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In my LaTeX code I have strings like:

\arXivid{1602.00735}

that create, in the generated PDF file, a link to, e.g. https://arxiv.org/abs/1602.00735.

I'd like to have the string \arXivid{1602.00735} clickable, like urls in goto-address-mode, opening the relative url in the browser.

How can I do it? Do I need to use a text-property?

I don't really need to fontify the string like goto-address-mode does.

Gabriele
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  • Can we eliminate the PDF from the equation and just make the \arXivid{1602.00735} clickable? Also, are you seeking to incorporate this behavior into the AUCTeX library such that the text-properties are automatically laid; e.g., as font-lock does its thing? – lawlist Jan 29 '21 at 22:27
  • The PDF stuff is only the explanation of what the LaTeX code does. It doesn't matter. I just need the string to be clickable and pointing to the correct url. – Gabriele Jan 29 '21 at 22:30
  • Have a look at org-set-font-lock-defaults and see how the links are activated as part of font-lock ... You may wish to do something similar with the AUCTeX or other similar library that you are using to fontify the buffer text. The answer to this question, however, is non-trivial (in my opinion) but nevertheless completely doable. – lawlist Jan 29 '21 at 22:36

1 Answers1

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The standard way to define clickable text is explained in the manual.

  • put an appropriate face, e.g. link and the text property keymap on the link text.
  • bind the follow-link event in that keymap to a function, e.g. arXivid-follow, that transforms the text into a link
  • the function gets an event that leads you to the click position where you can extract the id and transform it into a link
  • follow the link with browse-url

As lawlist indicated in his comment, you can let font-lock find and propertize the link text in the buffer.

The following code defines a minor mode arXivid-mode that adds the required keyword to font-lock-keywords.

(defun arXivid-link-at-point (&optional point)
  "Return \\arXivid{ID} link at POINT or nil if there is none."
  (save-excursion
    (when point
      (goto-char point))
    (skip-chars-backward "^[:space:]\\\\")
    (and
     (eq (char-before) ?\\)
     (looking-at "arXivid{\\([0-9.]+\\)}")
     (concat "https://arxiv.org/abs/" (match-string 1)))))

(defun arXivid-follow (event)
  "Follow \arXivid{ID} links."
  (interactive "e")
  (let ((window (posn-window (event-end event)))
        (pos (posn-point (event-end event)))
    link)
    (if (not (windowp window))
        (error "Something is very wrong..."))
    (with-current-buffer (window-buffer window)
      (goto-char pos)
      (let ((link (arXivid-link-at-point)))
    (when link
      (browse-url link))))))


(defvar arXivid-keymap
  (let ((map (make-sparse-keymap)))
    (define-key map [follow-link] #'arXivid-follow)
    map)
  "Keymap for \arXivid{ID} links.")


(defvar arXivid-keywords
  '(("\\arXivid{\([0-9.]+\)}"
     (0 (face link keymap ,arXivid-keymap) prepend))) "Additional font lock keywords forarXivid-mode'.")


(define-minor-mode arXivid-mode
  "Minor mode making \arXivid{ID} clickable."
  :lighter " arX"
  (if arXivid-mode
      (font-lock-add-keywords
       nil
       arXivid-keywords
       t)
    (font-lock-remove-keywords
     nil
     arXivid-keywords))
  (font-lock-flush)
  (font-lock-ensure))
Tobias
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  • It works. I'll try to add the follow link with a shortcut (C.c RET) feature, like in goto-address-mode, by myself. Thank you . – Gabriele Jan 30 '21 at 10:17
  • Is event in arXivid-follow a mouse click by default? Can I change it to allow follow-lin also by typing (C-c RET)? – Gabriele Jan 30 '21 at 11:26
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    Evaluating (info "(elisp) Input Events") should tell you all you need to know about events. – NickD Jan 30 '21 at 12:32
  • I tried: (defvar arXivid-keymap (let ((map (make-sparse-keymap))) (define-key map [follow-link] #'arXivid-follow) (define-key map (kbd "C-c RET") #'arXivid-follow) map) "Keymap for \\arXivid{ID} links.") but I get: Wrong type argument: commandp, arXivid-follow – Gabriele Jan 30 '21 at 15:56
  • Yes, that's a bug in @Tobias's code I think: it needs to be made interactive: just add (interactive) at the beginning of arXivid-follow and see whether that works. – NickD Jan 30 '21 at 21:36
  • @NickD Thanks for pointing out the bug. I have corrected it. Don't know how I could miss it from the man-page. – Tobias Jan 30 '21 at 23:41
  • Another way to get this working is to (ab)use bug-reference-mode – rpluim Feb 01 '21 at 14:09
  • When I exit arXivid-mode also the goto-address-mode fontification is supppressed. Should I add font-lock-fontify-buffer after font-lock-ensure in the define-minor-mode code? – Gabriele Feb 06 '21 at 10:13