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List:       kde-bugs-dist
Subject:    Bug#12769: Konquer cache corruption - cache unusable
From:       John Califf <jcaliff () compuzone ! net>
Date:       2000-10-12 23:26:58
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Package: konqueror kio
Version: latest snapshots - 11 October 2000

Severity: Critical

Description: 

When visiting certain web sites (repeatable) with cache size larger than
0 Konqueror starts getting 404 file not found error messages.  From
there on, more and more sites, even those previously visited during the
same session, get 404 messages until everything does and nothing loads.

One such site is Gnome Foundation's web site - Freshmeat also can
sometimes cause this problem.  The problems start after visiting such
sites and then visiting any other site or going back to another site.

Workaround:

The problem can be worked around simply by setting the cache size to
zero.  Konqueror is still pretty fast with most sites even without a
cache.  However, few users will associate these errors with an
increasingly corrupted cache.  Therefore I regard the bug as critical,
because the cache gets more and more corrupted without any indication to
the user that the cache is causing critical problems - failure of
Konqueror to load any pages, eventually.

Speculation:

The Gnome Foundation site and some others that cause cache corruption
use 8 bit RGB png images. I've noticed that starting about a month ago
Kde can't display certain types of png images, specifically 8 bit RGB
non-interlaced.  It can display indexed pngs such as are used on most
web sites, but not the RBG's of 8 bits depth. This is really a qt
problem, not a kde problem.  To test, I tried the qt example program
"showimg" and it returns the following error when trying to view such
pngs - "libpng error - too many IDAT's found."
note: this is with the very latest Qt 2.2.1 compiled with -system-libpng
using Qt's zlib.  Using or not using system-zlib makes no difference.  

There's nothing wrong with my libpng as these images show up fine with
non-Qt based viewers and in Mozilla.  They don't show up in Netscape
4.75 but don't cause file not found errors like Konqueror gives. My
libpng version is 1.05.  Maybe if I used Qt's own version of libpng this
problem would go away, but it takes along time to recompile.  I will try
again, but then if that really is the problem the compile flags for Qt
need to require using Qt's png and zlib only - and need to disallow
system libpng and zlib flags.

John

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