From 0afe38adf55608b26f04a77f312d4805ce568da6 Mon Sep 17 00:00:00 2001
From: Jim Fehrle
Date: Fri, 31 May 2019 16:59:19 -0700
Subject: Add hook for coq diff-highlighting routine

---
 coq/coq-diffs.el | 12 ++++++++----
 coq/coq.el       |  5 +++++
 2 files changed, 13 insertions(+), 4 deletions(-)

(limited to 'coq')

diff --git a/coq/coq-diffs.el b/coq/coq-diffs.el
index 7d5e8f58..67d2fcc7 100644
--- a/coq/coq-diffs.el
+++ b/coq/coq-diffs.el
@@ -29,6 +29,14 @@ For example '<diff.added>foo</diff.added>' inserts 'foo' in the buffer
 and applies the appropriate face.
 
 `coq-tag-map' defines the mapping from tag name to face."
+;; Coq inserts tags before splitting into lines.  Avoid highlighting
+;; white space at the beginning or end of lines in a conclusion or
+;; hypothesis that's split across multiple lines.
+
+;; Doesn't handle the unlikely case of escaping regular text
+;; that looks like a tag.  Unknown tags such as "<foo>" are
+;; shown as-is.  The user can turn off diffs in this very unlikely case.
+
   (let* ((len (length str))
          (off 0)
 	 (fstack)
@@ -38,17 +46,13 @@ and applies the appropriate face.
     (while (< off len)
       (string-match "^\\([ \t]*\\)\\(.*\n?\\)" str off)
       (setq off (match-end 0))
-      ;; FIXME: Why handle whitespace specially?
       (insert (match-string 1 str)) ;; begin-line white space
       (setq rhs (match-string 2 str))
-      ;; FIXME: Why handle whitespace specially?
       (string-match "[ \t\n]*\\'" rhs)
       (let* ((end-white (match-string 0 rhs)) ;; end-line white space
              (line (substring rhs 0 (- (length rhs) (length end-white))))
              (llen (length line))
              (loff 0))
-        ;; FIXME: I don't see any mechanism here to escape text, in case
-        ;; we need to include text that happen to look just like a tag!
         (while (and (< loff llen)
                     (string-match "<\\(/\\)?\\([a-zA-Z\\.]+\\)>" line loff))
           (let* ((end-mark (match-beginning 1))
diff --git a/coq/coq.el b/coq/coq.el
index 21b1acf9..0f6d6f84 100644
--- a/coq/coq.el
+++ b/coq/coq.el
@@ -58,6 +58,11 @@
 (require 'coq-abbrev)                   ; abbrev and coq specific menu
 (require 'coq-seq-compile)              ; sequential compilation of Requires
 (require 'coq-par-compile)              ; parallel compilation of Requires
+
+;; set hook for diff highlighting routine from non-Coq code
+(require 'coq-diffs)
+(setq pg-insert-text-function 'coq-insert-tagged-text)
+
 (defvar prettify-symbols-alist)
 
 
-- 
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