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.