Re: (version 3) [PATCH] New feature: Use dvisvgm to preview latex formular

[Nicolas Goaziou <mail@nicolasgoaziou.fr>]

Hello,

"Feng Shu" <tumashu@163.com> writes:

> I suggest to add (:generator my-generator-function) style configure
> to `org-latex-pdf-process', it is simple and powerful feature, we
> can use this feature to switch latex commands dynamicially, for example:
>
> (defun my-latex-pdf-process-generator (texfile snippet extra-info)
>   (cond
>    ((<a>) (<org-latex-pdf-process-style-command1>)
>    ((<b>) (<org-latex-pdf-process-style-command2>)))))
>
> although we can set org-latex-pdf-process to a function to do the same work,
> but this function is hard to write as org-latex-compile, it may only
> useful for developer instead of user....
>
> caller-info argument is for the above feature.

I understand the need to extend `org-latex-pdf-process'. However this
isn't a good way to look at it. In fact, it makes little sense to load
the whole export framework when you're only after displaying a LaTeX
snippet in the current buffer.

I think a better approach would be to create a generic tool to compile
a file to another format, e.g. `org-compile-file'. It would take a command
(as a list of strings or a function) and apply it to the source file
name. Then it would check if the output file was produced. Optionally,
it would allow to create a buffer so as to retrieve error messages.

Then, e.g., `org-latex-compile' or `org-preview-generate-image', could
extend this function, i.e., handle specific variables (e.g.,
`org-latex-pdf-process') and call it with appropriate arguments.

As example, here's a proof of concept for `org-compile-file' and
`org-latex-compile'.

  (defun org-compile-file (source process extension &optional spec log-buffer)
    "Compile a SOURCE file using PROCESS.

  PROCESS is either a function or a list of shell commands, as
  strings.

  If PROCESS is a function, it is called with a single argument:
  SOURCE file.  It must create a file with the same base name and
  directory as SOURCE, but using extension.

  If it is a list of commands, each of them is called using
  `shell-command'.  By default, in each command, %b, %f and %o are
  replaced, respectively, with SOURCE base name, SOURCE full name
  and SOURCE directory.  It is possible, however, to use different
  place-holders by specifying them in optional argument SPEC.  In
  this case, SPEC should be an alist (CHARACTER REPLACEMENT-STRING).

  When PROCESS is a list of commands, optional argument LOG-BUFFER
  can be set to a buffer or a buffer name.  `shell-command' then
  uses it as an output buffer, which may be used for collecting
  errors.

  `default-directory' is set to SOURCE directory during the whole
  process.

  Return output file or raise an error if it wasn't generated upon
  executing PROCESS."
    (let* ((base-name (file-name-sans-extension (file-name-nondirectory source)))
  	 (full-name (file-truename source))
  	 (out-dir (file-name-directory source))
  	 ;; Properly set working directory for compilation.
  	 (default-directory (if (file-name-absolute-p source)
  				(file-name-directory full-name)
  			      default-directory))
  	 (time (current-time)))
      (save-window-excursion
        (pcase process
          ((pred functionp) (funcall process (shell-quote-argument source)))
          ((pred consp)
           (let ((log (and log-buffer (get-buffer-create log-buffer)))
                 (spec (or spec
                           `((?b ,(shell-quote-argument base-name))
                             (?f ,(shell-quote-argument full-name))
                             (?o ,(shell-quote-argument out-dir))))))
             (dolist (command process)
               (shell-command (format-spec command spec) log))))
          (t (error "No valid command to process %S" source)))
        ;; Check for process failure.
        (let ((output (concat out-dire base-name extension)))
          (when (or (not (file-exists-p output))
                    ;; Only compare times up to whole seconds as some
                    ;; file-systems (e.g. HFS+) do not retain any finer
                    ;; granularity.
                    (time-less-p (cl-subseq (nth 5 (file-attributes output)) 0 2)
                                 (cl-subseq time 0 2)))
            (error (format "File %S wasn't produced" output)))
          output))))

  (defun org-latex-compile (texfile)
    "Compile a TeX file.

  TEXFILE is the name of the file being compiled.  Processing is
  done through the command specified in `org-latex-pdf-process'.

  Return PDF file name or an error if it couldn't be produced."
    (message "Processing LaTeX file %s..." texfile)
    (let* ((base-name (file-name-sans-extension (file-name-nondirectory texfile)))
  	 (full-name (file-truename texfile))
  	 (compiler (or (with-temp-buffer
  			 (save-excursion (insert-file-contents full-name))
  			 (when (and (search-forward-regexp
  				     (regexp-opt org-latex-compilers) (line-end-position 2) t)
  				    (progn (beginning-of-line)
  					   (looking-at-p "%")))
  			   (match-string 0)))
  		       "pdflatex"))
  	 (out-dir (file-name-directory texfile))
           (spec `((?B ,(shell-quote-argument org-latex-bib-compiler))
                   (?L ,(shell-quote-argument compiler))
                   (?b ,(shell-quote-argument base-name))
                   (?f ,(shell-quote-argument full-name))
                   (?o ,(shell-quote-argument out-dir))))
           (log-buffer (get-buffer-create "*Org PDF LaTeX Output*"))
           (outfile
            (org-compile-file
             texfile
             (let ((process org-latex-pdf-process))
               ;; A function is provided: Apply it.
               (if (functionp org-latex-pdf-process)
                   org-latex-pdf-process
                 ;; A list is provided: replace %b, %f and %o with
                 ;; appropriate values in each command before applying
                 ;; it.  Note that while "%latex" and "%bibtex" is used
                 ;; in `org-latex-pdf-process', they are replaced with
                 ;; "%L" and "%B" to adhere to format-spec.  Output is
                 ;; redirected to "*Org PDF LaTeX Output*" buffer.
                 (mapcar (lambda (command)
                           (replace-regexp-in-string
                            "%\\(latex\\|bibtex\\)\\>"
                            (lambda (str) (upcase (substring str 0 2)))
                            command))
                         org-latex-pdf-process)))
             ".pdf"
             log-buffer)))
      (when org-latex-remove-logfiles
        (mapc #'delete-file
              (directory-files
               out-dir t
               (concat (regexp-quote base-name)
                       "\\(?:\\.[0-9]+\\)?"
                       "\\."
                       (regexp-opt org-latex-logfiles-extensions)))))
      (let ((warnings (get-buffer-create(org-latex--collect-warnings outbuf))))
        (message (concat "PDF file produced"
                         (cond
                          ((eq warnings 'error) " with errors.")
                          (warnings (concat " with warnings: " warnings))
                          (t ".")))))
      ;; Return output file name.
      outfile))

> Remove the above two and only use the below *one* ?
>
> (make-obsolete-variable
>  'org-latex-preview-ltxpng-directory
>  "Set `org-latex-preview-ltximg-directory' instead." "25.1")

I think

  (make-obsolete-variable
  'org-latex-preview-ltxpng-directory
  'org-latex-preview-ltximg-directory "25.1")

is sufficient. The code you wrote is not wrong either, tho.

Regards,

-- 
Nicolas Goaziou