P.S.
For your conveniance, the minimal example:
\startMPpositiongraphic{mypos:arrow}
pair c[] ;
initialize_box(\MPpos{\MPvar{self}});
c[1] := cxy ;
initialize_box(\MPpos{\MPvar{to}});
c[2] := cxy ;
drawarrow c[1] -- c[2] withpen pencircle scaled 2bp ;
\stopMPpositiongraphic
\startpositionoverlay{arrow}
\setMPpositiongraphic{X-1}{mypos:arrow}{to=X-2}
\setMPpositiongraphic{X-2}{mypos:arrow}{to=X-3}
\stoppositionoverlay
\defineoverlay[arrow][\positionoverlay{arrow}]
\setupbackgrounds[page][background=arrow]
\starttext
\section {Anchors and layers}
In a previous section we saw that some \hpos{X-1}{words} were
\hpos{X-2}{circled} and connected by an \hpos{X-3}{arrow}.
As with most things in \CONTEXT, marking these words is separated
from declaring what to do with those words. This paragraph is keyed
in as:
\stoptext
2016-03-24 18:23 GMT+01:00 Piotr Kopszak <kops...@gmail.com>:
> Hello list,
>
> The solution shown here no longer works with recent beta (indeed, it
> probably ceased to work some time ago). How should it be corrected?
>
> Best
>
> Piotr
>
> 2010-10-24 0:14 GMT+02:00 Aditya Mahajan <adit...@umich.edu>:
>> On Sat, 23 Oct 2010, Herbert Voss wrote:
>>
>>> It is a hard job to understand how all works ...
>>
>>
>> I agree. That chapter is confusing if you do not know already how the
>> mechanism
>> works.
>>
>>> I tried to create the first example of the
>>> documentation "Page 257 Anchors and layers",
>>> but failed with mkii and iv. The page is created,
>>> but without the graphical elements. Not using
>>> \startbuffer--\stopbuffer makes no difference.
>>
>>
>> You are simply setting the positions. You also need to tell ConTeXt to do
>> something with the positions.
>>
>> 1. First define a position graphic that does something with the anchors that
>> it is passed.
>>
>> \startMPpositiongraphic{mypos:arrow}
>> pair c[] ;
>> initialize_box(\MPpos{\MPvar{self}});
>> c[1] := cxy ;
>> initialize_box(\MPpos{\MPvar{to}});
>> c[2] := cxy ;
>> drawarrow c[1] -- c[2] withpen pencircle scaled 2bp ;
>> \stopMPpositiongraphic
>>
>> cxy is the center of the box. See the defn of initialize_box in mp-core.mp
>> for other values. I wish these were better documented.
>>
>> 2. Then define a position overlay that specifies the relation between the
>> anchors.
>>
>> \startpositionoverlay{arrow}
>> \setMPpositiongraphic{X-1}{mypos:arrow}{to=X-2}
>> \setMPpositiongraphic{X-2}{mypos:arrow}{to=X-3}
>> \stoppositionoverlay
>>
>>
>> 3. Define an overlay that is mapped to MP position overlay.
>>
>> \defineoverlay[arrow][\positionoverlay{arrow}]
>>
>> 4. Hook the overlay as a page background
>>
>> \setupbackgrounds[page][background=arrow]
>>
>> 5. Then everything will work.
>>
>> \starttext
>>
>> \section {Anchors and layers}
>>
>> In a previous section we saw that some \hpos{X-1} {words} were
>> \hpos{X-2}{circled} and connected by an \hpos{X-3} {arrow}.
>> As with most things in \CONTEXT, marking these words is separated
>> from declaring what to do with those words. This paragraph is keyed
>> in as:
>>
>> \stoptext
>>
>> Aditya
>> ___________________________________________________________________________________
>> 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
>> ___________________________________________________________________________________
>
>
>
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___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the
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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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