Remember that problem I had with gdk-pixbuf in Slackware?
Some of you might be interested to learn the final solution. In my previous thread I found a solution of sorts, which was to build gdk-pixbuf from source and install it in /opt alongside the official version. But that's really a kludge, not a solution because it doesn't explain what was going wrong or how to fix it properly.
The actual solution is quite simple, though not obvious. The official Slackbuild for gdk-pixbuf uses the configuration flag "--enable-introspection". When you use this flag, you also need to have shared-mime-types installed in order for file format recognition to work, and I didn't. Remember, this wasn't a standard Slackware; it was my minimalist hand-rolled version, Slackbody. Of course the gdk-pixbuf package that I built by hand didn't have this flag set so it worked even without shared-mime-types.
Here is the relevant passage from the gdk-pixbuf documentation:
"gdk-pixbuf will use GIO for mime type detection if possible. For this to work, shared-mime-info needs to be installed and XDG_DATA_DIRS set accordingly at configure time. Otherwise, gdk-pixbuf falls back to its built-in sniffing implementation."
It's nice to be able to wrap this up.