[PATCH] Support for match highlighting on certain deficient terminals without CSI[0m

[Nix]

I'm cursed to use Intelliterm 6.0a at work, which supports all the xterm
colour-selection codes, *except* for CSI[0m, CSI[39m and CSI[49m (the
colour-resetting ones); you have to explicitly set the colours back to
the pre-existing ones when a match is over (and to work out the
pre-existing colours, you have to use, um, guesswork.)

This makes GNU grep's colour-selection code a bit annoyed.

Here's a patch that makes the disable-highlight code customizable just
as enable-highlight is, for any other unfortunates cursed with
substandard terminals:

2002-12-10  Nix  <address@hidden>

        * src/grep.c (grep_uncolor): New variable...
        * src/grep.c (main): ... set it, from GREP_UNCOLOR...
        * src/grep.c (prline): ... and emit it at match-unhighlight time.

2002-12-10  Nix  <address@hidden>

        * doc/grep.texi (Invoking): Document GREP_UNCOLOR.

 doc/grep.texi |   15 ++++++++++++---
 src/grep.c    |   18 +++++++++++++-----
 2 files changed, 25 insertions(+), 8 deletions(-)

diff -durN 2.5-orig/doc/grep.texi 2.5/doc/grep.texi
--- 2.5-orig/doc/grep.texi      Tue Jan 22 13:20:04 2002
+++ 2.5/doc/grep.texi   Mon Dec  9 14:02:22 2002
@@ -265,7 +265,9 @@
 @itemx address@hidden
 @opindex --colour
 @cindex highlight, color, colour
-The matching string is surrounded by the marker specify in @var{GREP_COLOR}.
+The matching string is preceded by the marker specified in @var{GREP_COLOR},
+and followed by that specified in @var{GREP_UNCOLOR} (if any) or by a
+conventional VT-terminal `return to normal' code otherwise.
 @var{WHEN} may be `never', `always', or `auto'.
 
 @item address@hidden
@@ -575,8 +577,15 @@
 @item GREP_COLOR
 @vindex GREP_COLOR
 @cindex highlight markers
-This variable specifies the surrounding markers use to highlight the matching
-text.  The default is control ascii red.
+This variable specifies the marker used to highlight matching text.  The
+default is control ascii red.
+
address@hidden GREP_UNCOLOR
address@hidden GREP_UNCOLOR
address@hidden highlight markers
+This variable specifies the marker used to return to normal after a
+region of matching text has passed.  The default is a VT-terminal code
+that does the job on such terminals.
 
 @item LC_ALL
 @itemx LC_COLLATE
diff -durN 2.5-orig/src/grep.c 2.5/src/grep.c
--- 2.5-orig/src/grep.c Wed Mar 13 14:49:52 2002
+++ 2.5/src/grep.c      Mon Dec  9 14:05:50 2002
@@ -66,7 +66,7 @@
 /* If nonzero, use mmap if possible.  */
 static int mmap_option;
 
-/* If nonzero, use grep_color marker.  */
+/* If nonzero, use grep_color and grep_uncolor markers.  */
 static int color_option;
 
 /* If nonzero, show only the part of a line matching the expression. */
@@ -76,6 +76,10 @@
    variable GREP_COLOR.  The default is to print red.  */
 static const char *grep_color = "01;31";
 
+/* The `color' to use to reset the screen colors to what they were before.  The
+   user can overwrite it using the environment variable GREP_UNCOLOR.  */
+static const char *grep_uncolor = "00";
+
 static struct exclude *excluded_patterns;
 static struct exclude *included_patterns;
 /* Short options.  */
@@ -543,7 +547,7 @@
            printf("\33[%sm", grep_color);
          fwrite(b, sizeof (char), match_size, stdout);
          if(color_option)
-           fputs("\33[00m", stdout);
+           printf("\33[%sm", grep_uncolor);
          fputs("\n", stdout);
          beg = b + match_size;
         }
@@ -574,7 +578,7 @@
              fwrite (beg, sizeof (char), match_offset, stdout);
              printf ("\33[%sm", grep_color);
              fwrite (b, sizeof (char), match_size, stdout);
-             fputs ("\33[00m", stdout);
+             printf ("\33[%sm", grep_uncolor);
              beg = b + match_size;
              ibeg = ibeg + match_offset + match_size;
            }
@@ -593,7 +597,7 @@
          fwrite (beg, sizeof (char), match_offset, stdout);
          printf ("\33[%sm", grep_color);
          fwrite (b, sizeof (char), match_size, stdout);
-         fputs ("\33[00m", stdout);
+         printf ("\33[%sm", grep_uncolor);
          beg = b + match_size;
        }
     }
@@ -1643,9 +1647,13 @@
 
   if (color_option)
     {
-      char *userval = getenv ("GREP_COLOR");
+      char *userval;
+      userval = getenv ("GREP_COLOR");
       if (userval != NULL && *userval != '\0')
        grep_color = userval;
+      userval = getenv ("GREP_UNCOLOR");
+      if (userval != NULL && *userval != '\0')
+       grep_uncolor = userval;
     }
 
   if (! matcher)


-- 
`Ah, but don't you feel the jackboot of state oppression whenever you have
 to deal with the uniformed storm-troopers of government bureaucracy, viz.
 the bus company ticket inspectors?
 Damn you for a Stalinist stooge!' --- Charlie Stross