scroll_csr_forward(n, top, bot, 0, maxy, blank);

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

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

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

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

	/*
	 * Clear the newly shifted-in text.
	 */
	if (res != ERR
	    && (non_dest_scroll_region || (memory_below && bot == maxy))) {
	    if (bot == maxy && clr_eos) {
		GoTo(bot - n, 0);
		ClrToEOS(BLANK);
	    } else {
		for (i = 0; i < n; i++) {
		    GoTo(bot - i, 0);
		    ClrToEOL(BLANK, 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");
		tputs(save_cursor, 0, _nc_outch);
	    }
	    TPUTS_TRACE("change_scroll_region");
	    tputs(tparm(change_scroll_region, top, bot), 0, _nc_outch);
	    if (cursor_saved) {
		TPUTS_TRACE("restore_cursor");
		tputs(restore_cursor, 0, _nc_outch);
	    } else {
		SP->_cursrow = SP->_curscol = -1;
	    }

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

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

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

	/*
	 * Clear the newly shifted-in text.
	 */
	if (res != ERR
	    && (non_dest_scroll_region || (memory_above && top == 0))) {
	    for (i = 0; i < -n; i++) {
		GoTo(i + top, 0);
		ClrToEOL(BLANK, 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;

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

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) {
	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);
	SP->_cursrow = screen_lines - 1;
	SP->_curscol = 0;

	ClrToEOL(BLANK, TRUE);
    }
#endif
}

#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 */