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, 1 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 421e5daa3e4..a54c655c36d 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -338,6 +338,12 @@ same as in modes where the character is not whitespace.
 Instead of only checking the modification time, Emacs now also checks
 the file's actual content before prompting the user.
 
+** Title case characters are properly converted to upper case.
+'upcase', 'upcase-region' et al. convert title case characters (such
+as Dz) into their upper case form (such as DZ).  As a downside,
+'capitalize' and 'upcase-initials' produce awkward words where first
+two letters are upper case, e.g. DŽungla (instead of Džungla).
+
 
 * Changes in Specialized Modes and Packages in Emacs 26.1
 
@@ -1028,7 +1034,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
 
 
 Local variables:
-coding: us-ascii
+coding: utf-8
 mode: outline
 paragraph-separate: "[  ]*$"
 end: