[Aimmath-developers] [ aimmath-Bugs-821823 ] Invisible images

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Bugs item #821823, was opened at 2003-10-11 16:19
Message generated for change (Comment added) made by npstrick
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 7
Submitted By: Neil Strickland (npstrick)
Assigned to: Nobody/Anonymous (nobody)
Summary: Invisible images

Initial Comment:
I have some questions that involve dynamically 
generated images (produced by p> plot(...), and handled 
by the `aim/ImageCache` class).  A significant number 
of students have reported that they cannot see the 
images: their browser indicates that the expected gif file 
cannot be downloaded.  I have not been able to 
reproduce this behaviour.  It may possibly be caused by 
different Maple processes messing up each other's 
images, but that is just a guess.  The code is supposed 
to prevent that from happening, anyway.


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>Comment By: Neil Strickland (npstrick)
Date: 2003-11-08 21:53

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The problem can be fixed in practice by increasing the 
timeout in the Clean method of the ImageCache class from 
600 to 6000 seconds.  This means that the relevant images 
must get deleted by the Clean method.  That method only 
deletes unlocked images, so the code that should lock the 
relevant images must be broken.  

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Comment By: Greg Gamble (gregg0)
Date: 2003-10-12 03:09

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At least some of the time this is caused by a student
clicking a link within the page before it has fully
downloaded. This may be a problem restricted to Internet
Explorer (possibly an IE bug?)  It's only come up for me
very occasionally, and
I've worked around it by generating the same page as
administrator and copying the .gif to the right name (after
scanning the source .html for the student's page)
in the imagecache/ directory. Sometimes the students can
help themselves by
backing out and re-entering the quiz. Possibly, if they hit
`Validate' and waited for
a full download the whole page would be regenerated ... but
I haven't tested that idea.  I don't think it's the result
of clashing Maple processes.

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