;; latex-live-preview.el by Jan Böcker <jan.boecker@jboecker.de>
;; Feel free to improve this.
;; License: Pick one of GNU GPL v3, BSD, MIT

;; This is a quick and dirty hack to show an automatically updated preview image
;; of the LaTeX formula at point in an org-mode buffer.

;; Usage:
;; * Eval the elisp code in this file in some way (e.g. M-x load-file or M-x eval-buffer)
;; * In your org buffer: M-x jb/toggle-latex-live-preview
;; * Split the window (e.g. C-x 2)
;; * open the exported image file (default: /tmp/livepreview.png) in
;;   the second buffer
;; * edit your Org file

;; To speed things up slightly, you might want to move the tempdir to a ramdisk.



;; the tempdir will contain the exported image and might be cluttered
;; with temporary files from running LaTeX if something goes wrong

(defconst jb/latex-live-preview-tempdir "/tmp/")  ; must include final /
(defconst jb/latex-live-preview-filename "livepreview.png")

(defvar jb/current-texfilebase "")
(defvar jb/current-tmpdir nil)
(defvar jb/current-tofile "")
(defvar jb/latex-preview-job nil)
(defvar jb/enable-live-preview nil)



(defun jb/ocfi (string tofile options buffer)
  "Modified version of org-create-formula-image"
  (require 'org-latex)
  (let* ((tmpdir (if (featurep 'xemacs)
		     (temp-directory)
		   temporary-file-directory))
	 (texfilebase (make-temp-name
		       (expand-file-name "orgtex" tmpdir)))
	 (texfile (concat texfilebase ".tex"))
	 (dvifile (concat texfilebase ".dvi"))
	 (pngfile (concat texfilebase ".png"))
	 (fnh (if (featurep 'xemacs)
                  (font-height (get-face-font 'default))
                (face-attribute 'default :height nil)))
	 (scale (or (plist-get options (if buffer :scale :html-scale)) 1.0))
	 (dpi (number-to-string (* scale (floor (* 0.9 (if buffer fnh 140.))))))
	 (fg (or (plist-get options (if buffer :foreground :html-foreground))
		 "Black"))
	 (bg (or (plist-get options (if buffer :background :html-background))
		 "Transparent")))
    (if (eq fg 'default) (setq fg (org-dvipng-color :foreground)))
    (if (eq bg 'default) (setq bg (org-dvipng-color :background)))
    (with-temp-file texfile
      (insert (org-splice-latex-header
	       org-format-latex-header
	       org-export-latex-default-packages-alist
	       org-export-latex-packages-alist t
	       org-format-latex-header-extra))
      (insert "\n\\begin{document}\n" string "\n\\end{document}\n")
      (require 'org-latex)
      (org-export-latex-fix-inputenc))
	(setq jb/current-texfilebase texfilebase)
	(setq jb/current-tmpdir tmpdir)
	(setq jb/current-tofile tofile)
	(jb/call-latex)
))

(defun jb/call-latex ()
  (cd tmpdir)
  (set-process-sentinel
   (start-process "live-latex-preview-latex" ; process name
				  nil ; no buffer
				  "latex"
				  "--halt-on-error"
				  (concat jb/current-texfilebase ".tex"))
   'jb/call-latex-sentinel)
  ;(message "latex-live-preview: started latex")
)

(defun jb/call-latex-sentinel (process event)
  ;(message "latex-sentinel: %s" event)
  (when (string= event "finished\n")
	(jb/call-dvipng))
  (when (string= event "exited abnormally with code 1\n")
	(setq jb/current-tmpdir nil)
	(jb/update-latex-preview)))

(defun jb/call-dvipng ()
  (let* ((tmpdir jb/current-tmpdir)
		 (buffer nil)
		 (options org-format-latex-options)
		 (texfilebase jb/current-texfilebase)
		 (texfile (concat texfilebase ".tex"))
		 (dvifile (concat texfilebase ".dvi"))
		 (pngfile (concat texfilebase ".png"))
		 (fnh (if (featurep 'xemacs)
                  (font-height (get-face-font 'default))
                (face-attribute 'default :height nil)))
		 (scale (or (plist-get options (if buffer :scale :html-scale)) 1.0))
		 (dpi (number-to-string (* scale (floor (* 0.9 (if buffer fnh 140.))))))
		 (fg (or (plist-get options (if buffer :foreground :html-foreground))
				 "Black"))
		 (bg (or (plist-get options (if buffer :background :html-background))
				 "Transparent")))
    (if (eq fg 'default) (setq fg (org-dvipng-color :foreground)))
    (if (eq bg 'default) (setq bg (org-dvipng-color :background)))

	(cd tmpdir)
	(set-process-sentinel
	 (start-process "live-latex-preview-dvipng"
					nil
					"dvipng"
					"-fg" fg "-bg" bg
					"-D" dpi
					;;"-x" scale "-y" scale
					"-T" "tight"
					"-o" pngfile
					dvifile)
	 'jb/call-dvipng-sentinel)
))



(defun jb/call-dvipng-sentinel (process event)
  (when (string= event "finished\n")
	(copy-file (concat jb/current-texfilebase ".png") jb/current-tofile 'replace)

	(loop for e in '(".dvi" ".tex" ".aux" ".log" ".png") do
	      (delete-file (concat jb/current-texfilebase e)))
	
	(when (get-buffer jb/latex-live-preview-filename)
	  (set-buffer jb/latex-live-preview-filename)	
	  (jb/refresh-current-image-buffer))
	
	(setq jb/current-tmpdir nil)
	(jb/update-latex-preview)
))

(defun jb/refresh-current-image-buffer ()
	(flet ((message (msg &rest args) nil))
	  (clear-image-cache)
	  (revert-buffer nil t t)
	  (image-mode)
))

(defun jb/update-latex-preview ()
  (when (and jb/latex-preview-job
			 (not jb/current-tmpdir))
	(jb/preview-fragment jb/latex-preview-job)
	(setq jb/latex-preview-job nil)))
	
(defun jb/preview-fragment (latex)
(save-excursion
 (let ((temporary-file-directory jb/latex-live-preview-tempdir))
   (jb/ocfi latex (concat jb/latex-live-preview-tempdir jb/latex-live-preview-filename) org-format-latex-options nil))
))



(defun jb/plfp ()
"Preview the latex fragment at point"
  (interactive)
  (catch 'exit
	(save-excursion
	  (save-restriction
		(let ((at (org-inside-LaTeX-fragment-p))
			  beg end msg start-delimiter end-delimiter
			  (add-end-delimiter nil))
		  (if (not at)
			  (progn
				(setq jb/latex-preview-job "$ $")
				(jb/update-latex-preview))
			(progn
			  (goto-char (cdr at))
			  (setq beg (point))
			  (setq start-delimiter (car at))
		;;	  (message "start-delimiter is %s " start-delimiter)

			  ;; Determine what the end of this block must look like
			  (setq end-delimiter (cdr (assoc start-delimiter
											  '(("$$" . "$$"),
												("\\[" . "\\]"),
												("\\(" . "\\)")))))
			  
			  ;; Set end-delimiter to \end{region} if block starts
			  ;; with \begin{region}
			  (when (not end-delimiter)
				(save-match-data
				  (if (not (string-match "\\\\begin{\\([^}]*\\)}" start-delimiter))
					  (throw 'exit nil))
				  (setq end-delimiter (concat "\\end{" (match-string 1 start-delimiter) "}"))))

		;;	  (message "end-delimiter is %s " end-delimiter)
			  
			  ;; set end of our region
			  (goto-char (1+ beg))
			  (setq end (re-search-forward (regexp-quote end-delimiter) nil t))
			  
			  ;; If there is no end delimiter, make a note that we
			  ;; need to add it later before creating the image.
			  ;; This will make the preview work on unfinished LaTeX blocks.
			  (when (not end) 
				(setq end (point-max))
				(setq add-end-delimiter t))

			  (narrow-to-region beg end)
		;;	  (message "-%s-" (buffer-string))
			  (goto-char beg)
			  
			  (setq jb/latex-preview-job (concat (buffer-string) (if add-end-delimiter end-delimiter "")  ))
			  (jb/update-latex-preview))))))))

(defun pseudo-message (format-string &rest args)
  nil)

(defun jb/ach (a b c)
  "hook for after-change-functions"
  (when jb/enable-live-preview
	(let ((message (lambda (s &rest args) nil)))
	  (jb/plfp)
	  (setq deactivate-mark nil))))

(defun jb/pch ()
  "hook for post-command-hook"
  (when jb/enable-live-preview
	(let ((message (lambda (s &rest args) nil)))
	  (jb/plfp)
	  (setq deactivate-mark nil))))

(defun jb/toggle-latex-live-preview ()
  "toggles the buffer-local variable jb/enable-live-preview"
  (interactive)
  (setq jb/current-tmpdir nil)
  (make-variable-buffer-local 'jb/enable-live-preview)
  (setq jb/enable-live-preview (not jb/enable-live-preview)))

(defun jb/clear-current-tmpdir ()
  (interactive)
  (setq jb/current-tmpdir nil))

(remove-hook 'after-change-functions 'jb/ach)
(remove-hook 'post-command-hook 'jb/pch)

(add-hook 'post-command-hook 'jb/pch)
(add-hook 'after-change-functions 'jb/ach)