From b0d62ccdd3795a0b879be700317b1053b58e5f8f Mon Sep 17 00:00:00 2001
From: Arun Isaac
Date: Sun, 30 Mar 2025 03:06:37 +0100
Subject: Add pdf link type.

* ennum-html.el (ennum-html-export-pdf): New function.
(org-link-parameters): Add pdf.
* ennum.el (ennum-setting): Add :pdf-width and :pdf-height settings.
(ennum-publish-link): Add pdf link type.
---
 ennum-html.el | 15 +++++++++++++++
 ennum.el      | 10 ++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/ennum-html.el b/ennum-html.el
index 5198a80..7e3eacb 100644
--- a/ennum-html.el
+++ b/ennum-html.el
@@ -372,6 +372,21 @@
  "video"
  :follow 'ennum-html-follow-video)
 
+(defun ennum-html-export-pdf (path desc backend)
+  (pcase backend
+    ((or 'ennum-html 'html)
+     (xmlgen
+      (let ((link-path (url-encode-url
+                        (expand-file-name* path (ennum-setting :static-directory)))))
+        `(object :data ,link-path
+                 :type "application/pdf"
+                 :width ,(ennum-setting :pdf-width)
+                 :height ,(ennum-setting :pdf-height)
+                 "Download " (a :href ,link-path ,path)))))))
+
+(org-link-set-parameters
+ "pdf" :export 'ennum-html-export-pdf)
+
 (defun ennum-html-export-static (path desc backend)
   (pcase backend
     ((or 'ennum-html 'html)
diff --git a/ennum.el b/ennum.el
index 0dd31a9..250a336 100644
--- a/ennum.el
+++ b/ennum.el
@@ -654,7 +654,8 @@ result as a string."
          :blog-scheme :index-posts-per-page
          :image-width :image-link-width
          :locale-alist :other-files-directory
-         :store :tag-directory :image-thumbnail-width
+         :pdf-width :pdf-height :store
+         :tag-directory :image-thumbnail-width
          :required-metadata)
      (plist-get (org-combine-plists
                  (list :atom-feed-number-of-posts 12
@@ -664,6 +665,11 @@ result as a string."
                        :image-link-width 1024
                        :index-posts-per-page 12
                        :locale-alist '(("en" . "C"))
+                       ;; These PDF dimensions preserve the √2 ratio
+                       ;; of A series paper.
+                       ;; https://en.wikipedia.org/wiki/Paper_size#A_series
+                       :pdf-width 640
+                       :pdf-height 905
                        :store ".ennum"
                        :tag-directory "tag"
                        :image-thumbnail-width 320
@@ -743,7 +749,7 @@ recognized as a directory, it should end in a slash. See
                  width))
               (list (ennum-setting :image-width)
                     (ennum-setting :image-link-width))))
-    ('static
+    ((or 'pdf 'static)
      (list
       (ennum-publish-copy
        (ennum--file-join (ennum-setting :static-directory)
-- 
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