(describe-categories, help-describe-category-set): New.

1 files changed, 31 insertions, 0 deletions

diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index 366c798b137..21e3fa993dd 100644
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -452,6 +452,37 @@ BUFFER defaults to the current buffer."
           (insert "\nThe parent syntax table is:")
           (describe-vector table 'internal-describe-syntax-value))))))
 
+(defun help-describe-category-set (value)
+  (insert (cond
+           ((null value) "default")
+           ((char-table-p value) "deeper char-table ...")
+           (t (condition-case err
+                  (category-set-mnemonics value)
+                (error "invalid"))))))
+
+;;;###autoload
+(defun describe-categories (&optional buffer)
+  "Describe the category specifications in the current category table.
+The descriptions are inserted in a buffer, which is then displayed."
+  (interactive)
+  (setq buffer (or buffer (current-buffer)))
+  (help-setup-xref (list #'describe-categories buffer) (interactive-p))
+  (with-output-to-temp-buffer (help-buffer)
+    (let ((table (with-current-buffer buffer (category-table))))
+      (with-current-buffer standard-output
+        (describe-vector table 'help-describe-category-set)
+        (let ((docs (char-table-extra-slot table 0)))
+          (if (or (not (vectorp docs)) (/= (length docs) 95))
+              (insert "Invalid first extra slot in this char table\n")
+            (insert "Meanings of mnemonic characters are:\n")
+            (dotimes (i 95)
+              (let ((elt (aref docs i)))
+                (when elt
+                  (insert (+ i ?\ ) ": " elt "\n"))))
+            (while (setq table (char-table-parent table))
+              (insert "\nThe parent category table is:")
+              (describe-vector table 'help-describe-category-set))))))))
+
 (provide 'help-fns)
 
 ;;; help-fns.el ends here