Re: [NTG-context] Symmetrical layer positioning?

17 Jul 2007

      Monday, July 16, 2007 Giuseppe Bilotta wrote:
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Monday, July 16, 2007 Aditya Mahajan wrote:
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On Mon, 16 Jul 2007, Giuseppe Bilotta wrote:
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Hello all,
is there a "secret power switch" to tell ConTeXt that a
particular layer has different positioning depending on
wether it's on a left or right page?
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You can possible use setups and use \doifoddpageelse to set the
layers. See
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http://archive.contextgarden.net/thread/20061102.171506.2fa793e2.en.html
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Thanks a lot. I don't know if using presets is actually
going to reduce the coding, though.
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In the mean time, I've found that layers have a doublesided
option. This apparently allows you to override the
left/right settings of a layer, so I tried
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\definelayer[title][
  x=\dimexpr\backspace+\wdall-\wdtit,
  y=\topspace,
  width=\wdtit,
  height=\httit,
  state=repeat,
  doublesided=true,
]
...
\setuplayer[lefttitle][
  x=\backspace,
]
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\definelayer[desc][
  x=\backspace,
  y=\topspace,
  width=\wddesc,
  height=\htdesc,
  state=repeat,
  doublesided=true,
]
...
\setuplayer[leftdesc][
  x=\dimexpr\backspace+\wdall-\wddesc,
]
...
\definelayer[figs][
  x=\dimexpr\backspace+\wdall-\wdfig,
  y=\dimexpr\topspace+\makeupheight-\htfig,
  width=\wdfig,
  height=\htfig,
]
...
\setuplayer[leftfigs][
  x=\backspace,
]
...
\setupbackgrounds[page][background={color,title,desc,figs},backgroundcolor=elux-ultralight]
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However, the 'main' setup is always used, the left one is
never used. Am I doing something wrong?
Apparently, I mistook what the doublesided option does for
layers. I've currently solved the problem in the following
way:

\unexpanded\def\titlexpos{%
  \ifodd\realpageno\dimexpr\wdinside+\wdall-\wdtit\else\wdinside\fi
}

\definelayer[title][
  x=\titlexpos,
  y=\topspace,
  width=\wdtit,
  height=\httit,
]

\unexpanded\def\descxpos{%
  \ifodd\realpageno\wdinside\else\dimexpr\wdinside+\wdall-\wddesc\fi
}

\definelayer[desc][
  x=\descxpos,
  y=\topspace,
  width=\wddesc,
  height=\htdesc,
]

\unexpanded\def\figsxpos{%
  \ifodd\realpageno\dimexpr\backspace+\wdall-\wdfig\else\wdinside\fi
}

\definelayer[figs][
  x=\figsxpos,
  y=\dimexpr\topspace+\makeupheight-\htfig,
  width=\wdfig,
  height=\htfig,
]

\setupbackgrounds[page][background={color,title,desc,figs},backgroundcolor=elux-ultralight]

However, this solution doesn't strike me as particularly
elegant. I've seen in page-lyr.tex that support for
left/right layers is currently in progress, but if I read
the code correctly it just creates three layers (name,
leftname, rightname) and they have to be filled
individually. It would be nice to have a simpler interface
to repeated layers with position recalculated on each page.

-- 
Giuseppe "Oblomov" Bilotta