Smallest lock for X?

[Jeremy C. Reed]

How to take over the X so can't escape it?

I am looking for the smallest X lock implementation. xlockmore without GL, 
TrueType, gtk, and XPM pixmaps is still over 1.2 MB. I don't want all its 
features.  I just want to disable typing and pointer for any other X 
clients until I authenticate for a "lock".

I have started looking at xlockmore code, but haven't found how it takes 
over the X yet.

Any suggestions?

Or what is the smallest X lock?

As for the screensaver, X's own built-in screensaver is good enough for 
me. I just want a way to lock it too.

  Jeremy C. Reed

p.s. My four-year-old opened my laptop and started typing, moving, and 
closing windows :)