Re: metafun

[Piotr Kopszak <kopszak@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 <adityam@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
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