add flipcard feature into ox-reveal

settings/org-settings.el

@@ -969,8 +969,54 @@ used as a communication channel."
 (use-package ox-reveal
   :defer t  ;; will be loaded via `org-export-backends' see above inside `org'
   :config
+  ;; #+REVEAL_EXTRA_CSS:
+  (setq org-reveal-extra-css (concat "file://" (expand-file-name user-emacs-directory) "scripts/flipcard/flipcard.css"))  ;; multiple files seperated with \n
+  ;; #+REVEAL_POSTAMBLE:
+  (setq org-reveal-postamble (replace-regexp-in-string "\n" "" (concat "<script>" (org-reveal--read-file (concat (expand-file-name user-emacs-directory) "scripts/flipcard/flipcard.js")) "\n</script>")))  ;; only one line!
   (setq org-reveal-root (concat "file://" (expand-file-name user-emacs-directory) "scripts/reveal.js"))
-  (setq org-reveal-single-file t))
+  (setq org-reveal-single-file t)
+  ;; overwrite to implement `org-reveal-single-file' (:reveal-single-file)
+  ;; used in `org-reveal-scripts' as reveal-4-plugin
+  (defun org-reveal-plugin-scripts-4 (info)
+    "Return scripts for initializing reveal.js 4.x builtin scripts"
+    (let ((plugins (org-reveal--get-plugins info)))
+      (if (not (null plugins))
+          ;; Generate plugin scripts
+          (let* ((available-plugins
+                  '(highlight ("RevealHighlight" . "highlight/highlight.js")
+                    markdown ("RevealMarkdown" . "markdown/markdown.js")
+                    search ("RevealSearch" . "search/search.js")
+                    notes ("RevealNotes" . "notes/notes.js")
+                    math ("RevealMath" . "math/math.js")
+                    zoom ("RevealZoom" . "zoom/zoom.js")))
+                 (plugin-info (seq-filter 'identity
+                                          (seq-map (lambda (p)
+                                                     (plist-get available-plugins p))
+                                                   plugins))))
+            (if (not (null plugin-info))
+                (cons
+                 ;; Plugin initialization script
+                 (let* ((root-path (file-name-as-directory (plist-get info :reveal-root)))  ;; changed
+                        (local-root-path (org-reveal--file-url-to-path root-path))          ;; changed
+                        (in-single-file (plist-get info :reveal-single-file)))              ;; changed
+                   (mapconcat
+                    (lambda (p)
+                      (if in-single-file
+                          (concat "<script>\n"
+                                  (org-reveal--read-file
+                                   (concat local-root-path "plugin/" (cdr p)))
+                                  "\n</script>")
+                        (format "<script src=\"%splugin/%s\"></script>\n" root-path (cdr p))))
+                    plugin-info
+                    ""))
+                 ;; Reveal initialization for plugins
+                 (format "plugins: [%s]"
+                         (mapconcat #'car plugin-info ",")))
+              ;; No available plugin info found. Perhaps wrong plugin
+              ;; names are given
+              (cons nil nil)))
+          ;; No plugins, return empty string
+        (cons nil nil)))))
 
 (use-package org-drill  ;; requires persist https://elpa.gnu.org/packages/persist.html
   :commands org-drill)