Comment 2 for bug 44264

I confirm this bug using dapper 20060526 and gnome-system-monitor 2.14.3-0ubuntu1.

I have investigated this issue for gaim icon, the same should also apply for xchat icon.

The icon that is being used for gaim by g-s-m is /usr/share/icons/gnome/24x24/apps/gaim.png

The icon used in gnome icon theme is the same as the one provided by gaim upstream. According to the freedesktop.org icon theme specification standard icons for 3rd party applications belong in /usr/share/icons/hicolor. That's probably why you filed a bug to hicolor-icon-theme.

Suggested solution:

1) Remove /usr/share/icons/gnome/24x24/apps/gaim.png
=> bug task for package gnome-icon-theme
2) update the icon cache with following command: sudo gtk-update-icon-cache -f /usr/share/icons/gnome

3) According to the icon theme specification we should at least have a 48x48 png icon, therefore add 48x48 version of gaim.png found in /usr/share/pixmaps/gaim.png to /usr/share/icons/hicolor/48x48/apps.
=> Should be provided by package hicolor-icon-theme or gaim package itself.

4) change /usr/share/icons/hicolor/index.theme to contain the following:

[48x48/apps]
Size=48
Context=Applications
Type=Scalable
MinSize=16
MaxSize=48

This will make 48x48 png icon for gaim or other applications downscalable to 16x16 pixels for window list icons and 24x24 for menus and panel icons.
There is no need to provide 16x16, 22x22 or 24x24 versions in the theme when they are just downscales of the 48x48 icon, the downscaling will be done by the icon theme implementation of gnome/kde and gives the same result.

5) update the icon cache with following command: sudo gtk-update-icon-cache -f /usr/share/icons/hicolor

6) Start gnome-system-monitor and look at the size of gaim icon, it will be 16x16 now.