Create pos_rehead to fix bugs when we go into chopline mode

with a "beheaded" position table
(that is, when position(TOP) is not the first char in its line).

command.c

@@ -2043,10 +2043,10 @@ public void commands(void)
  if (number > 0)
  shift_count = number;
  else
- number = (shift_count > 0) ?
- shift_count : sc_width / 2;
+ number = (shift_count > 0) ? shift_count : sc_width / 2;
  if (number > hshift)
  number = hshift;
+ pos_rehead();
  hshift -= number;
  screen_trashed = 1;
  break;
@@ -2058,8 +2058,8 @@ public void commands(void)
  if (number > 0)
  shift_count = number;
  else
- number = (shift_count > 0) ?
-  shift_count : sc_width / 2;
+ number = (shift_count > 0) ? shift_count : sc_width / 2;
+ pos_rehead();
  hshift += number;
  screen_trashed = 1;
  break;
@@ -2068,6 +2068,7 @@ public void commands(void)
  /*
  * Shift view left to margin.
  */
+ pos_rehead();
  hshift = 0;
  screen_trashed = 1;
  break;
@@ -2076,6 +2077,7 @@ public void commands(void)
  /*
  * Shift view right to view rightmost char on screen.
  */
+ pos_rehead();
  hshift = rrshift();
  screen_trashed = 1;
  break;

line.c

@@ -1329,7 +1329,7 @@ public void null_line(void)
  * lines which are not split for screen width.
  * {{ This is supposed to be more efficient than forw_line(). }}
  */
-public POSITION forw_raw_line(POSITION curr_pos, char **linep, int *line_lenp)
+public POSITION forw_raw_line_len(POSITION curr_pos, int read_len, char **linep, int *line_lenp)
 {
  int n;
  int c;
@@ -1360,6 +1360,11 @@ public POSITION forw_raw_line(POSITION curr_pos, char **linep, int *line_lenp)
  }
  }
  linebuf.buf[n++] = c;
+ if (read_len >= 0 && n >= read_len)
+ {
+ new_pos = ch_tell();
+ break;
+ }
  c = ch_forw_get();
  }
  linebuf.buf[n] = '\0';
@@ -1370,6 +1375,11 @@ public POSITION forw_raw_line(POSITION curr_pos, char **linep, int *line_lenp)
  return (new_pos);
 }
 
+public POSITION forw_raw_line(POSITION curr_pos, char **linep, int *line_lenp)
+{
+ return forw_raw_line_len(curr_pos, -1, linep, line_lenp);
+}
+
 /*
  * Analogous to back_line(), but deals with "raw lines".
  * {{ This is supposed to be more efficient than back_line(). }}

optfunc.c

@@ -312,6 +312,19 @@ public void opt_ks(int type, char *s)
 #endif /* HAVE_LESSKEYSRC */
 #endif /* USERFILE */
 
+/*
+ * Handler for -S option.
+ */
+public void opt__S(int type, char *s)
+{
+ switch (type)
+ {
+ case TOGGLE:
+ pos_rehead();
+ break;
+ }
+}
+
 #if TAGS
 /*
  * Handler for -t option.

opttbl.c

@@ -393,7 +393,7 @@ static struct loption option[] =
  }
  },
  { 'S', &S__optname,
- BOOL|REPAINT, OPT_OFF, &chopline, NULL,
+ BOOL|REPAINT, OPT_OFF, &chopline, opt__S,
  {
  "Fold long lines",
  "Chop long lines",

position.c

@@ -26,6 +26,9 @@ static int table_size = 0;
 
 extern int sc_width, sc_height;
 extern int header_lines;
+extern int screen_trashed;
+extern int hshift;
+extern int chopline;
 
 /*
  * Return the starting file position of a line displayed on the screen.
@@ -236,3 +239,73 @@ public int sindex_from_sline(int sline)
  */
  return (sline-1);
 }
+
+/*
+ * Given a line that starts at linepos,
+ * and the character at byte offset choff into that line,
+ * return the number of characters (not bytes) between the
+ * beginning of the line and the first byte of the choff character.
+ */
+static int pos_shift(POSITION linepos, int choff)
+{
+ char *line;
+ int line_len;
+ POSITION pos;
+ int cvt_ops;
+ int cvt_len;
+ int *chpos;
+ char *cline;
+
+ pos = forw_raw_line_len(linepos, choff, &line, &line_len);
+ if (pos == NULL_POSITION || line_len != choff)
+ return -1;
+ cvt_ops = get_cvt_ops(0);
+ cvt_len = cvt_length(line_len, cvt_ops);
+ chpos = cvt_alloc_chpos(cvt_len);
+ cline = (char *) ecalloc(1, line_len);
+ cvt_text(cline, line, chpos, &line_len, cvt_ops);
+ free(cline);
+ free(chpos);
+ return line_len;
+}
+
+/*
+ * Return the position of the first char of the line containing tpos.
+ * Thus if tpos is the first char of its line, just return tpos.
+ */
+static POSITION beginning_of_line(POSITION tpos)
+{
+ ch_seek(tpos);
+ while (ch_tell() != ch_zero())
+ {
+ int ch = ch_back_get();
+ if (ch == '\n')
+ {
+ (void) ch_forw_get();
+ break;
+ }
+ }
+ return ch_tell();
+}
+
+/*
+ * When viewing long lines, it may be that the first char in the top screen
+ * line is not the first char in its (file) line (the table is "beheaded").
+ * (The top line on the screen is the only one that can be in this state.)
+ * This function sets that entry to the position of the first char in the line.
+ */
+public void pos_rehead(void)
+{
+ POSITION linepos;
+ POSITION tpos = table[TOP];
+ if (!chopline)
+ return;
+ if (tpos == NULL_POSITION)
+ return;
+ linepos = beginning_of_line(tpos);
+ if (linepos == tpos)
+ return;
+ table[TOP] = linepos;
+ hshift = pos_shift(linepos, tpos - linepos);
+ screen_trashed = 1;
+}

search.c

@@ -210,7 +210,7 @@ public void init_search(void)
 /*
  * Determine which text conversions to perform before pattern matching.
  */
-static int get_cvt_ops(int search_type)
+public int get_cvt_ops(int search_type)
 {
  int ops = 0;
 
@@ -580,7 +580,7 @@ static void shift_visible(int start_off, int end_off)
  int swidth = sc_width - line_pfx_width();
  if (start_off >= hshift && end_off < hshift + swidth)
  return; /* already visible */
- hshift = (end_off < swidth) ? 0 : start_off < found_shift ? 0 : start_off - found_shift;
+ hshift = (end_off < swidth) ? 0 : (start_off < found_shift) ? 0 : (start_off - found_shift);
  screen_trashed = 1;
 }