[dragonfly.git] / contrib / less / forwback.c

/*
 * Copyright (C) 1984-2009  Mark Nudelman
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information about less, or for information on how to 
 * contact the author, see the README file.
 */


/*
 * Primitives for displaying the file on the screen,
 * scrolling either forward or backward.
 */

#include "less.h"
#include "position.h"

public int screen_trashed;
public int squished;
public int no_back_scroll = 0;
public int forw_prompt;

extern int sigs;
extern int top_scroll;
extern int quiet;
extern int sc_width, sc_height;
extern int plusoption;
extern int forw_scroll;
extern int back_scroll;
extern int ignore_eoi;
extern int clear_bg;
extern int final_attr;
extern int oldbot;
#if TAGS
extern char *tagoption;
#endif

/*
 * Sound the bell to indicate user is trying to move past end of file.
 */
	static void
eof_bell()
{
	if (quiet == NOT_QUIET)
		bell();
	else
		vbell();
}

/*
 * Check to see if the end of file is currently displayed.
 */
	public int
eof_displayed()
{
	POSITION pos;

	if (ignore_eoi)
		return (0);

	if (ch_length() == NULL_POSITION)
		/*
		 * If the file length is not known,
		 * we can't possibly be displaying EOF.
		 */
		return (0);

	/*
	 * If the bottom line is empty, we are at EOF.
	 * If the bottom line ends at the file length,
	 * we must be just at EOF.
	 */
	pos = position(BOTTOM_PLUS_ONE);
	return (pos == NULL_POSITION || pos == ch_length());
}

/*
 * Check to see if the entire file is currently displayed.
 */
	public int
entire_file_displayed()
{
	POSITION pos;

	/* Make sure last line of file is displayed. */
	if (!eof_displayed())
		return (0);

	/* Make sure first line of file is displayed. */
	pos = position(0);
	return (pos == NULL_POSITION || pos == 0);
}

/*
 * If the screen is "squished", repaint it.
 * "Squished" means the first displayed line is not at the top
 * of the screen; this can happen when we display a short file
 * for the first time.
 */
	public void
squish_check()
{
	if (!squished)
		return;
	squished = 0;
	repaint();
}

/*
 * Display n lines, scrolling forward, 
 * starting at position pos in the input file.
 * "force" means display the n lines even if we hit end of file.
 * "only_last" means display only the last screenful if n > screen size.
 * "nblank" is the number of blank lines to draw before the first
 *   real line.  If nblank > 0, the pos must be NULL_POSITION.
 *   The first real line after the blanks will start at ch_zero().
 */
	public void
forw(n, pos, force, only_last, nblank)
	register int n;
	POSITION pos;
	int force;
	int only_last;
	int nblank;
{
	int eof = 0;
	int nlines = 0;
	int do_repaint;
	static int first_time = 1;

	squish_check();

	/*
	 * do_repaint tells us not to display anything till the end, 
	 * then just repaint the entire screen.
	 * We repaint if we are supposed to display only the last 
	 * screenful and the request is for more than a screenful.
	 * Also if the request exceeds the forward scroll limit
	 * (but not if the request is for exactly a screenful, since
	 * repainting itself involves scrolling forward a screenful).
	 */
	do_repaint = (only_last && n > sc_height-1) || 
		(forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);

	if (!do_repaint)
	{
		if (top_scroll && n >= sc_height - 1 && pos != ch_length())
		{
			/*
			 * Start a new screen.
			 * {{ This is not really desirable if we happen
			 *    to hit eof in the middle of this screen,
			 *    but we don't yet know if that will happen. }}
			 */
			pos_clear();
			add_forw_pos(pos);
			force = 1;
			clear();
			home();
		}

		if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
		{
			/*
			 * This is not contiguous with what is
			 * currently displayed.  Clear the screen image 
			 * (position table) and start a new screen.
			 */
			pos_clear();
			add_forw_pos(pos);
			force = 1;
			if (top_scroll)
			{
				clear();
				home();
			} else if (!first_time)
			{
				putstr("...skipping...\n");
			}
		}
	}

	while (--n >= 0)
	{
		/*
		 * Read the next line of input.
		 */
		if (nblank > 0)
		{
			/*
			 * Still drawing blanks; don't get a line 
			 * from the file yet.
			 * If this is the last blank line, get ready to
			 * read a line starting at ch_zero() next time.
			 */
			if (--nblank == 0)
				pos = ch_zero();
		} else
		{
			/* 
			 * Get the next line from the file.
			 */
			pos = forw_line(pos);
			if (pos == NULL_POSITION)
			{
				/*
				 * End of file: stop here unless the top line 
				 * is still empty, or "force" is true.
				 * Even if force is true, stop when the last
				 * line in the file reaches the top of screen.
				 */
				eof = 1;
				if (!force && position(TOP) != NULL_POSITION)
					break;
				if (!empty_lines(0, 0) && 
				    !empty_lines(1, 1) &&
				     empty_lines(2, sc_height-1))
					break;
			}
		}
		/*
		 * Add the position of the next line to the position table.
		 * Display the current line on the screen.
		 */
		add_forw_pos(pos);
		nlines++;
		if (do_repaint)
			continue;
		/*
		 * If this is the first screen displayed and
		 * we hit an early EOF (i.e. before the requested
		 * number of lines), we "squish" the display down
		 * at the bottom of the screen.
		 * But don't do this if a + option or a -t option
		 * was given.  These options can cause us to
		 * start the display after the beginning of the file,
		 * and it is not appropriate to squish in that case.
		 */
		if (first_time && pos == NULL_POSITION && !top_scroll && 
#if TAGS
		    tagoption == NULL &&
#endif
		    !plusoption)
		{
			squished = 1;
			continue;
		}
		put_line();
#if 0
		/* {{ 
		 * Can't call clear_eol here.  The cursor might be at end of line
		 * on an ignaw terminal, so clear_eol would clear the last char
		 * of the current line instead of all of the next line.
		 * If we really need to do this on clear_bg terminals, we need
		 * to find a better way.
		 * }}
		 */
		if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
		{
			/*
			 * Writing the last character on the last line
			 * of the display may have scrolled the screen.
			 * If we were in standout mode, clear_bg terminals 
			 * will fill the new line with the standout color.
			 * Now we're in normal mode again, so clear the line.
			 */
			clear_eol();
		}
#endif
		forw_prompt = 1;
	}

	if (nlines == 0)
		eof_bell();
	else if (do_repaint)
		repaint();
	first_time = 0;
	(void) currline(BOTTOM);
}

/*
 * Display n lines, scrolling backward.
 */
	public void
back(n, pos, force, only_last)
	register int n;
	POSITION pos;
	int force;
	int only_last;
{
	int nlines = 0;
	int do_repaint;

	squish_check();
	do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
	while (--n >= 0)
	{
		/*
		 * Get the previous line of input.
		 */
		pos = back_line(pos);
		if (pos == NULL_POSITION)
		{
			/*
			 * Beginning of file: stop here unless "force" is true.
			 */
			if (!force)
				break;
		}
		/*
		 * Add the position of the previous line to the position table.
		 * Display the line on the screen.
		 */
		add_back_pos(pos);
		nlines++;
		if (!do_repaint)
		{
			home();
			add_line();
			put_line();
		}
	}

	if (nlines == 0)
		eof_bell();
	else if (do_repaint)
		repaint();
	else if (!oldbot)
		lower_left();
	(void) currline(BOTTOM);
}

/*
 * Display n more lines, forward.
 * Start just after the line currently displayed at the bottom of the screen.
 */
	public void
forward(n, force, only_last)
	int n;
	int force;
	int only_last;
{
	POSITION pos;

	if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
	{
		/*
		 * If the -e flag is set and we're trying to go
		 * forward from end-of-file, go on to the next file.
		 */
		if (edit_next(1))
			quit(QUIT_OK);
		return;
	}

	pos = position(BOTTOM_PLUS_ONE);
	if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
	{
		if (ignore_eoi)
		{
			/*
			 * ignore_eoi is to support A_F_FOREVER.
			 * Back up until there is a line at the bottom
			 * of the screen.
			 */
			if (empty_screen())
				pos = ch_zero();
			else
			{
				do
				{
					back(1, position(TOP), 1, 0);
					pos = position(BOTTOM_PLUS_ONE);
				} while (pos == NULL_POSITION);
			}
		} else
		{
			eof_bell();
			return;
		}
	}
	forw(n, pos, force, only_last, 0);
}

/*
 * Display n more lines, backward.
 * Start just before the line currently displayed at the top of the screen.
 */
	public void
backward(n, force, only_last)
	int n;
	int force;
	int only_last;
{
	POSITION pos;

	pos = position(TOP);
	if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
	{
		eof_bell();
		return;   
	}
	back(n, pos, force, only_last);
}

/*
 * Get the backwards scroll limit.
 * Must call this function instead of just using the value of
 * back_scroll, because the default case depends on sc_height and
 * top_scroll, as well as back_scroll.
 */
	public int
get_back_scroll()
{
	if (no_back_scroll)
		return (0);
	if (back_scroll >= 0)
		return (back_scroll);
	if (top_scroll)
		return (sc_height - 2);
	return (10000); /* infinity */
}
Commit	Line	Data
131ccf9c	1	/*
a9adbba3	2	* Copyright (C) 1984-2009 Mark Nudelman
131ccf9c PA	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
131ccf9c PA	20	public int screen_trashed;
	21	public int squished;
	22	public int no_back_scroll = 0;
	23	public int forw_prompt;
	24
	25	extern int sigs;
	26	extern int top_scroll;
	27	extern int quiet;
	28	extern int sc_width, sc_height;
	29	extern int plusoption;
	30	extern int forw_scroll;
	31	extern int back_scroll;
	32	extern int ignore_eoi;
	33	extern int clear_bg;
	34	extern int final_attr;
	35	extern int oldbot;
	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
	44	eof_bell()
	45	{
	46	if (quiet == NOT_QUIET)
	47	bell();
	48	else
	49	vbell();
	50	}
	51
	52	/*
8be36e5b	53	* Check to see if the end of file is currently displayed.
131ccf9c	54	*/
8be36e5b PA	55	public int
8be36e5b PA	56	eof_displayed()
131ccf9c PA	57	{
	58	POSITION pos;
	59
	60	if (ignore_eoi)
8be36e5b PA	61	return (0);
	62
	63	if (ch_length() == NULL_POSITION)
	64	/*
	65	* If the file length is not known,
	66	* we can't possibly be displaying EOF.
	67	*/
	68	return (0);
	69
131ccf9c PA	70	/*
	71	* If the bottom line is empty, we are at EOF.
	72	* If the bottom line ends at the file length,
	73	* we must be just at EOF.
	74	*/
	75	pos = position(BOTTOM_PLUS_ONE);
8be36e5b PA	76	return (pos == NULL_POSITION \|\| pos == ch_length());
	77	}
	78
	79	/*
	80	* Check to see if the entire file is currently displayed.
	81	*/
	82	public int
	83	entire_file_displayed()
	84	{
	85	POSITION pos;
	86
	87	/* Make sure last line of file is displayed. */
	88	if (!eof_displayed())
	89	return (0);
	90
	91	/* Make sure first line of file is displayed. */
	92	pos = position(0);
	93	return (pos == NULL_POSITION \|\| pos == 0);
131ccf9c PA	94	}
	95
	96	/*
	97	* If the screen is "squished", repaint it.
	98	* "Squished" means the first displayed line is not at the top
	99	* of the screen; this can happen when we display a short file
	100	* for the first time.
	101	*/
	102	public void
	103	squish_check()
	104	{
	105	if (!squished)
	106	return;
	107	squished = 0;
	108	repaint();
	109	}
	110
	111	/*
	112	* Display n lines, scrolling forward,
	113	* starting at position pos in the input file.
	114	* "force" means display the n lines even if we hit end of file.
	115	* "only_last" means display only the last screenful if n > screen size.
	116	* "nblank" is the number of blank lines to draw before the first
	117	* real line. If nblank > 0, the pos must be NULL_POSITION.
	118	* The first real line after the blanks will start at ch_zero().
	119	*/
	120	public void
	121	forw(n, pos, force, only_last, nblank)
	122	register int n;
	123	POSITION pos;
	124	int force;
	125	int only_last;
	126	int nblank;
	127	{
	128	int eof = 0;
	129	int nlines = 0;
	130	int do_repaint;
	131	static int first_time = 1;
	132
	133	squish_check();
	134
	135	/*
	136	* do_repaint tells us not to display anything till the end,
	137	* then just repaint the entire screen.
	138	* We repaint if we are supposed to display only the last
	139	* screenful and the request is for more than a screenful.
	140	* Also if the request exceeds the forward scroll limit
	141	* (but not if the request is for exactly a screenful, since
	142	* repainting itself involves scrolling forward a screenful).
	143	*/
	144	do_repaint = (only_last && n > sc_height-1) \|\|
	145	(forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
	146
	147	if (!do_repaint)
	148	{
	149	if (top_scroll && n >= sc_height - 1 && pos != ch_length())
	150	{
	151	/*
	152	* Start a new screen.
	153	* {{ This is not really desirable if we happen
	154	* to hit eof in the middle of this screen,
	155	* but we don't yet know if that will happen. }}
	156	*/
	157	pos_clear();
158	add_forw_pos(pos);
159	force = 1;
160	clear();
161	home();
162	}
163
164	if (pos != position(BOTTOM_PLUS_ONE) \|\| empty_screen())
165	{
166	/*
167	* This is not contiguous with what is
168	* currently displayed. Clear the screen image
169	* (position table) and start a new screen.
170	*/
171	pos_clear();
172	add_forw_pos(pos);
173	force = 1;
174	if (top_scroll)
175	{
176	clear();
177	home();
178	} else if (!first_time)
179	{
180	putstr("...skipping...\n");
181	}
182	}
183	}
184
185	while (--n >= 0)
186	{
187	/*
188	* Read the next line of input.
189	*/
190	if (nblank > 0)
191	{
192	/*
193	* Still drawing blanks; don't get a line
194	* from the file yet.
195	* If this is the last blank line, get ready to
196	* read a line starting at ch_zero() next time.
197	*/
198	if (--nblank == 0)
199	pos = ch_zero();
200	} else
201	{
202	/*
203	* Get the next line from the file.
204	*/
205	pos = forw_line(pos);
206	if (pos == NULL_POSITION)
207	{
208	/*
209	* End of file: stop here unless the top line
210	* is still empty, or "force" is true.
211	* Even if force is true, stop when the last
212	* line in the file reaches the top of screen.
213	*/
214	eof = 1;
215	if (!force && position(TOP) != NULL_POSITION)
216	break;
217	if (!empty_lines(0, 0) &&
218	!empty_lines(1, 1) &&
219	empty_lines(2, sc_height-1))
220	break;
221	}
222	}
223	/*
224	* Add the position of the next line to the position table.
225	* Display the current line on the screen.
226	*/
227	add_forw_pos(pos);
228	nlines++;
229	if (do_repaint)
230	continue;
231	/*
232	* If this is the first screen displayed and
233	* we hit an early EOF (i.e. before the requested
234	* number of lines), we "squish" the display down
235	* at the bottom of the screen.
236	* But don't do this if a + option or a -t option
237	* was given. These options can cause us to
238	* start the display after the beginning of the file,
239	* and it is not appropriate to squish in that case.
240	*/
241	if (first_time && pos == NULL_POSITION && !top_scroll &&
242	#if TAGS
243	tagoption == NULL &&
244	#endif
245	!plusoption)
246	{
247	squished = 1;
248	continue;
249	}
250	put_line();
251	#if 0
252	/* {{
253	* Can't call clear_eol here. The cursor might be at end of line
254	* on an ignaw terminal, so clear_eol would clear the last char
255	* of the current line instead of all of the next line.
256	* If we really need to do this on clear_bg terminals, we need
257	* to find a better way.
258	* }}
259	*/
260	if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
261	{
262	/*
263	* Writing the last character on the last line
264	* of the display may have scrolled the screen.
265	* If we were in standout mode, clear_bg terminals
266	* will fill the new line with the standout color.
267	* Now we're in normal mode again, so clear the line.
268	*/
269	clear_eol();
270	}
271	#endif
272	forw_prompt = 1;
273	}
274
131ccf9c PA	275	if (nlines == 0)
	276	eof_bell();
	277	else if (do_repaint)
	278	repaint();
	279	first_time = 0;
	280	(void) currline(BOTTOM);
	281	}
	282
	283	/*
	284	* Display n lines, scrolling backward.
	285	*/
	286	public void
	287	back(n, pos, force, only_last)
	288	register int n;
	289	POSITION pos;
	290	int force;
	291	int only_last;
	292	{
	293	int nlines = 0;
	294	int do_repaint;
	295
	296	squish_check();
	297	do_repaint = (n > get_back_scroll() \|\| (only_last && n > sc_height-1));
131ccf9c PA	298	while (--n >= 0)
	299	{
	300	/*
	301	* Get the previous line of input.
	302	*/
	303	pos = back_line(pos);
	304	if (pos == NULL_POSITION)
	305	{
	306	/*
	307	* Beginning of file: stop here unless "force" is true.
	308	*/
	309	if (!force)
	310	break;
	311	}
	312	/*
	313	* Add the position of the previous line to the position table.
	314	* Display the line on the screen.
	315	*/
	316	add_back_pos(pos);
	317	nlines++;
	318	if (!do_repaint)
	319	{
	320	home();
	321	add_line();
	322	put_line();
	323	}
	324	}
	325
131ccf9c PA	326	if (nlines == 0)
	327	eof_bell();
	328	else if (do_repaint)
	329	repaint();
	330	else if (!oldbot)
	331	lower_left();
	332	(void) currline(BOTTOM);
	333	}
	334
	335	/*
	336	* Display n more lines, forward.
	337	* Start just after the line currently displayed at the bottom of the screen.
	338	*/
	339	public void
	340	forward(n, force, only_last)
	341	int n;
	342	int force;
	343	int only_last;
	344	{
	345	POSITION pos;
	346
8be36e5b	347	if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
131ccf9c PA	348	{
	349	/*
	350	* If the -e flag is set and we're trying to go
	351	* forward from end-of-file, go on to the next file.
	352	*/
	353	if (edit_next(1))
	354	quit(QUIT_OK);
	355	return;
	356	}
	357
	358	pos = position(BOTTOM_PLUS_ONE);
	359	if (pos == NULL_POSITION && (!force \|\| empty_lines(2, sc_height-1)))
	360	{
	361	if (ignore_eoi)
	362	{
	363	/*
	364	* ignore_eoi is to support A_F_FOREVER.
	365	* Back up until there is a line at the bottom
	366	* of the screen.
	367	*/
	368	if (empty_screen())
	369	pos = ch_zero();
	370	else
	371	{
	372	do
	373	{
	374	back(1, position(TOP), 1, 0);
	375	pos = position(BOTTOM_PLUS_ONE);
	376	} while (pos == NULL_POSITION);
	377	}
	378	} else
	379	{
	380	eof_bell();
131ccf9c PA	381	return;
	382	}
	383	}
	384	forw(n, pos, force, only_last, 0);
	385	}
	386
	387	/*
	388	* Display n more lines, backward.
	389	* Start just before the line currently displayed at the top of the screen.
	390	*/
	391	public void
	392	backward(n, force, only_last)
	393	int n;
	394	int force;
	395	int only_last;
	396	{
	397	POSITION pos;
	398
	399	pos = position(TOP);
	400	if (pos == NULL_POSITION && (!force \|\| position(BOTTOM) == 0))
	401	{
	402	eof_bell();
	403	return;
	404	}
	405	back(n, pos, force, only_last);
	406	}
	407
	408	/*
	409	* Get the backwards scroll limit.
	410	* Must call this function instead of just using the value of
	411	* back_scroll, because the default case depends on sc_height and
	412	* top_scroll, as well as back_scroll.
	413	*/
	414	public int
	415	get_back_scroll()
	416	{
	417	if (no_back_scroll)
	418	return (0);
	419	if (back_scroll >= 0)
	420	return (back_scroll);
	421	if (top_scroll)
	422	return (sc_height - 2);
	423	return (10000); /* infinity */
	424	}