emacs/show: special case toggling display of images

According to emacs upstream [1], we can't expect overlay invisibility
and images to get along. This commit uses the previously stashed
undisplayer functions to actually remove the images from the buffer.
When the image is toggled, it is essentially redisplayed from scratch,
using the previously stashed redisplay data.

[1]: https://lists.gnu.org/archive/html/emacs-devel/2023-08/msg00593.html

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 54cf00c6392128c10f45499b78a02ee7525de0ff..4cc5aa57d91cc204b2800bf8e38c75f057231dc5 100644 (file)
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -644,8 +644,24 @@ message at DEPTH in the current thread."
                (when show
                  (button-put button :notmuch-lazy-part nil)
                  (notmuch-show-lazy-part lazy-part button))
-             ;; else there must be an overlay.
-             (overlay-put overlay 'invisible (not show))
+             (let* ((part (plist-get properties :notmuch-part))
+                    (undisplayer (plist-get part :undisplayer))
+                    (mime-type (plist-get part :computed-type))
+                    (redisplay-data (button-get button
+                                                :notmuch-redisplay-data))
+                    (imagep (string-match "^image/" mime-type)))
+               (cond
+                ((and imagep (not show) undisplayer)
+                 ;; call undisplayer thunk created by gnus.
+                 (funcall undisplayer)
+                 ;; there is an extra newline left
+                 (delete-region
+                  (+ 1 (button-end button))
+                  (+ 2 (button-end button))))
+                ((and imagep show redisplay-data)
+                 (notmuch-show-lazy-part redisplay-data button))
+                (t
+                 (overlay-put overlay 'invisible (not show)))))
              t)))))))
 
 ;;; Part content ID handling