Cached thumbnail corruption bug in XP/SP2?   

Hey folks,

We've been able to reproduce a problem with thumbnail "preview" images 
displayed in the lower left hand of the folder frame when a .bmp file is 
selected and the folder View mode is set to "Details".  The problem appears 
to have something to do with the hidden Thumbs.db thumbnail cache file.  We 
stumbled on it by accident, because of the test sequence we were performing 
on our custom file thumbnail extractor.  (Note that the problem has been 
reproduced on an independent box, i.e., one that we haven't added our 
extractor to.)

What you need:
* A few .bmp image files at different, but typically smaller sizes, e.g., 
96x96, 500x400, etc., including some where the actual image doesn't span the 
entire "canvas" of the .bmp.  (Not sure if this affects non-bmp image files 
yet - it doesn't appear to affect .ppt preview images.)
* A new, empty folder that is set to display hidden files.  This folder 
should not have a hidden "Thumbs.db" thumbnail cache file yet, and its View 
mode should be set to "Details" before starting.

Sequence:
1. Ensure that the empty folder is in "Details" View mode and does not have 
a "Thumbs.db" hidden file yet.
2. Copy several .bmp image files into the folder.
3. Select each .bmp file in turn, and examine the individual thumbnail 
preview image that appears in the lower left-hand of the folder frame for 
each file.
4. Now switch the folder View mode to "Thumbnails", and examine the various 
thumbnail images.  This should have the side effect of producing a 
"Thumbs.db" hidden file for cached thumbnails.
5. Switch the folder back to "Details" View mode.
6. Select each file in turn again, and examine the preview thumbnail that 
appears in the lower left side of the folder frame.

At this point, we typically see some kind of corruption in each of the 
preview thumbnails that appears in the lower left-hand side of the folder 
frame in "Details" View mode.  The corruption is never apparent in 
"Thumbnails" View mode.  If the folder is returned to "Details" View mode, 
and the hidden Thumbs.db file is then deleted, the preview thumbnail images 
in the lower left-hand side of the folder frame appear to be correct again. 
Switching to "Thumbnails" View again will reintroduce the same kind of 
corruption for each image as was seen the first time around.

linearred

date: Mon, 14 Apr 2008 11:51:26 -0500   author:   linearred am