Add percentage if coverage and maybe direction

[padrino-x]

Would be great if it was possible to set how much of the screen is covered and maybe if top/down or bottom/up.
Mabey this could even be achieved when activating FS using an URI(? that the term?).
I use different apps where it would be nice to cover only parts of the screen.
Then I could use automated fitting degrees of darkness. =)