PATCH: update region highlighting as line changes

[Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>]

This makes an attempt to keep the highlighted regions set by the zle
special parameter $region_highlight in sync as the line changes.  The
basics seem to be working.  The region is sticky: if you extend it in
front or at the back the region grows.  This can be made optional later
if necessary.

Things I haven't done:

- Remove entries from the array if the region shrinks to zero or is cut
entirely.  This would probably be sensible.

- Remove entries from the array if the line changes wholesale, e.g. you
move up and down in the history.  This also seems sensible.  One day 
it might be possible to retain the highlighting as you move through the
history in the same way it already remembers edits on other history
lines until you hit return.

- Look at ZLE function widgets to see if they can be made more aware of
how much of the line is changing.  If you simply replace LBUFFER and
RBUFFER it's hard to know how to update the highlighted regions.
I think we'd need a smarter way of updating stuff around the cursor.
You can do it just by invoking zle widgets but it's not as convenient.
Maybe simply using the normal delete and insert functions to resize
the buffer before or after the cursor would help a lot.

- Add undo control for the highlighting.  It already works for undoing
inserts and deletions, the only thing that doesn't work is undoing the
highlighting itself and I think that would be a bit over the top.

Index: Doc/Zsh/zle.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/zle.yo,v
retrieving revision 1.90
diff -p -u -r1.90 zle.yo
--- Doc/Zsh/zle.yo	17 Dec 2010 17:10:48 -0000	1.90
+++ Doc/Zsh/zle.yo	18 Feb 2011 21:04:54 -0000
@@ -842,10 +842,7 @@ specifies that the first twenty characte
 any predisplay string should be highlighted in bold.
 
 Note that the effect of tt(region_highlight) is not saved and disappears
-as soon as the line is accepted.  The line editor makes no attempt to
-keep the highlighting effect synchronised with the line as it is edited;
-hence region highlighting is best limited to static effects within
-user widgets.
+as soon as the line is accepted.
 )
 vindex(WIDGET)
 item(tt(WIDGET) (scalar))(
Index: Src/Zle/compcore.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/compcore.c,v
retrieving revision 1.104
diff -p -u -r1.104 compcore.c
--- Src/Zle/compcore.c	14 Dec 2010 10:35:39 -0000	1.104
+++ Src/Zle/compcore.c	18 Feb 2011 21:04:54 -0000
@@ -1395,8 +1395,6 @@ set_comp_sep(void)
     LinkNode n;
     /* Save word position */
     int owe = we, owb = wb;
-    /* Save cursor position and line length */
-    int ocs, oll;
     /*
      * Values of word beginning and end and cursor after subtractions
      * due to separators.   I think these are indexes into zlemetaline,
@@ -1481,8 +1479,7 @@ set_comp_sep(void)
 
     /* Put the string in the lexer buffer and call the lexer to *
      * get the words we have to expand.                        */
-    ocs = zlemetacs;
-    oll = zlemetall;
+    zle_save_positions();
     ol = zlemetaline;
     addedx = 1;
     noerrs = 1;
@@ -1639,9 +1636,8 @@ set_comp_sep(void)
     lexrestore();
     wb = owb;
     we = owe;
-    zlemetacs = ocs;
     zlemetaline = ol;
-    zlemetall = oll;
+    zle_restore_positions();
     if (cur < 0 || i < 1)
 	return 1;
     owb = offs;
Index: Src/Zle/compresult.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/compresult.c,v
retrieving revision 1.79
diff -p -u -r1.79 compresult.c
--- Src/Zle/compresult.c	15 Aug 2010 18:40:06 -0000	1.79
+++ Src/Zle/compresult.c	18 Feb 2011 21:04:54 -0000
@@ -698,8 +698,10 @@ hasbrpsfx(Cmatch m, char *pre, char *suf
     {
 	char *op = lastprebr, *os = lastpostbr;
 	VARARR(char, oline, zlemetall);
-	int oll = zlemetall, ocs = zlemetacs, ole = lastend, opcs = brpcs, oscs = brscs, ret;
+	int oll = zlemetall, newll, ole = lastend;
+	int opcs = brpcs, oscs = brscs, ret;
 
+	zle_save_positions();
 	memcpy(oline, zlemetaline, zlemetall);
 
 	lastprebr = lastpostbr = NULL;
@@ -710,7 +712,10 @@ hasbrpsfx(Cmatch m, char *pre, char *suf
 	foredel(zlemetall, CUT_RAW);
 	spaceinline(oll);
 	memcpy(zlemetaline, oline, oll);
-	zlemetacs = ocs;
+	/* we do not want to restore zlemetall */
+	newll = zlemetall;
+	zle_restore_positions();
+	zlemetall = newll;
 	lastend = ole;
 	brpcs = opcs;
 	brscs = oscs;
Index: Src/Zle/zle.h
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/zle.h,v
retrieving revision 1.42
diff -p -u -r1.42 zle.h
--- Src/Zle/zle.h	22 Mar 2010 19:49:07 -0000	1.42
+++ Src/Zle/zle.h	18 Feb 2011 21:04:54 -0000
@@ -385,6 +385,47 @@ enum suffixflags {
     SUFFLAGS_SPACE = 0x0001	/* Add a space when removing suffix */
 };
 
+
+/* Flags for the region_highlight structure */
+enum {
+    /* Offsets include predisplay */
+    ZRH_PREDISPLAY = 1
+};
+
+/*
+ * Attributes used for highlighting regions.
+ * and mark.
+ */
+struct region_highlight {
+    /* Attributes turned on in the region */
+    int atr;
+    /* Start of the region */
+    int start;
+    /* Start of the region in metafied ZLE line */
+    int start_meta;
+    /*
+     * End of the region:  position of the first character not highlighted
+     * (the same system as for point and mark).
+     */
+    int end;
+    /* End of the region in metafied ZLE line */
+    int end_meta;
+    /*
+     * Any of the flags defined above.
+     */
+    int flags;
+};
+
+/*
+ * Count of special uses of region highlighting, which account
+ * for the first few elements of region_highlights.
+ * 0: region between point and mark
+ * 1: isearch region
+ * 2: suffix
+ */
+#define N_SPECIAL_HIGHLIGHTS	(3)
+
+
 #ifdef MULTIBYTE_SUPPORT
 /*
  * We use a wint_t here, since we need an invalid character as a
@@ -420,15 +461,28 @@ typedef REFRESH_ELEMENT *REFRESH_STRING;
 
 
 #if defined(MULTIBYTE_SUPPORT) && defined(__STDC_ISO_10646__)
+/*
+ * With ISO 10646 there is a private range defined within
+ * the encoding.  We use this for storing single-byte
+ * characters in sections of strings that wouldn't convert to wide
+ * characters.  This allows to preserve the string when transformed
+ * back to multibyte strings.
+ */
+
+/* The start of the private range we use, for 256 characters */
 #define ZSH_INVALID_WCHAR_BASE	(0xe000U)
+/* Detect a wide character within our range */
 #define ZSH_INVALID_WCHAR_TEST(x)			\
     ((unsigned)(x) >= ZSH_INVALID_WCHAR_BASE &&		\
      (unsigned)(x) <= (ZSH_INVALID_WCHAR_BASE + 255u))
+/* Turn a wide character in that range back to single byte */
 #define ZSH_INVALID_WCHAR_TO_CHAR(x)			\
     ((char)((unsigned)(x) - ZSH_INVALID_WCHAR_BASE))
+/* Turn a wide character in that range to an integer */
 #define ZSH_INVALID_WCHAR_TO_INT(x)			\
     ((int)((unsigned)(x) - ZSH_INVALID_WCHAR_BASE))
-#define ZSH_CHAR_TO_INVALID_WCHAR(x)		\
+/* Turn a single byte character into a private wide character */
+#define ZSH_CHAR_TO_INVALID_WCHAR(x)			\
     ((wchar_t)(STOUC(x) + ZSH_INVALID_WCHAR_BASE))
 #endif
 
Index: Src/Zle/zle_refresh.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/zle_refresh.c,v
retrieving revision 1.84
diff -p -u -r1.84 zle_refresh.c
--- Src/Zle/zle_refresh.c	17 Dec 2010 23:05:31 -0000	1.84
+++ Src/Zle/zle_refresh.c	18 Feb 2011 21:04:54 -0000
@@ -210,50 +210,21 @@ int predisplaylen, postdisplaylen;
 
 static int default_atr_on, special_atr_on;
 
-/* Flags for the region_highlight structure */
-enum {
-    /* Offsets include predisplay */
-    ZRH_PREDISPLAY = 1
-};
-
-/*
- * Attributes used for highlighting regions.
- * and mark.
- */
-struct region_highlight {
-    /* Attributes turned on in the region */
-    int atr;
-    /* Start of the region */
-    int start;
-    /*
-     * End of the region:  position of the first character not highlighted
-     * (the same system as for point and mark).
-     */
-    int end;
-    /*
-     * Any of the flags defined above.
-     */
-    int flags;
-};
 /*
  * Array of region highlights, no special termination.
  * The first element (0) always describes the region between
  * point and mark.  Any other elements are set by the user
  * via the parameter region_highlight.
  */
+
+/**/
 struct region_highlight *region_highlights;
-/*
- * Count of special uses of region highlighting, which account
- * for the first few elements of region_highlights.
- * 0: region between point and mark
- * 1: isearch region
- * 2: suffix
- */
-#define N_SPECIAL_HIGHLIGHTS	(3)
+
 /*
  * Number of elements in region_highlights.
  * This includes the special elements above.
  */
+/**/
 int n_region_highlights;
 
 /*
Index: Src/Zle/zle_tricky.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/zle_tricky.c,v
retrieving revision 1.104
diff -p -u -r1.104 zle_tricky.c
--- Src/Zle/zle_tricky.c	14 Dec 2010 10:35:39 -0000	1.104
+++ Src/Zle/zle_tricky.c	18 Feb 2011 21:04:54 -0000
@@ -2675,14 +2675,13 @@ int
 doexpandhist(void)
 {
     char *ol;
-    int oll, ocs, ne = noerrs, err, ona = noaliases;
+    int ne = noerrs, err, ona = noaliases;
 
     UNMETACHECK();
 
     pushheap();
     metafy_line();
-    oll = zlemetall;
-    ocs = zlemetacs;
+    zle_save_positions();
     ol = dupstring(zlemetaline);
     expanding = 1;
     excs = zlemetacs;
@@ -2725,8 +2724,7 @@ doexpandhist(void)
     }
 
     strcpy(zlemetaline, ol);
-    zlemetall = oll;
-    zlemetacs = ocs;
+    zle_restore_positions();
     unmetafy_line();
 
     popheap();
Index: Src/Zle/zle_utils.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/zle_utils.c,v
retrieving revision 1.58
diff -p -u -r1.58 zle_utils.c
--- Src/Zle/zle_utils.c	11 Feb 2011 19:32:21 -0000	1.58
+++ Src/Zle/zle_utils.c	18 Feb 2011 21:04:55 -0000
@@ -179,6 +179,8 @@ zlecharasstring(ZLE_CHAR_T inchar, char 
  * string length, without the NULL byte.
  *
  * If outcsp is non-NULL, assign the new character position.
+ * If outcsp is &zlemetacs, update the positions in the region_highlight
+ * array, too.  This is a bit of a hack.
  *
  * If useheap is 1, memory is returned from the heap, else is allocated
  * for later freeing.
@@ -190,6 +192,7 @@ zlelineasstring(ZLE_STRING_T instr, int 
 		int *outcsp, int useheap)
 {
     int outcs, outll;
+    struct region_highlight *rhp;
 
 #ifdef MULTIBYTE_SUPPORT
     char *s;
@@ -201,9 +204,22 @@ zlelineasstring(ZLE_STRING_T instr, int 
 
     outcs = 0;
     memset(&mbs, 0, sizeof(mbs));
-    for (i=0; i < inll; i++, incs--) {
+    for (i=0; i < inll; i++) {
 	if (incs == 0)
 	    outcs = mb_len;
+	incs--;
+	if (region_highlights && outcsp == &zlemetacs) {
+	    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+		 rhp < region_highlights + n_region_highlights;
+		 rhp++) {
+		if (rhp->start == 0)
+		    rhp->start_meta = mb_len;
+		rhp->start--;
+		if (rhp->end == 0)
+		    rhp->end_meta = mb_len;
+		rhp->end--;
+	    }
+	}
 #ifdef __STDC_ISO_10646__
 	if (ZSH_INVALID_WCHAR_TEST(instr[i])) {
 	    s[mb_len++] = ZSH_INVALID_WCHAR_TO_CHAR(instr[i]);
@@ -222,12 +238,30 @@ zlelineasstring(ZLE_STRING_T instr, int 
     }
     if (incs == 0)
 	outcs = mb_len;
+    if (region_highlights && outcsp == &zlemetacs) {
+	for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+	     rhp < region_highlights + n_region_highlights;
+	     rhp++) {
+	    if (rhp->start == 0)
+		rhp->start_meta = mb_len;
+	    if (rhp->end == 0)
+		rhp->end_meta = mb_len;
+	}
+    }
     s[mb_len] = '\0';
 
     outll = mb_len;
 #else
     outll = inll;
     outcs = incs;
+    if (region_highlights && outcsp == &zlemetacs) {
+	for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+	     rhp < region_highlights + n_region_highlights;
+	     rhp++) {
+	    rhp->start_meta = rhp->start;
+	    rhp->end_meta = rhp->end;
+	}
+    }
 #endif
 
     /*
@@ -243,11 +277,33 @@ zlelineasstring(ZLE_STRING_T instr, int 
 #endif
 	char *stopcs = strp + outcs;
 	char *stopll = strp + outll;
+	char *startp = strp;
 
+	if (region_highlights && outcsp == &zlemetacs) {
+	    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+		 rhp < region_highlights + n_region_highlights;
+		 rhp++) {
+		/* Used as temporary storage */
+		rhp->start = rhp->start_meta;
+		rhp->end = rhp->end_meta;
+	    }
+	}
 	while (strp < stopll) {
 	    if (imeta(*strp)) {
 		if (strp < stopcs)
 		    outcs++;
+		if (region_highlights && outcsp == &zlemetacs) {
+		    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+			 rhp < region_highlights + n_region_highlights;
+			 rhp++) {
+			if (strp < startp + rhp->start) {
+			    rhp->start_meta++;
+			}
+			if (strp < startp + rhp->end) {
+			    rhp->end_meta++;
+			}
+		    }
+		}
 		outll++;
 	    }
 	    strp++;
@@ -290,6 +346,9 @@ zlelineasstring(ZLE_STRING_T instr, int 
  * each metafied character) is converted into the corresponding
  * character position in *outcs.
  *
+ * If, further, outcs is &zlecs, we update the positions in the
+ * region_highlight array, too.  (This is a bit of a hack.)
+ *
  * Note that instr is modified in place, hence should be copied
  * first if necessary;
  *
@@ -304,6 +363,7 @@ stringaszleline(char *instr, int incs, i
 {
     ZLE_STRING_T outstr;
     int ll, sz;
+    struct region_highlight *rhp;
 #ifdef MULTIBYTE_SUPPORT
     mbstate_t mbs;
 #endif
@@ -316,10 +376,32 @@ stringaszleline(char *instr, int incs, i
 	 * is all the processing required to calculate outcs.
 	 */
 	char *inptr = instr, *cspos = instr + incs;
-	while (*inptr && inptr < cspos) {
+	if (region_highlights && outcs == &zlecs) {
+	    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+		 rhp < region_highlights + n_region_highlights;
+		 rhp++) {
+		rhp->start = rhp->start_meta;
+		rhp->end = rhp->end_meta;
+	    }
+	}
+	while (*inptr) {
 	    if (*inptr == Meta) {
+		if (inptr < cspos) {
+		    incs--;
+		}
+		if (region_highlights && outcs == &zlecs) {
+		    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+			 rhp < region_highlights + n_region_highlights;
+			 rhp++) {
+			if (inptr - instr < rhp->start) {
+			    rhp->start_meta--;
+			}
+			if (inptr - instr < rhp->end) {
+			    rhp->end_meta--;
+			}
+		    }
+		}
 		inptr++;
-		incs--;
 	    }
 	    inptr++;
 	}
@@ -385,6 +467,20 @@ stringaszleline(char *instr, int incs, i
 		int offs = inptr - instr;
 		if (offs <= incs && incs < offs + (int)cnt)
 		    *outcs = outptr - outstr;
+		if (region_highlights && outcs == &zlecs) {
+		    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+			 rhp < region_highlights + n_region_highlights;
+			 rhp++) {
+			if (offs <= rhp->start_meta &&
+			    rhp->start_meta < offs + (int)cnt) {
+			    rhp->start = outptr - outstr;
+			}
+			if (offs <= rhp->end_meta &&
+			    rhp->end_meta < offs + (int)cnt) {
+			    rhp->end = outptr - outstr;
+			}
+		    }
+		}
 	    }
 
 	    inptr += cnt;
@@ -404,6 +500,14 @@ stringaszleline(char *instr, int incs, i
     *outll = ll;
     if (outcs)
 	*outcs = incs;
+    if (region_highlights && outcs == &zlecs) {
+	for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+	     rhp < region_highlights + n_region_highlights;
+	     rhp++) {
+	    rhp->start = rhp->start_meta;
+	    rhp->end = rhp->end_meta;
+	}
+    }
 #endif
 
     return outstr;
@@ -432,6 +536,158 @@ zlegetline(int *ll, int *cs)
 }
 
 
+/* Forward reference */
+struct zle_region;
+
+/* A non-special entry in region_highlight */
+struct zle_region  {
+    struct zle_region *next;
+    /* Entries of region_highlight, as needed */
+    int atr;
+    int start;
+    int end;
+    int flags;
+};
+
+/* Forward reference */
+struct zle_position;
+
+/* A saved set of position information */
+struct zle_position {
+    /* Link pointer */
+    struct zle_position *next;
+    /* Cursor position */
+    int cs;
+    /* Mark */
+    int mk;
+    /* Line length */
+    int ll;
+    struct zle_region *regions;
+};
+
+/* LIFO stack of positions */
+struct zle_position *zle_positions;
+
+/*
+ * Save positions including cursor, end-of-line and
+ * (non-special) region highlighting.
+ *
+ * Must be matched by a subsequent zle_restore_positions().
+ */
+
+/**/
+void
+zle_save_positions(void)
+{
+    struct region_highlight *rhp;
+    struct zle_position *newpos;
+    struct zle_region **newrhpp, *newrhp;
+
+    newpos = (struct zle_position *)zalloc(sizeof(*newpos));
+
+    newpos->mk = mark;
+    if (zlemetaline) {
+	/* Use metafied information */
+	newpos->cs = zlemetacs;
+	newpos->ll = zlemetall;
+    } else {
+	/* Use unmetafied information */
+	newpos->cs = zlecs;
+	newpos->ll = zlell;
+
+    }
+
+    newrhpp = &newpos->regions;
+    *newrhpp = NULL;
+    if (region_highlights) {
+	for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+	     rhp < region_highlights + n_region_highlights;
+	     rhp++) {
+	    /*
+	     * This is a FIFO stack, so we preserve the order
+	     * of entries when we restore region_highlights.
+	     */
+	    newrhp = *newrhpp = (struct zle_region *)zalloc(sizeof(**newrhpp));
+	    newrhp->next = NULL;
+	    newrhp->atr = rhp->atr;
+	    newrhp->flags = rhp->flags;
+	    if (zlemetaline) {
+		newrhp->start = rhp->start_meta;
+		newrhp->end = rhp->end_meta;
+	    } else {
+		newrhp->start = rhp->start;
+		newrhp->end = rhp->end;
+	    }
+	    newrhpp = &newrhp->next;
+	}
+    }
+
+    newpos->next = zle_positions;
+    zle_positions = newpos;
+}
+
+/*
+ * Restore positions previously saved.
+ * Relies on zlemetaline being restored correctly beforehand,
+ * so that it can tell whether to use metafied positions or not.
+ */
+
+/**/
+void
+zle_restore_positions(void)
+{
+    struct zle_position *oldpos = zle_positions;
+    struct zle_region *oldrhp;
+    struct region_highlight *rhp;
+    int nreg;
+
+    zle_positions = oldpos->next;
+
+    mark = oldpos->mk;
+    if (zlemetaline) {
+	/* Use metafied information */
+	zlemetacs = oldpos->cs;
+	zlemetall = oldpos->ll;
+    } else {
+	/* Use unmetafied information */
+	zlecs = oldpos->cs;
+	zlell = oldpos->ll;
+    }
+
+    /* Count number of regions and see if the array needs resizing */
+    for (nreg = 0, oldrhp = oldpos->regions;
+	 oldrhp;
+	 nreg++, oldrhp = oldrhp->next)
+	;
+    if (nreg + N_SPECIAL_HIGHLIGHTS != n_region_highlights) {
+	n_region_highlights = nreg + N_SPECIAL_HIGHLIGHTS;
+	region_highlights = (struct region_highlight *)
+	    zrealloc(region_highlights,
+		     sizeof(struct region_highlight) * n_region_highlights);
+    }
+    oldrhp = oldpos->regions;
+    rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+    while (oldrhp) {
+	struct zle_region *nextrhp = oldrhp->next;
+
+	rhp->atr = oldrhp->atr;
+	rhp->flags = oldrhp->flags;
+	if (zlemetaline) {
+	    rhp->start_meta = oldrhp->start;
+	    rhp->end_meta = oldrhp->end;
+	} else {
+	    rhp->start = oldrhp->start;
+	    rhp->end = oldrhp->end;
+	}
+
+	zfree(oldrhp, sizeof(*oldrhp));
+	oldrhp = nextrhp;
+	rhp++;
+    }
+
+    zfree(oldpos, sizeof(*oldpos));
+}
+
 /*
  * Basic utility functions for adding to line or removing from line.
  * At this level the counts supplied are raw character counts, so
@@ -450,6 +706,7 @@ mod_export void
 spaceinline(int ct)
 {
     int i;
+    struct region_highlight *rhp;
 
     if (zlemetaline) {
 	sizeline(ct + zlemetall);
@@ -460,6 +717,19 @@ spaceinline(int ct)
 
 	if (mark > zlemetacs)
 	    mark += ct;
+
+	if (region_highlights) {
+	    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+		 rhp < region_highlights + n_region_highlights;
+		 rhp++) {
+		if (rhp->start_meta >= zlemetacs) {
+		    rhp->start_meta += ct;
+		}
+		if (rhp->end_meta >= zlemetacs) {
+		    rhp->end_meta += ct;
+		}
+	    }
+	}
     } else {
 	sizeline(ct + zlell);
 	for (i = zlell; --i >= zlecs;)
@@ -469,26 +739,85 @@ spaceinline(int ct)
 
 	if (mark > zlecs)
 	    mark += ct;
+
+	if (region_highlights) {
+	    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+		 rhp < region_highlights + n_region_highlights;
+		 rhp++) {
+		if (rhp->start >= zlecs) {
+		    rhp->start += ct;
+		}
+		if (rhp->end >= zlecs) {
+		    rhp->end += ct;
+		}
+	    }
+	}
     }
     region_active = 0;
 }
 
+/*
+ * Within the ZLE line, cut the "cnt" characters from position "to".
+ */
+
 /**/
 void
 shiftchars(int to, int cnt)
 {
+    struct region_highlight *rhp;
+
     if (mark >= to + cnt)
 	mark -= cnt;
     else if (mark > to)
 	mark = to;
 
     if (zlemetaline) {
+	/* before to is updated... */
+	if (region_highlights) {
+	    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+		 rhp < region_highlights + n_region_highlights;
+		 rhp++) {
+		if (rhp->start_meta > to) {
+		    if (rhp->start_meta > to + cnt)
+			rhp->start_meta -= cnt;
+		    else
+			rhp->start_meta = to;
+		}
+		if (rhp->end_meta > to) {
+		    if (rhp->end_meta > to + cnt)
+			rhp->end_meta -= cnt;
+		    else
+			rhp->end_meta = to;
+		}
+	    }
+	}
+
 	while (to + cnt < zlemetall) {
 	    zlemetaline[to] = zlemetaline[to + cnt];
 	    to++;
 	}
 	zlemetaline[zlemetall = to] = '\0';
     } else {
+	/* before to is updated... */
+	if (region_highlights) {
+	    for (rhp = region_highlights + N_SPECIAL_HIGHLIGHTS;
+		 rhp < region_highlights + n_region_highlights;
+		 rhp++) {
+		if (rhp->start > to) {
+		    if (rhp->start > to + cnt)
+			rhp->start -= cnt;
+		    else
+			rhp->start = to;
+		}
+		if (rhp->end > to) {
+		    if (rhp->end > to + cnt)
+			rhp->end -= cnt;
+		    else
+			rhp->end = to;
+		}
+	    }
+	}
+
 	while (to + cnt < zlell) {
 	    zleline[to] = zleline[to + cnt];
 	    to++;

-- 
Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/