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1;;; Clang Code-Completion minor mode, for use with C/Objective-C/C++.
2
3;;; Commentary:
4
5;; This minor mode uses Clang's command line interface for code
6;; completion to provide code completion results for C, Objective-C,
7;; and C++ source files. When enabled, Clang will provide
8;; code-completion results in a secondary buffer based on the code
9;; being typed. For example, after typing "struct " (triggered via the
10;; space), Clang will provide the names of all structs visible from
11;; the current scope. After typing "p->" (triggered via the ">"),
12;; Clang will provide the names of all of the members of whatever
13;; class/struct/union "p" points to. Note that this minor mode isn't
14;; meant for serious use: it is meant to help experiment with code
15;; completion based on Clang. It needs your help to make it better!
16;;
17;; To use the Clang code completion mode, first make sure that the
18;; "clang" variable below refers to the "clang" executable,
19;; which is typically installed in libexec/. Then, place
20;; clang-completion-mode.el somewhere in your Emacs load path. You can
21;; add a new load path to Emacs by adding some like the following to
22;; your .emacs:
23;;
24;;   (setq load-path (cons "~/.emacs.d" load-path))
25;;
26;; Then, use
27;;
28;;   M-x load-library
29;;
30;; to load the library in your Emacs session or add the following to
31;; your .emacs to always load this mode (not recommended):
32;;
33;;   (load-library "clang-completion-mode")
34;;
35;; Once you have done this, you can set various parameters with
36;;
37;;   M-x customize-group RET clang-completion-mode RET
38;;
39;; Finally, to try Clang-based code completion in a particular buffer,
40;; use M-x clang-completion-mode. When "Clang" shows up in the mode
41;; line, Clang's code-completion is enabled.
42;;
43;; Clang's code completion is based on parsing the complete source
44;; file up to the point where the cursor is located. Therefore, Clang
45;; needs all of the various compilation flags (include paths, dialect
46;; options, etc.) to provide code-completion results. Currently, these
47;; need to be placed into the clang-flags variable in a format
48;; acceptable to clang. This is a hack: patches are welcome to
49;; improve the interface between this Emacs mode and Clang!
50;;
51
52;;; Code:
53;;; The clang executable
54(defcustom clang "clang"
55  "The location of the Clang compiler executable"
56  :type 'file
57  :group 'clang-completion-mode)
58
59;;; Extra compilation flags to pass to clang.
60(defcustom clang-flags nil
61  "Extra flags to pass to the Clang executable.
62This variable will typically contain include paths, e.g., -I~/MyProject."
63  :type '(repeat (string :tag "Argument" ""))
64  :group 'clang-completion-mode)
65
66;;; The prefix header to use with Clang code completion.
67(setq clang-completion-prefix-header "")
68
69;;; The substring we will use to filter completion results
70(setq clang-completion-substring "")
71
72;;; The current completion buffer
73(setq clang-completion-buffer nil)
74
75(setq clang-result-string "")
76
77;;; Compute the current line in the buffer
78(defun current-line ()
79  "Return the vertical position of point..."
80  (+ (count-lines (point-min) (point))
81     (if (= (current-column) 0) 1 0)
82     -1))
83
84;;; Set the Clang prefix header
85(defun clang-prefix-header ()
86  (interactive)
87  (setq clang-completion-prefix-header
88        (read-string "Clang prefix header> " "" clang-completion-prefix-header
89                     "")))
90
91;; Process "filter" that keeps track of the code-completion results
92;; produced. We store all of the results in a string, then the
93;; sentinel processes the entire string at once.
94(defun clang-completion-stash-filter (proc string)
95  (setq clang-result-string (concat clang-result-string string)))
96
97;; Filter the given list based on a predicate.
98(defun filter (condp lst)
99    (delq nil
100          (mapcar (lambda (x) (and (funcall condp x) x)) lst)))
101
102;; Determine whether FIXME: explain better
103(defun is-completion-line (line)
104  (or (string-match "OVERLOAD:" line)
105      (string-match (concat "COMPLETION: " clang-completion-substring) line)))
106
107
108;; re-process the completions when further input narrows the field
109(defun clang-completion-display (buffer)
110  (fill-buffer buffer))
111
112(defun fill-buffer (buffer)
113  (let* ((all-lines (split-string clang-result-string "\n"))
114         (completion-lines (filter 'is-completion-line all-lines)))
115    (if (consp completion-lines)
116        (progn
117         ;; Erase the process buffer.
118         (let ((cur (current-buffer)))
119           (set-buffer buffer)
120           (goto-char (point-min))
121           (erase-buffer)
122           (set-buffer cur))
123
124         ;; Display the process buffer.
125         (display-buffer buffer)
126
127         ;; Insert the code-completion string into the process buffer.
128         (with-current-buffer buffer
129           (insert (mapconcat 'identity completion-lines "\n")))
130         ))))
131
132;; Process "sentinel" that, on successful code completion, replaces the
133;; contents of the code-completion buffer with the new code-completion results
134;; and ensures that the buffer is visible.
135(defun clang-completion-sentinel (proc event)
136  (fill-buffer (process-buffer proc)))
137
138(defun clang-complete ()
139  (let* ((cc-point (concat (buffer-file-name)
140                           ":"
141                           (number-to-string (+ 1 (current-line)))
142                           ":"
143                           (number-to-string (+ 1 (current-column)))))
144         (cc-pch (if (equal clang-completion-prefix-header "") nil
145                   (list "-include-pch"
146                         (concat clang-completion-prefix-header ".pch"))))
147         (cc-flags (if (listp clang-flags) clang-flags nil))
148         (cc-command (append `(,clang "-cc1" "-fsyntax-only")
149                             cc-flags
150                             cc-pch
151                             `("-code-completion-at" ,cc-point)
152                             (list (buffer-file-name))))
153         (cc-buffer-name (concat "*Clang Completion for " (buffer-name) "*")))
154    ;; Start the code-completion process.
155    (if (buffer-file-name)
156        (progn
157          ;; If there is already a code-completion process, kill it first.
158          (let ((cc-proc (get-process "Clang Code-Completion")))
159            (if cc-proc
160                (delete-process cc-proc)))
161
162          (setq clang-completion-substring "")
163          (setq clang-result-string "")
164          (setq clang-completion-buffer cc-buffer-name)
165
166          (let ((cc-proc (apply 'start-process
167                                (append (list "Clang Code-Completion" cc-buffer-name)
168                                        cc-command))))
169            (set-process-filter cc-proc 'clang-completion-stash-filter)
170            (set-process-sentinel cc-proc 'clang-completion-sentinel)
171            )))))
172
173;; Code-completion when one of the trigger characters is typed into
174;; the buffer, e.g., '(', ',' or '.'.
175(defun clang-complete-self-insert (arg)
176  (interactive "p")
177  (self-insert-command arg)
178  (save-buffer)
179  (clang-complete))
180
181;; When the user has typed a character that requires the filter to be
182;; updated, do so (and update the display of results).
183(defun clang-update-filter ()
184  (setq clang-completion-substring (thing-at-point 'symbol))
185  (if (get-process "Clang Code-Completion")
186      ()
187    (clang-completion-display clang-completion-buffer)
188    ))
189
190;; Invoked when the user types an alphanumeric character or "_" to
191;; update the filter for the currently-active code completion.
192(defun clang-filter-self-insert (arg)
193  (interactive "p")
194  (self-insert-command arg)
195  (clang-update-filter)
196  )
197
198;; Invoked when the user types the backspace key to update the filter
199;; for the currently-active code completion.
200(defun clang-backspace ()
201  (interactive)
202  (delete-backward-char 1)
203  (clang-update-filter))
204
205;; Invoked when the user types the delete key to update the filter
206;; for the currently-active code completion.
207(defun clang-delete ()
208  (interactive)
209  (delete-backward-char 1)
210  (clang-update-filter))
211
212;; Set up the keymap for the Clang minor mode.
213(defvar clang-completion-mode-map nil
214  "Keymap for Clang Completion Mode.")
215
216(if (null clang-completion-mode-map)
217    (fset 'clang-completion-mode-map
218          (setq clang-completion-mode-map (make-sparse-keymap))))
219
220(if (not (assq 'clang-completion-mode minor-mode-map-alist))
221    (setq minor-mode-map-alist
222          (cons (cons 'clang-completion-mode clang-completion-mode-map)
223                minor-mode-map-alist)))
224
225;; Punctuation characters trigger code completion.
226(dolist (char '("(" "," "." ">" ":" "=" ")" " "))
227  (define-key clang-completion-mode-map char 'clang-complete-self-insert))
228
229;; Alphanumeric characters (and "_") filter the results of the
230;; currently-active code completion.
231(dolist (char '("A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O"
232                "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z"
233                "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o"
234                "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"
235                "_" "0" "1" "2" "3" "4" "5" "6" "7" "8" "9"))
236  (define-key clang-completion-mode-map char 'clang-filter-self-insert))
237
238;; Delete and backspace filter the results of the currently-active
239;; code completion.
240(define-key clang-completion-mode-map [(backspace)] 'clang-backspace)
241(define-key clang-completion-mode-map [(delete)] 'clang-delete)
242
243;; Set up the Clang minor mode.
244(define-minor-mode clang-completion-mode
245  "Clang code-completion mode"
246  nil
247  " Clang"
248  clang-completion-mode-map)
249
250