Filter to put decorative initial letters

[Juan Manuel Macías]

Hi,

These past holidays I've been experimenting with some little useful, but
fun stuff. This is an export filter to put a decorative initial letter
in the first paragraphs of the first level sections, using the LaTeX
package lettrine (https://www.ctan.org/pkg/lettrine).

A screenshot: https://i.imgur.com/mLQVHFC.png

#+BIND: org-export-filter-parse-tree-functions (lettrine)

#+begin_src emacs-lisp :exports results :results none
  (defun lettrine (tree backend info)
    (when (org-export-derived-backend-p backend 'latex)
      (org-element-map tree 'headline
        (lambda (section)
          (when (eq 1 (org-element-property :level section))
            (let* ((contents (org-element-interpret-data (org-element-contents 
section)))
                   (lettrine-opt (org-export-get-node-property 
:LETTRINE_OPTIONS section t))
                   (contents-lettrine (with-temp-buffer
                                        (insert contents)
                                        (save-excursion
                                          (goto-char (point-min))
                                          (re-search-forward 
"\\(\\b.\\)\\([^\s]+\\b\\)" nil t)
                                          (replace-match (concat "\\\\lettrine"
                                                                 (if 
lettrine-opt (format "[%s]"
                                                                                
          lettrine-opt) "")
                                                                 "{" "\\1" "}" 
"{" "\\2" "}")
                                                         t nil)
                                          (org-element-parse-buffer)))))
              (apply #'org-element-set-contents
                     section
                     (list contents-lettrine)))))
        info)
      tree))
#+end_src

Best regards,

Juan Manuel