Add --proc-backspace, --proc-tab and --proc-return options.

Also fix bug toggling -U while search highlighting is active.

NEWS

@@ -29,6 +29,8 @@
 
 * Add --intr option (github #224).
 
+* Add --proc-backspace, --proc-tab and --proc-return options.
+
 * Add --show-preproc-errors option (github #258).
 
 * Add LESS_LINES and LESS_COLUMNS environment variables.

command.c

@@ -37,6 +37,7 @@ extern int ignore_eoi;
 extern int secure;
 extern int hshift;
 extern int bs_mode;
+extern int proc_backspace;
 extern int show_attn;
 extern int status_col;
 extern POSITION highest_hilite;
@@ -84,6 +85,7 @@ static int optgetname;
 static POSITION bottompos;
 static int save_hshift;
 static int save_bs_mode;
+static int save_proc_backspace;
 #if PIPEC
 static char pipec;
 #endif
@@ -1608,6 +1610,7 @@ public void commands(void)
  */
  hshift = save_hshift;
  bs_mode = save_bs_mode;
+ proc_backspace = save_proc_backspace;
  if (edit_prev(1) == 0)
  break;
  }
@@ -1716,6 +1719,8 @@ public void commands(void)
  hshift = 0;
  save_bs_mode = bs_mode;
  bs_mode = BS_SPECIAL;
+ save_proc_backspace = proc_backspace;
+ proc_backspace = OPT_OFF;
  (void) edit(FAKE_HELPFILE);
  break;
 

less.hlp

@@ -188,7 +188,7 @@
  -T [_t_a_g_s_f_i_l_e] --tag-file=[_t_a_g_s_f_i_l_e]
  Use an alternate tags file.
  -u -U .... --underline-special --UNDERLINE-SPECIAL
- Change handling of backspaces.
+ Change handling of backspaces, tabs and carriage returns.
  -V ........ --version
  Display the version number of "less".
  -w ........ --hilite-unread
@@ -247,6 +247,18 @@
  Set default options for every search.
  --show-preproc-errors
  Display a message if preprocessor exits with an error status.
+ --proc-backspace
+ Process backspaces for bold/underline.
+ --SPECIAL-BACKSPACE
+ Treat backspaces as control characters.
+ --proc-return
+ Delete carriage returns before newline.
+ --SPECIAL-RETURN
+ Treat carriage returns as control characters.
+ --proc-tab
+ Expand tabs to spaces.
+ --SPECIAL-TAB
+ Treat tabs as control characters.
  --status-col-width=_N
  Set the width of the -J status column to _N characters.
  --status-line

less.nro.VER

@@ -654,7 +654,7 @@ Underlined text.
 .RE
 
 .RS
-The uppercase letters can be used only when the \-\-use-color option is enabled.
+The uppercase letters and digits can be used only when the \-\-use-color option is enabled.
 When text color is specified by both an uppercase letter and a lowercase letter,
 the uppercase letter takes precedence. 
 For example, error messages are normally displayed as standout text.
@@ -692,7 +692,7 @@ White
 .IP "y"
 Yellow
 .PP
-The corresponding upper-case letter denotes a brighter shade of the color.
+The corresponding uppercase letter denotes a brighter shade of the color.
 For example, \-DNGk displays line numbers as bright green text on a black 
 background, and \-DEbR displays error messages as blue text on a 
 bright red background.
@@ -1071,6 +1071,9 @@ Unicode formatting characters, such as the Byte Order Mark,
 are sent to the terminal.
 Text which is overstruck or underlined can be searched for
 if neither \-u nor \-U is in effect.
+.sp
+See also the \-\-proc-backspace, \-\-proc-tab,
+and \-\-proc-return options.
 .IP "\-V or \-\-version"
 Displays the version number of
 .BR less .
@@ -1271,6 +1274,38 @@ Line number 1 is assigned to the first line after any header lines.
 Searches do not include header lines or header columns.
 .IP "\-\-no-vbell"
 Disables the terminal's visual bell.
+.IP "\-\-proc-backspace"
+If set, backspaces are handled as if neither the \-u option 
+nor the \-U option were set, even if one of those options is set.
+That is, backspaces adjacent to underscores cause text to be
+displayed in underline mode, and backspaces between identical
+characters cause text to be displayed in boldface mode.
+This allows control of backspace handling separate from 
+handling of tabs and carriage returns.
+If not set, backspace handling is controlled by the \-u and \-U options.
+.IP "\-\-PROC-BACKSPACE"
+If set, backspaces are handles as if the \-u option were set;
+that is backspaces are treated as control characters.
+.IP "\-\-proc-return"
+If set, carriage returns are handled as if neither the \-u option 
+nor the \-U option were set, even if one of those options is set.
+That is, a carriage return immediately before a newline is deleted.
+This allows control of carriage return handling separate from 
+handling of backspaces and tabs.
+If not set, carriage return handling is controlled by the \-u and \-U options.
+.IP "\-\-PROC-RETURN"
+If set, carriage returns are handles as if the \-u option were set;
+that is carriage returns are treated as control characters.
+.IP "\-\-proc-tab"
+If set, tabs are handled as if neither the \-u option 
+nor the \-U option were set, even if one of those options is set.
+That is, tabs are expanded to spaces.
+This allows control of tab handling separate from 
+handling of backspaces and carriage returns.
+If not set, tab handling is controlled by the \-u and \-U options.
+.IP "\-\-PROC-TAB"
+If set, tabs are handles as if the \-u option were set;
+that is tabs are treated as control characters.
 .IP "\-\-redraw-on-quit"
 When quitting, after sending the terminal deinitialization string,
 redraws the entire last screen.

line.c

@@ -81,6 +81,9 @@ static int do_append(LWCHAR ch, char *rep, POSITION pos);
 
 extern int sigs;
 extern int bs_mode;
+extern int proc_backspace;
+extern int proc_tab;
+extern int proc_return;
 extern int linenums;
 extern int ctldisp;
 extern int twiddle;
@@ -893,7 +896,7 @@ public int pappend(int c, POSITION pos)
  pendc = '\0';
  }
 
- if (c == '\r' && bs_mode == BS_SPECIAL)
+ if (c == '\r' && (proc_return == OPT_ON || (bs_mode == BS_SPECIAL && proc_return == OPT_OFF)))
  {
  if (mbc_buf_len > 0) /* utf_mode must be on. */
  {
@@ -1021,15 +1024,15 @@ static int store_ansi(LWCHAR ch, char *rep, POSITION pos)
 
 static int store_bs(LWCHAR ch, char *rep, POSITION pos)
 {
- if (bs_mode == BS_CONTROL)
+ if (proc_backspace == OPT_ONPLUS || (bs_mode == BS_CONTROL && proc_backspace == OPT_OFF))
  return store_control_char(ch, rep, pos);
  if (linebuf.end > 0 &&
  ((linebuf.end <= linebuf.print && linebuf.buf[linebuf.end-1] == '\0') ||
  (linebuf.end > 0 && linebuf.attr[linebuf.end - 1] & (AT_ANSI|AT_BINARY))))
  STORE_PRCHAR('\b', pos);
- else if (bs_mode == BS_NORMAL)
+ else if (proc_backspace == OPT_OFF && bs_mode == BS_NORMAL)
  STORE_CHAR(ch, AT_NORMAL, NULL, pos);
- else if (bs_mode == BS_SPECIAL)
+ else if (proc_backspace == OPT_ON || (bs_mode == BS_SPECIAL && proc_backspace == OPT_OFF))
  overstrike = backc();
  return 0;
 }
@@ -1117,15 +1120,9 @@ static int do_append(LWCHAR ch, char *rep, POSITION pos)
  /*
  * Expand a tab into spaces.
  */
- switch (bs_mode)
- {
- case BS_CONTROL:
+ if (proc_tab == OPT_ONPLUS || (bs_mode == BS_CONTROL && proc_tab == OPT_OFF))
  return store_control_char(ch, rep, pos);
- case BS_NORMAL:
- case BS_SPECIAL:
- STORE_TAB(a, pos);
- break;
- }
+ STORE_TAB(a, pos);
  return (0);
  }
  if ((!utf_mode || is_ascii_char(ch)) && control_char((char)ch))

opttbl.c

@@ -76,6 +76,9 @@ public int def_search_type; /* */
 public int exit_F_on_close; /* Exit F command when input closes */
 public int modelines; /* Lines to read looking for modelines */
 public int show_preproc_error; /* Display msg when preproc exits with error */
+public int proc_backspace; /* Special handling of backspace */
+public int proc_tab; /* Special handling of tab */
+public int proc_return; /* Special handling of carriage return */
 public char intr_char = CONTROL('X'); /* Char to interrupt reads */
 #if HILITE_SEARCH
 public int hilite_search; /* Highlight matched search patterns? */
@@ -164,6 +167,9 @@ static struct optname no_vbell_optname = { "no-vbell", NULL };
 static struct optname intr_optname = { "intr", NULL };
 static struct optname wordwrap_optname = { "wordwrap", NULL };
 static struct optname show_preproc_error_optname = { "show-preproc-errors", NULL };
+static struct optname proc_backspace_optname = { "proc-backspace", NULL };
+static struct optname proc_tab_optname = { "proc-tab", NULL };
+static struct optname proc_return_optname = { "proc-return", NULL };
 #if LESSTEST
 static struct optname ttyin_name_optname = { "tty", NULL };
 #endif /*LESSTEST*/
@@ -403,7 +409,7 @@ static struct loption option[] =
  },
 #endif
  { 'u', &u_optname,
- TRIPLE|REPAINT, OPT_OFF, &bs_mode, NULL,
+ TRIPLE|REPAINT|HL_REPAINT, OPT_OFF, &bs_mode, NULL,
  {
  "Display underlined text in underline mode",
  "Backspaces cause overstrike",
@@ -678,6 +684,30 @@ static struct loption option[] =
  NULL
  }
  },
+ { OLETTER_NONE, &proc_backspace_optname,
+ TRIPLE|REPAINT|HL_REPAINT, OPT_OFF, &proc_backspace, NULL,
+ {
+ "Backspace handling is specified by the -U option",
+ "Display underline text in underline mode",
+ "Print backspaces as ^H"
+ }
+ },
+ { OLETTER_NONE, &proc_tab_optname,
+ TRIPLE|REPAINT|HL_REPAINT, OPT_OFF, &proc_tab, NULL,
+ {
+ "Tab handling is specified by the -U option",
+ "Expand tabs to spaces",
+ "Print tabs as ^I"
+ }
+ },
+ { OLETTER_NONE, &proc_return_optname,
+ TRIPLE|REPAINT|HL_REPAINT, OPT_OFF, &proc_return, NULL,
+ {
+ "Carriage return handling is specified by the -U option",
+ "Delete carriage return before newline",
+ "Print carriage return as ^M"
+ }
+ },
 #if LESSTEST
  { OLETTER_NONE, &ttyin_name_optname,
  STRING|NO_TOGGLE, 0, NULL, opt_ttyin_name,

search.c

@@ -26,6 +26,8 @@ extern int linenums;
 extern int sc_height;
 extern int jump_sline;
 extern int bs_mode;
+extern int proc_backspace;
+extern int proc_return;
 extern int ctldisp;
 extern int status_col;
 extern void *ml_search;
@@ -213,9 +215,9 @@ static int get_cvt_ops(int search_type)
 
  if (is_caseless && (!re_handles_caseless || (search_type & SRCH_NO_REGEX)))
  ops |= CVT_TO_LC;
- if (bs_mode == BS_SPECIAL)
+ if (proc_backspace == OPT_ON || (bs_mode == BS_SPECIAL && proc_backspace == OPT_OFF))
  ops |= CVT_BS;
- if (bs_mode != BS_CONTROL)
+ if (proc_return == OPT_ON || (bs_mode != BS_CONTROL && proc_backspace == OPT_OFF))
  ops |= CVT_CRLF;
  if (ctldisp == OPT_ONPLUS)
  ops |= CVT_ANSI;
@@ -271,6 +273,7 @@ public void repaint_hilite(int on)
  continue;
  (void) forw_line(pos);
  goto_line(sindex);
+ clear_eol();
  put_line();
  }
  overlay_header();

version.c

@@ -972,7 +972,7 @@ v620 1/12/23 Add --modelines option; add --intr option;
 v621 1/15/23 Add --wordwrap option; add LESS_LINES & LESS_COLUMNS.
 v622 1/27/23 Add --show-preproc-errors option.
 v623 2/2/23 Add # command; add ^S search modifier.
-v624
+v624 Add --proc-backspace, --proc-tab and --proc-return options.
 */
 
 char version[] = "624x";