Add M and ESC-M commands.

Fix buffering bug when using stdin with LESSOPEN pipe
(h,q displays corrupt data).

NEWS.VER

@@ -18,6 +18,8 @@
 * When using -S, mark truncated lines with a special character.
  The character can be changed or disabled via the new --rscroll option.
 
+* New command M visually marks the last line displayed on the screen.
+
 * Status column (enabled via -J) now shows mark letters.
 
 * Do same ANSI escape code filtering for tag matching that we do for 
@@ -27,6 +29,8 @@
 
 * Fix bug initializing default charset on Windows.
 
+* Fix buffering bug when using stdin with a LESSOPEN pipe.
+
 * Update Unicode tables to 2017-03-08.
 
 * Pass-thru Unicode formating chars (Cf type) instead of treating them

ch.c

@@ -860,13 +860,12 @@ ch_init(f, flags)
  calloc(1, sizeof(struct filestate));
  thisfile->buflist.next = thisfile->buflist.prev = END_OF_CHAIN;
  thisfile->nbufs = 0;
- thisfile->flags = 0;
+ thisfile->flags = flags;
  thisfile->fpos = 0;
  thisfile->block = 0;
  thisfile->offset = 0;
  thisfile->file = -1;
  thisfile->fsize = NULL_POSITION;
- ch_flags = flags;
  init_hashtbl();
  /*
  * Try to seek; set CH_CANSEEK if it works.
@@ -891,7 +890,7 @@ ch_close()
  if (thisfile == NULL)
  return;
 
- if (ch_flags & (CH_CANSEEK|CH_HELPFILE))
+ if ((ch_flags & (CH_CANSEEK|CH_POPENED|CH_HELPFILE)) && !(ch_flags & CH_KEEPOPEN))
  {
  /*
  * We can seek or re-open, so we don't need to keep buffers.

cmd.h

@@ -63,6 +63,7 @@
 #define A_LLSHIFT 58
 #define A_RRSHIFT 59
 #define A_SETATTN 60
+#define A_CLRATTN 61
 
 #define A_INVALID 100
 #define A_NOACTION 101

command.c

@@ -30,6 +30,7 @@ extern int hshift;
 extern int bs_mode;
 extern int show_attn;
 extern int sticky_attn;
+extern int status_col;
 extern POSITION highest_hilite;
 extern char *every_first_cmd;
 extern char *curr_altfilename;
@@ -85,10 +86,8 @@ static void multi_search();
  static void
 cmd_exec()
 {
-#if HILITE_SEARCH
  if (!sticky_attn)
  clear_attn();
-#endif
  clear_bot();
  flush();
 }
@@ -1787,10 +1786,15 @@ commands()
  break;
 
  case A_SETATTN:
+ status_col = 1;
  set_attnpos(position(BOTTOM), 1);
  repaint();
  break;
 
+ case A_CLRATTN:
+ clear_attn();
+ break;
+
  case A_PREFIX:
  /*
  * The command is incomplete (more chars are needed).

decode.c

@@ -134,6 +134,7 @@ static unsigned char cmdtable[] =
  '&',0, A_FILTER,
  'm',0, A_SETMARK,
  'M',0, A_SETATTN,
+ ESC,'M',0, A_CLRATTN,
  '\'',0, A_GOMARK,
  CONTROL('X'),CONTROL('X'),0, A_GOMARK,
  'E',0, A_EXAMINE,

edit.c

@@ -263,11 +263,17 @@ edit_ifile(ifile)
  }
 
  filename = save(get_filename(ifile));
+
  /*
  * See if LESSOPEN specifies an "alternate" file to open.
  */
  alt_pipe = NULL;
- alt_filename = open_altfile(filename, &f, &alt_pipe);
+ if (strcmp(filename, FAKE_HELPFILE) == 0 ||
+ strcmp(filename, FAKE_EMPTYFILE) == 0)
+ alt_filename = NULL;
+ else
+ alt_filename = open_altfile(filename, &f, &alt_pipe);
+
  open_filename = (alt_filename != NULL) ? alt_filename : filename;
  qopen_filename = shell_unquote(open_filename);
 
@@ -282,6 +288,8 @@ edit_ifile(ifile)
  * via popen(), and pclose() wants to close it.
  */
  chflags |= CH_POPENED;
+ if (strcmp(open_filename, "-") == 0)
+ chflags |= CH_KEEPOPEN;
  } else if (strcmp(open_filename, "-") == 0)
  {
  /* 

filename.c

@@ -961,6 +961,7 @@ close_altfile(altfilename, filename, pipefd)
 
  if (secure)
  return;
+ ch_ungetchar(-1);
  if (pipefd != NULL)
  {
 #if OS2

less.h

@@ -507,7 +507,6 @@ struct wchar_range_table
 #define CH_HELPFILE 010
 #define CH_NODATA 020 /* Special case for zero length files */
 
-
 #define ch_zero() ((POSITION)0)
 
 #define FAKE_HELPFILE "@/\\less/\\help/\\file/\\@"

less.nro.VER

@@ -188,6 +188,13 @@ Marks are preserved when a new file is examined,
 so the ' command can be used to switch between input files.
 .IP "^X^X"
 Same as single quote.
+.IP M
+Visually marks the last line displayed on the screen.
+The status column is enabled to show the mark if it is not already enabled via the -J option.
+This can be useful to keep track of a particular line while moving in the file
+or while new lines are displayed during the F command.
+.IP "ESC-M"
+Removes the mark set by a previous M command.
 .IP /pattern
 Search forward in the file for the N-th line containing the pattern.
 N defaults to 1.

version.c

@@ -818,6 +818,8 @@ v501 7/12/17 Make sure rscroll char is standout by default.
 v502 7/13/17 Control rscroll char via command line option not env variable.
 v503 7/13/17 Switch to git.
 v504 7/13/17 Call opt_rscroll at startup; change mkhelp.c to mkhelp.pl.
+v505 7/17/17 Add M and ESC-M commands; 
+ fix buffer handling with stdin and LESSOPEN.
 */
 
-char version[] = "504";
+char version[] = "505";