Looks up an icon in an icon theme for a particular window scale, scales it to the given size and renders it into a pixbuf. This is a convenience function; if more details about the icon are needed, use IconTheme.lookupIcon followed by IconInfo.loadIcon.
Note that you probably want to listen for icon theme changes and update the icon. This is usually done by connecting to the GtkWidget::style-set signal. If for some reason you do not want to update the icon when the icon theme changes, you should consider using Pixbuf.copy to make a private copy of the pixbuf returned by this function. Otherwise GTK+ may need to keep the old icon theme loaded, which would be a waste of memory.
the name of the icon to lookup
the desired icon size. The resulting icon may not be exactly this size; see IconInfo.loadIcon.
flags modifying the behavior of the icon lookup
the rendered icon; this may be a newly created icon or a new reference to an internal icon, so you must not modify the icon. Use g_object_unref() to release your reference to the icon. NULL if the icon isn’t found.
GException on failure.