Re: Symmetrical layer positioning?

[Giuseppe Bilotta <gip.bilotta@iol.it>]

Monday, July 16, 2007 Giuseppe Bilotta wrote:

> Monday, July 16, 2007 Aditya Mahajan wrote:

>> On Mon, 16 Jul 2007, Giuseppe Bilotta wrote:

>>> 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?

>> You can possible use setups and use \doifoddpageelse to set the
>> layers. See

>> http://archive.contextgarden.net/thread/20061102.171506.2fa793e2.en.html

> Thanks a lot. I don't know if using presets is actually
> going to reduce the coding, though.

> 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

> \definelayer[title][
>   x=\dimexpr\backspace+\wdall-\wdtit,
>   y=\topspace,
>   width=\wdtit,
>   height=\httit,
>   state=repeat,
>   doublesided=true,
> ]

> \setuplayer[lefttitle][
>   x=\backspace,
> ]

> \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]


> 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

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