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