From e695cb0dd19d1cbce0c49a71a913527a227a9e09 Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Thu, 6 Dec 2001 12:59:37 +0000
Subject: Allow the user to specify the Help topic ID string for particular
 sections. Useful if another program needs to jump to a particular topic.
 (Really we should support the proper CTXOMAP / HELP_WM_HELP system for doing
 this, but I don't like numeric IDs; you'd have to parse a bunch of #defines
 in order to sensibly synchronise the IDs between help file and code.)

[originally from svn r1457]
---
 bk_whlp.c       | 27 ++++++++++++++++++++++++++-
 buttress.h      |  1 +
 error.c         | 10 +++++++++-
 inputs/test.but |  6 +++++-
 4 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/bk_whlp.c b/bk_whlp.c
index cf4757d..c5ebdb9 100644
--- a/bk_whlp.c
+++ b/bk_whlp.c
@@ -82,6 +82,23 @@ void whlp_backend(paragraph *sourceform, keywordlist *keywords,
 		     WHLP_FONT_STRIKEOUT, 0, 0, 0);
 
     /*
+     * Loop over the source form finding out whether the user has
+     * specified particular help topic names for anything.
+     */
+    for (p = sourceform; p; p = p->next) {
+	p->private_data = NULL;
+	if (p->type == para_Config && p->parent) {
+	    if (!ustricmp(p->keyword, L"winhelp-topic")) {
+		char *topicname;
+		whlp_convert(uadv(p->keyword), &topicname, 0);
+		/* Store the topic name in the private_data field of the
+		 * containing section. */
+		p->parent->private_data = topicname;
+	    }
+	}
+    }
+
+    /*
      * Loop over the source form registering WHLP_TOPICs for
      * everything.
      */
@@ -94,7 +111,15 @@ void whlp_backend(paragraph *sourceform, keywordlist *keywords,
 	    p->type == para_UnnumberedChapter ||
 	    p->type == para_Heading ||
 	    p->type == para_Subsect) {
-	    p->private_data = whlp_register_topic(h, NULL, NULL);
+	    char *topicid = p->private_data;
+	    char *errstr;
+
+	    p->private_data = whlp_register_topic(h, topicid, &errstr);
+	    if (!p->private_data) {
+		p->private_data = whlp_register_topic(h, NULL, NULL);
+		error(err_winhelp_ctxclash, &p->fpos, topicid, errstr);
+	    }
+	    sfree(topicid);
 	}
     }
 
diff --git a/buttress.h b/buttress.h
index 0fd69a9..19e6cf8 100644
--- a/buttress.h
+++ b/buttress.h
@@ -205,6 +205,7 @@ enum {
     err_cantopenw,		       /* can't open output file for write */
     err_macroexists,		       /* this macro already exists */
     err_sectjump,		       /* jump a heading level, eg \C -> \S */
+    err_winhelp_ctxclash,	       /* WinHelp context ID hash clash */
     err_whatever                       /* random error of another type */
 };
 
diff --git a/error.c b/error.c
index c81aa8c..d115073 100644
--- a/error.c
+++ b/error.c
@@ -16,7 +16,7 @@
 static void do_error(int code, va_list ap) {
     char error[1024];
     char auxbuf[256];
-    char *sp;
+    char *sp, *sp2;
     wchar_t *wsp;
     filepos fpos;
     int flags;
@@ -167,6 +167,14 @@ static void do_error(int code, va_list ap) {
 	sprintf(error, "expected higher heading levels before this one");
 	flags = FILEPOS;
 	break;
+      case err_winhelp_ctxclash:
+	fpos = *va_arg(ap, filepos *);
+	sp = va_arg(ap, char *);
+	sp2 = va_arg(ap, char *);
+	sprintf(error, "Windows Help context id `%.200s' clashes with "
+		"previously defined `%.200s'", sp, sp2);
+	flags = FILEPOS;
+	break;
       case err_whatever:
 	sp = va_arg(ap, char *);
         vsprintf(error, sp, ap);
diff --git a/inputs/test.but b/inputs/test.but
index d342a8e..9b79903 100644
--- a/inputs/test.but
+++ b/inputs/test.but
@@ -19,7 +19,7 @@ a bit]
 
 \define{coopt} co\u00F6{-o}pt
 
-\versionid $Id: test.but,v 1.15 2001/12/04 19:12:18 simon Exp $
+\versionid $Id: test.but,v 1.16 2001/12/06 12:59:37 simon Exp $
 
 \C{ch\\ap} First chapter title; for similar wrapping reasons this
 chapter title will be ludicrously long. I wonder how much more
@@ -37,6 +37,8 @@ fragments}.
 guessing the reason why this time, and here's yet more text to pad
 it out to three lines of output)
 
+\cfg{winhelp-topic}{M359HPEHGW}
+
 Here's a code paragraph:
 
 \c No leading spaces
@@ -100,6 +102,8 @@ and here's a reference to it: \k{sub-sub}.
 
 \A{app} Needless appendix
 
+\# \cfg{winhelp-topic}{Y5VQEXZQVJ} (uncomment this and it clashes)
+
 Here's an \i{appendix}, for no terribly good reason at all. See
 \k{book}.
 
-- 
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