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