1 files changed, 186 insertions, 0 deletions
diff --git a/cm-mode.el b/cm-mode.el
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+;; Wrapper for CodeMirror-style emacs modes. Highlighting is done by
+;; running a stateful parser (with first-class state object) over the
+;; buffer, line by line, using the output to add 'face properties, and
+;; storing the parser state at the end of each line. Indentation is
+;; done based on the parser state at the start of the line.
+
+(eval-when-compile (require 'cl))
+
+;; Mode data structure
+
+(defun make-cm-mode (token &optional start-state copy-state
+                           compare-state indent)
+  (vector token
+          (or start-state (lambda () 'null))
+          (or copy-state 'cm-default-copy-state)
+          (or compare-state 'eq)
+          indent))
+(defmacro cm-mode-token (x) `(aref ,x 0))
+(defmacro cm-mode-start-state (x) `(aref ,x 1))
+(defmacro cm-mode-copy-state (x) `(aref ,x 2))
+(defmacro cm-mode-compare-state (x) `(aref ,x 3))
+(defmacro cm-mode-indent (x) `(aref ,x 4))
+
+(defvar cm-cur-mode nil)
+(defvar cm-worklist nil)
+
+(defun cm-default-copy-state (state)
+  (if (consp state) (copy-sequence state) state))
+
+(defun cm-clear-work-items (from to)
+  (let ((prev-cons nil)
+        (rem cm-worklist))
+    (while rem
+      (let ((pos (marker-position (car rem))))
+        (cond ((or (< pos from) (> pos to)) (setf prev-cons rem))
+              (prev-cons (setf (cdr prev-cons) (cdr rem)))
+              (t (setf cm-worklist (cdr rem))))
+        (setf rem (cdr rem))))))
+
+(defun cm-min-worklist-item ()
+  (let ((rest cm-worklist) (min most-positive-fixnum))
+    (while rest
+      (let ((pos (marker-position (car rest))))
+        (when (< pos min) (setf min pos)))
+      (setf rest (cdr rest)))
+    min))
+
+;; Indentation
+
+(defun cm-indent ()
+  (let (indent-pos)
+    (save-excursion
+      (beginning-of-line)
+      (let* ((buf (current-buffer))
+             (state (cm-preserve-state buf 'cm-state-for-point))
+             (old-indent (current-indentation)))
+        (back-to-indentation)
+        (setf indent-pos (point))
+        (let ((new-indent (funcall (cm-mode-indent cm-cur-mode) state)))
+          (unless (= old-indent new-indent)
+            (indent-line-to new-indent)
+            (setf indent-pos (point))
+            (beginning-of-line)
+            (cm-preserve-state buf
+             (lambda ()
+               (cm-highlight-line state)
+               (when (< (point) (point-max))
+                 (put-text-property (point) (+ (point) 1) 'cm-parse-state state))))))))
+    (when (< (point) indent-pos)
+      (goto-char indent-pos))))
+
+(defun cm-backtrack-to-state ()
+  (let ((backtracked 0)
+        (min-indent most-positive-fixnum)
+        min-indented)
+    (loop
+     (when (= (point) (point-min))
+       (return (funcall (cm-mode-start-state cm-cur-mode))))
+     (let ((st (get-text-property (- (point) 1) 'cm-parse-state)))
+       (when (and st (save-excursion
+                       (backward-char)
+                       (beginning-of-line)
+                       (not (looking-at "[	 ]*$"))))
+         (return (funcall (cm-mode-copy-state cm-cur-mode) st))))
+     (let ((i (current-indentation)))
+       (when (< i min-indent)
+         (setf min-indent i min-indented (point))))
+     (when (> (incf backtracked) 30)
+       (goto-char min-indented)
+       (return (funcall (cm-mode-start-state cm-cur-mode))))
+     (forward-line -1))))
+
+(defun cm-state-for-point ()
+  (let ((pos (point))
+        (state (cm-backtrack-to-state)))
+    (while (< (point) pos)
+      (cm-highlight-line state)
+      (put-text-property (point) (+ (point) 1) 'cm-parse-state
+                         (funcall (cm-mode-copy-state cm-cur-mode) state))
+      (forward-char))
+    state))
+
+;; Highlighting
+
+(defun cm-highlight-line (state)
+  (let ((eol (point-at-eol)))
+    (remove-text-properties (point) eol '(face))
+    (loop
+     (let ((p (point)))
+       (when (= p eol) (return))
+       (let ((style (funcall (cm-mode-token cm-cur-mode) state)))
+         (when (= p (point)) (print (point)) (error "Nothing consumed."))
+         (when (> p eol) (error "Parser moved past EOL"))
+         (when style
+           (put-text-property p (point) 'face style)))))))
+
+(defun cm-find-state-before-point ()
+  (loop
+   (beginning-of-line)
+   (when (= (point) 1)
+     (return (funcall (cm-mode-start-state cm-cur-mode))))
+   (let ((cur (get-text-property (- (point) 1) 'cm-parse-state)))
+     (when cur (return (funcall (cm-mode-copy-state cm-cur-mode) cur))))
+   (backward-char)))
+
+(defun cm-schedule-work (delay)
+  (run-with-idle-timer delay nil 'cm-preserve-state (current-buffer) 'cm-do-some-work))
+
+(defun cm-preserve-state (buffer f &rest args)
+  (with-current-buffer buffer
+    (let ((modified (buffer-modified-p))
+          (buffer-undo-list t)
+          (inhibit-read-only t)
+          (inhibit-point-motion-hooks t)
+          (inhibit-modification-hooks t))
+      (unwind-protect (apply f args)
+        (unless modified
+          (restore-buffer-modified-p nil))))))
+
+(defun cm-do-some-work-inner ()
+  (let ((end-time (time-add (current-time) (list 0 0 500)))
+        (quitting nil))
+    (while (and (not quitting) cm-worklist)
+      (goto-char (cm-min-worklist-item))
+      (let ((state (cm-find-state-before-point))
+            (startpos (point))
+            (timer-idle-list nil))
+        (loop
+         (cm-highlight-line state)
+         (when (= (point) (point-max)) (return))
+         (let ((old (get-text-property (point) 'cm-parse-state)))
+           (when (and old (funcall (cm-mode-compare-state cm-cur-mode) state old))
+             (return))
+           (put-text-property (point) (+ (point) 1) 'cm-parse-state
+                              (funcall (cm-mode-copy-state cm-cur-mode) state)))
+         (when (or (let ((timer-idle-list nil)) (input-pending-p))
+                   (time-less-p end-time (current-time)))
+           (setf quitting t) (return))
+         (forward-char))
+        (cm-clear-work-items startpos (point)))
+      (when quitting
+        (push (copy-marker (+ (point) 1)) cm-worklist)
+        (cm-schedule-work 0.05)))))
+
+(defun cm-do-some-work ()
+  (save-excursion 
+    (condition-case cnd (cm-do-some-work-inner)
+      (error (print cnd) (error cnd)))))
+
+(defun cm-after-change-function (from to oldlen)
+  (cm-preserve-state (current-buffer) 'remove-text-properties from to '(cm-parse-state))
+  (push (copy-marker from) cm-worklist)
+  (cm-schedule-work 0.2))
+
+;; Entry function
+
+(defun cm-mode (mode)
+  (set (make-local-variable 'cm-cur-mode) mode)
+  (set (make-local-variable 'cm-worklist) (list (copy-marker 1)))
+  (when (cm-mode-indent mode)
+    (set (make-local-variable 'indent-line-function) 'cm-indent))
+  (add-hook 'after-change-functions 'cm-after-change-function t t)
+  (add-hook 'after-revert-hook (lambda () (cm-after-change-function 1 (point-max) nil)) t t)
+  (cm-schedule-work 0.05))
+
+(provide 'cm-mode)