tildify: add `tildify-space' and `tildify-mode'

* lisp/textmodes/tildify.el (tildify-space): A new function
which can be used as a `post-self-insert-hook' to automatically
convert spaces into hard spaces.
(tildify-space-pattern): A new variable specifying pattern where
`tildify-space' should take effect.
(tildify-space-predicates): A new variable specifying list of
predicate functions that all must return non-nil for
`tildify-space' to take effect.
(tildify-space-region-predicate): A new functions meant to be
used as a predicate in `tildify-space-predicates' list.
(tildify-mode): A new minor mode enabling `tildify-space' as a
`post-self-insert-hook'

* tests/automated/tildify-tests.el (tildify-space-test--test):
A new helper function for testing `tildify-space' function.
(tildify-space-test-html, tildify-space-test-html-nbsp)
(tildify-space-test-xml, tildify-space-test-tex): New tests for
`tildify-space' function.

2 files changed, 102 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 22a06a9168c..8bcfe977a9c 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,18 @@
+2014-01-20  Michal Nazarewicz  <mina86@mina86.com>
+
+        * textmodes/tildify.el (tildify-space): A new function
+        which can be used as a `post-self-insert-hook' to automatically
+        convert spaces into hard spaces.
+        (tildify-space-pattern): A new variable specifying pattern where
+        `tildify-space' should take effect.
+        (tildify-space-predicates): A new variable specifying list of
+        predicate functions that all must return non-nil for
+        `tildify-space' to take effect.
+        (tildify-space-region-predicate): A new functions meant to be
+        used as a predicate in `tildify-space-predicates' list.
+        (tildify-mode): A new minor mode enabling `tildify-space' as a
+        `post-self-insert-hook'
+
 2015-01-20  Daniel Colascione  <dancol@dancol.org>
 
         * vc/vc-dir.el (vc-dir): Default to repository root, not
diff --git a/lisp/textmodes/tildify.el b/lisp/textmodes/tildify.el
index 9382b32845d..b11d7dae272 100644
--- a/lisp/textmodes/tildify.el
+++ b/lisp/textmodes/tildify.el
@@ -4,7 +4,7 @@
 
 ;; Author:     Milan Zamazal <pdm@zamazal.org>
 ;;             Michal Nazarewicz <mina86@mina86.com>
-;; Version:    4.5.7
+;; Version:    4.6
 ;; Keywords:   text, TeX, SGML, wp
 
 ;; This file is part of GNU Emacs.
@@ -401,6 +401,92 @@ replacements done and response is one of symbols: t (all right), nil
                         (t t))))))
 
 
+;;; *** Tildify Mode ***
+
+(defcustom tildify-space-pattern "[,:;(][ \t]*[a]\\|\\<[AIKOSUVWZikosuvwz]"
+  "Pattern specifying whether to insert a hard space at point.
+
+If the pattern matches `looking-back', a hard space needs to be inserted instead
+of a space at point.  The regexp is always case sensitive, regardless of the
+current `case-fold-search' setting."
+  :version "25.1"
+  :group 'tildify
+  :type 'string)
+
+(defcustom tildify-space-predicates '(tildify-space-region-predicate)
+  "A list of predicate functions for `tildify-space' function."
+  :version "25.1"
+  :group 'tildify
+  :type '(repeat 'function))
+
+
+;;;###autoload
+(defun tildify-space ()
+  "Convert space before point into a hard space if the context is right.
+
+If
+ * character before point is a space character,
+ * character before that has “w” character syntax (i.e. it's a word
+   constituent),
+ * `tildify-space-pattern' matches when `looking-back' (no more than 10
+   characters) from before the space character, and
+ * all predicates in `tildify-space-predicates' return non-nil,
+replace the space character with a hard space specified by
+`tildify-space-string' (note that the function does not take
+`tildify-string-alist' into consideration).
+
+Return t if conversion happened, nil otherwise.
+
+This function is meant to be used as a `post-self-insert-hook'."
+  (interactive)
+  (let ((p (point)) case-fold-search)
+    (when (and (> (- p (point-min)) 2)
+               (eq (preceding-char) ?\s)
+               (eq (char-syntax (char-before (1- p))) ?w)
+               (not (string-equal " " tildify-space-string))
+               (save-excursion
+                 (goto-char (1- p))
+                 (looking-back tildify-space-pattern
+                               (max (point-min) (- p 10))))
+               (run-hook-with-args-until-failure 'tildify-space-predicates))
+      (delete-char -1)
+      (insert tildify-space-string)
+      t)))
+
+(defun tildify-space-region-predicate ()
+  "Check whether character before point should be tildified.
+Based on `tildify-foreach-region-function', check whether character before,
+which is assumed to be a space character, should be replaced with a hard space."
+  (catch 'found
+    (tildify--foreach-region (lambda (_b _e) (throw 'found t)) (1- (point)) (point))))
+
+;;;###autoload
+(define-minor-mode tildify-mode
+  "Adds electric behaviour to space character.
+
+When space is inserted into a buffer in a position where hard space is required
+instead (determined by `tildify-space-pattern' and `tildify-space-predicates'),
+that space character is replaced by a hard space specified by
+`tildify-space-string'.  Converting of the space is done by `tildify-space'.
+
+When `tildify-mode' is enabled, if `tildify-string-alist' specifies a hard space
+representation for current major mode, the `tildify-space-string' buffer-local
+variable will be set to the representation."
+  nil " ~" nil
+  (when tildify-mode
+    (let ((space (tildify--pick-alist-entry tildify-string-alist)))
+      (if (not (string-equal " " (or space tildify-space-string)))
+          (when space
+            (setq tildify-space-string space))
+        (message (eval-when-compile
+                   (concat "Hard space is a single space character, tildify-"
+                           "mode won't have any effect, disabling.")))
+        (setq tildify-mode nil))))
+  (if tildify-mode
+      (add-hook 'post-self-insert-hook 'tildify-space nil t)
+    (remove-hook 'post-self-insert-hook 'tildify-space t)))
+
+
 ;;; *** Announce ***
 
 (provide 'tildify)