Trouble binding print screen in XMonad - xorg

Question

I'm trying to bind the print screen key in Xmonad, but it doesn't seem to work.
I have the following code in my xmonad.hs:
myKeys conf#(XConfig {XMonad.modMask = modm}) = M.fromList $
[
...
, ((0, xK_Print), spawn "scrot -q 1 $HOME/pictures/screenshots/%Y-%m-%d-%H:%M:%S.png")
...
]
However, if I press print screen nothing happens (the file isn't there). Replacing xK_Print with xK_F12 works.
Using xev, I found the keysym of print screen:
KeyPress event, serial 32, synthetic NO, window 0x1a00001,
root 0x90, subw 0x0, time 8532454, (593,435), root:(594,454),
state 0x10, keycode 218 (keysym 0xff61, Print), same_screen YES,
XKeysymToKeycode returns keycode: 107
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False
KeyRelease event, serial 32, synthetic NO, window 0x1a00001,
root 0x90, subw 0x0, time 8532501, (593,435), root:(594,454),
state 0x10, keycode 218 (keysym 0xff61, Print), same_screen YES,
XKeysymToKeycode returns keycode: 107
XLookupString gives 0 bytes:
XFilterEvent returns: False
which seems to be 0xff61. But using this instead of xK_Print doesn't work as well (I checked with ghci and xK_Print is just an alias for 0xff61).
How can I bind the print screen key to something?
Of course I can use another key for the job, but it feels silly not using print screen to take a screenshot.

Answer 1

Try changing the $HOME to a full, hardcoded path. I think that when xmonad.hs runs, it doesn't have access to all the environment variables.
To debug this, do the following:
Map that key to something that you know works (i.e., duplicate the key binding that you used for another, working key).
If that works, then you know that Xmonad can "see" the key.
Now map that key to what you want, but send any errors to a file. E.g.,
.... spawn "scrot -q 1 $HOME/pictures/screenshots/%Y-%m-%d-%H:%M:%S.png > /home/me/errors.log 2>&1")
See what errors you get, and deal with them.