This little hack for X turns the spacebar key into another control key when used in combination.
When used alone, it behaves like the ordinary space bar on the key release event.
Especially useful with Emacs.

compile with:
g   -o Space2Ctrl Space2Ctrl.cpp -L/usr/X11R6/lib -lX11 -lXtst

To install libx11:
in Ubuntu: sudo apt-get install libx11-dev

To install libXTst:
in Ubuntu: sudo apt-get install libxtst-dev

Needs module XRecord installed. To install it, add line Load "record" to Section "Module" in /etc/X11/xorg.conf like this:

Section "Module"
	Load  "record"
EndSection