Dialog: Emit focusin and focusout signals

[tbabej]

Emit signals on change of focus to enable hooking handlers for focusin and focusout events on particular widgets.

[pfalcon]

Thanks, but why?

[tbabej]

In my particular case, I am designing a dialog where "hovering" over a particular checkbox should display help text explaining that particular choice in more detail - which is implemented through a label text.

[pfalcon]

Thanks for explanation, that indeed may be useful in some cases. But there's no real mouse "hovering" in TUI (usually), and there's other known patterns to achieve that functionality (e.g. pressing F1 in a field to get a help dialog). So, I'm marking this as a "contrib", so the people interested in this functionality could add/pick it up.

[pfalcon]

Btw, I'm planning to make some backwards-incompatible changes: #59. Feedback whether that should be 1.3/1.4 or 2.0 is welcome.