[Fedora-packaging] desktop file icon/pixmap locations

[Chuck Anderson]

Where should icons for desktop files be stored?  Some packages use 
/usr/share/pixmaps.  Others use subdirectories under 
/usr/share/pixmaps (some directories are unowned too).  Some use a 
private directory under /usr/share/<name>.  Still others use 
/usr/share/icons/.

Icon=/usr/share/sane/xsane/xsane-logo.xpm

>rpm -ql gnome-utils | grep /usr/share/pixmaps
/usr/share/pixmaps/gsearchtool/thumbnail_frame.png
file /usr/share/pixmaps/gsearchtool is not owned by any package

How should the icon be referred to in a desktop file?  Some use 
absolute paths, others no path at all.  desktop-file-install complains 
if there is a relative or partial path.

Icon=/usr/share/system-config-lvm/pixmaps/lv_icon.png
Icon=/usr/share/system-config-selinux/system-config-selinux.png

Some desktop file icons don't use an extention, but some do:

Icon=accessories-calculator
Icon=accessories-dictionary.png

It looks like the majority of the desktop files on my F9 system are 
using the form without an extension.

All of this is confusing.  For new applications, what should they use?  
What are the semantics for the various syntaxes that are used?  What 
should be done for upstream packages that have icons?  What if they 
are in xpm format rather than png?

Thanks.