Why does org-preview-latex-fragment work about 10 times slower in OSX than on linux?

Question

I'm using the native cocoa emacs on OSX as well as on debian in a virtual machine.

When I run the aforementioned function in order to generate latex previews (on the same file) in the OSX or in the VM Emacs, I get huge performance differences: it takes at least 10 times as long to generate the previews in OSX as in the VM (running on the same machine, with the same document!!).

I imagine it is one of the programs in the stack of things that work to produce those previews? Or is calling a subprocess very expensive in OSX? (because it appears one is called for each preview)?

I would be happy to provide additional info, just don't know what... Thanks in advance!

Answer 1

There are two approach to preview latex frags:

1. latex -> pdflatex-> dvi -> dvi2png -> png : fast

2. latex -> xelatex -> pdf -> imagemagick -> png: slow

may be you used the second one...

Answer 2

Eval this (test) function, and check message, you may find which step is slow.....

       (defun test (&optional options buffer)
         "This calls dvipng."
         (require 'ox-latex)
         (setq  test-timestamp  (float-time))
         (message "test1: %s" (- (float-time) test-timestamp))
         (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 (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")))
           (message "test2: %s" (- (float-time) test-timestamp))
           (if (eq fg 'default) (setq fg (org-dvipng-color :foreground))
             (unless (string= fg "Transparent") (setq fg (org-dvipng-color-format fg))))
           (if (eq bg 'default) (setq bg (org-dvipng-color :background))
             (unless (string= bg "Transparent") (setq bg (org-dvipng-color-format bg))))
           (message "test3: %s" (- (float-time) test-timestamp))
           (let ((latex-header (org-create-formula--latex-header)))
             (with-temp-file texfile
        (insert latex-header)
        (insert "\n\\begin{document}\n" "$y=ax+b+c+d$" "\n\\end{document}\n")))
           (message "test4: %s" (- (float-time) test-timestamp))
           (let ((dir default-directory))
             (condition-case nil
          (progn
            (cd tmpdir)
            (call-process "latex" nil nil nil texfile))
        (error nil))
             (cd dir))
           (message "test5: %s" (- (float-time) test-timestamp))
           (if (not (file-exists-p dvifile))
        (progn (message "Failed to create dvi file from %s" texfile) nil)
             (condition-case nil
          (call-process "dvipng" nil nil nil
                "-fg" fg "-bg" bg
                "-D" dpi
                ;;"-x" scale "-y" scale
                "-T" "tight"
                "-o" pngfile
                dvifile)
        (error nil))
             (message "test6: %s" (- (float-time) test-timestamp))
             (if (not (file-exists-p pngfile))
          (if org-format-latex-signal-error
              (error "Failed to create png file from %s" texfile)
            (message "Failed to create png file from %s" texfile)
            nil)
        ;; Use the requested file name and clean up
        (copy-file pngfile "~/testpic.png" 'replace)
        (message "test7: %s" (- (float-time) test-timestamp))
        pngfile))))