This code comes from e90ec741, copied directly from gpdf (and that happened 18 years ago). The purpose of this code seems to have been to provide aliases to icons (so they could be called from 2 different names), and serve a similar purpose as GtkIconTheme does today.
The whole concept of GtkIconFactory, GtkIconSet, and GtkIconSource was deprecated in GTK 3.10 back in 2013, so simply get rid of it. This has no impact in Evince, since the icons can still be found through GtkIconTheme.
To make sure that this is a non-breaking change in libevview, rename stock_filters-invert icon. The said icon is exported in the API through
and the internal name "stock_filters-invert" was never documented. Therefore, renaming the icon to "inverted" as exposed by the API should still make the icon available to consumers (via EV_STOCK_INVERTED_COLORS), without the need to use GtkIconFactory.
Relates !302 (closed)