casing: don’t assume letters are *either* upper- or lower-case (bug#24603)

A compatibility digraph characters, such as Dž, are neither upper- nor
lower-case.  At the moment however, those are reported as upper-case¹
despite the fact that they change when upper-cased.

Stop checking if a character is upper-case before trying to up-case it
so that title-case characters are handled correctly.  This fixes one of
the issues mentioned in bug#24603.

¹ Because they change when converted to lower-case.  Notice an asymmetry
  in that for a character to be considered lower-case it must not be
  upper-case (plus the usual condition of changing when upper-cased).

* src/buffer.h (upcase1): Delete.
(upcase): Change to upcase character unconditionally just like downcase
does it.  This is what upcase1 was.

* src/casefiddle.c (casify_object, casify_region): Use upcase instead
of upcase1 and don’t check !uppercasep(x) before calling upcase.

* src/keyboard.c (read_key_sequence): Don’t check if uppercase(x), just
downcase(x) and see if it changed.

* test/src/casefiddle-tests.el (casefiddle-tests--characters,
casefiddle-tests-casing): Update test cases which are now passing.

1 files changed, 7 insertions, 13 deletions

diff --git a/src/casefiddle.c b/src/casefiddle.c
index 28ffcb298ff..b2b87e7a858 100644
--- a/src/casefiddle.c
+++ b/src/casefiddle.c
@@ -64,13 +64,9 @@ casify_object (enum case_action flag, Lisp_Object obj)
         multibyte = 1;
       if (! multibyte)
         MAKE_CHAR_MULTIBYTE (c1);
-      c = downcase (c1);
-      if (inword)
-        XSETFASTINT (obj, c | flags);
-      else if (c == (XFASTINT (obj) & ~flagbits))
+      c = flag == CASE_DOWN ? downcase (c1) : upcase (c1);
+      if (c != c1)
         {
-          if (! inword)
-            c = upcase1 (c1);
           if (! multibyte)
             MAKE_CHAR_UNIBYTE (c);
           XSETFASTINT (obj, c | flags);
@@ -95,7 +91,7 @@ casify_object (enum case_action flag, Lisp_Object obj)
             c = downcase (c);
           else if (!uppercasep (c)
                    && (!inword || flag != CASE_CAPITALIZE_UP))
-            c = upcase1 (c1);
+            c = upcase (c1);
           if ((int) flag >= (int) CASE_CAPITALIZE)
             inword = (SYNTAX (c) == Sword);
           if (c != c1)
@@ -127,9 +123,8 @@ casify_object (enum case_action flag, Lisp_Object obj)
           c = STRING_CHAR_AND_LENGTH (SDATA (obj) + i_byte, len);
           if (inword && flag != CASE_CAPITALIZE_UP)
             c = downcase (c);
-          else if (!uppercasep (c)
-                   && (!inword || flag != CASE_CAPITALIZE_UP))
-            c = upcase1 (c);
+          else if (!inword || flag != CASE_CAPITALIZE_UP)
+            c = upcase (c);
           if ((int) flag >= (int) CASE_CAPITALIZE)
             inword = (SYNTAX (c) == Sword);
           o += CHAR_STRING (c, o);
@@ -236,9 +231,8 @@ casify_region (enum case_action flag, Lisp_Object b, Lisp_Object e)
       c2 = c;
       if (inword && flag != CASE_CAPITALIZE_UP)
         c = downcase (c);
-      else if (!uppercasep (c)
-               && (!inword || flag != CASE_CAPITALIZE_UP))
-        c = upcase1 (c);
+      else if (!inword || flag != CASE_CAPITALIZE_UP)
+        c = upcase (c);
       if ((int) flag >= (int) CASE_CAPITALIZE)
         inword = ((SYNTAX (c) == Sword)
                   && (inword || !syntax_prefix_flag_p (c)));