emacs-28 bb475e1: Clarify two image-dired docstrings

[Stefan Kangas]

branch: emacs-28
commit bb475e10b9f0b1b76618dc6cb33237e36d30bbc3
Author: Stefan Kangas <stefan@marxist.se>
Commit: Stefan Kangas <stefan@marxist.se>

    Clarify two image-dired docstrings
    
    * lisp/image-dired.el (image-dired-dir): Doc fix; clarify that
    thumbnails will be saved in "$XDG_CACHE_HOME/thumbnails", as per the
    Thumbnail Managing Standard.
    (image-dired-thumb-size): Doc fix; clarify that this option will be
    ignored when using the Thumbnail Managing Standard.
---
 lisp/image-dired.el | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/lisp/image-dired.el b/lisp/image-dired.el
index e5fbfcf..2c28964 100644
--- a/lisp/image-dired.el
+++ b/lisp/image-dired.el
@@ -163,7 +163,12 @@
   :group 'multimedia)
 
 (defcustom image-dired-dir (locate-user-emacs-file "image-dired/")
-  "Directory where thumbnail images are stored."
+  "Directory where thumbnail images are stored.
+
+The value of this option will be ignored if Image Dired is
+customized to use the Thumbnail Managing Standard; they will be
+saved in \"$XDG_CACHE_HOME/thumbnails/\" instead.  See
+`image-dired-thumbnail-storage'."
   :type 'directory)
 
 (defcustom image-dired-thumbnail-storage 'use-image-dired-dir
@@ -406,7 +411,11 @@ Used by `image-dired-gallery-generate' to leave out 
\"hidden\" images."
    (t 100))
   "Size of thumbnails, in pixels.
 This is the default size for both `image-dired-thumb-width'
-and `image-dired-thumb-height'."
+and `image-dired-thumb-height'.
+
+The value of this option will be ignored if Image Dired is
+customized to use the Thumbnail Managing Standard; the standard
+sizes will be used instead.  See `image-dired-thumbnail-storage'."
   :type 'integer)
 
 (defcustom image-dired-thumb-width image-dired-thumb-size