Barrier should not be visually on top of child widget

[stargazing-dino]

A custom user built barrier shouldn't visually obscure the child widget. This doesn't really match with what a user would expect and naturally bars a lot of users from using the tooltip as a sort of coach or app guide such as the following:

A couple of possibilities to get what we want would be to:

1. shadermasks (credit caseycrogers)
2. a duplicate overlay entry of the child
3. a clip mask or user defined clip mask

or something else

coachmaker does something similar so it might help to get inspiration from them.