PATCH: $PREDISPLAY/$POSTDISPLAY

[Peter Stephenson <pws@xxxxxxx>]

Peter Stephenson wrote:
> Another thing I thought of which might be useful is a way to protect
> areas of the display, so for example if you are using a widget like
> select-list you can't move off the list until you accept something or
> break.  I think you could do something like this without too much
> difficulty by using a special parameter like $PREDISPLAY (maybe also
> $POSTDISPLAY, since this gives you more control than zle -M), which would
> insert the given lines before (or after) $BUFFER.  This could probably
> be done within zle_refresh (and zle_parameter, of course).  It would
> probably have to be line-orientated to avoid weird interactions with the
> normal buffer, although maybe even that restriction is avoidable.

This is what I had in mind.  zle_refresh is one of the few reasonably
modular parts of zle, so it turns out having only chunks of a line works
fine.

Note the way these parameters survive across invocations of zle.  This
was simply because it was the most natural way of writing it.  We can
make zleread() reinitialise them if it seems preferable.

Hmm, it would be nice to get bits of these optionally in inverse video.
In fact, it would be nice to get a lot of other stuff such as the region
between point and mark in inverse video.

Here's a trivial example of how this works with recursive-edit.

pre-post-example () {
        PREDISPLAY="*** You can't edit this bit ***
" POSTDISPLAY="
*** Nor this bit ***"
        zle recursive-edit
        PREDISPLAY= POSTDISPLAY= 
}

Index: Src/Zle/zle_params.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/zle_params.c,v
retrieving revision 1.4
diff -u -r1.4 zle_params.c
--- Src/Zle/zle_params.c	24 Jun 2002 09:52:01 -0000	1.4
+++ Src/Zle/zle_params.c	1 Jul 2002 11:05:24 -0000
@@ -85,6 +85,10 @@
 	unset_cutbuffer, NULL },
     { "killring", PM_ARRAY, FN(set_killring), FN(get_killring),
 	unset_killring, NULL },
+    { "PREDISPLAY", PM_SCALAR, FN(set_predisplay), FN(get_predisplay),
+	zleunsetfn, NULL },
+    { "POSTDISPLAY", PM_SCALAR, FN(set_postdisplay), FN(get_postdisplay),
+	zleunsetfn, NULL },
     { NULL, 0, NULL, NULL, NULL, NULL }
 };
 
@@ -461,4 +465,54 @@
 	set_killring(pm, NULL);
 	stdunsetfn(pm, exp);
     }
+}
+
+static void
+set_prepost(unsigned char **textvar, int *lenvar, char *x)
+{
+    if (*lenvar) {
+	zfree(*textvar, *lenvar);
+	*textvar = NULL;
+	*lenvar = 0;
+    }
+    if (x) {
+	unmetafy(x, lenvar);
+	*textvar = (unsigned char *)zalloc(*lenvar);
+	memcpy((char *)*textvar, x, *lenvar);
+	free(x);
+    }
+}
+
+static char *
+get_prepost(unsigned char *text, int len)
+{
+    return metafy((char *)text, len, META_HEAPDUP);
+}
+
+/**/
+static void
+set_predisplay(Param pm, char *x)
+{
+    set_prepost(&predisplay, &predisplaylen, x);
+}
+
+/**/
+static char *
+get_predisplay(Param pm)
+{
+    return get_prepost(predisplay, predisplaylen);
+}
+
+/**/
+static void
+set_postdisplay(Param pm, char *x)
+{
+    set_prepost(&postdisplay, &postdisplaylen, x);
+}
+
+/**/
+static char *
+get_postdisplay(Param pm)
+{
+    return get_prepost(postdisplay, postdisplaylen);
 }
Index: Src/Zle/zle_refresh.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/Zle/zle_refresh.c,v
retrieving revision 1.6
diff -u -r1.6 zle_refresh.c
--- Src/Zle/zle_refresh.c	19 Feb 2002 00:06:54 -0000	1.6
+++ Src/Zle/zle_refresh.c	1 Jul 2002 11:05:24 -0000
@@ -81,6 +81,16 @@
 /**/
 int trashedzle;
 
+/*
+ * Information used by PREDISPLAY and POSTDISPLAY parameters which
+ * add non-editable text to that being displayed.
+ */
+/**/
+unsigned char *predisplay, *postdisplay;
+/**/
+int predisplaylen, postdisplaylen;
+
+
 #ifdef HAVE_SELECT
 /* cost of last update */
 /**/
@@ -278,6 +288,10 @@
 	*sen,			/* pointer to end of the video buffer (eol)  */
 	*scs;			/* pointer to cursor position in real buffer */
     char **qbuf;		/* tmp					     */
+    unsigned char *tmpline;	/* line with added pre/post text */
+    int tmpcs, tmpll;		/* ditto cursor position and line length */
+    int tmpalloced;		/* flag to free tmpline when finished */
+	
 
     /* If this is called from listmatches() (indirectly via trashzle()), and *
      * that was called from the end of zrefresh(), then we don't need to do  *
@@ -286,6 +300,25 @@
     if (inlist)
 	return;
 
+    if (predisplaylen || postdisplaylen) {
+	/* There is extra text to display at the start or end of the line */
+	tmpline = zalloc(ll + predisplaylen + postdisplaylen);
+	if (predisplaylen)
+	    memcpy(tmpline, predisplay, predisplaylen);
+	if (ll)
+	    memcpy(tmpline+predisplaylen, line, ll);
+	if (postdisplaylen)
+	    memcpy(tmpline+predisplaylen+ll, postdisplay, postdisplaylen);
+	tmpcs = cs + predisplaylen;
+	tmpll = predisplaylen + ll + postdisplaylen;
+	tmpalloced = 1;
+    } else {
+	tmpline = line;
+	tmpcs = cs;
+	tmpll = ll;
+	tmpalloced = 0;
+    }
+
     if (clearlist && listshown > 0) {
 	if (tccan(TCCLEAREOD)) {
 	    int ovln = vln, ovcs = vcs;
@@ -392,18 +425,18 @@
    width comparisons can be made with winw, height comparisons with winh */
 
     if (termflags & TERM_SHORT) {
-	singlerefresh();
+	singlerefresh(tmpline, tmpll, tmpcs);
 	goto singlelineout;
     }
 
-    if (cs < 0) {
+    if (tmpcs < 0) {
 #ifdef DEBUG
 	fprintf(stderr, "BUG: negative cursor position\n");
 	fflush(stderr); 
 #endif
-	cs = 0;
+	tmpcs = 0;
     }
-    scs = line + cs;
+    scs = tmpline + tmpcs;
     numscrolls = 0;
 
 /* first, we generate the video line buffers so we know what to put on
@@ -414,9 +447,9 @@
 	*nbuf = (char *)zalloc(winw + 2);
 
     s = (unsigned char *)(nbuf[ln = 0] + lpromptw);
-    t = line;
+    t = tmpline;
     sen = (unsigned char *)(*nbuf + winw);
-    for (; t < line+ll; t++) {
+    for (; t < tmpline+tmpll; t++) {
 	if (t == scs)			/* if cursor is here, remember it */
 	    nvcs = s - (unsigned char *)(nbuf[nvln = ln]);
 
@@ -459,7 +492,7 @@
 	nvln++;
     }
 
-    if (t != line + ll)
+    if (t != tmpline + tmpll)
 	more_end = 1;
 
     if (statusline) {
@@ -646,6 +679,9 @@
 singlelineout:
     fflush(shout);		/* make sure everything is written out */
 
+    if (tmpalloced)
+	zfree(tmpline, tmpll);
+
     /* if we have a new list showing, note it; if part of the list has been
     overwritten, redisplay it. */
     if (showinglist == -2 || (showinglist > 0 && showinglist < nlnct)) {
@@ -1082,7 +1118,7 @@
 
 /**/
 static void
-singlerefresh(void)
+singlerefresh(unsigned char *tmpline, int tmpll, int tmpcs)
 {
     char *vbuf, *vp,		/* video buffer and pointer    */
 	**qbuf,			/* tmp			       */
@@ -1093,19 +1129,19 @@
 
     nlnct = 1;
 /* generate the new line buffer completely */
-    for (vsiz = 1 + lpromptw, t0 = 0; t0 != ll; t0++, vsiz++)
-	if (line[t0] == '\t')
+    for (vsiz = 1 + lpromptw, t0 = 0; t0 != tmpll; t0++, vsiz++)
+	if (tmpline[t0] == '\t')
 	    vsiz = (vsiz | 7) + 1;
-	else if (icntrl(line[t0]))
+	else if (icntrl(tmpline[t0]))
 	    vsiz++;
     vbuf = (char *)zalloc(vsiz);
 
-    if (cs < 0) {
+    if (tmpcs < 0) {
 #ifdef DEBUG
 	fprintf(stderr, "BUG: negative cursor position\n");
 	fflush(stderr); 
 #endif
-	cs = 0;
+	tmpcs = 0;
     }
 
     /* only use last part of prompt */
@@ -1113,25 +1149,25 @@
     vbuf[lpromptw] = '\0';
     vp = vbuf + lpromptw;
 
-    for (t0 = 0; t0 != ll; t0++) {
-	if (line[t0] == '\t')
+    for (t0 = 0; t0 != tmpll; t0++) {
+	if (tmpline[t0] == '\t')
 	    for (*vp++ = ' '; (vp - vbuf) & 7; )
 		*vp++ = ' ';
-	else if (line[t0] == '\n') {
+	else if (tmpline[t0] == '\n') {
 	    *vp++ = '\\';
 	    *vp++ = 'n';
-	} else if (line[t0] == 0x7f) {
+	} else if (tmpline[t0] == 0x7f) {
 	    *vp++ = '^';
 	    *vp++ = '?';
-	} else if (icntrl(line[t0])) {
+	} else if (icntrl(tmpline[t0])) {
 	    *vp++ = '^';
-	    *vp++ = line[t0] | '@';
+	    *vp++ = tmpline[t0] | '@';
 	} else
-	    *vp++ = line[t0];
-	if (t0 == cs)
+	    *vp++ = tmpline[t0];
+	if (t0 == tmpcs)
 	    nvcs = vp - vbuf - 1;
     }
-    if (t0 == cs)
+    if (t0 == tmpcs)
 	nvcs = vp - vbuf;
     *vp = '\0';
 
Index: Doc/Zsh/zle.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/zle.yo,v
retrieving revision 1.23
diff -u -r1.23 zle.yo
--- Doc/Zsh/zle.yo	1 Jul 2002 09:54:48 -0000	1.23
+++ Doc/Zsh/zle.yo	1 Jul 2002 11:05:24 -0000
@@ -662,6 +662,22 @@
 contains the contents of the lines before the one the cursor is
 currently in.
 )
+vindex(PREDISPLAY)
+item(tt(PREDISPLAY) (scalar))(
+Text to be displayed before the start of the editable text buffer.  This
+does not have to be a complete line; to display a complete line, a newline
+must be appended explicitly.  Note that the text survives between calls to zle
+and hence must be removed explicitly by assigning an empty value to the
+parameter.
+)
+vindex(POSTDISPLAY)
+item(tt(POSTDISPLAY) (scalar))(
+Text to be displayed after the end of the editable text buffer.  This
+does not have to be a complete line; to display a complete line, a newline
+must be prepended explicitly.  Note that the text survives between calls to
+zle and hence must be removed explicitly by assigning an empty value to the
+parameter.
+)
 vindex(RBUFFER)
 item(tt(RBUFFER) (scalar))(
 The part of the buffer that lies to the right of the cursor position.

-- 
Peter Stephenson <pws@xxxxxxx>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 392070


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