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+;;; Clang Code-Completion minor mode, for use with C/Objective-C/C++.
+
+;;; Commentary:
+
+;; This minor mode uses Clang's command line interface for code
+;; completion to provide code completion results for C, Objective-C,
+;; and C++ source files. When enabled, Clang will provide
+;; code-completion results in a secondary buffer based on the code
+;; being typed. For example, after typing "struct " (triggered via the
+;; space), Clang will provide the names of all structs visible from
+;; the current scope. After typing "p->" (triggered via the ">"),
+;; Clang will provide the names of all of the members of whatever
+;; class/struct/union "p" points to. Note that this minor mode isn't
+;; meant for serious use: it is meant to help experiment with code
+;; completion based on Clang. It needs your help to make it better!
+;;
+;; To use the Clang code completion mode, first make sure that the
+;; "clang" variable below refers to the "clang" executable,
+;; which is typically installed in libexec/. Then, place
+;; clang-completion-mode.el somewhere in your Emacs load path. You can
+;; add a new load path to Emacs by adding some like the following to
+;; your .emacs:
+;;
+;; (setq load-path (cons "~/.emacs.d" load-path))
+;;
+;; Then, use
+;;
+;; M-x load-library
+;;
+;; to load the library in your Emacs session or add the following to
+;; your .emacs to always load this mode (not recommended):
+;;
+;; (load-library "clang-completion-mode")
+;;
+;; Finally, to try Clang-based code completion in a particular buffer,
+;; use M-x clang-completion-mode. When "Clang-CC" shows up in the mode
+;; line, Clang's code-completion is enabled.
+;;
+;; Clang's code completion is based on parsing the complete source
+;; file up to the point where the cursor is located. Therefore, Clang
+;; needs all of the various compilation flags (include paths, dialect
+;; options, etc.) to provide code-completion results. Currently, these
+;; need to be placed into the clang-flags variable in a format
+;; acceptable to clang. This is a hack: patches are welcome to
+;; improve the interface between this Emacs mode and Clang!
+;;
+
+;;; Code:
+;;; The clang executable
+(defcustom clang "clang"
+ "The location of the Clang compiler executable"
+ :type 'file
+ :group 'clang-completion-mode)
+
+;;; Extra compilation flags to pass to clang.
+(defcustom clang-flags nil
+ "Extra flags to pass to the Clang executable.
+This variable will typically contain include paths, e.g., -I~/MyProject."
+ :type '(repeat (string :tag "Argument" ""))
+ :group 'clang-completion-mode)
+
+;;; The prefix header to use with Clang code completion.
+(setq clang-completion-prefix-header "")
+
+;;; The substring we will use to filter completion results
+(setq clang-completion-substring "")
+
+;;; The current completion buffer
+(setq clang-completion-buffer nil)
+
+(setq clang-result-string "")
+
+;;; Compute the current line in the buffer
+(defun current-line ()
+ "Return the vertical position of point..."
+ (+ (count-lines (point-min) (point))
+ (if (= (current-column) 0) 1 0)
+ -1))
+
+;;; Set the Clang prefix header
+(defun clang-prefix-header ()
+ (interactive)
+ (setq clang-completion-prefix-header
+ (read-string "Clang prefix header> " "" clang-completion-prefix-header
+ "")))
+
+;; Process "filter" that keeps track of the code-completion results
+;; produced. We store all of the results in a string, then the
+;; sentinel processes the entire string at once.
+(defun clang-completion-stash-filter (proc string)
+ (setq clang-result-string (concat clang-result-string string)))
+
+;; Filter the given list based on a predicate.
+(defun filter (condp lst)
+ (delq nil
+ (mapcar (lambda (x) (and (funcall condp x) x)) lst)))
+
+;; Determine whether
+(defun is-completion-line (line)
+ (or (string-match "OVERLOAD:" line)
+ (string-match (concat "COMPLETION: " clang-completion-substring) line)))
+
+(defun clang-completion-display (buffer)
+ (let* ((all-lines (split-string clang-result-string "\n"))
+ (completion-lines (filter 'is-completion-line all-lines)))
+ (if (consp completion-lines)
+ (progn
+ ;; Erase the process buffer
+ (let ((cur (current-buffer)))
+ (set-buffer buffer)
+ (goto-char (point-min))
+ (erase-buffer)
+ (set-buffer cur))
+
+ ;; Display the process buffer
+ (display-buffer buffer)
+
+ ;; Insert the code-completion string into the process buffer.
+ (with-current-buffer buffer
+ (insert (mapconcat 'identity completion-lines "\n")))
+ ))))
+
+;; Process "sentinal" that, on successful code completion, replaces the
+;; contents of the code-completion buffer with the new code-completion results
+;; and ensures that the buffer is visible.
+(defun clang-completion-sentinel (proc event)
+ (let* ((all-lines (split-string clang-result-string "\n"))
+ (completion-lines (filter 'is-completion-line all-lines)))
+ (if (consp completion-lines)
+ (progn
+ ;; Erase the process buffer
+ (let ((cur (current-buffer)))
+ (set-buffer (process-buffer proc))
+ (goto-char (point-min))
+ (erase-buffer)
+ (set-buffer cur))
+
+ ;; Display the process buffer
+ (display-buffer (process-buffer proc))
+
+ ;; Insert the code-completion string into the process buffer.
+ (with-current-buffer (process-buffer proc)
+ (insert (mapconcat 'identity completion-lines "\n")))
+ ))))
+
+(defun clang-complete ()
+ (let* ((cc-point (concat (buffer-file-name)
+ ":"
+ (number-to-string (+ 1 (current-line)))
+ ":"
+ (number-to-string (+ 1 (current-column)))))
+ (cc-pch (if (equal clang-completion-prefix-header "") nil
+ (list "-include-pch"
+ (concat clang-completion-prefix-header ".pch"))))
+ (cc-flags (if (listp clang-flags) clang-flags nil))
+ (cc-command (append `(,clang "-cc1" "-fsyntax-only")
+ cc-flags
+ cc-pch
+ `("-code-completion-at" ,cc-point)
+ (list (buffer-file-name))))
+ (cc-buffer-name (concat "*Clang Completion for " (buffer-name) "*")))
+ ;; Start the code-completion process
+ (if (buffer-file-name)
+ (progn
+ ;; If there is already a code-completion process, kill it first.
+ (let ((cc-proc (get-process "Clang Code-Completion")))
+ (if cc-proc
+ (delete-process cc-proc)))
+
+ (setq clang-completion-substring "")
+ (setq clang-result-string "")
+ (setq clang-completion-buffer cc-buffer-name)
+
+ (let ((cc-proc (apply 'start-process
+ (append (list "Clang Code-Completion" cc-buffer-name)
+ cc-command))))
+ (set-process-filter cc-proc 'clang-completion-stash-filter)
+ (set-process-sentinel cc-proc 'clang-completion-sentinel)
+ )))))
+
+;; Code-completion when one of the trigger characters is typed into
+;; the buffer, e.g., '(', ',' or '.'.
+(defun clang-complete-self-insert (arg)
+ (interactive "p")
+ (self-insert-command arg)
+ (save-buffer)
+ (clang-complete))
+
+;; When the user has typed a character that requires the filter to be
+;; updated, do so (and update the display of results).
+(defun clang-update-filter ()
+ (setq clang-completion-substring (thing-at-point 'symbol))
+ (if (get-process "Clang Code-Completion")
+ ()
+ (clang-completion-display clang-completion-buffer)
+ ))
+
+;; Invoked when the user types an alphanumeric character or "_" to
+;; update the filter for the currently-active code completion.
+(defun clang-filter-self-insert (arg)
+ (interactive "p")
+ (self-insert-command arg)
+ (clang-update-filter)
+ )
+
+;; Invoked when the user types the backspace key to update the filter
+;; for the currently-active code completion.
+(defun clang-backspace ()
+ (interactive)
+ (delete-backward-char 1)
+ (clang-update-filter))
+
+;; Invoked when the user types the delete key to update the filter
+;; for the currently-active code completion.
+(defun clang-delete ()
+ (interactive)
+ (delete-backward-char 1)
+ (clang-update-filter))
+
+;; Set up the keymap for the Clang minor mode.
+(defvar clang-completion-mode-map nil
+ "Keymap for Clang Completion Mode.")
+
+(if (null clang-completion-mode-map)
+ (fset 'clang-completion-mode-map
+ (setq clang-completion-mode-map (make-sparse-keymap))))
+
+(if (not (assq 'clang-completion-mode minor-mode-map-alist))
+ (setq minor-mode-map-alist
+ (cons (cons 'clang-completion-mode clang-completion-mode-map)
+ minor-mode-map-alist)))
+
+;; Punctuation characters trigger code completion.
+(dolist (char '("(" "," "." ">" ":" "=" ")" " "))
+ (define-key clang-completion-mode-map char 'clang-complete-self-insert))
+
+;; Alphanumeric characters (and "_") filter the results of the
+;; currently-active code completion.
+(dolist (char '("A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O"
+ "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z"
+ "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o"
+ "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"
+ "_" "0" "1" "2" "3" "4" "5" "6" "7" "8" "9"))
+ (define-key clang-completion-mode-map char 'clang-filter-self-insert))
+
+;; Delete and backspace filter the results of the currently-active
+;; code completion.
+(define-key clang-completion-mode-map [(backspace)] 'clang-backspace)
+(define-key clang-completion-mode-map [(delete)] 'clang-delete)
+
+;; Set up the Clang minor mode.
+(define-minor-mode clang-completion-mode
+ "Clang code-completion mode"
+ nil
+ " Clang"
+ clang-completion-mode-map)
+