Slitherine

Clicking on silk shows silk in some regions but not all, in Cairo there is silk but it is not shown.
Guess that is connected with how many trade goods are shown in the regions and it doesn't show up on trade map (shift-2) either.
To get it to work the goods will have to be in the shown goods, meaning the order of chosen goods should be dynamically changed when clicking to show.

btw. where in the code can I see how this is done or is it in the engine?