void gtk_icon_source_set_size ( GtkIconSource* source, GtkIconSize size )
Sets the icon size this icon source is intended to be used with.
Setting the icon size on an icon source makes no difference
if the size is wildcarded. Therefore, you should usually
gtk_icon_source_set_size_wildcarded() to un-wildcard it
in addition to calling this function.
Deprecated since: 3.10