425 lines
8.9 KiB
C
425 lines
8.9 KiB
C
/*
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* Copyright (C) 1984-2009 Mark Nudelman
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*
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* You may distribute under the terms of either the GNU General Public
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* License or the Less License, as specified in the README file.
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*
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* For more information about less, or for information on how to
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* contact the author, see the README file.
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*/
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/*
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* Primitives for displaying the file on the screen,
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* scrolling either forward or backward.
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*/
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#include "less.h"
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#include "position.h"
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public int screen_trashed;
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public int squished;
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public int no_back_scroll = 0;
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public int forw_prompt;
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extern int sigs;
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extern int top_scroll;
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extern int quiet;
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extern int sc_width, sc_height;
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extern int plusoption;
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extern int forw_scroll;
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extern int back_scroll;
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extern int ignore_eoi;
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extern int clear_bg;
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extern int final_attr;
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extern int oldbot;
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#if TAGS
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extern char *tagoption;
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#endif
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/*
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* Sound the bell to indicate user is trying to move past end of file.
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*/
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static void
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eof_bell()
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{
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if (quiet == NOT_QUIET)
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bell();
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else
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vbell();
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}
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/*
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* Check to see if the end of file is currently displayed.
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*/
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public int
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eof_displayed()
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{
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POSITION pos;
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if (ignore_eoi)
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return (0);
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if (ch_length() == NULL_POSITION)
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/*
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* If the file length is not known,
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* we can't possibly be displaying EOF.
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*/
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return (0);
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/*
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* If the bottom line is empty, we are at EOF.
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* If the bottom line ends at the file length,
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* we must be just at EOF.
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*/
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pos = position(BOTTOM_PLUS_ONE);
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return (pos == NULL_POSITION || pos == ch_length());
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}
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/*
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* Check to see if the entire file is currently displayed.
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*/
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public int
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entire_file_displayed()
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{
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POSITION pos;
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/* Make sure last line of file is displayed. */
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if (!eof_displayed())
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return (0);
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/* Make sure first line of file is displayed. */
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pos = position(0);
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return (pos == NULL_POSITION || pos == 0);
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}
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/*
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* If the screen is "squished", repaint it.
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* "Squished" means the first displayed line is not at the top
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* of the screen; this can happen when we display a short file
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* for the first time.
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*/
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public void
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squish_check()
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{
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if (!squished)
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return;
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squished = 0;
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repaint();
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}
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/*
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* Display n lines, scrolling forward,
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* starting at position pos in the input file.
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* "force" means display the n lines even if we hit end of file.
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* "only_last" means display only the last screenful if n > screen size.
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* "nblank" is the number of blank lines to draw before the first
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* real line. If nblank > 0, the pos must be NULL_POSITION.
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* The first real line after the blanks will start at ch_zero().
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*/
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public void
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forw(n, pos, force, only_last, nblank)
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register int n;
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POSITION pos;
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int force;
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int only_last;
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int nblank;
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{
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int eof = 0;
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int nlines = 0;
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int do_repaint;
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static int first_time = 1;
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squish_check();
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/*
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* do_repaint tells us not to display anything till the end,
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* then just repaint the entire screen.
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* We repaint if we are supposed to display only the last
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* screenful and the request is for more than a screenful.
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* Also if the request exceeds the forward scroll limit
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* (but not if the request is for exactly a screenful, since
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* repainting itself involves scrolling forward a screenful).
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*/
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do_repaint = (only_last && n > sc_height-1) ||
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(forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
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if (!do_repaint)
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{
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if (top_scroll && n >= sc_height - 1 && pos != ch_length())
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{
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/*
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* Start a new screen.
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* {{ This is not really desirable if we happen
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* to hit eof in the middle of this screen,
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* but we don't yet know if that will happen. }}
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*/
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pos_clear();
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add_forw_pos(pos);
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force = 1;
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clear();
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home();
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}
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if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
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{
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/*
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* This is not contiguous with what is
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* currently displayed. Clear the screen image
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* (position table) and start a new screen.
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*/
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pos_clear();
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add_forw_pos(pos);
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force = 1;
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if (top_scroll)
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{
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clear();
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home();
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} else if (!first_time)
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{
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putstr("...skipping...\n");
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}
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}
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}
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while (--n >= 0)
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{
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/*
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* Read the next line of input.
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*/
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if (nblank > 0)
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{
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/*
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* Still drawing blanks; don't get a line
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* from the file yet.
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* If this is the last blank line, get ready to
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* read a line starting at ch_zero() next time.
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*/
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if (--nblank == 0)
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pos = ch_zero();
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} else
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{
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/*
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* Get the next line from the file.
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*/
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pos = forw_line(pos);
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if (pos == NULL_POSITION)
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{
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/*
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* End of file: stop here unless the top line
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* is still empty, or "force" is true.
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* Even if force is true, stop when the last
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* line in the file reaches the top of screen.
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*/
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eof = 1;
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if (!force && position(TOP) != NULL_POSITION)
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break;
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if (!empty_lines(0, 0) &&
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!empty_lines(1, 1) &&
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empty_lines(2, sc_height-1))
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break;
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}
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}
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/*
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* Add the position of the next line to the position table.
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* Display the current line on the screen.
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*/
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add_forw_pos(pos);
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nlines++;
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if (do_repaint)
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continue;
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/*
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* If this is the first screen displayed and
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* we hit an early EOF (i.e. before the requested
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* number of lines), we "squish" the display down
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* at the bottom of the screen.
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* But don't do this if a + option or a -t option
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* was given. These options can cause us to
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* start the display after the beginning of the file,
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* and it is not appropriate to squish in that case.
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*/
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if (first_time && pos == NULL_POSITION && !top_scroll &&
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#if TAGS
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tagoption == NULL &&
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#endif
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!plusoption)
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{
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squished = 1;
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continue;
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}
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put_line();
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#if 0
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/* {{
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* Can't call clear_eol here. The cursor might be at end of line
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* on an ignaw terminal, so clear_eol would clear the last char
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* of the current line instead of all of the next line.
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* If we really need to do this on clear_bg terminals, we need
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* to find a better way.
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* }}
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*/
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if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
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{
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/*
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* Writing the last character on the last line
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* of the display may have scrolled the screen.
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* If we were in standout mode, clear_bg terminals
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* will fill the new line with the standout color.
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* Now we're in normal mode again, so clear the line.
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*/
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clear_eol();
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}
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#endif
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forw_prompt = 1;
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}
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if (nlines == 0)
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eof_bell();
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else if (do_repaint)
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repaint();
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first_time = 0;
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(void) currline(BOTTOM);
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}
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/*
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* Display n lines, scrolling backward.
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*/
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public void
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back(n, pos, force, only_last)
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register int n;
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POSITION pos;
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int force;
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int only_last;
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{
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int nlines = 0;
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int do_repaint;
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squish_check();
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do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
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while (--n >= 0)
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{
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/*
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* Get the previous line of input.
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*/
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pos = back_line(pos);
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if (pos == NULL_POSITION)
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{
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/*
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* Beginning of file: stop here unless "force" is true.
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*/
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if (!force)
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break;
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}
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/*
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* Add the position of the previous line to the position table.
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* Display the line on the screen.
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*/
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add_back_pos(pos);
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nlines++;
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if (!do_repaint)
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{
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home();
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add_line();
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put_line();
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}
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}
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if (nlines == 0)
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eof_bell();
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else if (do_repaint)
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repaint();
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else if (!oldbot)
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lower_left();
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(void) currline(BOTTOM);
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}
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/*
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* Display n more lines, forward.
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* Start just after the line currently displayed at the bottom of the screen.
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*/
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public void
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forward(n, force, only_last)
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int n;
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int force;
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int only_last;
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{
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POSITION pos;
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if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
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{
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/*
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* If the -e flag is set and we're trying to go
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* forward from end-of-file, go on to the next file.
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*/
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if (edit_next(1))
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quit(QUIT_OK);
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return;
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}
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pos = position(BOTTOM_PLUS_ONE);
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if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
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{
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if (ignore_eoi)
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{
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/*
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* ignore_eoi is to support A_F_FOREVER.
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* Back up until there is a line at the bottom
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* of the screen.
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*/
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if (empty_screen())
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pos = ch_zero();
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else
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{
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do
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{
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back(1, position(TOP), 1, 0);
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pos = position(BOTTOM_PLUS_ONE);
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} while (pos == NULL_POSITION);
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}
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} else
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{
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eof_bell();
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return;
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}
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}
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forw(n, pos, force, only_last, 0);
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}
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/*
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* Display n more lines, backward.
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* Start just before the line currently displayed at the top of the screen.
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*/
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public void
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backward(n, force, only_last)
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int n;
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int force;
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int only_last;
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{
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POSITION pos;
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pos = position(TOP);
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if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
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{
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eof_bell();
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return;
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}
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back(n, pos, force, only_last);
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}
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/*
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* Get the backwards scroll limit.
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* Must call this function instead of just using the value of
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* back_scroll, because the default case depends on sc_height and
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* top_scroll, as well as back_scroll.
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*/
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public int
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get_back_scroll()
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{
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if (no_back_scroll)
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return (0);
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if (back_scroll >= 0)
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return (back_scroll);
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if (top_scroll)
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return (sc_height - 2);
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return (10000); /* infinity */
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}
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