1 /*
2 * Copyright (C) 1984-2024 Mark Nudelman
3 *
4 * You may distribute under the terms of either the GNU General Public
5 * License or the Less License, as specified in the README file.
6 *
7 * For more information, see the README file.
8 */
9
10
11 /*
12 * Primitives for displaying the file on the screen,
13 * scrolling either forward or backward.
14 */
15
16 #include "less.h"
17 #include "position.h"
18
19 extern int less_is_more;
20
21 public lbool squished;
22 public int no_back_scroll = 0;
23 public int forw_prompt;
24 public int first_time = 1;
25 public lbool no_eof_bell = FALSE;
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 lbool plusoption;
34 extern int forw_scroll;
35 extern int back_scroll;
36 extern int ignore_eoi;
37 extern int header_lines;
38 extern int header_cols;
39 extern int full_screen;
40 extern POSITION header_start_pos;
41 #if HILITE_SEARCH
42 extern size_t size_linebuf;
43 extern int hilite_search;
44 extern int status_col;
45 #endif
46 #if TAGS
47 extern char *tagoption;
48 #endif
49
50 /*
51 * Sound the bell to indicate user is trying to move past end of file.
52 */
eof_bell(void)53 public void eof_bell(void)
54 {
55 if (no_eof_bell)
56 return;
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 lbool eof_displayed(void)
74 {
75 POSITION pos;
76
77 if (ignore_eoi)
78 return (FALSE);
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 (FALSE);
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 lbool entire_file_displayed(void)
100 {
101 POSITION pos;
102
103 /* Make sure last line of file is displayed. */
104 if (!eof_displayed())
105 return (FALSE);
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 = FALSE;
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 header_start_pos
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) != header_start_pos)
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 int ln;
165 lbool moved = FALSE;
166
167 if (header_lines > 0)
168 {
169 /* Draw header_lines lines from start of file at top of screen. */
170 POSITION pos = header_start_pos;
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 POSITION pos = header_start_pos;
185 home();
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,lbool force,lbool only_last,int nblank)216 public void forw(int n, POSITION pos, lbool force, lbool only_last, int nblank)
217 {
218 int nlines = 0;
219 lbool do_repaint;
220
221 if (pos != NULL_POSITION)
222 pos = after_header_pos(pos);
223 squish_check();
224
225 /*
226 * do_repaint tells us not to display anything till the end,
227 * then just repaint the entire screen.
228 * We repaint if we are supposed to display only the last
229 * screenful and the request is for more than a screenful.
230 * Also if the request exceeds the forward scroll limit
231 * (but not if the request is for exactly a screenful, since
232 * repainting itself involves scrolling forward a screenful).
233 */
234 do_repaint = (only_last && n > sc_height-1) ||
235 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
236
237 #if HILITE_SEARCH
238 if (pos != NULL_POSITION && (hilite_search == OPT_ONPLUS || is_filtering() || status_col)) {
239 prep_hilite(pos, pos + (POSITION) (4*size_linebuf), ignore_eoi ? 1 : -1);
240 pos = next_unfiltered(pos);
241 }
242 #endif
243
244 if (!do_repaint)
245 {
246 if (top_scroll && n >= sc_height - 1 && pos != ch_length())
247 {
248 /*
249 * Start a new screen.
250 * {{ This is not really desirable if we happen
251 * to hit eof in the middle of this screen,
252 * but we don't yet know if that will happen. }}
253 */
254 pos_clear();
255 add_forw_pos(pos);
256 force = TRUE;
257 if (less_is_more == 0) {
258 clear();
259 home();
260 }
261 }
262
263 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
264 {
265 /*
266 * This is not contiguous with what is
267 * currently displayed. Clear the screen image
268 * (position table) and start a new screen.
269 */
270 pos_clear();
271 add_forw_pos(pos);
272 force = TRUE;
273 if (top_scroll)
274 {
275 clear();
276 home();
277 } else if (!first_time && !is_filtering() && full_screen)
278 {
279 putstr("...skipping...\n");
280 }
281 }
282 }
283
284 while (--n >= 0)
285 {
286 /*
287 * Read the next line of input.
288 */
289 if (nblank > 0)
290 {
291 /*
292 * Still drawing blanks; don't get a line
293 * from the file yet.
294 * If this is the last blank line, get ready to
295 * read a line starting at ch_zero() next time.
296 */
297 if (--nblank == 0)
298 pos = ch_zero();
299 } else
300 {
301 /*
302 * Get the next line from the file.
303 */
304 pos = forw_line(pos);
305 #if HILITE_SEARCH
306 pos = next_unfiltered(pos);
307 #endif
308 if (pos == NULL_POSITION)
309 {
310 /*
311 * End of file: stop here unless the top line
312 * is still empty, or "force" is true.
313 * Even if force is true, stop when the last
314 * line in the file reaches the top of screen.
315 */
316 if (!force && position(TOP) != NULL_POSITION)
317 break;
318 if (!empty_lines(0, 0) &&
319 !empty_lines(1, 1) &&
320 empty_lines(2, sc_height-1))
321 break;
322 }
323 }
324 /*
325 * Add the position of the next line to the position table.
326 * Display the current line on the screen.
327 */
328 add_forw_pos(pos);
329 nlines++;
330 if (do_repaint)
331 continue;
332 /*
333 * If this is the first screen displayed and
334 * we hit an early EOF (i.e. before the requested
335 * number of lines), we "squish" the display down
336 * at the bottom of the screen.
337 * But don't do this if a + option or a -t option
338 * was given. These options can cause us to
339 * start the display after the beginning of the file,
340 * and it is not appropriate to squish in that case.
341 */
342 if ((first_time || less_is_more) &&
343 pos == NULL_POSITION && !top_scroll &&
344 header_lines == 0 && header_cols == 0 &&
345 #if TAGS
346 tagoption == NULL &&
347 #endif
348 !plusoption)
349 {
350 squished = TRUE;
351 continue;
352 }
353 put_line();
354 #if 0
355 /* {{
356 * Can't call clear_eol here. The cursor might be at end of line
357 * on an ignaw terminal, so clear_eol would clear the last char
358 * of the current line instead of all of the next line.
359 * If we really need to do this on clear_bg terminals, we need
360 * to find a better way.
361 * }}
362 */
363 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
364 {
365 /*
366 * Writing the last character on the last line
367 * of the display may have scrolled the screen.
368 * If we were in standout mode, clear_bg terminals
369 * will fill the new line with the standout color.
370 * Now we're in normal mode again, so clear the line.
371 */
372 clear_eol();
373 }
374 #endif
375 forw_prompt = 1;
376 }
377 if (nlines == 0 && !ignore_eoi)
378 eof_bell();
379 else if (do_repaint)
380 repaint();
381 else
382 {
383 overlay_header();
384 /* lower_left(); {{ considered harmful? }} */
385 }
386 first_time = 0;
387 (void) currline(BOTTOM);
388 }
389
390 /*
391 * Display n lines, scrolling backward.
392 */
back(int n,POSITION pos,lbool force,lbool only_last)393 public void back(int n, POSITION pos, lbool force, lbool only_last)
394 {
395 int nlines = 0;
396 lbool do_repaint;
397
398 squish_check();
399 do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1) || header_lines > 0);
400 #if HILITE_SEARCH
401 if (pos != NULL_POSITION && (hilite_search == OPT_ONPLUS || is_filtering() || status_col)) {
402 prep_hilite((pos < (POSITION) (3*size_linebuf)) ? 0 : pos - (POSITION) (3*size_linebuf), pos, -1);
403 }
404 #endif
405 while (--n >= 0)
406 {
407 /*
408 * Get the previous line of input.
409 */
410 #if HILITE_SEARCH
411 pos = prev_unfiltered(pos);
412 #endif
413 pos = back_line(pos);
414 if (pos == NULL_POSITION)
415 {
416 /*
417 * Beginning of file: stop here unless "force" is true.
418 */
419 if (!force)
420 break;
421 }
422 if (pos != after_header_pos(pos))
423 {
424 /*
425 * Don't allow scrolling back to before the current header line.
426 */
427 break;
428 }
429 /*
430 * Add the position of the previous line to the position table.
431 * Display the line on the screen.
432 */
433 add_back_pos(pos);
434 nlines++;
435 if (!do_repaint)
436 {
437 home();
438 add_line();
439 put_line();
440 }
441 }
442 if (nlines == 0)
443 eof_bell();
444 else if (do_repaint)
445 repaint();
446 else
447 {
448 overlay_header();
449 lower_left();
450 }
451 (void) currline(BOTTOM);
452 }
453
454 /*
455 * Display n more lines, forward.
456 * Start just after the line currently displayed at the bottom of the screen.
457 */
forward(int n,lbool force,lbool only_last)458 public void forward(int n, lbool force, lbool only_last)
459 {
460 POSITION pos;
461
462 if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
463 {
464 /*
465 * If the -e flag is set and we're trying to go
466 * forward from end-of-file, go on to the next file.
467 */
468 if (edit_next(1))
469 quit(QUIT_OK);
470 return;
471 }
472
473 pos = position(BOTTOM_PLUS_ONE);
474 if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
475 {
476 if (ignore_eoi)
477 {
478 /*
479 * ignore_eoi is to support A_F_FOREVER.
480 * Back up until there is a line at the bottom
481 * of the screen.
482 */
483 if (empty_screen())
484 pos = ch_zero();
485 else
486 {
487 do
488 {
489 back(1, position(TOP), 1, 0);
490 pos = position(BOTTOM_PLUS_ONE);
491 } while (pos == NULL_POSITION && !ABORT_SIGS());
492 }
493 } else
494 {
495 eof_bell();
496 return;
497 }
498 }
499 forw(n, pos, force, only_last, 0);
500 }
501
502 /*
503 * Display n more lines, backward.
504 * Start just before the line currently displayed at the top of the screen.
505 */
backward(int n,lbool force,lbool only_last)506 public void backward(int n, lbool force, lbool only_last)
507 {
508 POSITION pos;
509
510 pos = position(TOP);
511 if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
512 {
513 eof_bell();
514 return;
515 }
516 back(n, pos, force, only_last);
517 }
518
519 /*
520 * Get the backwards scroll limit.
521 * Must call this function instead of just using the value of
522 * back_scroll, because the default case depends on sc_height and
523 * top_scroll, as well as back_scroll.
524 */
get_back_scroll(void)525 public int get_back_scroll(void)
526 {
527 if (no_back_scroll)
528 return (0);
529 if (back_scroll >= 0)
530 return (back_scroll);
531 if (top_scroll)
532 return (sc_height - 2);
533 return (10000); /* infinity */
534 }
535
536 /*
537 * Will the entire file fit on one screen?
538 */
get_one_screen(void)539 public int get_one_screen(void)
540 {
541 int nlines;
542 POSITION pos = ch_zero();
543
544 for (nlines = 0; nlines < sc_height; nlines++)
545 {
546 pos = forw_line(pos);
547 if (pos == NULL_POSITION) break;
548 }
549 return (nlines < sc_height);
550 }
551