abo-abo · November 7, 2013 21:55 · Nov 7, 2013
diff --git a/calign.el b/calign.el
@@ -0,0 +1,67 @@
+(defun extract-argument-positions (str)
+  "Given a single line C/C++ string, return list of arguments in form:
+\(start-position end-position string\) for each argument"
+  (let ((args (list))
+        (pos 0))
+    (while (string-match "\\(?: [^ (\n]+\\)\\(?:,[\n ]\\|)\\|,$\\|;$\\|[ ]+=[ ]+\\)" str pos)
+      (push (list (match-beginning 0)
+                  (match-end 0)
+                  (substring (match-string-no-properties 0 str) 0 -1))
+            args)
+      (setq pos (match-end 0)))
+    (reverse args)))
+
+(defun selected-lines ()
+  "Returns list of pairs (beginning-of-line-position . string)
+for each line selected"
+  (interactive)
+  (when (region-active-p)
+    (let ((start (save-excursion (goto-char (region-beginning))
+                                            (line-beginning-position)))
+          (end (save-excursion (goto-char (region-end)) (line-end-position)))
+          (lines nil)
+          tstr)
+      (goto-char start)
+      (while (< (point) end)
+        (setq tstr (buffer-substring-no-properties
+                    (point)
+                     (line-end-position)))
+        (unless (string= tstr "")
+          (push (cons (point) tstr)
+                lines))
+        (beginning-of-line 2))
+      lines)))
+
+(defun c-align-function-arguments ()
+  "Aligns selected C/C++ arguments list with spaces"
+  (interactive)
+  (let ((lines (selected-lines)))
+    (when (> (length lines) 1)
+      (let* ((pts-begin (mapcar #'car lines))
+             (pts-arg-rel (mapcar (lambda (x)
+                                   (caar
+                                    (extract-argument-positions
+                                     (cdr x))))
+                                 lines))
+             (pt-arg-max (apply #'max pts-arg-rel)))
+        (cl-mapcar (lambda (b x)
+                   (goto-char (+ b x))
+                   (insert (make-string (- pt-arg-max x) ? )))
+                 pts-begin
+                 pts-arg-rel)))))
+
+(defmacro define-key-regionp (keymap key command)
+  "In KEYMAP, define KEY as DEF.
+DEF is called only when mark is active.
+Otherwise, KEY is inserted."
+  `(define-key ,keymap ,key (lambda()(interactive)
+                              (if (region-active-p)
+                                  (call-interactively ,command)
+                                (if (eq major-mode 'org-mode)
+                                    (org-self-insert-command 1)
+                                  (self-insert-command 1))))))
+(setq-default indent-tabs-mode nil)
+(add-hook
+ 'c-mode-common-hook
+ (lambda ()
+   (define-key-regionp c-mode-base-map "3" 'c-align-function-arguments)))