xref: /netbsd-src/lib/libcurses/refresh.c (revision ce0bb6e8d2e560ecacbe865a848624f94498063b)
1 /*
2  * Copyright (c) 1981, 1993, 1994
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #ifndef lint
35 static char sccsid[] = "@(#)refresh.c	8.7 (Berkeley) 8/13/94";
36 #endif /* not lint */
37 
38 #include <string.h>
39 
40 #include "curses.h"
41 
42 static int curwin;
43 static short ly, lx;
44 
45 static void	domvcur __P((int, int, int, int));
46 static int	makech __P((WINDOW *, int));
47 static void	quickch __P((WINDOW *));
48 static void	scrolln __P((WINDOW *, int, int, int, int, int));
49 
50 /*
51  * wrefresh --
52  *	Make the current screen look like "win" over the area coverd by
53  *	win.
54  */
55 int
56 wrefresh(win)
57 	register WINDOW *win;
58 {
59 	register __LINE *wlp;
60 	register int retval;
61 	register short wy;
62 	int dnum;
63 
64 	/* Initialize loop parameters. */
65 	ly = curscr->cury;
66 	lx = curscr->curx;
67 	wy = 0;
68 	curwin = (win == curscr);
69 
70 	if (!curwin)
71 		for (wy = 0; wy < win->maxy; wy++) {
72 			wlp = win->lines[wy];
73 			if (wlp->flags & __ISDIRTY)
74 				wlp->hash = __hash((char *)wlp->line,
75 				    win->maxx * __LDATASIZE);
76 		}
77 
78 	if (win->flags & __CLEAROK || curscr->flags & __CLEAROK || curwin) {
79 		if ((win->flags & __FULLWIN) || curscr->flags & __CLEAROK) {
80 			tputs(CL, 0, __cputchar);
81 			ly = 0;
82 			lx = 0;
83 			if (!curwin) {
84 				curscr->flags &= ~__CLEAROK;
85 				curscr->cury = 0;
86 				curscr->curx = 0;
87 				werase(curscr);
88 			}
89 			__touchwin(win);
90 		}
91 		win->flags &= ~__CLEAROK;
92 	}
93 	if (!CA) {
94 		if (win->curx != 0)
95 			putchar('\n');
96 		if (!curwin)
97 			werase(curscr);
98 	}
99 #ifdef DEBUG
100 	__CTRACE("wrefresh: (%0.2o): curwin = %d\n", win, curwin);
101 	__CTRACE("wrefresh: \tfirstch\tlastch\n");
102 #endif
103 
104 #ifndef NOQCH
105 	if ((win->flags & __FULLWIN) && !curwin) {
106 		/*
107 		 * Invoke quickch() only if more than a quarter of the lines
108 		 * in the window are dirty.
109 		 */
110 		for (wy = 0, dnum = 0; wy < win->maxy; wy++)
111 			if (win->lines[wy]->flags & (__ISDIRTY | __FORCEPAINT))
112 				dnum++;
113 		if (!__noqch && dnum > (int) win->maxy / 4)
114 			quickch(win);
115 	}
116 #endif
117 
118 #ifdef DEBUG
119 { int i, j;
120 		__CTRACE("#####################################\n");
121 		for (i = 0; i < curscr->maxy; i++) {
122 			__CTRACE("C: %d:", i);
123 			__CTRACE(" 0x%x \n", curscr->lines[i]->hash);
124 			for (j = 0; j < curscr->maxx; j++)
125 				__CTRACE("%c",
126 			           curscr->lines[i]->line[j].ch);
127 			__CTRACE("\n");
128 			for (j = 0; j < curscr->maxx; j++)
129 				__CTRACE("%x",
130 			           curscr->lines[i]->line[j].attr);
131 			__CTRACE("\n");
132 			__CTRACE("W: %d:", i);
133 			__CTRACE(" 0x%x \n", win->lines[i]->hash);
134 			__CTRACE(" 0x%x ", win->lines[i]->flags);
135 			for (j = 0; j < win->maxx; j++)
136 				__CTRACE("%c",
137 			           win->lines[i]->line[j].ch);
138 			__CTRACE("\n");
139 			for (j = 0; j < win->maxx; j++)
140 				__CTRACE("%x",
141 			           win->lines[i]->line[j].attr);
142 			__CTRACE("\n");
143 		}
144 }
145 #endif /* DEBUG */
146 
147 	for (wy = 0; wy < win->maxy; wy++) {
148 #ifdef DEBUG
149 		__CTRACE("%d\t%d\t%d\n",
150 		    wy, *win->lines[wy]->firstchp, *win->lines[wy]->lastchp);
151 #endif
152 		if (!curwin)
153 			curscr->lines[wy]->hash = win->lines[wy]->hash;
154 		if (win->lines[wy]->flags & (__ISDIRTY | __FORCEPAINT)) {
155 			if (makech(win, wy) == ERR)
156 				return (ERR);
157 			else {
158 				if (*win->lines[wy]->firstchp >= win->ch_off)
159 					*win->lines[wy]->firstchp = win->maxx +
160 					    win->ch_off;
161 				if (*win->lines[wy]->lastchp < win->maxx +
162 				    win->ch_off)
163 					*win->lines[wy]->lastchp = win->ch_off;
164 				if (*win->lines[wy]->lastchp <
165 				    *win->lines[wy]->firstchp) {
166 #ifdef DEBUG
167 					__CTRACE("wrefresh: line %d notdirty \n", wy);
168 #endif
169 					win->lines[wy]->flags &= ~__ISDIRTY;
170 				}
171 			}
172 
173 		}
174 #ifdef DEBUG
175 		__CTRACE("\t%d\t%d\n", *win->lines[wy]->firstchp,
176 			*win->lines[wy]->lastchp);
177 #endif
178 	}
179 
180 #ifdef DEBUG
181 	__CTRACE("refresh: ly=%d, lx=%d\n", ly, lx);
182 #endif
183 
184 	if (win == curscr)
185 		domvcur(ly, lx, win->cury, win->curx);
186 	else {
187 		if (win->flags & __LEAVEOK) {
188 			curscr->cury = ly;
189 			curscr->curx = lx;
190 			ly -= win->begy;
191 			lx -= win->begx;
192 			if (ly >= 0 && ly < win->maxy && lx >= 0 &&
193 			    lx < win->maxx) {
194 				win->cury = ly;
195 				win->curx = lx;
196 			} else
197 				win->cury = win->curx = 0;
198 		} else {
199 			domvcur(ly, lx, win->cury + win->begy,
200 			    win->curx + win->begx);
201 			curscr->cury = win->cury + win->begy;
202 			curscr->curx = win->curx + win->begx;
203 		}
204 	}
205 	retval = OK;
206 
207 	(void)fflush(stdout);
208 	return (retval);
209 }
210 
211 /*
212  * makech --
213  *	Make a change on the screen.
214  */
215 static int
216 makech(win, wy)
217 	register WINDOW *win;
218 	int wy;
219 {
220 	static __LDATA blank = {' ', 0};
221 	__LDATA *nsp, *csp, *cp, *cep;
222 	u_int force;
223 	int clsp, nlsp;			/* Last space in lines. */
224 	int lch, wx, y;
225 	char *ce;
226 
227 	/* Is the cursor still on the end of the last line? */
228 	if (wy > 0 && win->lines[wy - 1]->flags & __ISPASTEOL) {
229 		domvcur(ly, lx, ly + 1, 0);
230 		ly++;
231 		lx = 0;
232 	}
233 	wx = *win->lines[wy]->firstchp - win->ch_off;
234 	if (wx < 0)
235 		wx = 0;
236 	else if (wx >= win->maxx)
237 		return (OK);
238 	lch = *win->lines[wy]->lastchp - win->ch_off;
239 	if (lch < 0)
240 		return (OK);
241 	else if (lch >= (int) win->maxx)
242 		lch = win->maxx - 1;
243 	y = wy + win->begy;
244 
245 	if (curwin)
246 		csp = &blank;
247 	else
248 		csp = &curscr->lines[wy + win->begy]->line[wx + win->begx];
249 
250 	nsp = &win->lines[wy]->line[wx];
251 	force = win->lines[wy]->flags & __FORCEPAINT;
252 	win->lines[wy]->flags &= ~__FORCEPAINT;
253 	if (CE && !curwin) {
254 		for (cp = &win->lines[wy]->line[win->maxx - 1];
255 		     cp->ch == ' ' && cp->attr == 0; cp--)
256 			if (cp <= win->lines[wy]->line)
257 				break;
258 		nlsp = cp - win->lines[wy]->line;
259 	}
260 	if (!curwin)
261 		ce = CE;
262 	else
263 		ce = NULL;
264 
265 	if (force) {
266 		if (CM)
267 			tputs(tgoto(CM, lx, ly), 0, __cputchar);
268 		else {
269 			tputs(HO, 0, __cputchar);
270 			__mvcur(0, 0, ly, lx, 1);
271 		}
272 	}
273 
274 	while (wx <= lch) {
275 		if (!force && memcmp(nsp, csp, sizeof(__LDATA)) == 0) {
276 			if (wx <= lch) {
277 				while (wx <= lch &&
278 				    memcmp(nsp, csp, sizeof(__LDATA)) == 0) {
279 					nsp++;
280 					if (!curwin)
281 						++csp;
282 					++wx;
283 				}
284 				continue;
285 			}
286 			break;
287 		}
288 		domvcur(ly, lx, y, wx + win->begx);
289 
290 #ifdef DEBUG
291 		__CTRACE("makech: 1: wx = %d, ly= %d, lx = %d, newy = %d, newx = %d, force =%d\n",
292 		    wx, ly, lx, y, wx + win->begx, force);
293 #endif
294 		ly = y;
295 		lx = wx + win->begx;
296 		while ((force || memcmp(nsp, csp, sizeof(__LDATA)) != 0)
297 		    && wx <= lch) {
298 
299 			if (ce != NULL &&
300 			    win->maxx + win->begx == curscr->maxx &&
301 			    wx >= nlsp && nsp->ch == ' ' && nsp->attr == 0) {
302 				/* Check for clear to end-of-line. */
303 				cep = &curscr->lines[wy]->line[win->maxx - 1];
304 				while (cep->ch == ' ' && cep->attr == 0)
305 					if (cep-- <= csp)
306 						break;
307 				clsp = cep - curscr->lines[wy]->line -
308 				       win->begx * __LDATASIZE;
309 #ifdef DEBUG
310 			__CTRACE("makech: clsp = %d, nlsp = %d\n", clsp, nlsp);
311 #endif
312 				if ((clsp - nlsp >= strlen(CE)
313 				    && clsp < win->maxx * __LDATASIZE) ||
314 				    wy == win->maxy - 1) {
315 					if (curscr->flags & __WSTANDOUT) {
316 						tputs(SE, 0, __cputchar);
317 						curscr->flags &= ~__WSTANDOUT;
318 					}
319 					tputs(CE, 0, __cputchar);
320 					lx = wx + win->begx;
321 					while (wx++ <= clsp) {
322 						csp->ch = ' ';
323 						csp->attr = 0;
324 						csp++;
325 					}
326 					return (OK);
327 				}
328 				ce = NULL;
329 			}
330 
331 			/*
332 			 * Enter/exit standout mode as appropriate.
333 			 * XXX
334 			 * Should use UC if SO/SE not available.
335 			 */
336 			if (nsp->attr & __STANDOUT) {
337 				if (!(curscr->flags & __WSTANDOUT) &&
338 				    SO != NULL && SE != NULL) {
339 					tputs(SO, 0, __cputchar);
340 					curscr->flags |= __WSTANDOUT;
341 				}
342 			} else
343 				if (curscr->flags & __WSTANDOUT &&
344 				    SE != NULL) {
345 					tputs(SE, 0, __cputchar);
346 					curscr->flags &= ~__WSTANDOUT;
347 				}
348 
349 			wx++;
350 			if (wx >= win->maxx && wy == win->maxy - 1 && !curwin)
351 				if (win->flags & __SCROLLOK) {
352 					if (curscr->flags & __WSTANDOUT
353 					    && win->flags & __ENDLINE)
354 						if (!MS) {
355 							tputs(SE, 0,
356 							    __cputchar);
357 							curscr->flags &=
358 							    ~__WSTANDOUT;
359 						}
360 					if (!(win->flags & __SCROLLWIN)) {
361 						if (!curwin) {
362 							csp->attr = nsp->attr;
363 							putchar(csp->ch = nsp->ch);
364 						} else
365 							putchar(nsp->ch);
366 					}
367 					if (wx + win->begx < curscr->maxx) {
368 						domvcur(ly, wx + win->begx,
369 						    win->begy + win->maxy - 1,
370 						    win->begx + win->maxx - 1);
371 					}
372 					ly = win->begy + win->maxy - 1;
373 					lx = win->begx + win->maxx - 1;
374 					return (OK);
375 				}
376 			if (wx < win->maxx || wy < win->maxy - 1 ||
377 			    !(win->flags & __SCROLLWIN)) {
378 				if (!curwin) {
379 					csp->attr = nsp->attr;
380 					putchar(csp->ch = nsp->ch);
381 					csp++;
382 				} else
383 					putchar(nsp->ch);
384 			}
385 #ifdef DEBUG
386 			__CTRACE("makech: putchar(%c)\n", nsp->ch & 0177);
387 #endif
388 			if (UC && (nsp->attr & __STANDOUT)) {
389 				putchar('\b');
390 				tputs(UC, 0, __cputchar);
391 			}
392 			nsp++;
393 #ifdef DEBUG
394 		__CTRACE("makech: 2: wx = %d, lx = %d\n", wx, lx);
395 #endif
396 		}
397 		if (lx == wx + win->begx)	/* If no change. */
398 			break;
399 		lx = wx + win->begx;
400 		if (lx >= COLS && AM)
401 			lx = COLS - 1;
402 		else if (wx >= win->maxx) {
403 			domvcur(ly, lx, ly, win->maxx + win->begx - 1);
404 			lx = win->maxx + win->begx - 1;
405 		}
406 
407 #ifdef DEBUG
408 		__CTRACE("makech: 3: wx = %d, lx = %d\n", wx, lx);
409 #endif
410 	}
411 
412 	/* Don't leave the screen in standout mode. */
413 	if (curscr->flags & __WSTANDOUT) {
414 		tputs(SE, 0, __cputchar);
415 		curscr->flags &= ~__WSTANDOUT;
416 	}
417 	return (OK);
418 }
419 
420 /*
421  * domvcur --
422  *	Do a mvcur, leaving standout mode if necessary.
423  */
424 static void
425 domvcur(oy, ox, ny, nx)
426 	int oy, ox, ny, nx;
427 {
428 	if (curscr->flags & __WSTANDOUT && !MS) {
429 		tputs(SE, 0, __cputchar);
430 		curscr->flags &= ~__WSTANDOUT;
431 	}
432 
433 	__mvcur(oy, ox, ny, nx, 1);
434 }
435 
436 /*
437  * Quickch() attempts to detect a pattern in the change of the window
438  * in order to optimize the change, e.g., scroll n lines as opposed to
439  * repainting the screen line by line.
440  */
441 
442 static void
443 quickch(win)
444 	WINDOW *win;
445 {
446 #define THRESH		(int) win->maxy / 4
447 
448 	register __LINE *clp, *tmp1, *tmp2;
449 	register int bsize, curs, curw, starts, startw, i, j;
450 	int n, target, cur_period, bot, top, sc_region;
451 	__LDATA buf[1024];
452 	u_int blank_hash;
453 
454 	/*
455 	 * Find how many lines from the top of the screen are unchanged.
456 	 */
457 	for (top = 0; top < win->maxy; top++)
458 		if (win->lines[top]->flags & __FORCEPAINT ||
459 		    win->lines[top]->hash != curscr->lines[top]->hash
460 		    || memcmp(win->lines[top]->line,
461 		    curscr->lines[top]->line,
462 		    win->maxx * __LDATASIZE) != 0)
463 			break;
464 		else
465 			win->lines[top]->flags &= ~__ISDIRTY;
466        /*
467 	* Find how many lines from bottom of screen are unchanged.
468 	*/
469 	for (bot = win->maxy - 1; bot >= 0; bot--)
470 		if (win->lines[bot]->flags & __FORCEPAINT ||
471 		    win->lines[bot]->hash != curscr->lines[bot]->hash
472 		    || memcmp(win->lines[bot]->line,
473 		    curscr->lines[bot]->line,
474 		    win->maxx * __LDATASIZE) != 0)
475 			break;
476 		else
477 			win->lines[bot]->flags &= ~__ISDIRTY;
478 
479 #ifdef NO_JERKINESS
480 	/*
481 	 * If we have a bottom unchanged region return.  Scrolling the
482 	 * bottom region up and then back down causes a screen jitter.
483 	 * This will increase the number of characters sent to the screen
484 	 * but it looks better.
485 	 */
486 	if (bot < win->maxy - 1)
487 		return;
488 #endif /* NO_JERKINESS */
489 
490 	/*
491 	 * Search for the largest block of text not changed.
492 	 * Invariants of the loop:
493 	 * - Startw is the index of the beginning of the examined block in win.
494          * - Starts is the index of the beginning of the examined block in
495 	 *    curscr.
496 	 * - Curs is the index of one past the end of the exmined block in win.
497 	 * - Curw is the index of one past the end of the exmined block in
498 	 *   curscr.
499 	 * - bsize is the current size of the examined block.
500          */
501 	for (bsize = bot - top; bsize >= THRESH; bsize--) {
502 		for (startw = top; startw <= bot - bsize; startw++)
503 			for (starts = top; starts <= bot - bsize;
504 			     starts++) {
505 				for (curw = startw, curs = starts;
506 				     curs < starts + bsize; curw++, curs++)
507 					if (win->lines[curw]->flags &
508 					    __FORCEPAINT ||
509 					    (win->lines[curw]->hash !=
510 					    curscr->lines[curs]->hash ||
511 				            memcmp(win->lines[curw]->line,
512 					    curscr->lines[curs]->line,
513 					    win->maxx * __LDATASIZE) != 0))
514 						break;
515 				if (curs == starts + bsize)
516 					goto done;
517 			}
518 	}
519  done:
520 	/* Did not find anything */
521 	if (bsize < THRESH)
522 		return;
523 
524 #ifdef DEBUG
525 	__CTRACE("quickch:bsize=%d,starts=%d,startw=%d,curw=%d,curs=%d,top=%d,bot=%d\n",
526 		bsize, starts, startw, curw, curs, top, bot);
527 #endif
528 
529 	/*
530 	 * Make sure that there is no overlap between the bottom and top
531 	 * regions and the middle scrolled block.
532 	 */
533 	if (bot < curs)
534 		bot = curs - 1;
535 	if (top > starts)
536 		top = starts;
537 
538 	n = startw - starts;
539 
540 #ifdef DEBUG
541 		__CTRACE("#####################################\n");
542 		for (i = 0; i < curscr->maxy; i++) {
543 			__CTRACE("C: %d:", i);
544 			__CTRACE(" 0x%x \n", curscr->lines[i]->hash);
545 			for (j = 0; j < curscr->maxx; j++)
546 				__CTRACE("%c",
547 			           curscr->lines[i]->line[j].ch);
548 			__CTRACE("\n");
549 			for (j = 0; j < curscr->maxx; j++)
550 				__CTRACE("%x",
551 			           curscr->lines[i]->line[j].attr);
552 			__CTRACE("\n");
553 			__CTRACE("W: %d:", i);
554 			__CTRACE(" 0x%x \n", win->lines[i]->hash);
555 			__CTRACE(" 0x%x ", win->lines[i]->flags);
556 			for (j = 0; j < win->maxx; j++)
557 				__CTRACE("%c",
558 			           win->lines[i]->line[j].ch);
559 			__CTRACE("\n");
560 			for (j = 0; j < win->maxx; j++)
561 				__CTRACE("%x",
562 			           win->lines[i]->line[j].attr);
563 			__CTRACE("\n");
564 		}
565 #endif
566 
567 	/* So we don't have to call __hash() each time */
568 	for (i = 0; i < win->maxx; i++) {
569 		buf[i].ch = ' ';
570 		buf[i].attr = 0;
571 	}
572 	blank_hash = __hash((char *) buf, win->maxx * __LDATASIZE);
573 
574 	/*
575 	 * Perform the rotation to maintain the consistency of curscr.
576 	 * This is hairy since we are doing an *in place* rotation.
577 	 * Invariants of the loop:
578 	 * - I is the index of the current line.
579 	 * - Target is the index of the target of line i.
580 	 * - Tmp1 points to current line (i).
581 	 * - Tmp2 and points to target line (target);
582 	 * - Cur_period is the index of the end of the current period.
583 	 *   (see below).
584 	 *
585 	 * There are 2 major issues here that make this rotation non-trivial:
586 	 * 1.  Scrolling in a scrolling region bounded by the top
587 	 *     and bottom regions determined (whose size is sc_region).
588 	 * 2.  As a result of the use of the mod function, there may be a
589 	 *     period introduced, i.e., 2 maps to 4, 4 to 6, n-2 to 0, and
590 	 *     0 to 2, which then causes all odd lines not to be rotated.
591 	 *     To remedy this, an index of the end ( = beginning) of the
592 	 *     current 'period' is kept, cur_period, and when it is reached,
593 	 *     the next period is started from cur_period + 1 which is
594 	 *     guaranteed not to have been reached since that would mean that
595 	 *     all records would have been reached. (think about it...).
596 	 *
597 	 * Lines in the rotation can have 3 attributes which are marked on the
598 	 * line so that curscr is consistent with the visual screen.
599 	 * 1.  Not dirty -- lines inside the scrolled block, top region or
600 	 *                  bottom region.
601 	 * 2.  Blank lines -- lines in the differential of the scrolling
602 	 *		      region adjacent to top and bot regions
603 	 *                    depending on scrolling direction.
604 	 * 3.  Dirty line -- all other lines are marked dirty.
605 	 */
606 	sc_region = bot - top + 1;
607 	i = top;
608 	tmp1 = curscr->lines[top];
609 	cur_period = top;
610 	for (j = top; j <= bot; j++) {
611 		target = (i - top + n + sc_region) % sc_region + top;
612 		tmp2 = curscr->lines[target];
613 		curscr->lines[target] = tmp1;
614 		/* Mark block as clean and blank out scrolled lines. */
615 		clp = curscr->lines[target];
616 #ifdef DEBUG
617 		__CTRACE("quickch: n=%d startw=%d curw=%d i = %d target=%d ",
618 			n, startw, curw, i, target);
619 #endif
620 		if ((target >= startw && target < curw) || target < top
621 		    || target > bot) {
622 #ifdef DEBUG
623 			__CTRACE("-- notdirty");
624 #endif
625 			win->lines[target]->flags &= ~__ISDIRTY;
626 		} else if ((n > 0 && target >= top && target < top + n) ||
627 		           (n < 0 && target <= bot && target > bot + n)) {
628 			if (clp->hash != blank_hash ||  memcmp(clp->line,
629 			    buf, win->maxx * __LDATASIZE) !=0) {
630 				(void)memcpy(clp->line,  buf,
631 				    win->maxx * __LDATASIZE);
632 #ifdef DEBUG
633 				__CTRACE("-- blanked out: dirty");
634 #endif
635 				clp->hash = blank_hash;
636 				__touchline(win, target, 0, win->maxx - 1, 0);
637 			} else {
638 				__touchline(win, target, 0, win->maxx - 1, 0);
639 #ifdef DEBUG
640 				__CTRACE(" -- blank line already: dirty");
641 #endif
642 			}
643 		} else {
644 #ifdef DEBUG
645 			__CTRACE(" -- dirty");
646 #endif
647 			__touchline(win, target, 0, win->maxx - 1, 0);
648 		}
649 #ifdef DEBUG
650 		__CTRACE("\n");
651 #endif
652 		if (target == cur_period) {
653 			i = target + 1;
654 			tmp1 = curscr->lines[i];
655 			cur_period = i;
656 		} else {
657 			tmp1 = tmp2;
658 			i = target;
659 		}
660 	}
661 #ifdef DEBUG
662 		__CTRACE("$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$\n");
663 		for (i = 0; i < curscr->maxy; i++) {
664 			__CTRACE("C: %d:", i);
665 			for (j = 0; j < curscr->maxx; j++)
666 				__CTRACE("%c",
667 			           curscr->lines[i]->line[j].ch);
668 			__CTRACE("\n");
669 			__CTRACE("W: %d:", i);
670 			for (j = 0; j < win->maxx; j++)
671 				__CTRACE("%c", win->lines[i]->line[j].ch);
672 			__CTRACE("\n");
673 		}
674 #endif
675 	if (n != 0) {
676 		WINDOW *wp;
677 		scrolln(win, starts, startw, curs, bot, top);
678 		/*
679 		 * Need to repoint any subwindow lines to the rotated
680 		 * line structured.
681 		 */
682 		for (wp = win->nextp; wp != win; wp = wp->nextp)
683 			__set_subwin(win, wp);
684 	}
685 }
686 
687 /*
688  * scrolln --
689  *	Scroll n lines, where n is starts - startw.
690  */
691 static void
692 scrolln(win, starts, startw, curs, bot, top)
693 	WINDOW *win;
694 	int starts, startw, curs, bot, top;
695 {
696 	int i, oy, ox, n;
697 
698 	oy = curscr->cury;
699 	ox = curscr->curx;
700 	n = starts - startw;
701 
702 	/*
703 	 * XXX
704 	 * The initial tests that set __noqch don't let us reach here unless
705 	 * we have either CS + HO + SF/sf/SR/sr, or AL + DL.  SF/sf and SR/sr
706 	 * scrolling can only shift the entire scrolling region, not just a
707 	 * part of it, which means that the quickch() routine is going to be
708 	 * sadly disappointed in us if we don't have CS as well.
709 	 *
710 	 * If CS, HO and SF/sf are set, can use the scrolling region.  Because
711 	 * the cursor position after CS is undefined, we need HO which gives us
712 	 * the ability to move to somewhere without knowledge of the current
713 	 * location of the cursor.  Still call __mvcur() anyway, to update its
714 	 * idea of where the cursor is.
715 	 *
716 	 * When the scrolling region has been set, the cursor has to be at the
717 	 * last line of the region to make the scroll happen.
718 	 *
719 	 * Doing SF/SR or AL/DL appears faster on the screen than either sf/sr
720 	 * or al/dl, and, some terminals have AL/DL, sf/sr, and CS, but not
721 	 * SF/SR.  So, if we're scrolling almost all of the screen, try and use
722 	 * AL/DL, otherwise use the scrolling region.  The "almost all" is a
723 	 * shameless hack for vi.
724 	 */
725 	if (n > 0) {
726 		if (CS != NULL && HO != NULL && (SF != NULL ||
727 		    (AL == NULL || DL == NULL ||
728 		    top > 3 || bot + 3 < win->maxy) && sf != NULL)) {
729 			tputs(__tscroll(CS, top, bot + 1), 0, __cputchar);
730 			__mvcur(oy, ox, 0, 0, 1);
731 			tputs(HO, 0, __cputchar);
732 			__mvcur(0, 0, bot, 0, 1);
733 			if (SF != NULL)
734 				tputs(__tscroll(SF, n, 0), 0, __cputchar);
735 			else
736 				for (i = 0; i < n; i++)
737 					tputs(sf, 0, __cputchar);
738 			tputs(__tscroll(CS, 0, win->maxy), 0, __cputchar);
739 			__mvcur(bot, 0, 0, 0, 1);
740 			tputs(HO, 0, __cputchar);
741 			__mvcur(0, 0, oy, ox, 1);
742 			return;
743 		}
744 
745 		/* Scroll up the block. */
746 		if (SF != NULL && top == 0) {
747 			__mvcur(oy, ox, bot, 0, 1);
748 			tputs(__tscroll(SF, n, 0), 0, __cputchar);
749 		} else if (DL != NULL) {
750 			__mvcur(oy, ox, top, 0, 1);
751 			tputs(__tscroll(DL, n, 0), 0, __cputchar);
752 		} else if (dl != NULL) {
753 			__mvcur(oy, ox, top, 0, 1);
754 			for (i = 0; i < n; i++)
755 				tputs(dl, 0, __cputchar);
756 		} else if (sf != NULL && top == 0) {
757 			__mvcur(oy, ox, bot, 0, 1);
758 			for (i = 0; i < n; i++)
759 				tputs(sf, 0, __cputchar);
760 		} else
761 			abort();
762 
763 		/* Push down the bottom region. */
764 		__mvcur(top, 0, bot - n + 1, 0, 1);
765 		if (AL != NULL)
766 			tputs(__tscroll(AL, n, 0), 0, __cputchar);
767 		else if (al != NULL)
768 			for (i = 0; i < n; i++)
769 				tputs(al, 0, __cputchar);
770 		else
771 			abort();
772 		__mvcur(bot - n + 1, 0, oy, ox, 1);
773 	} else {
774 		/*
775 		 * !!!
776 		 * n < 0
777 		 *
778 		 * If CS, HO and SR/sr are set, can use the scrolling region.
779 		 * See the above comments for details.
780 		 */
781 		if (CS != NULL && HO != NULL && (SR != NULL ||
782 		    (AL == NULL || DL == NULL ||
783 		    top > 3 || bot + 3 < win->maxy) && sr != NULL)) {
784 			tputs(__tscroll(CS, top, bot + 1), 0, __cputchar);
785 			__mvcur(oy, ox, 0, 0, 1);
786 			tputs(HO, 0, __cputchar);
787 			__mvcur(0, 0, top, 0, 1);
788 
789 			if (SR != NULL)
790 				tputs(__tscroll(SR, -n, 0), 0, __cputchar);
791 			else
792 				for (i = n; i < 0; i++)
793 					tputs(sr, 0, __cputchar);
794 			tputs(__tscroll(CS, 0, win->maxy), 0, __cputchar);
795 			__mvcur(top, 0, 0, 0, 1);
796 			tputs(HO, 0, __cputchar);
797 			__mvcur(0, 0, oy, ox, 1);
798 			return;
799 		}
800 
801 		/* Preserve the bottom lines. */
802 		__mvcur(oy, ox, bot + n + 1, 0, 1);
803 		if (SR != NULL && bot == win->maxy)
804 			tputs(__tscroll(SR, -n, 0), 0, __cputchar);
805 		else if (DL != NULL)
806 			tputs(__tscroll(DL, -n, 0), 0, __cputchar);
807 		else if (dl != NULL)
808 		       	for (i = n; i < 0; i++)
809 				tputs(dl, 0, __cputchar);
810 		else if (sr != NULL && bot == win->maxy)
811 		       	for (i = n; i < 0; i++)
812 				tputs(sr, 0, __cputchar);
813 		else
814 			abort();
815 
816 		/* Scroll the block down. */
817 		__mvcur(bot + n + 1, 0, top, 0, 1);
818 		if (AL != NULL)
819 			tputs(__tscroll(AL, -n, 0), 0, __cputchar);
820 		else if (al != NULL)
821 			for (i = n; i < 0; i++)
822 				tputs(al, 0, __cputchar);
823 		else
824 			abort();
825 		__mvcur(top, 0, oy, ox, 1);
826 	}
827 }
828