Icon sets have a list of GTK2.IconSource, which they use as base icons for
rendering icons in different states and sizes. Icons are scaled, made to
look insensitive, etc. in render_icon(), but GTK2.IconSet needs base images
to work with. The base images and when to use them are described by a
GTK2.IconSource.
This function copies source, so you can reuse the same source immediately
without affecting the icon set.
An example of when you'd use this function: a web browser's "Back to
Previous Page" icon might point in a different direciton in Hebrew and in
English; it might look different when insensitive; and it might change size
depending on toolbar mode (small/large icons). So a single icon set would
contain all those variants of the icon, and you might add a separate source
for each one.
You should nearly always add a "default" icon source with all fields
wildcarded, which will be used as a fallback if no more specific source
matches. GTK2.IconSet always prefers more specific icon sources to more
generic icon sources. The order in which you add the sources to the icon
set does not matter.
GTK2.IconSet