(c-enable-xemacs-performance-kludge-p): New variable.

1 files changed, 45 insertions, 0 deletions

diff --git a/lisp/progmodes/cc-vars.el b/lisp/progmodes/cc-vars.el
index 06dc8432eb6..9982337a57a 100644
--- a/lisp/progmodes/cc-vars.el
+++ b/lisp/progmodes/cc-vars.el
@@ -426,5 +426,50 @@ as designated in the variable `c-file-style'.")
 
 
 
+;; Figure out what features this Emacs has
+;;;###autoload
+(defconst c-emacs-features
+  (let ((infodock-p (boundp 'infodock-version))
+        (comments
+         ;; XEmacs 19 and beyond use 8-bit modify-syntax-entry flags.
+         ;; Emacs 19 uses a 1-bit flag.  We will have to set up our
+         ;; syntax tables differently to handle this.
+         (let ((table (copy-syntax-table))
+               entry)
+           (modify-syntax-entry ?a ". 12345678" table)
+           (cond
+            ;; XEmacs 19, and beyond Emacs 19.34
+            ((arrayp table)
+             (setq entry (aref table ?a))
+             ;; In Emacs, table entries are cons cells
+             (if (consp entry) (setq entry (car entry))))
+            ;; XEmacs 20
+            ((fboundp 'get-char-table) (setq entry (get-char-table ?a table)))
+            ;; before and including Emacs 19.34
+            ((and (fboundp 'char-table-p)
+                  (char-table-p table))
+             (setq entry (car (char-table-range table [?a]))))
+            ;; incompatible
+            (t (error "CC Mode is incompatible with this version of Emacs")))
+           (if (= (logand (lsh entry -16) 255) 255)
+               '8-bit
+             '1-bit))))
+    (if infodock-p
+        (list comments 'infodock)
+      (list comments)))
+  "A list of features extant in the Emacs you are using.
+There are many flavors of Emacs out there, each with different
+features supporting those needed by CC Mode.  Here's the current
+supported list, along with the values for this variable:
+
+ XEmacs 19:                  (8-bit)
+ XEmacs 20:                  (8-bit)
+ Emacs 19:                   (1-bit)
+
+Infodock (based on XEmacs) has an additional symbol on this list:
+'infodock.")
+
+
+
 (provide 'cc-vars)
 ;;; cc-vars.el ends here