ZDoom

What does this do?
It allows taking screenshots when a menu is open. Works in main menu, option menus, Strife dialogs, etc.



Limitations:
L1. "Captured screenshot..." message doesn't appear if the level is not started yet. The screen shot is still taken.
L2. Some keys are not supported:
L2.1. because they are used by menus: arrow keys, Enter, etc.
L2.2. because I didn't found how to process them: keypad keys.
L3. If screenshot key is bound to a key that also has a meaning for main menu (for example, 'N' selects "New Game"), first press of this key do the menu action, and the second press will make a screen shot.

Taking screenshots in menus has been mentioned several times by now: 1, 2.

This is not a clean solution. I'm almost sure that this won't be accepted due to this implementation's hacky nature.
Still, this can be a starting point for a discussion.

Pull request here.

Should I try to improve this, or it's a lost case?

Less of a lost case and more of devs just being busy or have other priorities.
Just ask Marisa.

But this certainly is intriguing!

I've posted a message @GitHub. The feature looks interesting. Why do you say is hacky?

drfrag wrote: You should add a default case to the switch to return 0. You don't need the Fx function keys, those are used for something else in game. For the keys with a different function in menus i'd ignore them, the screenshot should not be taken. Couldn't you add a Printf to print the message when in menus?

Since it seems there was no interest and also there was a conflict i've gone ahead and merged it as is.
It's GPL v3 so yes i've "sucked" the code . Hope there's no offense.
It required some low level support for the print screen key and i've made some cosmetic changes too. You still could make another PR to enhance it.
https://github.com/drfrag666/gzdoom/commits/g3.3mgw

I didn't merge the code because it was unfinished and 'dirty' according to the author. That's a first grade guarantee that I won't use it.