[PATCH] do not save failed thumbnails for unreadable images

Michael J. Chudobiak mjc at avtechpulse.com
Fri May 11 06:37:24 PDT 2012

 thumbnail/thumbnail-spec.sgml |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/thumbnail/thumbnail-spec.sgml b/thumbnail/thumbnail-spec.sgml
index cb539b6..b9c8411 100644
--- a/thumbnail/thumbnail-spec.sgml
+++ b/thumbnail/thumbnail-spec.sgml
@@ -455,7 +455,13 @@
     in the thumbnail directories should have set their permissions to 600. This
     way we assure that if a user creates a thumbnail for a file where only he
     has read-permissions no other user can take a glance on it through the
-    backdoor with the thumbnails.</para> 
+    backdoor with the thumbnails.</para>
+    <para>Programs should first check to ensure that the original image file is
+    readable. If it is not, the program should not attempt to read a thumbnail
+    from the cache, and it should not save any information in the cache
+    (including "failed" thumbnails). Otherwise, thumbnailing will be prevented
+    even if the permissions are changed to permit reading.</para>
     <sect2><title>Concurrent Thumbnail Creation</title> <para>An important goal
@@ -597,7 +603,7 @@ if (file.mtime != thumb.MTime) {
        with the name of the program appended by the version number
        (eg. <prompt>~/.thumbnails/fail/nautilus-1.0</prompt>).</para>
-    <para> For every thumbnail generation failure the program creates an empty
+    <para> For every thumbnail generation failure of a readable image the program creates an empty
        PNG file. If it's possible to obtain some additional information from
        the image (see <link linkend="addinfos">Store Additional
        Information</link>) they should be stored together with the thumbnail


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