bug#50752: 28.0.50; easy-menu-define lowers the menu-bar key

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> I think we can leave the behavior with raw bytes as it is, and still
> document this use case as being meant for ASCII conversions, leaving
> the subtle case of raw bytes ... subtle.

Yup.

The following patch seems to do the trick, and should be conservative
enough for emacs-28, I think.

diff --git a/src/casefiddle.c b/src/casefiddle.c
index a7a2541490..edc9dec2d7 100644
--- a/src/casefiddle.c
+++ b/src/casefiddle.c
@@ -297,6 +297,16 @@ do_casify_multibyte_string (struct casing_context *ctx, 
Lisp_Object obj)
   return obj;
 }
 
+static int
+ascii_casify_character (bool downcase, int c)
+{
+  Lisp_Object cased = CHAR_TABLE_REF (downcase?
+                                     uniprop_table (Qlowercase) :
+                                     uniprop_table (Quppercase),
+                                     c);
+  return FIXNATP (cased) ? XFIXNAT (cased) : c;
+}
+
 static Lisp_Object
 do_casify_unibyte_string (struct casing_context *ctx, Lisp_Object obj)
 {
@@ -310,11 +320,12 @@ do_casify_unibyte_string (struct casing_context *ctx, 
Lisp_Object obj)
       cased = case_single_character (ctx, ch);
       if (ch == cased)
        continue;
-      cased = make_char_unibyte (cased);
-      /* If the char can't be converted to a valid byte, just don't
-        change it.  */
-      if (SINGLE_BYTE_CHAR_P (cased))
-       SSET (obj, i, cased);
+      /* If down/upcasing changed an ASCII character into a non-ASCII
+        character (this can happen in some locales, like the Turkish
+        "I"), downcase using the ASCII char table.  */
+      if (SINGLE_BYTE_CHAR_P (ch) && !SINGLE_BYTE_CHAR_P (cased))
+       cased = ascii_casify_character (ctx->flag == CASE_DOWN, ch);
+      SSET (obj, i, make_char_unibyte (cased));
     }
   return obj;
 }
@@ -651,6 +662,8 @@ syms_of_casefiddle (void)
   DEFSYM (Qbounds, "bounds");
   DEFSYM (Qidentity, "identity");
   DEFSYM (Qtitlecase, "titlecase");
+  DEFSYM (Qlowercase, "lowercase");
+  DEFSYM (Quppercase, "uppercase");
   DEFSYM (Qspecial_uppercase, "special-uppercase");
   DEFSYM (Qspecial_lowercase, "special-lowercase");
   DEFSYM (Qspecial_titlecase, "special-titlecase");

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no