1/*
2 * Copyright (C) 1984-2007  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
20public int hit_eof;	/* Keeps track of how many times we hit end of file */
21public int screen_trashed;
22public int squished;
23public int no_back_scroll = 0;
24public int forw_prompt;
25public int display_next_file_or_exit = 0;
26
27extern int sigs;
28extern int top_scroll;
29extern int quiet;
30extern int sc_width, sc_height;
31extern int plusoption;
32extern int forw_scroll;
33extern int back_scroll;
34extern int ignore_eoi;
35extern int clear_bg;
36extern int final_attr;
37extern int oldbot;
38extern int unix2003_compat;
39#if TAGS
40extern char *tagoption;
41#endif
42
43/*
44 * Sound the bell to indicate user is trying to move past end of file.
45 */
46	static void
47eof_bell()
48{
49	if (quiet == NOT_QUIET)
50		bell();
51	else
52		vbell();
53}
54
55/*
56 * Check to see if the end of file is currently "displayed".
57 */
58	static void
59eof_check()
60{
61	POSITION pos;
62
63	if (ignore_eoi)
64		return;
65	if (ABORT_SIGS())
66		return;
67	/*
68	 * If the bottom line is empty, we are at EOF.
69	 * If the bottom line ends at the file length,
70	 * we must be just at EOF.
71	 */
72	pos = position(BOTTOM_PLUS_ONE);
73	if (pos == NULL_POSITION || pos == ch_length())
74		hit_eof++;
75}
76
77/*
78 * If the screen is "squished", repaint it.
79 * "Squished" means the first displayed line is not at the top
80 * of the screen; this can happen when we display a short file
81 * for the first time.
82 */
83	public void
84squish_check()
85{
86	if (!squished)
87		return;
88	squished = 0;
89	repaint();
90}
91
92/*
93 * Display n lines, scrolling forward,
94 * starting at position pos in the input file.
95 * "force" means display the n lines even if we hit end of file.
96 * "only_last" means display only the last screenful if n > screen size.
97 * "nblank" is the number of blank lines to draw before the first
98 *   real line.  If nblank > 0, the pos must be NULL_POSITION.
99 *   The first real line after the blanks will start at ch_zero().
100 */
101	public void
102forw(n, pos, force, only_last, nblank)
103	register int n;
104	POSITION pos;
105	int force;
106	int only_last;
107	int nblank;
108{
109	int eof = 0;
110	int nlines = 0;
111	int do_repaint;
112	static int first_time = 1;
113
114	squish_check();
115
116	/*
117	 * do_repaint tells us not to display anything till the end,
118	 * then just repaint the entire screen.
119	 * We repaint if we are supposed to display only the last
120	 * screenful and the request is for more than a screenful.
121	 * Also if the request exceeds the forward scroll limit
122	 * (but not if the request is for exactly a screenful, since
123	 * repainting itself involves scrolling forward a screenful).
124	 */
125	do_repaint = (only_last && n > sc_height-1) ||
126		(forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
127
128	if (!do_repaint)
129	{
130		if (top_scroll && n >= sc_height - 1 && pos != ch_length())
131		{
132			/*
133			 * Start a new screen.
134			 * {{ This is not really desirable if we happen
135			 *    to hit eof in the middle of this screen,
136			 *    but we don't yet know if that will happen. }}
137			 */
138			pos_clear();
139			add_forw_pos(pos);
140			force = 1;
141			if (!unix2003_compat) {
142				clear();
143				home();
144			}
145		}
146
147		if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
148		{
149			/*
150			 * This is not contiguous with what is
151			 * currently displayed.  Clear the screen image
152			 * (position table) and start a new screen.
153			 */
154			pos_clear();
155			add_forw_pos(pos);
156			force = 1;
157			if (top_scroll)
158			{
159				clear();
160				home();
161			} else if (!first_time)
162			{
163				putstr("...skipping...\n");
164			}
165		}
166	}
167
168	while (--n >= 0)
169	{
170		/*
171		 * Read the next line of input.
172		 */
173		if (nblank > 0)
174		{
175			/*
176			 * Still drawing blanks; don't get a line
177			 * from the file yet.
178			 * If this is the last blank line, get ready to
179			 * read a line starting at ch_zero() next time.
180			 */
181			if (--nblank == 0)
182				pos = ch_zero();
183		} else
184		{
185			/*
186			 * Get the next line from the file.
187			 */
188			pos = forw_line(pos);
189			if (pos == NULL_POSITION)
190			{
191				/*
192				 * End of file: stop here unless the top line
193				 * is still empty, or "force" is true.
194				 * Even if force is true, stop when the last
195				 * line in the file reaches the top of screen.
196				 */
197				eof = 1;
198				if (!force && position(TOP) != NULL_POSITION)
199					break;
200				if (!empty_lines(0, 0) &&
201				    !empty_lines(1, 1) &&
202				     empty_lines(2, sc_height-1))
203					break;
204			}
205		}
206		/*
207		 * Add the position of the next line to the position table.
208		 * Display the current line on the screen.
209		 */
210		add_forw_pos(pos);
211		nlines++;
212		if (do_repaint)
213			continue;
214		/*
215		 * If this is the first screen displayed and
216		 * we hit an early EOF (i.e. before the requested
217		 * number of lines), we "squish" the display down
218		 * at the bottom of the screen.
219		 * But don't do this if a + option or a -t option
220		 * was given.  These options can cause us to
221		 * start the display after the beginning of the file,
222		 * and it is not appropriate to squish in that case.
223		 */
224		if (first_time && pos == NULL_POSITION && !top_scroll &&
225#if TAGS
226		    tagoption == NULL &&
227#endif
228		    !plusoption)
229		{
230			squished = 1;
231			continue;
232		}
233		put_line();
234#if 0
235		/* {{
236		 * Can't call clear_eol here.  The cursor might be at end of line
237		 * on an ignaw terminal, so clear_eol would clear the last char
238		 * of the current line instead of all of the next line.
239		 * If we really need to do this on clear_bg terminals, we need
240		 * to find a better way.
241		 * }}
242		 */
243		if (clear_bg && apply_at_specials(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#endif
255		forw_prompt = 1;
256	}
257
258	if (ignore_eoi)
259		hit_eof = 0;
260	else if (eof && !ABORT_SIGS())
261		hit_eof++;
262	else
263		eof_check();
264	if (nlines == 0)
265		eof_bell();
266	else if (do_repaint)
267		repaint();
268	first_time = 0;
269	(void) currline(BOTTOM);
270}
271
272/*
273 * Display n lines, scrolling backward.
274 */
275	public void
276back(n, pos, force, only_last)
277	register int n;
278	POSITION pos;
279	int force;
280	int only_last;
281{
282	int nlines = 0;
283	int do_repaint;
284
285	squish_check();
286	do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
287	hit_eof = 0;
288	while (--n >= 0)
289	{
290		/*
291		 * Get the previous line of input.
292		 */
293		pos = back_line(pos);
294		if (pos == NULL_POSITION)
295		{
296			/*
297			 * Beginning of file: stop here unless "force" is true.
298			 */
299			if (!force)
300				break;
301		}
302		/*
303		 * Add the position of the previous line to the position table.
304		 * Display the line on the screen.
305		 */
306		add_back_pos(pos);
307		nlines++;
308		if (!do_repaint)
309		{
310			home();
311			add_line();
312			put_line();
313		}
314	}
315
316	eof_check();
317	if (nlines == 0)
318		eof_bell();
319	else if (do_repaint)
320		repaint();
321	else if (!oldbot)
322		lower_left();
323	(void) currline(BOTTOM);
324}
325
326/*
327 * Display n more lines, forward.
328 * Start just after the line currently displayed at the bottom of the screen.
329 */
330	public void
331forward(n, force, only_last)
332	int n;
333	int force;
334	int only_last;
335{
336	POSITION pos;
337
338	if (get_quit_at_eof() && hit_eof && !(ch_getflags() & CH_HELPFILE))
339	{
340		/*
341		 * If the -e flag is set and we're trying to go
342		 * forward from end-of-file, go on to the next file.
343		 */
344		if (edit_next(1))
345			quit(QUIT_OK);
346		return;
347	}
348
349	pos = position(BOTTOM_PLUS_ONE);
350	if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
351	{
352		if (ignore_eoi)
353		{
354			/*
355			 * ignore_eoi is to support A_F_FOREVER.
356			 * Back up until there is a line at the bottom
357			 * of the screen.
358			 */
359			if (empty_screen())
360				pos = ch_zero();
361			else
362			{
363				do
364				{
365					back(1, position(TOP), 1, 0);
366					pos = position(BOTTOM_PLUS_ONE);
367				} while (pos == NULL_POSITION);
368			}
369		} else
370		{
371			eof_bell();
372			hit_eof++;
373			return;
374		}
375	}
376	forw(n, pos, force, only_last, 0);
377}
378
379/*
380 * Display n more lines, backward.
381 * Start just before the line currently displayed at the top of the screen.
382 */
383	public void
384backward(n, force, only_last)
385	int n;
386	int force;
387	int only_last;
388{
389	POSITION pos;
390
391	pos = position(TOP);
392	if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
393	{
394		eof_bell();
395		return;
396	}
397	back(n, pos, force, only_last);
398}
399
400/*
401 * Get the backwards scroll limit.
402 * Must call this function instead of just using the value of
403 * back_scroll, because the default case depends on sc_height and
404 * top_scroll, as well as back_scroll.
405 */
406	public int
407get_back_scroll()
408{
409	if (no_back_scroll)
410		return (0);
411	if (back_scroll >= 0)
412		return (back_scroll);
413	if (top_scroll)
414		return (sc_height - 2);
415	return (10000); /* infinity */
416}
417