1 /* $NetBSD: forwback.c,v 1.5 2023/10/06 05:49:49 simonb Exp $ */
2
3 /*
4 * Copyright (C) 1984-2023 Mark Nudelman
5 *
6 * You may distribute under the terms of either the GNU General Public
7 * License or the Less License, as specified in the README file.
8 *
9 * For more information, see the README file.
10 */
11
12
13 /*
14 * Primitives for displaying the file on the screen,
15 * scrolling either forward or backward.
16 */
17
18 #include "less.h"
19 #include "position.h"
20
21 public int screen_trashed;
22 public int squished;
23 public int no_back_scroll = 0;
24 public int forw_prompt;
25 public int first_time = 1;
26
27 extern int sigs;
28 extern int top_scroll;
29 extern int quiet;
30 extern int sc_width, sc_height;
31 extern int hshift;
32 extern int auto_wrap;
33 extern int more_mode;
34 extern int plusoption;
35 extern int forw_scroll;
36 extern int back_scroll;
37 extern int ignore_eoi;
38 extern int clear_bg;
39 extern int final_attr;
40 extern int header_lines;
41 extern int header_cols;
42 extern int full_screen;
43 #if HILITE_SEARCH
44 extern int size_linebuf;
45 extern int hilite_search;
46 extern int status_col;
47 #endif
48 #if TAGS
49 extern char *tagoption;
50 #endif
51
52 /*
53 * Sound the bell to indicate user is trying to move past end of file.
54 */
eof_bell(void)55 public void eof_bell(void)
56 {
57 #if HAVE_TIME
58 static time_type last_eof_bell = 0;
59 time_type now = get_time();
60 if (now == last_eof_bell) /* max once per second */
61 return;
62 last_eof_bell = now;
63 #endif
64 if (quiet == NOT_QUIET)
65 bell();
66 else
67 vbell();
68 }
69
70 /*
71 * Check to see if the end of file is currently displayed.
72 */
eof_displayed(void)73 public int eof_displayed(void)
74 {
75 POSITION pos;
76
77 if (ignore_eoi)
78 return (0);
79
80 if (ch_length() == NULL_POSITION)
81 /*
82 * If the file length is not known,
83 * we can't possibly be displaying EOF.
84 */
85 return (0);
86
87 /*
88 * If the bottom line is empty, we are at EOF.
89 * If the bottom line ends at the file length,
90 * we must be just at EOF.
91 */
92 pos = position(BOTTOM_PLUS_ONE);
93 return (pos == NULL_POSITION || pos == ch_length());
94 }
95
96 /*
97 * Check to see if the entire file is currently displayed.
98 */
entire_file_displayed(void)99 public int entire_file_displayed(void)
100 {
101 POSITION pos;
102
103 /* Make sure last line of file is displayed. */
104 if (!eof_displayed())
105 return (0);
106
107 /* Make sure first line of file is displayed. */
108 pos = position(0);
109 return (pos == NULL_POSITION || pos == 0);
110 }
111
112 /*
113 * If the screen is "squished", repaint it.
114 * "Squished" means the first displayed line is not at the top
115 * of the screen; this can happen when we display a short file
116 * for the first time.
117 */
squish_check(void)118 public void squish_check(void)
119 {
120 if (!squished)
121 return;
122 squished = 0;
123 repaint();
124 }
125
126 /*
127 * Read the first pfx columns of the next line.
128 * If skipeol==0 stop there, otherwise read and discard chars to end of line.
129 */
forw_line_pfx(POSITION pos,int pfx,int skipeol)130 static POSITION forw_line_pfx(POSITION pos, int pfx, int skipeol)
131 {
132 int save_sc_width = sc_width;
133 int save_auto_wrap = auto_wrap;
134 int save_hshift = hshift;
135 /* Set fake sc_width to force only pfx chars to be read. */
136 sc_width = pfx + line_pfx_width();
137 auto_wrap = 0;
138 hshift = 0;
139 pos = forw_line_seg(pos, skipeol, FALSE, FALSE);
140 sc_width = save_sc_width;
141 auto_wrap = save_auto_wrap;
142 hshift = save_hshift;
143 return pos;
144 }
145
146 /*
147 * Set header text color.
148 * Underline last line of headers, but not at beginning of file
149 * (where there is no gap between the last header line and the next line).
150 */
set_attr_header(int ln)151 static void set_attr_header(int ln)
152 {
153 set_attr_line(AT_COLOR_HEADER);
154 if (ln+1 == header_lines && position(0) != ch_zero())
155 set_attr_line(AT_UNDERLINE);
156 }
157
158 /*
159 * Display file headers, overlaying text already drawn
160 * at top and left of screen.
161 */
overlay_header(void)162 public int overlay_header(void)
163 {
164 POSITION pos = ch_zero(); /* header lines are at beginning of file */
165 int ln;
166 int moved = FALSE;
167
168 if (header_lines > 0)
169 {
170 /* Draw header_lines lines from start of file at top of screen. */
171 home();
172 for (ln = 0; ln < header_lines; ++ln)
173 {
174 pos = forw_line(pos);
175 set_attr_header(ln);
176 clear_eol();
177 put_line();
178 }
179 moved = TRUE;
180 }
181 if (header_cols > 0)
182 {
183 /* Draw header_cols columns at left of each line. */
184 home();
185 pos = ch_zero();
186 for (ln = 0; ln < sc_height-1; ++ln)
187 {
188 if (ln >= header_lines) /* switch from header lines to normal lines */
189 pos = position(ln);
190 if (pos == NULL_POSITION)
191 putchr('\n');
192 else
193 {
194 /* Need skipeol for all header lines except the last one. */
195 pos = forw_line_pfx(pos, header_cols, ln+1 < header_lines);
196 set_attr_header(ln);
197 put_line();
198 }
199 }
200 moved = TRUE;
201 }
202 if (moved)
203 lower_left();
204 return moved;
205 }
206
207 /*
208 * Display n lines, scrolling forward,
209 * starting at position pos in the input file.
210 * "force" means display the n lines even if we hit end of file.
211 * "only_last" means display only the last screenful if n > screen size.
212 * "nblank" is the number of blank lines to draw before the first
213 * real line. If nblank > 0, the pos must be NULL_POSITION.
214 * The first real line after the blanks will start at ch_zero().
215 */
forw(int n,POSITION pos,int force,int only_last,int nblank)216 public void forw(int n, POSITION pos, int force, int only_last, int nblank)
217 {
218 int nlines = 0;
219 int do_repaint;
220
221 squish_check();
222
223 /*
224 * do_repaint tells us not to display anything till the end,
225 * then just repaint the entire screen.
226 * We repaint if we are supposed to display only the last
227 * screenful and the request is for more than a screenful.
228 * Also if the request exceeds the forward scroll limit
229 * (but not if the request is for exactly a screenful, since
230 * repainting itself involves scrolling forward a screenful).
231 */
232 do_repaint = (only_last && n > sc_height-1) ||
233 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
234
235 #if HILITE_SEARCH
236 if (pos != NULL_POSITION && (hilite_search == OPT_ONPLUS || is_filtering() || status_col)) {
237 prep_hilite(pos, pos + 4*size_linebuf, ignore_eoi ? 1 : -1);
238 pos = next_unfiltered(pos);
239 }
240 #endif
241
242 if (!do_repaint)
243 {
244 if (top_scroll && n >= sc_height - 1 && pos != ch_length())
245 {
246 /*
247 * Start a new screen.
248 * {{ This is not really desirable if we happen
249 * to hit eof in the middle of this screen,
250 * but we don't yet know if that will happen. }}
251 */
252 pos_clear();
253 add_forw_pos(pos);
254 force = 1;
255 clear();
256 home();
257 }
258
259 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
260 {
261 /*
262 * This is not contiguous with what is
263 * currently displayed. Clear the screen image
264 * (position table) and start a new screen.
265 */
266 pos_clear();
267 add_forw_pos(pos);
268 force = 1;
269 if (top_scroll)
270 {
271 clear();
272 home();
273 } else if (!first_time && !is_filtering() && full_screen)
274 {
275 putstr("...skipping...\n");
276 }
277 }
278 }
279
280 while (--n >= 0)
281 {
282 /*
283 * Read the next line of input.
284 */
285 if (nblank > 0)
286 {
287 /*
288 * Still drawing blanks; don't get a line
289 * from the file yet.
290 * If this is the last blank line, get ready to
291 * read a line starting at ch_zero() next time.
292 */
293 if (--nblank == 0)
294 pos = ch_zero();
295 } else
296 {
297 /*
298 * Get the next line from the file.
299 */
300 pos = forw_line(pos);
301 #if HILITE_SEARCH
302 pos = next_unfiltered(pos);
303 #endif
304 if (pos == NULL_POSITION)
305 {
306 /*
307 * End of file: stop here unless the top line
308 * is still empty, or "force" is true.
309 * Even if force is true, stop when the last
310 * line in the file reaches the top of screen.
311 */
312 if (!force && position(TOP) != NULL_POSITION)
313 break;
314 if (!empty_lines(0, 0) &&
315 !empty_lines(1, 1) &&
316 empty_lines(2, sc_height-1))
317 break;
318 }
319 }
320 /*
321 * Add the position of the next line to the position table.
322 * Display the current line on the screen.
323 */
324 add_forw_pos(pos);
325 nlines++;
326 if (do_repaint)
327 continue;
328 /*
329 * If this is the first screen displayed and
330 * we hit an early EOF (i.e. before the requested
331 * number of lines), we "squish" the display down
332 * at the bottom of the screen.
333 * But don't do this if a + option or a -t option
334 * was given. These options can cause us to
335 * start the display after the beginning of the file,
336 * and it is not appropriate to squish in that case.
337 */
338 if ((first_time || more_mode) &&
339 pos == NULL_POSITION && !top_scroll &&
340 #if TAGS
341 tagoption == NULL &&
342 #endif
343 !plusoption)
344 {
345 squished = 1;
346 continue;
347 }
348 put_line();
349 #if 0
350 /* {{
351 * Can't call clear_eol here. The cursor might be at end of line
352 * on an ignaw terminal, so clear_eol would clear the last char
353 * of the current line instead of all of the next line.
354 * If we really need to do this on clear_bg terminals, we need
355 * to find a better way.
356 * }}
357 */
358 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
359 {
360 /*
361 * Writing the last character on the last line
362 * of the display may have scrolled the screen.
363 * If we were in standout mode, clear_bg terminals
364 * will fill the new line with the standout color.
365 * Now we're in normal mode again, so clear the line.
366 */
367 clear_eol();
368 }
369 #endif
370 forw_prompt = 1;
371 }
372
373 if (header_lines > 0)
374 {
375 /*
376 * Don't allow ch_zero to appear on screen except at top of screen.
377 * Otherwise duplicate header lines may be displayed.
378 */
379 if (onscreen(ch_zero()) > 0)
380 {
381 jump_loc(ch_zero(), 0); /* {{ yuck }} */
382 return;
383 }
384 }
385 if (nlines == 0 && !ignore_eoi)
386 eof_bell();
387 else if (do_repaint)
388 repaint();
389 else
390 {
391 overlay_header();
392 /* lower_left(); {{ considered harmful? }} */
393 }
394 first_time = 0;
395 (void) currline(BOTTOM);
396 }
397
398 /*
399 * Display n lines, scrolling backward.
400 */
back(int n,POSITION pos,int force,int only_last)401 public void back(int n, POSITION pos, int force, int only_last)
402 {
403 int nlines = 0;
404 int do_repaint;
405
406 squish_check();
407 do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1) || header_lines > 0);
408 #if HILITE_SEARCH
409 if (pos != NULL_POSITION && (hilite_search == OPT_ONPLUS || is_filtering() || status_col)) {
410 prep_hilite((pos < 3*size_linebuf) ? 0 : pos - 3*size_linebuf, pos, -1);
411 }
412 #endif
413 while (--n >= 0)
414 {
415 /*
416 * Get the previous line of input.
417 */
418 #if HILITE_SEARCH
419 pos = prev_unfiltered(pos);
420 #endif
421
422 pos = back_line(pos);
423 if (pos == NULL_POSITION)
424 {
425 /*
426 * Beginning of file: stop here unless "force" is true.
427 */
428 if (!force)
429 break;
430 }
431 /*
432 * Add the position of the previous line to the position table.
433 * Display the line on the screen.
434 */
435 add_back_pos(pos);
436 nlines++;
437 if (!do_repaint)
438 {
439 home();
440 add_line();
441 put_line();
442 }
443 }
444 if (nlines == 0)
445 eof_bell();
446 else if (do_repaint)
447 repaint();
448 else
449 {
450 overlay_header();
451 lower_left();
452 }
453 (void) currline(BOTTOM);
454 }
455
456 /*
457 * Display n more lines, forward.
458 * Start just after the line currently displayed at the bottom of the screen.
459 */
forward(int n,int force,int only_last)460 public void forward(int n, int force, int only_last)
461 {
462 POSITION pos;
463
464 if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
465 {
466 /*
467 * If the -e flag is set and we're trying to go
468 * forward from end-of-file, go on to the next file.
469 */
470 if (edit_next(1))
471 quit(QUIT_OK);
472 return;
473 }
474
475 pos = position(BOTTOM_PLUS_ONE);
476 if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
477 {
478 if (ignore_eoi)
479 {
480 /*
481 * ignore_eoi is to support A_F_FOREVER.
482 * Back up until there is a line at the bottom
483 * of the screen.
484 */
485 if (empty_screen())
486 pos = ch_zero();
487 else
488 {
489 do
490 {
491 back(1, position(TOP), 1, 0);
492 pos = position(BOTTOM_PLUS_ONE);
493 } while (pos == NULL_POSITION && !ABORT_SIGS());
494 }
495 } else
496 {
497 eof_bell();
498 return;
499 }
500 }
501 forw(n, pos, force, only_last, 0);
502 }
503
504 /*
505 * Display n more lines, backward.
506 * Start just before the line currently displayed at the top of the screen.
507 */
backward(int n,int force,int only_last)508 public void backward(int n, int force, int only_last)
509 {
510 POSITION pos;
511
512 pos = position(TOP);
513 if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
514 {
515 eof_bell();
516 return;
517 }
518 back(n, pos, force, only_last);
519 }
520
521 /*
522 * Get the backwards scroll limit.
523 * Must call this function instead of just using the value of
524 * back_scroll, because the default case depends on sc_height and
525 * top_scroll, as well as back_scroll.
526 */
get_back_scroll(void)527 public int get_back_scroll(void)
528 {
529 if (no_back_scroll)
530 return (0);
531 if (back_scroll >= 0)
532 return (back_scroll);
533 if (top_scroll)
534 return (sc_height - 2);
535 return (10000); /* infinity */
536 }
537
538 /*
539 * Will the entire file fit on one screen?
540 */
get_one_screen(void)541 public int get_one_screen(void)
542 {
543 int nlines;
544 POSITION pos = ch_zero();
545
546 for (nlines = 0; nlines < sc_height; nlines++)
547 {
548 pos = forw_line(pos);
549 if (pos == NULL_POSITION) break;
550 }
551 return (nlines < sc_height);
552 }
553