[maemo-developers] rx-51 xkb file: how does FOUR_LEVEL type work?

[From: Denis DeLaRoca]

On Mon, 1 Feb 2010, Arkady Glazov wrote:

> N900 hardware keyboard does not support simultaneous pressing three 
> keys. You must "lock" function key by double press Fn and after them 
> shift+ letter

Understood! But notice that for my sample xkb config, to print the "[" 
char that I slotted at the 4th level, I would have to:

 	a) lock Fn (by double press)
 	b) shift (by single press)
 	c) type "h" key once

but it doesn't work. However, let's say I had programmed my "c" key as

 	key <AB03>	{ [c, C, ccedilla, Ccedilla ] };

then the "ç" (lowercase cedilla) is accessible via "Fn" and "Ç" (uppercase 
cedilla) is accessible via "locked-Fn" plus "Shift-c."

So why does FOUR_LEVEL, or its variants, appear to only work for lowercase 
/ uppercase character pairs but not for any other character combinations. 
Specifically, is the Hildon layer enforcing this behaviour?

--denis