[PATCH] Persistently save downloaded inline remote images

[Ferdinand Pieper]

Currently remote images are downloaded upon each display.
As most of the time the images do not change in between redisplays, we can 
instead buffer the images locally and only update the local copy when the 
remote image is updated.

Attached is a proposed patch.


Best,

>From aa34ad1176f4599c5a3c2678806644f16a3d22a2 Mon Sep 17 00:00:00 2001
From: fpi <git@pie.tf>
Date: Tue, 23 Jun 2020 15:59:28 +0200
Subject: [PATCH] org.el: Persistently save downloaded inline remote images

* lisp/org.el (org--create-inline-image): Save downloaded inline
remote images to temporary directory to persist them for future
`org-display-inline-images' calls.
---
 lisp/org.el | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/lisp/org.el b/lisp/org.el
index 4d46b4173..7b649d6d0 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -16277,10 +16277,22 @@ according to the value of 
`org-display-remote-inline-images'."
         (file-or-data
          (pcase org-display-remote-inline-images
            ((guard (not remote?)) file)
-           (`download (with-temp-buffer
-                        (set-buffer-multibyte nil)
-                        (insert-file-contents-literally file)
-                        (buffer-string)))
+           (`download (let ((new (concat temporary-file-directory
+                                         "tramp/"
+                                         (file-remote-p file 'host)
+                                         (file-local-name file))))
+                        ;; dont download file if local copy exists & is newer 
than remote
+                        (if (and (file-exists-p new)
+                                 (file-newer-than-file-p new file))
+                            (with-temp-buffer
+                              (set-buffer-multibyte nil)
+                              (insert-file-contents-literally new)
+                              (buffer-string))
+                          (with-temp-file new
+                            (make-directory (file-name-directory new) t)
+                            (set-buffer-multibyte nil)
+                            (insert-file-contents-literally file)
+                            (buffer-string)))))
            (`cache (let ((revert-without-query '(".")))
                      (with-current-buffer (find-file-noselect file)
                        (buffer-string))))
-- 
2.20.1