File: [local] / src / usr.bin / less / forwback.c (download)
Revision 1.13, Sat May 18 00:08:06 2024 UTC (3 weeks, 2 days ago) by jsg
Branch: MAIN
CVS Tags: HEAD Changes since 1.12: +0 -2 lines
remove externs for removed vars
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/*
* Copyright (C) 1984-2012 Mark Nudelman
* Modified for use with illumos by Garrett D'Amore.
* Copyright 2014 Garrett D'Amore <garrett@damore.org>
*
* 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"
int screen_trashed;
int squished;
int no_back_scroll = 0;
int forw_prompt;
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 oldbot;
extern char *tagoption;
/*
* Sound the bell to indicate user is trying to move past end of file.
*/
static void
eof_bell(void)
{
if (quiet == NOT_QUIET)
ring_bell();
else
vbell();
}
/*
* Check to see if the end of file is currently displayed.
*/
int
eof_displayed(void)
{
off_t pos;
if (ignore_eoi)
return (0);
if (ch_length() == -1)
/*
* 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 == -1 || pos == ch_length());
}
/*
* Check to see if the entire file is currently displayed.
*/
int
entire_file_displayed(void)
{
off_t 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 == -1 || 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.
*/
void
squish_check(void)
{
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 -1.
* The first real line after the blanks will start at ch_zero().
*/
void
forw(int n, off_t pos, int force, int only_last, int nblank)
{
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;
do_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) {
do_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 == -1) {
/*
* 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) != -1)
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 == -1 && !top_scroll &&
tagoption == NULL && !plusoption) {
squished = 1;
continue;
}
put_line();
forw_prompt = 1;
}
if (nlines == 0)
eof_bell();
else if (do_repaint)
repaint();
first_time = 0;
(void) currline(BOTTOM);
}
/*
* Display n lines, scrolling backward.
*/
void
back(int n, off_t 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 == -1) {
/*
* 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.
*/
void
forward(int n, int force, int only_last)
{
off_t 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 == -1 && (!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 == -1);
}
} 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.
*/
void
backward(int n, int force, int only_last)
{
off_t pos;
pos = position(TOP);
if (pos == -1 && (!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.
*/
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 */
}