Add less 643

third_party/less/forwback.c

@@ -0,0 +1,549 @@
+/*
+ * Copyright (C) 1984-2023  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, 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;
+public int first_time = 1;
+
+extern int sigs;
+extern int top_scroll;
+extern int quiet;
+extern int sc_width, sc_height;
+extern int hshift;
+extern int auto_wrap;
+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 header_lines;
+extern int header_cols;
+extern int full_screen;
+#if HILITE_SEARCH
+extern int size_linebuf;
+extern int hilite_search;
+extern int status_col;
+#endif
+#if TAGS
+extern char *tagoption;
+#endif
+
+/*
+ * Sound the bell to indicate user is trying to move past end of file.
+ */
+public void eof_bell(void)
+{
+#if HAVE_TIME
+	static time_type last_eof_bell = 0;
+	time_type now = get_time();
+	if (now == last_eof_bell) /* max once per second */
+		return;
+	last_eof_bell = now;
+#endif
+	if (quiet == NOT_QUIET)
+		bell();
+	else
+		vbell();
+}
+
+/*
+ * Check to see if the end of file is currently displayed.
+ */
+public int eof_displayed(void)
+{
+	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(void)
+{
+	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(void)
+{
+	if (!squished)
+		return;
+	squished = 0;
+	repaint();
+}
+
+/*
+ * Read the first pfx columns of the next line.
+ * If skipeol==0 stop there, otherwise read and discard chars to end of line.
+ */
+static POSITION forw_line_pfx(POSITION pos, int pfx, int skipeol)
+{
+	int save_sc_width = sc_width;
+	int save_auto_wrap = auto_wrap;
+	int save_hshift = hshift;
+	/* Set fake sc_width to force only pfx chars to be read. */
+	sc_width = pfx + line_pfx_width();
+	auto_wrap = 0;
+	hshift = 0;
+	pos = forw_line_seg(pos, skipeol, FALSE, FALSE);
+	sc_width = save_sc_width;
+	auto_wrap = save_auto_wrap;
+	hshift = save_hshift;
+	return pos;
+}
+
+/*
+ * Set header text color.
+ * Underline last line of headers, but not at beginning of file
+ * (where there is no gap between the last header line and the next line).
+ */
+static void set_attr_header(int ln)
+{
+	set_attr_line(AT_COLOR_HEADER);
+	if (ln+1 == header_lines && position(0) != ch_zero())
+		set_attr_line(AT_UNDERLINE);
+}
+
+/*
+ * Display file headers, overlaying text already drawn
+ * at top and left of screen.
+ */
+public int overlay_header(void)
+{
+	POSITION pos = ch_zero(); /* header lines are at beginning of file */
+	int ln;
+	int moved = FALSE;
+
+	if (header_lines > 0)
+	{
+		/* Draw header_lines lines from start of file at top of screen. */
+		home();
+		for (ln = 0; ln < header_lines; ++ln)
+		{
+			pos = forw_line(pos);
+			set_attr_header(ln);
+			clear_eol();
+			put_line();
+		}
+		moved = TRUE;
+	}
+	if (header_cols > 0)
+	{
+		/* Draw header_cols columns at left of each line. */
+		home();
+		pos = ch_zero();
+		for (ln = 0; ln < sc_height-1; ++ln)
+		{
+			if (ln >= header_lines) /* switch from header lines to normal lines */
+				pos = position(ln);
+			if (pos == NULL_POSITION)
+				putchr('\n');
+			else 
+			{
+				/* Need skipeol for all header lines except the last one. */
+				pos = forw_line_pfx(pos, header_cols, ln+1 < header_lines);
+				set_attr_header(ln);
+				put_line();
+			}
+		}
+		moved = TRUE;
+	}
+	if (moved)
+		lower_left();
+	return moved;
+}
+
+/*
+ * 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(int n, POSITION pos, int force, int only_last, int nblank)
+{
+	int nlines = 0;
+	int do_repaint;
+
+	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 HILITE_SEARCH
+	if (pos != NULL_POSITION && (hilite_search == OPT_ONPLUS || is_filtering() || status_col)) {
+		prep_hilite(pos, pos + 4*size_linebuf, ignore_eoi ? 1 : -1);
+		pos = next_unfiltered(pos);
+	}
+#endif
+
+	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 && !is_filtering() && full_screen)
+			{
+				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 HILITE_SEARCH
+			pos = next_unfiltered(pos);
+#endif
+			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.
+				 */
+				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 && 
+		    header_lines == 0 && header_cols == 0 &&
+#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 (header_lines > 0)
+	{
+		/*
+		 * Don't allow ch_zero to appear on screen except at top of screen.
+		 * Otherwise duplicate header lines may be displayed.
+		 */
+		if (onscreen(ch_zero()) > 0)
+		{
+			jump_loc(ch_zero(), 0); /* {{ yuck }} */
+			return;
+		}
+	}
+	if (nlines == 0 && !ignore_eoi)
+		eof_bell();
+	else if (do_repaint)
+		repaint();
+	else
+	{
+		overlay_header();
+		/* lower_left(); {{ considered harmful? }} */
+	}
+	first_time = 0;
+	(void) currline(BOTTOM);
+}
+
+/*
+ * Display n lines, scrolling backward.
+ */
+public void back(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) || header_lines > 0);
+#if HILITE_SEARCH
+	if (pos != NULL_POSITION && (hilite_search == OPT_ONPLUS || is_filtering() || status_col)) {
+		prep_hilite((pos < 3*size_linebuf) ? 0 : pos - 3*size_linebuf, pos, -1);
+	}
+#endif
+	while (--n >= 0)
+	{
+		/*
+		 * Get the previous line of input.
+		 */
+#if HILITE_SEARCH
+		pos = prev_unfiltered(pos);
+#endif
+
+		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
+	{
+		overlay_header();
+		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(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 && !ABORT_SIGS());
+			}
+		} 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(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(void)
+{
+	if (no_back_scroll)
+		return (0);
+	if (back_scroll >= 0)
+		return (back_scroll);
+	if (top_scroll)
+		return (sc_height - 2);
+	return (10000); /* infinity */
+}
+
+/*
+ * Will the entire file fit on one screen?
+ */
+public int get_one_screen(void)
+{
+	int nlines;
+	POSITION pos = ch_zero();
+
+	for (nlines = 0;  nlines < sc_height;  nlines++)
+	{
+		pos = forw_line(pos);
+		if (pos == NULL_POSITION) break;
+	}
+	return (nlines < sc_height);
+}