How to enlarge latex fragments in org mode at the same time as the buffer text?

Question

I'm using org-mode in emacs, but I think the question is also relevant for auctex users.

In org-mode you can show latex fragments, as the manual demonstrates.

But: these fragments (mostly math formulae) seem to have constant size. When I type C-x C-+ or C-x C-- only the buffer text size changes. How can I change the fragments size from the buffer?

(I know I can make the fragments larger or smaller with org-format-latex-options, but this is permanent. I want to change the size of the fragments (the png files) like the text.)

Answer 1

Updated answer: (thanks for the feedback)

(defun update-org-latex-fragments ()
  (org-latex-preview '(64))
  (plist-put org-format-latex-options :scale text-scale-mode-amount)
  (org-latex-preview '(16)))
(add-hook 'text-scale-mode-hook 'update-org-latex-fragments)

Old answer:

Here is a start: hook into text-scale-mode-hook and update org-format-latex-options accordingly.

(defun update-org-latex-fragments ()
  (org-toggle-latex-fragment '(16))
  (plist-put org-format-latex-options :scale text-scale-mode-amount)
  (org-toggle-latex-fragment '(16)))
(add-hook 'text-scale-mode-hook 'update-org-latex-fragments)

A scaling factor might be needed before text-scale-mode-amount though...

Answer 2

Based on the answer from thisirs, I am using the following with success. The scale factor in this example is 2.3:

(defun update-org-latex-fragment-scale ()
  (let ((text-scale-factor (expt text-scale-mode-step text-scale-mode-amount)))
    (plist-put org-format-latex-options :scale (* 2.3 text-scale-factor)))
)
(add-hook 'text-scale-mode-hook 'update-org-latex-fragment-scale)

Note that I have removed the code that toggles the preview, since I prefer to do that manually, and it can take a while if there are many fragments to preview. This code only adjusts the scale of previewed fragments, so that the next time they are displayed using C-c C-x C-l, they will have an appropriate size that matches the text.

Answer 3

That is already built-in if you use texfrag-mode in Orgmode instead of the built-in LaTeX fragment support of Orgmode.

Just regenerate the LaTeX fragments with C-c C-p C-d after changing the size with C-x C-+ C-+ .... The size of the LaTeX fragments will fit the size of the surrounding text.

Normal text size:

After pressing C-x C-+ C-+ C-x and C-c C-p C-d:

Sidenote: With the last version of texfrag you can also activate texfrag-show-last-mode. With that minor mode activated Texfrag shows the last rendered LaTeX-fragment as handle if you edit the formula:

Answer 4

Code in other answers is helpful, but it re-renders latex preview on every change of text scale, even if not asked to do so, and even when C-x C-+ is pressed multiple times in a row, which is slow.

I'd rather do re-render manually. And I'd like org-format-latex-options to be left unmodified.

(setq my-org-latex-preview-scale 1.0)   ; depends on the font used in emacs or just on user preference
(defun org-latex-preview-advice (orig-func &rest args)
  (let ((old-val (copy-tree org-format-latex-options)))     ; plist-put is maybe-destructive, weird. So, we have to restore old value ourselves
    (setq org-format-latex-options (plist-put org-format-latex-options
                                              :scale
                                              (* my-org-latex-preview-scale (expt text-scale-mode-step text-scale-mode-amount))))
    (apply orig-func args)
    (setq org-format-latex-options old-val)))
(advice-add 'org-latex-preview :around #'org-latex-preview-advice)

Answer 5

A different, modern solution is to preview latex fragments in Org mode using MathJax instead of LaTeX. The package math-preview implements this and with it the font size in the previews is adapted to the font size of the buffer.