changing dimensions of the page in a document

[Uwe Koloska <uwe.koloska@mailbox.tu-dresden.de>]

Hello,

I tried to make a screen document and some pages shall receive a different 
layout like in demos-en.  I know (and Hans and the manual has said) that 
setting margin and margindistance doesn't affect backspace, but the 
following document shows the contrary.  What's going wrong here?

\setuppapersize
  [S6][S6]

\setuplayout 
  [header=0cm,
   topspace=.5cm,
   backspace=.5cm,       % (1)
   leftmargin=0cm,
   margindistance=.5cm, 
   rightmargin=0cm,
   rightedge=3cm,
   width=fit]

\showframe

\starttext

\section{Eins}
\input tufte

\page
\setuplayout
  [leftmargin=.8cm,backspace=1.7cm,leftmargindistance=.4cm] % (2)
%\setuplayout
% [leftmargin=.7cm,backspace=1.7cm,leftmargindistance=.5cm] % (3)
\section{Zwei}
\input hofstadter

\stoptext

This works ok -- but if I change only one parameter of leftmargin or 
backspace in (1) or (2) the layout jumps.  And if I use (3) instead of (2) 
all my thoughts about a relationship between the settings went away :-|

If I change
  \setuplayout[leftmargin=.5cm,backspace=1.3cm,leftmargindistance=.3cm]
to
  \setuplayout[leftmargin=.4cm,backspace=1.3cm,leftmargindistance=.3cm]
in the example, the layout frames jump ...

  |  |      text     |  |edge| |
  |   |mar|  | text | |edge|   |

this is only a rough scetch.  If it doesn't jump for you, I can give you 
the resulting pdf that shows it ...

Hope someone can clarify this!
Uwe

-- 
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