pdf: Reimplement 'de facto' tooltip feature keeping the ABI
Structs in EvForm are not opaque, and commit e2ad8611 introduced a ABI change. However, having a private structure helps solve the issue without breaking the ABI.
Ideally, every struct should be opaque.
@nbenitez what do you think about this alternative solution?
I only hesitate whether make them properties or not.
@chpe do you have any opinion on this?