1 /*
2 * Copyright (C) 1984-2002 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 about less, or for information on how to
8 * contact the author, see the README file.
9 */
10
11
12 /*
13 * Primitives for displaying the file on the screen,
14 * scrolling either forward or backward.
15 */
16
17 #include "less.h"
18 #include "position.h"
19
20 public int hit_eof; /* Keeps track of how many times we hit end of file */
21 public int screen_trashed;
22 public int squished;
23 public int no_back_scroll = 0;
24
25 extern int sigs;
26 extern int top_scroll;
27 extern int quiet;
28 extern int sc_width, sc_height;
29 extern int quit_at_eof;
30 extern int plusoption;
31 extern int forw_scroll;
32 extern int back_scroll;
33 extern int ignore_eoi;
34 extern int clear_bg;
35 extern int final_attr;
36 #if TAGS
37 extern char *tagoption;
38 #endif
39
40 /*
41 * Sound the bell to indicate user is trying to move past end of file.
42 */
43 static void
eof_bell()44 eof_bell()
45 {
46 if (quiet == NOT_QUIET)
47 bell();
48 else
49 vbell();
50 }
51
52 /*
53 * Check to see if the end of file is currently "displayed".
54 */
55 static void
eof_check()56 eof_check()
57 {
58 POSITION pos;
59
60 if (ignore_eoi)
61 return;
62 if (ABORT_SIGS())
63 return;
64 /*
65 * If the bottom line is empty, we are at EOF.
66 * If the bottom line ends at the file length,
67 * we must be just at EOF.
68 */
69 pos = position(BOTTOM_PLUS_ONE);
70 if (pos == NULL_POSITION || pos == ch_length())
71 hit_eof++;
72 }
73
74 /*
75 * If the screen is "squished", repaint it.
76 * "Squished" means the first displayed line is not at the top
77 * of the screen; this can happen when we display a short file
78 * for the first time.
79 */
80 static void
squish_check()81 squish_check()
82 {
83 if (!squished)
84 return;
85 squished = 0;
86 repaint();
87 }
88
89 /*
90 * Display n lines, scrolling forward,
91 * starting at position pos in the input file.
92 * "force" means display the n lines even if we hit end of file.
93 * "only_last" means display only the last screenful if n > screen size.
94 * "nblank" is the number of blank lines to draw before the first
95 * real line. If nblank > 0, the pos must be NULL_POSITION.
96 * The first real line after the blanks will start at ch_zero().
97 */
98 public void
forw(n,pos,force,only_last,nblank)99 forw(n, pos, force, only_last, nblank)
100 register int n;
101 POSITION pos;
102 int force;
103 int only_last;
104 int nblank;
105 {
106 int eof = 0;
107 int nlines = 0;
108 int do_repaint;
109 static int first_time = 1;
110
111 squish_check();
112
113 /*
114 * do_repaint tells us not to display anything till the end,
115 * then just repaint the entire screen.
116 * We repaint if we are supposed to display only the last
117 * screenful and the request is for more than a screenful.
118 * Also if the request exceeds the forward scroll limit
119 * (but not if the request is for exactly a screenful, since
120 * repainting itself involves scrolling forward a screenful).
121 */
122 do_repaint = (only_last && n > sc_height-1) ||
123 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
124
125 if (!do_repaint)
126 {
127 /*
128 * Forget any current line shift we might have
129 * (from the last line of the previous screenful).
130 */
131 extern int cshift;
132 cshift = 0;
133
134 if (top_scroll && n >= sc_height - 1 && pos != ch_length())
135 {
136 /*
137 * Start a new screen.
138 * {{ This is not really desirable if we happen
139 * to hit eof in the middle of this screen,
140 * but we don't yet know if that will happen. }}
141 */
142 pos_clear();
143 add_forw_pos(pos);
144 force = 1;
145 if (top_scroll == OPT_ONPLUS || first_time)
146 clear();
147 home();
148 } else
149 {
150 clear_bot();
151 }
152
153 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
154 {
155 /*
156 * This is not contiguous with what is
157 * currently displayed. Clear the screen image
158 * (position table) and start a new screen.
159 */
160 pos_clear();
161 add_forw_pos(pos);
162 force = 1;
163 if (top_scroll)
164 {
165 if (top_scroll == OPT_ONPLUS)
166 clear();
167 home();
168 } else if (!first_time)
169 {
170 putstr("...skipping...\n");
171 }
172 }
173 }
174
175 while (--n >= 0)
176 {
177 /*
178 * Read the next line of input.
179 */
180 if (nblank > 0)
181 {
182 /*
183 * Still drawing blanks; don't get a line
184 * from the file yet.
185 * If this is the last blank line, get ready to
186 * read a line starting at ch_zero() next time.
187 */
188 if (--nblank == 0)
189 pos = ch_zero();
190 } else
191 {
192 /*
193 * Get the next line from the file.
194 */
195 pos = forw_line(pos);
196 if (pos == NULL_POSITION)
197 {
198 /*
199 * End of file: stop here unless the top line
200 * is still empty, or "force" is true.
201 * Even if force is true, stop when the last
202 * line in the file reaches the top of screen.
203 */
204 eof = 1;
205 if (!force && position(TOP) != NULL_POSITION)
206 break;
207 if (!empty_lines(0, 0) &&
208 !empty_lines(1, 1) &&
209 empty_lines(2, sc_height-1))
210 break;
211 }
212 }
213 /*
214 * Add the position of the next line to the position table.
215 * Display the current line on the screen.
216 */
217 add_forw_pos(pos);
218 nlines++;
219 if (do_repaint)
220 continue;
221 /*
222 * If this is the first screen displayed and
223 * we hit an early EOF (i.e. before the requested
224 * number of lines), we "squish" the display down
225 * at the bottom of the screen.
226 * But don't do this if a + option or a -t option
227 * was given. These options can cause us to
228 * start the display after the beginning of the file,
229 * and it is not appropriate to squish in that case.
230 */
231 if (first_time && pos == NULL_POSITION && !top_scroll &&
232 #if TAGS
233 tagoption == NULL &&
234 #endif
235 !plusoption)
236 {
237 squished = 1;
238 continue;
239 }
240 if (top_scroll == OPT_ON)
241 clear_eol();
242 put_line();
243 if (clear_bg && final_attr != AT_NORMAL)
244 {
245 /*
246 * Writing the last character on the last line
247 * of the display may have scrolled the screen.
248 * If we were in standout mode, clear_bg terminals
249 * will fill the new line with the standout color.
250 * Now we're in normal mode again, so clear the line.
251 */
252 clear_eol();
253 }
254 }
255
256 if (ignore_eoi)
257 hit_eof = 0;
258 else if (eof && !ABORT_SIGS())
259 hit_eof++;
260 else
261 eof_check();
262 if (nlines == 0)
263 eof_bell();
264 else if (do_repaint)
265 repaint();
266 first_time = 0;
267 (void) currline(BOTTOM);
268 }
269
270 /*
271 * Display n lines, scrolling backward.
272 */
273 public void
back(n,pos,force,only_last)274 back(n, pos, force, only_last)
275 register int n;
276 POSITION pos;
277 int force;
278 int only_last;
279 {
280 int nlines = 0;
281 int do_repaint;
282
283 squish_check();
284 do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
285 hit_eof = 0;
286 while (--n >= 0)
287 {
288 /*
289 * Get the previous line of input.
290 */
291 pos = back_line(pos);
292 if (pos == NULL_POSITION)
293 {
294 /*
295 * Beginning of file: stop here unless "force" is true.
296 */
297 if (!force)
298 break;
299 }
300 /*
301 * Add the position of the previous line to the position table.
302 * Display the line on the screen.
303 */
304 add_back_pos(pos);
305 nlines++;
306 if (!do_repaint)
307 {
308 home();
309 add_line();
310 put_line();
311 }
312 }
313
314 eof_check();
315 if (nlines == 0)
316 eof_bell();
317 else if (do_repaint)
318 repaint();
319 (void) currline(BOTTOM);
320 }
321
322 /*
323 * Display n more lines, forward.
324 * Start just after the line currently displayed at the bottom of the screen.
325 */
326 public void
forward(n,force,only_last)327 forward(n, force, only_last)
328 int n;
329 int force;
330 int only_last;
331 {
332 POSITION pos;
333
334 if (quit_at_eof && hit_eof && !(ch_getflags() & CH_HELPFILE))
335 {
336 /*
337 * If the -e flag is set and we're trying to go
338 * forward from end-of-file, go on to the next file.
339 */
340 if (edit_next(1))
341 quit(QUIT_OK);
342 return;
343 }
344
345 pos = position(BOTTOM_PLUS_ONE);
346 if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
347 {
348 if (ignore_eoi)
349 {
350 /*
351 * ignore_eoi is to support A_F_FOREVER.
352 * Back up until there is a line at the bottom
353 * of the screen.
354 */
355 if (empty_screen())
356 pos = ch_zero();
357 else
358 {
359 do
360 {
361 back(1, position(TOP), 1, 0);
362 pos = position(BOTTOM_PLUS_ONE);
363 } while (pos == NULL_POSITION);
364 }
365 } else
366 {
367 eof_bell();
368 hit_eof++;
369 return;
370 }
371 }
372 forw(n, pos, force, only_last, 0);
373 }
374
375 /*
376 * Display n more lines, backward.
377 * Start just before the line currently displayed at the top of the screen.
378 */
379 public void
backward(n,force,only_last)380 backward(n, force, only_last)
381 int n;
382 int force;
383 int only_last;
384 {
385 POSITION pos;
386
387 pos = position(TOP);
388 if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
389 {
390 eof_bell();
391 return;
392 }
393 back(n, pos, force, only_last);
394 }
395
396 /*
397 * Get the backwards scroll limit.
398 * Must call this function instead of just using the value of
399 * back_scroll, because the default case depends on sc_height and
400 * top_scroll, as well as back_scroll.
401 */
402 public int
get_back_scroll()403 get_back_scroll()
404 {
405 if (no_back_scroll)
406 return (0);
407 if (back_scroll >= 0)
408 return (back_scroll);
409 if (top_scroll)
410 return (sc_height - 2);
411 return (10000); /* infinity */
412 }
413