/*
* 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 more_mode;
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 (!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 || more_mode) &&
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 (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;
/*
* 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();
