When you click a link in a field, that sends a link event to the field. If the field doesn’t handle it, it bubbles up to the card the field is on - in this case, the contraption’s prototype. If the prototype doesn’t handle the event, it bubbles up to the default event handlers, including this one:
on link x do
go[x]
end
If you want clicking a link to anything other than go straight to the target, you have to add your own on link... handler to interrupt the default handling.
The easiest thing is just to put it into the prototype’s script, especially if you always want clicking a link in one of these text fields to display an alert before moving on, something like:
on link target do
alert["You have clicked a link. This will be reported to the authorities."]
go[target]
end
If you want different contraptions to have different behaviour, you’ll want the link event inside the prototype to become a link event on the contraption, by putting something like this in the prototype’s script:
on link target do
# forward the event to the contraption
card.event["link" target]
end
Then you can put different on link... handlers on different copies of the contraption, for different behaviour.