Can Fvwm emit a string to an app on a keypress ?

I’d like to fill in login prompts (firefox) by pressing a function key (maybe with modifiers). Is that something that can be done in Fvwm?

Look for an application called “xse”. You’ll also want to make liberal use of “xcb”, most likely. (Effectively you can do it just by emulating the pressing of Shift + Ins).

– Thomas Adam