Layers, overlays

Layers, overlays

[Procházka Lukáš Ing. - Pontex s. r. o.]

Hello,

I'd like to ask two questions which appeared on topic "Layer vs. overlay".

Q1: What does \tightlayer[...] exactly do? (No item on wiki.)

Q2: Why some layer properties are specified on \definelayer (beforetext: width=\overlaywidth,height=\overlayheight) and some during overlay setups (beforetext: preset=righttop)? - Related code given before:

----
\starttext
   \definelayer  [beforetext][width=\overlaywidth,height=\overlayheight]
   \defineoverlay[beforetext][{\setups[beforetext]\tightlayer[beforetext]}]

   \startsetups[beforetext]
     \setlayer[beforetext][preset=righttop]
       {\framed[width=2in]{foo}}
   \stopsetups

   bar
\stoptext
----

TIA.

Best regards,

Lukas


-- 
Ing. Lukáš Procházka [mailto:LPr@pontex.cz]
Pontex s. r. o.      [mailto:pontex@pontex.cz] [http://www.pontex.cz]
Bezová 1658
147 14 Praha 4

Tel: +420 244 062 238
Fax: +420 244 461 038

___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________

Re: Layers, overlays

[Sietse Brouwer]

Hello Lukáš,

I don't understand layers and overlays. This is what I could learn
about \tightlayer from the source; I hope that reviving your question
will help somebody else actually answer it.

\tightlayer is defined in pack-lyr.mkiv.

\unexpanded\def\tightlayer[#1]%
  {\hbox
     {\def\currentlayer{#1}% todo: left/right
      \setbox\nextbox\emptybox       % hoogte/breedte are
\wd\nextbox/\ht\nextbox
      \hsize\layerparameter\c!width  % \overlaywidth   = \hsize
      \vsize\layerparameter\c!height % \overlaywheight = \vsize
      \composedlayer{#1}}}

The last command flushes the layer we are about to place:
\composedlayer{x} is syntactic sugar for \flushlayer[x]. (Braces vs.
brackets.)

So it seems that what \tightlayer does is create a layer object
exactly as large as its contents? What this is good for, and how it
relates to overlays, I do not know.

Good luck!

--Sietse
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : http://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________