xref: /original-bsd/lib/libcurses/refresh.c (revision 3705696b)
1 /*
2  * Copyright (c) 1981, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * %sccs.include.redist.c%
6  */
7 
8 #ifndef lint
9 static char sccsid[] = "@(#)refresh.c	8.1 (Berkeley) 07/20/93";
10 #endif /* not lint */
11 
12 #include <curses.h>
13 #include <string.h>
14 
15 static int curwin;
16 static short ly, lx;
17 
18 static void	domvcur __P((int, int, int, int));
19 static int	makech __P((WINDOW *, int));
20 static void	quickch __P((WINDOW *));
21 static void	scrolln __P((WINDOW *, int, int, int, int, int));
22 
23 /*
24  * wrefresh --
25  *	Make the current screen look like "win" over the area coverd by
26  *	win.
27  */
28 int
29 wrefresh(win)
30 	register WINDOW *win;
31 {
32 	register __LINE *wlp;
33 	register int retval;
34 	register short wy;
35 	int dnum;
36 
37 	/* Initialize loop parameters. */
38 	ly = curscr->cury;
39 	lx = curscr->curx;
40 	wy = 0;
41 	curwin = (win == curscr);
42 
43 	if (!curwin)
44 		for (wy = 0; wy < win->maxy; wy++) {
45 			wlp = win->lines[wy];
46 			if (wlp->flags & __ISDIRTY)
47 				wlp->hash =
48 				   __hash((char *) wlp->line, win->maxx * __LDATASIZE);
49 		}
50 
51 	if (win->flags & __CLEAROK || curscr->flags & __CLEAROK || curwin) {
52 		if ((win->flags & __FULLWIN) || curscr->flags & __CLEAROK) {
53 			tputs(CL, 0, __cputchar);
54 			ly = 0;
55 			lx = 0;
56 			if (!curwin) {
57 				curscr->flags &= ~__CLEAROK;
58 				curscr->cury = 0;
59 				curscr->curx = 0;
60 				werase(curscr);
61 			}
62 			__touchwin(win);
63 		}
64 		win->flags &= ~__CLEAROK;
65 	}
66 	if (!CA) {
67 		if (win->curx != 0)
68 			putchar('\n');
69 		if (!curwin)
70 			werase(curscr);
71 	}
72 #ifdef DEBUG
73 	__CTRACE("wrefresh: (%0.2o): curwin = %d\n", win, curwin);
74 	__CTRACE("wrefresh: \tfirstch\tlastch\n");
75 #endif
76 
77 #ifndef NOQCH
78 	if ((win->flags & __FULLWIN) && !curwin) {
79 		/*
80 		 * Invoke quickch() only if more than a quarter of the lines
81 		 * in the window are dirty.
82 		 */
83 		for (wy = 0, dnum = 0; wy < win->maxy; wy++)
84 			if (win->lines[wy]->flags & (__ISDIRTY | __FORCEPAINT))
85 				dnum++;
86 		if (!__noqch && dnum > (int) win->maxy / 4)
87 			quickch(win);
88 	}
89 #endif
90 
91 #ifdef DEBUG
92 { int i, j;
93 		__CTRACE("#####################################\n");
94 		for (i = 0; i < curscr->maxy; i++) {
95 			__CTRACE("C: %d:", i);
96 			__CTRACE(" 0x%x \n", curscr->lines[i]->hash);
97 			for (j = 0; j < curscr->maxx; j++)
98 				__CTRACE("%c",
99 			           curscr->lines[i]->line[j].ch);
100 			__CTRACE("\n");
101 			for (j = 0; j < curscr->maxx; j++)
102 				__CTRACE("%x",
103 			           curscr->lines[i]->line[j].attr);
104 			__CTRACE("\n");
105 			__CTRACE("W: %d:", i);
106 			__CTRACE(" 0x%x \n", win->lines[i]->hash);
107 			__CTRACE(" 0x%x ", win->lines[i]->flags);
108 			for (j = 0; j < win->maxx; j++)
109 				__CTRACE("%c",
110 			           win->lines[i]->line[j].ch);
111 			__CTRACE("\n");
112 			for (j = 0; j < win->maxx; j++)
113 				__CTRACE("%x",
114 			           win->lines[i]->line[j].attr);
115 			__CTRACE("\n");
116 		}
117 }
118 #endif /* DEBUG */
119 
120 	for (wy = 0; wy < win->maxy; wy++) {
121 #ifdef DEBUG
122 		__CTRACE("%d\t%d\t%d\n",
123 		    wy, *win->lines[wy]->firstchp, *win->lines[wy]->lastchp);
124 #endif
125 		if (!curwin)
126 			curscr->lines[wy]->hash = win->lines[wy]->hash;
127 		if (win->lines[wy]->flags & (__ISDIRTY | __FORCEPAINT)) {
128 			if (makech(win, wy) == ERR)
129 				return (ERR);
130 			else {
131 				if (*win->lines[wy]->firstchp >= win->ch_off)
132 					*win->lines[wy]->firstchp = win->maxx +
133 					    win->ch_off;
134 				if (*win->lines[wy]->lastchp < win->maxx +
135 				    win->ch_off)
136 					*win->lines[wy]->lastchp = win->ch_off;
137 				if (*win->lines[wy]->lastchp <
138 				    *win->lines[wy]->firstchp) {
139 #ifdef DEBUG
140 					__CTRACE("wrefresh: line %d notdirty \n", wy);
141 #endif
142 					win->lines[wy]->flags &= ~__ISDIRTY;
143 				}
144 			}
145 
146 		}
147 #ifdef DEBUG
148 		__CTRACE("\t%d\t%d\n", *win->lines[wy]->firstchp,
149 			*win->lines[wy]->lastchp);
150 #endif
151 	}
152 
153 #ifdef DEBUG
154 	__CTRACE("refresh: ly=%d, lx=%d\n", ly, lx);
155 #endif
156 
157 	if (win == curscr)
158 		domvcur(ly, lx, win->cury, win->curx);
159 	else {
160 		if (win->flags & __LEAVEOK) {
161 			curscr->cury = ly;
162 			curscr->curx = lx;
163 			ly -= win->begy;
164 			lx -= win->begx;
165 			if (ly >= 0 && ly < win->maxy && lx >= 0 &&
166 			    lx < win->maxx) {
167 				win->cury = ly;
168 				win->curx = lx;
169 			} else
170 				win->cury = win->curx = 0;
171 		} else {
172 			domvcur(ly, lx, win->cury + win->begy,
173 			    win->curx + win->begx);
174 			curscr->cury = win->cury + win->begy;
175 			curscr->curx = win->curx + win->begx;
176 		}
177 	}
178 	retval = OK;
179 
180 	(void)fflush(stdout);
181 	return (retval);
182 }
183 
184 /*
185  * makech --
186  *	Make a change on the screen.
187  */
188 static int
189 makech(win, wy)
190 	register WINDOW *win;
191 	int wy;
192 {
193 	static __LDATA blank = {' ', 0};
194 	register int nlsp, clsp;		/* Last space in lines. */
195 	register int wx, lch, y;
196 	register __LDATA *nsp, *csp, *cp, *cep;
197 	u_int force;
198 	char *ce;
199 
200 	/* Is the cursor still on the end of the last line? */
201 	if (wy > 0 && win->lines[wy - 1]->flags & __ISPASTEOL) {
202 		domvcur(ly, lx, ly + 1, 0);
203 		ly++;
204 		lx = 0;
205 	}
206 	wx = *win->lines[wy]->firstchp - win->ch_off;
207 	if (wx < 0)
208 		wx = 0;
209 	else if (wx >= win->maxx)
210 		return (OK);
211 	lch = *win->lines[wy]->lastchp - win->ch_off;
212 	if (lch < 0)
213 		return (OK);
214 	else if (lch >= (int) win->maxx)
215 		lch = win->maxx - 1;
216 	y = wy + win->begy;
217 
218 	if (curwin)
219 		csp = &blank;
220 	else
221 		csp = &curscr->lines[wy + win->begy]->line[wx + win->begx];
222 
223 	nsp = &win->lines[wy]->line[wx];
224 	force = win->lines[wy]->flags & __FORCEPAINT;
225 	win->lines[wy]->flags &= ~__FORCEPAINT;
226 	if (CE && !curwin) {
227 		for (cp = &win->lines[wy]->line[win->maxx - 1];
228 		     cp->ch == ' ' && cp->attr == 0; cp--)
229 			if (cp <= win->lines[wy]->line)
230 				break;
231 		nlsp = cp - win->lines[wy]->line;
232 	}
233 	if (!curwin)
234 		ce = CE;
235 	else
236 		ce = NULL;
237 
238 	if (force) {
239 		if (CM)
240 			tputs(tgoto(CM, lx, ly), 0, __cputchar);
241 		else {
242 			tputs(HO, 0, __cputchar);
243 			__mvcur(0, 0, ly, lx, 1);
244 		}
245 	}
246 	while (wx <= lch) {
247 		if (!force && memcmp(nsp, csp, sizeof(__LDATA)) == 0) {
248 			if (wx <= lch) {
249 				while (wx <= lch &&
250 				       memcmp(nsp, csp, sizeof(__LDATA)) == 0) {
251 					    nsp++;
252 					    if (!curwin)
253 						    csp++;
254 					    ++wx;
255 				    }
256 				continue;
257 			}
258 			break;
259 		}
260 		domvcur(ly, lx, y, wx + win->begx);
261 
262 #ifdef DEBUG
263 		__CTRACE("makech: 1: wx = %d, ly= %d, lx = %d, newy = %d, newx = %d, force =%d\n",
264 		    wx, ly, lx, y, wx + win->begx, force);
265 #endif
266 		ly = y;
267 		lx = wx + win->begx;
268 		while ((force || memcmp(nsp, csp, sizeof(__LDATA)) != 0)
269 		    && wx <= lch) {
270 
271 			if (ce != NULL && win->maxx + win->begx ==
272 			    curscr->maxx && wx >= nlsp && nsp->ch == ' ') {
273 				/* Check for clear to end-of-line. */
274 				cep = &curscr->lines[wy]->line[win->maxx - 1];
275 				while (cep->ch == ' ' && cep->attr == 0)
276 					if (cep-- <= csp)
277 						break;
278 				clsp = cep - curscr->lines[wy]->line -
279 				       win->begx * __LDATASIZE;
280 #ifdef DEBUG
281 			__CTRACE("makech: clsp = %d, nlsp = %d\n", clsp, nlsp);
282 #endif
283 				if ((clsp - nlsp >= strlen(CE)
284 				    && clsp < win->maxx * __LDATASIZE) ||
285 				    wy == win->maxy - 1) {
286 #ifdef DEBUG
287 					__CTRACE("makech: using CE\n");
288 #endif
289 					tputs(CE, 0, __cputchar);
290 					lx = wx + win->begx;
291 					while (wx++ <= clsp) {
292 						csp->ch = ' ';
293 						csp->attr = 0;
294 						csp++;
295 					}
296 					return (OK);
297 				}
298 				ce = NULL;
299 			}
300 
301 			/* Enter/exit standout mode as appropriate. */
302 			if (SO && (nsp->attr & __STANDOUT) !=
303 			    (curscr->flags & __WSTANDOUT)) {
304 				if (nsp->attr & __STANDOUT) {
305 					tputs(SO, 0, __cputchar);
306 					curscr->flags |= __WSTANDOUT;
307 				} else {
308 					tputs(SE, 0, __cputchar);
309 					curscr->flags &= ~__WSTANDOUT;
310 				}
311 			}
312 
313 			wx++;
314 			if (wx >= win->maxx && wy == win->maxy - 1 && !curwin)
315 				if (win->flags & __SCROLLOK) {
316 					if (curscr->flags & __WSTANDOUT
317 					    && win->flags & __ENDLINE)
318 						if (!MS) {
319 							tputs(SE, 0,
320 							    __cputchar);
321 							curscr->flags &=
322 							    ~__WSTANDOUT;
323 						}
324 					if (!(win->flags & __SCROLLWIN)) {
325 						if (!curwin) {
326 							csp->attr = nsp->attr;
327 							putchar(csp->ch = nsp->ch);
328 						} else
329 							putchar(nsp->ch);
330 					}
331 					if (wx + win->begx < curscr->maxx) {
332 						domvcur(ly, wx + win->begx,
333 						    win->begy + win->maxy - 1,
334 						    win->begx + win->maxx - 1);
335 					}
336 					ly = win->begy + win->maxy - 1;
337 					lx = win->begx + win->maxx - 1;
338 					return (OK);
339 				}
340 			if (wx < win->maxx || wy < win->maxy - 1 ||
341 			    !(win->flags & __SCROLLWIN)) {
342 				if (!curwin) {
343 					csp->attr = nsp->attr;
344 					putchar(csp->ch = nsp->ch);
345 					csp++;
346 				} else
347 					putchar(nsp->ch);
348 			}
349 #ifdef DEBUG
350 			__CTRACE("makech: putchar(%c)\n", nsp->ch & 0177);
351 #endif
352 			if (UC && (nsp->attr & __STANDOUT)) {
353 				putchar('\b');
354 				tputs(UC, 0, __cputchar);
355 			}
356 			nsp++;
357 #ifdef DEBUG
358 		__CTRACE("makech: 2: wx = %d, lx = %d\n", wx, lx);
359 #endif
360 		}
361 		if (lx == wx + win->begx)	/* If no change. */
362 			break;
363 		lx = wx + win->begx;
364 		if (lx >= COLS && AM)
365 			lx = COLS - 1;
366 		else if (wx >= win->maxx) {
367 			domvcur(ly, lx, ly, win->maxx + win->begx - 1);
368 			lx = win->maxx + win->begx - 1;
369 		}
370 
371 #ifdef DEBUG
372 		__CTRACE("makech: 3: wx = %d, lx = %d\n", wx, lx);
373 #endif
374 	}
375 	return (OK);
376 }
377 
378 /*
379  * domvcur --
380  *	Do a mvcur, leaving standout mode if necessary.
381  */
382 static void
383 domvcur(oy, ox, ny, nx)
384 	int oy, ox, ny, nx;
385 {
386 	if (curscr->flags & __WSTANDOUT && !MS) {
387 		tputs(SE, 0, __cputchar);
388 		curscr->flags &= ~__WSTANDOUT;
389 	}
390 
391 	__mvcur(oy, ox, ny, nx, 1);
392 }
393 
394 /*
395  * Quickch() attempts to detect a pattern in the change of the window
396  * in order to optimize the change, e.g., scroll n lines as opposed to
397  * repainting the screen line by line.
398  */
399 
400 static void
401 quickch(win)
402 	WINDOW *win;
403 {
404 #define THRESH		(int) win->maxy / 4
405 
406 	register __LINE *clp, *tmp1, *tmp2;
407 	register int bsize, curs, curw, starts, startw, i, j;
408 	int n, target, cur_period, bot, top, sc_region;
409 	__LDATA buf[1024];
410 	u_int blank_hash;
411 
412 	/*
413 	 * Find how many lines from the top of the screen are unchanged.
414 	 */
415 	for (top = 0; top < win->maxy; top++)
416 		if (win->lines[top]->flags & __FORCEPAINT ||
417 		    win->lines[top]->hash != curscr->lines[top]->hash
418 		    || memcmp(win->lines[top]->line,
419 		    curscr->lines[top]->line,
420 		    win->maxx * __LDATASIZE) != 0)
421 			break;
422 		else
423 			win->lines[top]->flags &= ~__ISDIRTY;
424        /*
425 	* Find how many lines from bottom of screen are unchanged.
426 	*/
427 	for (bot = win->maxy - 1; bot >= 0; bot--)
428 		if (win->lines[bot]->flags & __FORCEPAINT ||
429 		    win->lines[bot]->hash != curscr->lines[bot]->hash
430 		    || memcmp(win->lines[bot]->line,
431 		    curscr->lines[bot]->line,
432 		    win->maxx * __LDATASIZE) != 0)
433 			break;
434 		else
435 			win->lines[bot]->flags &= ~__ISDIRTY;
436 
437 #ifdef NO_JERKINESS
438 	/*
439 	 * If we have a bottom unchanged region return.  Scrolling the
440 	 * bottom region up and then back down causes a screen jitter.
441 	 * This will increase the number of characters sent to the screen
442 	 * but it looks better.
443 	 */
444 	if (bot < win->maxy - 1)
445 		return;
446 #endif /* NO_JERKINESS */
447 
448 	/*
449 	 * Search for the largest block of text not changed.
450 	 * Invariants of the loop:
451 	 * - Startw is the index of the beginning of the examined block in win.
452          * - Starts is the index of the beginning of the examined block in
453 	 *    curscr.
454 	 * - Curs is the index of one past the end of the exmined block in win.
455 	 * - Curw is the index of one past the end of the exmined block in
456 	 *   curscr.
457 	 * - bsize is the current size of the examined block.
458          */
459 	for (bsize = bot - top; bsize >= THRESH; bsize--) {
460 		for (startw = top; startw <= bot - bsize; startw++)
461 			for (starts = top; starts <= bot - bsize;
462 			     starts++) {
463 				for (curw = startw, curs = starts;
464 				     curs < starts + bsize; curw++, curs++)
465 					if (win->lines[curw]->flags &
466 					    __FORCEPAINT ||
467 					    (win->lines[curw]->hash !=
468 					    curscr->lines[curs]->hash ||
469 				            memcmp(win->lines[curw]->line,
470 					    curscr->lines[curs]->line,
471 					    win->maxx * __LDATASIZE) != 0))
472 						break;
473 				if (curs == starts + bsize)
474 					goto done;
475 			}
476 	}
477  done:
478 	/* Did not find anything */
479 	if (bsize < THRESH)
480 		return;
481 
482 #ifdef DEBUG
483 	__CTRACE("quickch:bsize=%d,starts=%d,startw=%d,curw=%d,curs=%d,top=%d,bot=%d\n",
484 		bsize, starts, startw, curw, curs, top, bot);
485 #endif
486 
487 	/*
488 	 * Make sure that there is no overlap between the bottom and top
489 	 * regions and the middle scrolled block.
490 	 */
491 	if (bot < curs)
492 		bot = curs - 1;
493 	if (top > starts)
494 		top = starts;
495 
496 	n = startw - starts;
497 
498 #ifdef DEBUG
499 		__CTRACE("#####################################\n");
500 		for (i = 0; i < curscr->maxy; i++) {
501 			__CTRACE("C: %d:", i);
502 			__CTRACE(" 0x%x \n", curscr->lines[i]->hash);
503 			for (j = 0; j < curscr->maxx; j++)
504 				__CTRACE("%c",
505 			           curscr->lines[i]->line[j].ch);
506 			__CTRACE("\n");
507 			for (j = 0; j < curscr->maxx; j++)
508 				__CTRACE("%x",
509 			           curscr->lines[i]->line[j].attr);
510 			__CTRACE("\n");
511 			__CTRACE("W: %d:", i);
512 			__CTRACE(" 0x%x \n", win->lines[i]->hash);
513 			__CTRACE(" 0x%x ", win->lines[i]->flags);
514 			for (j = 0; j < win->maxx; j++)
515 				__CTRACE("%c",
516 			           win->lines[i]->line[j].ch);
517 			__CTRACE("\n");
518 			for (j = 0; j < win->maxx; j++)
519 				__CTRACE("%x",
520 			           win->lines[i]->line[j].attr);
521 			__CTRACE("\n");
522 		}
523 #endif
524 
525 	/* So we don't have to call __hash() each time */
526 	for (i = 0; i < win->maxx; i++) {
527 		buf[i].ch = ' ';
528 		buf[i].attr = 0;
529 	}
530 	blank_hash = __hash((char *) buf, win->maxx * __LDATASIZE);
531 
532 	/*
533 	 * Perform the rotation to maintain the consistency of curscr.
534 	 * This is hairy since we are doing an *in place* rotation.
535 	 * Invariants of the loop:
536 	 * - I is the index of the current line.
537 	 * - Target is the index of the target of line i.
538 	 * - Tmp1 points to current line (i).
539 	 * - Tmp2 and points to target line (target);
540 	 * - Cur_period is the index of the end of the current period.
541 	 *   (see below).
542 	 *
543 	 * There are 2 major issues here that make this rotation non-trivial:
544 	 * 1.  Scrolling in a scrolling region bounded by the top
545 	 *     and bottom regions determined (whose size is sc_region).
546 	 * 2.  As a result of the use of the mod function, there may be a
547 	 *     period introduced, i.e., 2 maps to 4, 4 to 6, n-2 to 0, and
548 	 *     0 to 2, which then causes all odd lines not to be rotated.
549 	 *     To remedy this, an index of the end ( = beginning) of the
550 	 *     current 'period' is kept, cur_period, and when it is reached,
551 	 *     the next period is started from cur_period + 1 which is
552 	 *     guaranteed not to have been reached since that would mean that
553 	 *     all records would have been reached. (think about it...).
554 	 *
555 	 * Lines in the rotation can have 3 attributes which are marked on the
556 	 * line so that curscr is consistent with the visual screen.
557 	 * 1.  Not dirty -- lines inside the scrolled block, top region or
558 	 *                  bottom region.
559 	 * 2.  Blank lines -- lines in the differential of the scrolling
560 	 *		      region adjacent to top and bot regions
561 	 *                    depending on scrolling direction.
562 	 * 3.  Dirty line -- all other lines are marked dirty.
563 	 */
564 	sc_region = bot - top + 1;
565 	i = top;
566 	tmp1 = curscr->lines[top];
567 	cur_period = top;
568 	for (j = top; j <= bot; j++) {
569 		target = (i - top + n + sc_region) % sc_region + top;
570 		tmp2 = curscr->lines[target];
571 		curscr->lines[target] = tmp1;
572 		/* Mark block as clean and blank out scrolled lines. */
573 		clp = curscr->lines[target];
574 #ifdef DEBUG
575 		__CTRACE("quickch: n=%d startw=%d curw=%d i = %d target=%d ",
576 			n, startw, curw, i, target);
577 #endif
578 		if ((target >= startw && target < curw) || target < top
579 		    || target > bot) {
580 #ifdef DEBUG
581 			__CTRACE("-- notdirty");
582 #endif
583 			win->lines[target]->flags &= ~__ISDIRTY;
584 		} else if ((n > 0 && target >= top && target < top + n) ||
585 		           (n < 0 && target <= bot && target > bot + n)) {
586 			if (clp->hash != blank_hash ||  memcmp(clp->line,
587 			    buf, win->maxx * __LDATASIZE) !=0) {
588 				(void)memcpy(clp->line,  buf,
589 				    win->maxx * __LDATASIZE);
590 #ifdef DEBUG
591 				__CTRACE("-- blanked out: dirty");
592 #endif
593 				clp->hash = blank_hash;
594 				__touchline(win, target, 0, win->maxx - 1, 0);
595 			} else {
596 				__touchline(win, target, 0, win->maxx - 1, 0);
597 #ifdef DEBUG
598 				__CTRACE(" -- blank line already: dirty");
599 #endif
600 			}
601 		} else {
602 #ifdef DEBUG
603 			__CTRACE(" -- dirty");
604 #endif
605 			__touchline(win, target, 0, win->maxx - 1, 0);
606 		}
607 #ifdef DEBUG
608 		__CTRACE("\n");
609 #endif
610 		if (target == cur_period) {
611 			i = target + 1;
612 			tmp1 = curscr->lines[i];
613 			cur_period = i;
614 		} else {
615 			tmp1 = tmp2;
616 			i = target;
617 		}
618 	}
619 #ifdef DEBUG
620 		__CTRACE("$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$\n");
621 		for (i = 0; i < curscr->maxy; i++) {
622 			__CTRACE("C: %d:", i);
623 			for (j = 0; j < curscr->maxx; j++)
624 				__CTRACE("%c",
625 			           curscr->lines[i]->line[j].ch);
626 			__CTRACE("\n");
627 			__CTRACE("W: %d:", i);
628 			for (j = 0; j < win->maxx; j++)
629 				__CTRACE("%c",
630 			           win->lines[i]->line[j].ch);
631 			__CTRACE("\n");
632 		}
633 #endif
634 	if (n != 0) {
635 		WINDOW *wp;
636 		scrolln(win, starts, startw, curs, bot, top);
637 		/*
638 		 * Need to repoint any subwindow lines to the rotated
639 		 * line structured.
640 		 */
641 		for (wp = win->nextp; wp != win; wp = wp->nextp)
642 			__set_subwin(win, wp);
643 	}
644 }
645 
646 /*
647  * Scrolln performs the scroll by n lines, where n is starts - startw.
648  */
649 static void
650 scrolln(win, starts, startw, curs, bot, top)
651 	WINDOW *win;
652 	int starts, startw, curs, bot, top;
653 {
654 	int i, oy, ox, n;
655 
656 	oy = curscr->cury;
657 	ox = curscr->curx;
658 	n = starts - startw;
659 
660 	if (n > 0) {
661 		__mvcur(oy, ox, top, 0, 1);
662 		/* Scroll up the block */
663 		if (DL)
664 			tputs(__tscroll(DL, n), 0, __cputchar);
665 		else
666 			for(i = 0; i < n; i++)
667 				tputs(dl, 0, __cputchar);
668 
669 		/*
670 		 * Push down the bottom region.
671 		 */
672 		__mvcur(top, 0, bot - n + 1, 0, 1);
673 		if (AL)
674 			tputs(__tscroll(AL, n), 0, __cputchar);
675 		else
676 			for(i = 0; i < n; i++)
677 				tputs(al, 0, __cputchar);
678 		__mvcur(bot - n + 1, 0, oy, ox, 1);
679 	} else {
680 		/* Preserve the bottom lines */
681 		__mvcur(oy, ox, bot + n + 1, 0, 1);	/* n < 0 */
682 		if (DL)
683 			tputs(__tscroll(DL, -n), 0, __cputchar);
684 		else
685 		       	for(i = n; i < 0; i++)
686 				tputs(dl, 0, __cputchar);
687 		__mvcur(bot + n + 1, 0, top, 0, 1);
688 
689 		/* Scroll the block down */
690 		if (AL)
691 			tputs(__tscroll(AL, -n), 0, __cputchar);
692 		else
693 			for(i = n; i < 0; i++)
694 				tputs(al, 0, __cputchar);
695 		__mvcur(top, 0, oy, ox, 1);
696 	}
697 }
698