3 * Copyright (C) 1984-2019 Mark Nudelman
5 * You may distribute under the terms of either the GNU General Public
6 * License or the Less License, as specified in the README file.
8 * For more information, see the README file.
13 * Primitives for displaying the file on the screen,
14 * scrolling either forward or backward.
20 public int screen_trashed;
22 public int no_back_scroll = 0;
23 public int forw_prompt;
24 public int same_pos_bell = 1;
27 extern int top_scroll;
29 extern int sc_width, sc_height;
30 extern int less_is_more;
31 extern int plusoption;
32 extern int forw_scroll;
33 extern int back_scroll;
34 extern int ignore_eoi;
36 extern int final_attr;
39 extern int size_linebuf;
40 extern int hilite_search;
41 extern int status_col;
44 extern char *tagoption;
48 * Sound the bell to indicate user is trying to move past end of file.
53 if (quiet == NOT_QUIET)
60 * Check to see if the end of file is currently displayed.
63 eof_displayed(VOID_PARAM)
70 if (ch_length() == NULL_POSITION)
72 * If the file length is not known,
73 * we can't possibly be displaying EOF.
78 * If the bottom line is empty, we are at EOF.
79 * If the bottom line ends at the file length,
80 * we must be just at EOF.
82 pos = position(BOTTOM_PLUS_ONE);
83 return (pos == NULL_POSITION || pos == ch_length());
87 * Check to see if the entire file is currently displayed.
90 entire_file_displayed(VOID_PARAM)
94 /* Make sure last line of file is displayed. */
98 /* Make sure first line of file is displayed. */
100 return (pos == NULL_POSITION || pos == 0);
104 * If the screen is "squished", repaint it.
105 * "Squished" means the first displayed line is not at the top
106 * of the screen; this can happen when we display a short file
107 * for the first time.
110 squish_check(VOID_PARAM)
119 * Display n lines, scrolling forward,
120 * starting at position pos in the input file.
121 * "force" means display the n lines even if we hit end of file.
122 * "only_last" means display only the last screenful if n > screen size.
123 * "nblank" is the number of blank lines to draw before the first
124 * real line. If nblank > 0, the pos must be NULL_POSITION.
125 * The first real line after the blanks will start at ch_zero().
128 forw(n, pos, force, only_last, nblank)
137 static int first_time = 1;
142 * do_repaint tells us not to display anything till the end,
143 * then just repaint the entire screen.
144 * We repaint if we are supposed to display only the last
145 * screenful and the request is for more than a screenful.
146 * Also if the request exceeds the forward scroll limit
147 * (but not if the request is for exactly a screenful, since
148 * repainting itself involves scrolling forward a screenful).
150 do_repaint = (only_last && n > sc_height-1) ||
151 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
154 if (hilite_search == OPT_ONPLUS || is_filtering() || status_col) {
155 prep_hilite(pos, pos + 4*size_linebuf, ignore_eoi ? 1 : -1);
156 pos = next_unfiltered(pos);
162 if (top_scroll && n >= sc_height - 1 && pos != ch_length())
165 * Start a new screen.
166 * {{ This is not really desirable if we happen
167 * to hit eof in the middle of this screen,
168 * but we don't yet know if that will happen. }}
173 if (less_is_more == 0) {
179 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
182 * This is not contiguous with what is
183 * currently displayed. Clear the screen image
184 * (position table) and start a new screen.
193 } else if (!first_time)
195 putstr("...skipping...\n");
203 * Read the next line of input.
208 * Still drawing blanks; don't get a line
210 * If this is the last blank line, get ready to
211 * read a line starting at ch_zero() next time.
218 * Get the next line from the file.
220 pos = forw_line(pos);
222 pos = next_unfiltered(pos);
224 if (pos == NULL_POSITION)
227 * End of file: stop here unless the top line
228 * is still empty, or "force" is true.
229 * Even if force is true, stop when the last
230 * line in the file reaches the top of screen.
232 if (!force && position(TOP) != NULL_POSITION)
234 if (!empty_lines(0, 0) &&
235 !empty_lines(1, 1) &&
236 empty_lines(2, sc_height-1))
241 * Add the position of the next line to the position table.
242 * Display the current line on the screen.
249 * If this is the first screen displayed and
250 * we hit an early EOF (i.e. before the requested
251 * number of lines), we "squish" the display down
252 * at the bottom of the screen.
253 * But don't do this if a + option or a -t option
254 * was given. These options can cause us to
255 * start the display after the beginning of the file,
256 * and it is not appropriate to squish in that case.
258 if ((first_time || less_is_more) &&
259 pos == NULL_POSITION && !top_scroll &&
271 * Can't call clear_eol here. The cursor might be at end of line
272 * on an ignaw terminal, so clear_eol would clear the last char
273 * of the current line instead of all of the next line.
274 * If we really need to do this on clear_bg terminals, we need
275 * to find a better way.
278 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
281 * Writing the last character on the last line
282 * of the display may have scrolled the screen.
283 * If we were in standout mode, clear_bg terminals
284 * will fill the new line with the standout color.
285 * Now we're in normal mode again, so clear the line.
293 if (nlines == 0 && !ignore_eoi && same_pos_bell)
298 (void) currline(BOTTOM);
302 * Display n lines, scrolling backward.
305 back(n, pos, force, only_last)
315 do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
317 if (hilite_search == OPT_ONPLUS || is_filtering() || status_col) {
318 prep_hilite((pos < 3*size_linebuf) ? 0 : pos - 3*size_linebuf, pos, -1);
324 * Get the previous line of input.
327 pos = prev_unfiltered(pos);
330 pos = back_line(pos);
331 if (pos == NULL_POSITION)
334 * Beginning of file: stop here unless "force" is true.
340 * Add the position of the previous line to the position table.
341 * Display the line on the screen.
353 if (nlines == 0 && same_pos_bell)
359 (void) currline(BOTTOM);
363 * Display n more lines, forward.
364 * Start just after the line currently displayed at the bottom of the screen.
367 forward(n, force, only_last)
374 if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
377 * If the -e flag is set and we're trying to go
378 * forward from end-of-file, go on to the next file.
385 pos = position(BOTTOM_PLUS_ONE);
386 if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
391 * ignore_eoi is to support A_F_FOREVER.
392 * Back up until there is a line at the bottom
401 back(1, position(TOP), 1, 0);
402 pos = position(BOTTOM_PLUS_ONE);
403 } while (pos == NULL_POSITION);
411 forw(n, pos, force, only_last, 0);
415 * Display n more lines, backward.
416 * Start just before the line currently displayed at the top of the screen.
419 backward(n, force, only_last)
427 if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
432 back(n, pos, force, only_last);
436 * Get the backwards scroll limit.
437 * Must call this function instead of just using the value of
438 * back_scroll, because the default case depends on sc_height and
439 * top_scroll, as well as back_scroll.
442 get_back_scroll(VOID_PARAM)
446 if (back_scroll >= 0)
447 return (back_scroll);
449 return (sc_height - 2);
450 return (10000); /* infinity */
454 * Will the entire file fit on one screen?
457 get_one_screen(VOID_PARAM)
460 POSITION pos = ch_zero();
462 for (nlines = 0; nlines < sc_height; nlines++)
464 pos = forw_line(pos);
465 if (pos == NULL_POSITION) break;
467 return (nlines < sc_height);