[NTG-context] Poster with layers

[Eckhart Guthöhrlein]

\setlayerframed is great - no need to define a layer for each piece of
content. That was new to me.
Now, to make sure that I have understood correctly by comparing code and
output:

> \setlayerframed
>   [page]
>   [preset=lefttop]
>   [align=normal,
>    width=.25\paperwidth,
>    frame=off]
>   {\getbuffer}

This will be placed with its top left corner at the top left edge of the
page.

> \setlayerframed
>   [page]
>   [offset=.2\paperwidth,
>    preset=righttop]
>   [width=.2\paperwidth,
>    align=normal]
>   {\getbuffer}

With the top right corner at the top right edge of the page, with an
offset (both x and y) of 0.2\paperwidth.

> \setlayerframed
>   [page]
>   [preset=middle]
>   [offset=1cm]
>   {\externalfigure[whatever][width=4cm,height=5cm]}

Centered on the page.

Ok. But it doesn't solve my problem. What I want to do is:
- Place X somewhere.
- Place Y with its top left corner 2cm below bottom center point of X.
	(Or some other reference point among tl, t , tr, l, c, r, bl, b, br.)

You see, I don't know exactly what goes into the layers and how big it
is, but I want to place someting else exactly beneath it.

Can this be done?

-- 
Eckhart