1 /*
2 * Copyright (C) 1984-2023 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 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 plusoption;
34 extern int forw_scroll;
35 extern int back_scroll;
36 extern int ignore_eoi;
37 extern int clear_bg;
38 extern int final_attr;
39 extern int header_lines;
40 extern int header_cols;
41 extern int full_screen;
42 #if HILITE_SEARCH
43 extern int size_linebuf;
44 extern int hilite_search;
45 extern int status_col;
46 #endif
47 #if TAGS
48 extern char *tagoption;
49 #endif
50
51 /*
52 * Sound the bell to indicate user is trying to move past end of file.
53 */
eof_bell(void)54 public void eof_bell(void)
55 {
56 #if HAVE_TIME
57 static time_type last_eof_bell = 0;
58 time_type now = get_time();
59 if (now == last_eof_bell) /* max once per second */
60 return;
61 last_eof_bell = now;
62 #endif
63 if (quiet == NOT_QUIET)
64 bell();
65 else
66 vbell();
67 }
68
69 /*
70 * Check to see if the end of file is currently displayed.
71 */
eof_displayed(void)72 public int eof_displayed(void)
73 {
74 POSITION pos;
75
76 if (ignore_eoi)
77 return (0);
78
79 if (ch_length() == NULL_POSITION)
80 /*
81 * If the file length is not known,
82 * we can't possibly be displaying EOF.
83 */
84 return (0);
85
86 /*
87 * If the bottom line is empty, we are at EOF.
88 * If the bottom line ends at the file length,
89 * we must be just at EOF.
90 */
91 pos = position(BOTTOM_PLUS_ONE);
92 return (pos == NULL_POSITION || pos == ch_length());
93 }
94
95 /*
96 * Check to see if the entire file is currently displayed.
97 */
entire_file_displayed(void)98 public int entire_file_displayed(void)
99 {
100 POSITION pos;
101
102 /* Make sure last line of file is displayed. */
103 if (!eof_displayed())
104 return (0);
105
106 /* Make sure first line of file is displayed. */
107 pos = position(0);
108 return (pos == NULL_POSITION || pos == 0);
109 }
110
111 /*
112 * If the screen is "squished", repaint it.
113 * "Squished" means the first displayed line is not at the top
114 * of the screen; this can happen when we display a short file
115 * for the first time.
116 */
squish_check(void)117 public void squish_check(void)
118 {
119 if (!squished)
120 return;
121 squished = 0;
122 repaint();
123 }
124
125 /*
126 * Read the first pfx columns of the next line.
127 * If skipeol==0 stop there, otherwise read and discard chars to end of line.
128 */
forw_line_pfx(POSITION pos,int pfx,int skipeol)129 static POSITION forw_line_pfx(POSITION pos, int pfx, int skipeol)
130 {
131 int save_sc_width = sc_width;
132 int save_auto_wrap = auto_wrap;
133 int save_hshift = hshift;
134 /* Set fake sc_width to force only pfx chars to be read. */
135 sc_width = pfx + line_pfx_width();
136 auto_wrap = 0;
137 hshift = 0;
138 pos = forw_line_seg(pos, skipeol, FALSE, FALSE);
139 sc_width = save_sc_width;
140 auto_wrap = save_auto_wrap;
141 hshift = save_hshift;
142 return pos;
143 }
144
145 /*
146 * Set header text color.
147 * Underline last line of headers, but not at beginning of file
148 * (where there is no gap between the last header line and the next line).
149 */
set_attr_header(int ln)150 static void set_attr_header(int ln)
151 {
152 set_attr_line(AT_COLOR_HEADER);
153 if (ln+1 == header_lines && position(0) != ch_zero())
154 set_attr_line(AT_UNDERLINE);
155 }
156
157 /*
158 * Display file headers, overlaying text already drawn
159 * at top and left of screen.
160 */
overlay_header(void)161 public int overlay_header(void)
162 {
163 POSITION pos = ch_zero(); /* header lines are at beginning of file */
164 int ln;
165 int moved = FALSE;
166
167 if (header_lines > 0)
168 {
169 /* Draw header_lines lines from start of file at top of screen. */
170 home();
171 for (ln = 0; ln < header_lines; ++ln)
172 {
173 pos = forw_line(pos);
174 set_attr_header(ln);
175 clear_eol();
176 put_line();
177 }
178 moved = TRUE;
179 }
180 if (header_cols > 0)
181 {
182 /* Draw header_cols columns at left of each line. */
183 home();
184 pos = ch_zero();
185 for (ln = 0; ln < sc_height-1; ++ln)
186 {
187 if (ln >= header_lines) /* switch from header lines to normal lines */
188 pos = position(ln);
189 if (pos == NULL_POSITION)
190 putchr('\n');
191 else
192 {
193 /* Need skipeol for all header lines except the last one. */
194 pos = forw_line_pfx(pos, header_cols, ln+1 < header_lines);
195 set_attr_header(ln);
196 put_line();
197 }
198 }
199 moved = TRUE;
200 }
201 if (moved)
202 lower_left();
203 return moved;
204 }
205
206 /*
207 * Display n lines, scrolling forward,
208 * starting at position pos in the input file.
209 * "force" means display the n lines even if we hit end of file.
210 * "only_last" means display only the last screenful if n > screen size.
211 * "nblank" is the number of blank lines to draw before the first
212 * real line. If nblank > 0, the pos must be NULL_POSITION.
213 * The first real line after the blanks will start at ch_zero().
214 */
forw(int n,POSITION pos,int force,int only_last,int nblank)215 public void forw(int n, POSITION pos, int force, int only_last, int nblank)
216 {
217 int nlines = 0;
218 int do_repaint;
219
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 + 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 = 1;
254 if (less_is_more == 0) {
255 clear();
256 home();
257 }
258 }
259
260 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
261 {
262 /*
263 * This is not contiguous with what is
264 * currently displayed. Clear the screen image
265 * (position table) and start a new screen.
266 */
267 pos_clear();
268 add_forw_pos(pos);
269 force = 1;
270 if (top_scroll)
271 {
272 clear();
273 home();
274 } else if (!first_time && !is_filtering() && full_screen)
275 {
276 putstr("...skipping...\n");
277 }
278 }
279 }
280
281 while (--n >= 0)
282 {
283 /*
284 * Read the next line of input.
285 */
286 if (nblank > 0)
287 {
288 /*
289 * Still drawing blanks; don't get a line
290 * from the file yet.
291 * If this is the last blank line, get ready to
292 * read a line starting at ch_zero() next time.
293 */
294 if (--nblank == 0)
295 pos = ch_zero();
296 } else
297 {
298 /*
299 * Get the next line from the file.
300 */
301 pos = forw_line(pos);
302 #if HILITE_SEARCH
303 pos = next_unfiltered(pos);
304 #endif
305 if (pos == NULL_POSITION)
306 {
307 /*
308 * End of file: stop here unless the top line
309 * is still empty, or "force" is true.
310 * Even if force is true, stop when the last
311 * line in the file reaches the top of screen.
312 */
313 if (!force && position(TOP) != NULL_POSITION)
314 break;
315 if (!empty_lines(0, 0) &&
316 !empty_lines(1, 1) &&
317 empty_lines(2, sc_height-1))
318 break;
319 }
320 }
321 /*
322 * Add the position of the next line to the position table.
323 * Display the current line on the screen.
324 */
325 add_forw_pos(pos);
326 nlines++;
327 if (do_repaint)
328 continue;
329 /*
330 * If this is the first screen displayed and
331 * we hit an early EOF (i.e. before the requested
332 * number of lines), we "squish" the display down
333 * at the bottom of the screen.
334 * But don't do this if a + option or a -t option
335 * was given. These options can cause us to
336 * start the display after the beginning of the file,
337 * and it is not appropriate to squish in that case.
338 */
339 if ((first_time || less_is_more) &&
340 pos == NULL_POSITION && !top_scroll &&
341 header_lines == 0 && header_cols == 0 &&
342 #if TAGS
343 tagoption == NULL &&
344 #endif
345 !plusoption)
346 {
347 squished = 1;
348 continue;
349 }
350 put_line();
351 #if 0
352 /* {{
353 * Can't call clear_eol here. The cursor might be at end of line
354 * on an ignaw terminal, so clear_eol would clear the last char
355 * of the current line instead of all of the next line.
356 * If we really need to do this on clear_bg terminals, we need
357 * to find a better way.
358 * }}
359 */
360 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
361 {
362 /*
363 * Writing the last character on the last line
364 * of the display may have scrolled the screen.
365 * If we were in standout mode, clear_bg terminals
366 * will fill the new line with the standout color.
367 * Now we're in normal mode again, so clear the line.
368 */
369 clear_eol();
370 }
371 #endif
372 forw_prompt = 1;
373 }
374
375 if (header_lines > 0)
376 {
377 /*
378 * Don't allow ch_zero to appear on screen except at top of screen.
379 * Otherwise duplicate header lines may be displayed.
380 */
381 if (onscreen(ch_zero()) > 0)
382 {
383 jump_loc(ch_zero(), 0); /* {{ yuck }} */
384 return;
385 }
386 }
387 if (nlines == 0 && !ignore_eoi)
388 eof_bell();
389 else if (do_repaint)
390 repaint();
391 else
392 {
393 overlay_header();
394 /* lower_left(); {{ considered harmful? }} */
395 }
396 first_time = 0;
397 (void) currline(BOTTOM);
398 }
399
400 /*
401 * Display n lines, scrolling backward.
402 */
back(int n,POSITION pos,int force,int only_last)403 public void back(int n, POSITION pos, int force, int only_last)
404 {
405 int nlines = 0;
406 int do_repaint;
407
408 squish_check();
409 do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1) || header_lines > 0);
410 #if HILITE_SEARCH
411 if (pos != NULL_POSITION && (hilite_search == OPT_ONPLUS || is_filtering() || status_col)) {
412 prep_hilite((pos < 3*size_linebuf) ? 0 : pos - 3*size_linebuf, pos, -1);
413 }
414 #endif
415 while (--n >= 0)
416 {
417 /*
418 * Get the previous line of input.
419 */
420 #if HILITE_SEARCH
421 pos = prev_unfiltered(pos);
422 #endif
423
424 pos = back_line(pos);
425 if (pos == NULL_POSITION)
426 {
427 /*
428 * Beginning of file: stop here unless "force" is true.
429 */
430 if (!force)
431 break;
432 }
433 /*
434 * Add the position of the previous line to the position table.
435 * Display the line on the screen.
436 */
437 add_back_pos(pos);
438 nlines++;
439 if (!do_repaint)
440 {
441 home();
442 add_line();
443 put_line();
444 }
445 }
446 if (nlines == 0)
447 eof_bell();
448 else if (do_repaint)
449 repaint();
450 else
451 {
452 overlay_header();
453 lower_left();
454 }
455 (void) currline(BOTTOM);
456 }
457
458 /*
459 * Display n more lines, forward.
460 * Start just after the line currently displayed at the bottom of the screen.
461 */
forward(int n,int force,int only_last)462 public void forward(int n, int force, int only_last)
463 {
464 POSITION pos;
465
466 if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
467 {
468 /*
469 * If the -e flag is set and we're trying to go
470 * forward from end-of-file, go on to the next file.
471 */
472 if (edit_next(1))
473 quit(QUIT_OK);
474 return;
475 }
476
477 pos = position(BOTTOM_PLUS_ONE);
478 if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
479 {
480 if (ignore_eoi)
481 {
482 /*
483 * ignore_eoi is to support A_F_FOREVER.
484 * Back up until there is a line at the bottom
485 * of the screen.
486 */
487 if (empty_screen())
488 pos = ch_zero();
489 else
490 {
491 do
492 {
493 back(1, position(TOP), 1, 0);
494 pos = position(BOTTOM_PLUS_ONE);
495 } while (pos == NULL_POSITION && !ABORT_SIGS());
496 }
497 } else
498 {
499 eof_bell();
500 return;
501 }
502 }
503 forw(n, pos, force, only_last, 0);
504 }
505
506 /*
507 * Display n more lines, backward.
508 * Start just before the line currently displayed at the top of the screen.
509 */
backward(int n,int force,int only_last)510 public void backward(int n, int force, int only_last)
511 {
512 POSITION pos;
513
514 pos = position(TOP);
515 if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
516 {
517 eof_bell();
518 return;
519 }
520 back(n, pos, force, only_last);
521 }
522
523 /*
524 * Get the backwards scroll limit.
525 * Must call this function instead of just using the value of
526 * back_scroll, because the default case depends on sc_height and
527 * top_scroll, as well as back_scroll.
528 */
get_back_scroll(void)529 public int get_back_scroll(void)
530 {
531 if (no_back_scroll)
532 return (0);
533 if (back_scroll >= 0)
534 return (back_scroll);
535 if (top_scroll)
536 return (sc_height - 2);
537 return (10000); /* infinity */
538 }
539
540 /*
541 * Will the entire file fit on one screen?
542 */
get_one_screen(void)543 public int get_one_screen(void)
544 {
545 int nlines;
546 POSITION pos = ch_zero();
547
548 for (nlines = 0; nlines < sc_height; nlines++)
549 {
550 pos = forw_line(pos);
551 if (pos == NULL_POSITION) break;
552 }
553 return (nlines < sc_height);
554 }
555