[NTG-context] metafun 2

[Adam Reviczky]

Hi Hans,

One MetaPost feature that I was looking forward to is the ability to create
a fill between two shapes.
Something like a difference function of two path's.

For logos I use the workaround with creating a path alongside the excluded
areas but it is always cumbersome.

I have briefly mentioned it back here:
https://mailman.ntg.nl/pipermail/ntg-context/2011/056910.html

Just for illustration purposes, if I wanted to fill the area in between two
circles:

*path p ;
**p := fullcircle scaled 1cm ;
**path q ;
**q := fullcircle scaled .5cm ;
*

Instead of creating a new path along both circles with:


*r := p -- reverse q -- cycle ;*

It would be nice to have something like:

*fill p excluding q ;*

or something like that.

I mainly have use-cases for differences in shapes, but filling the
intersection of two shapes would be the same idea.

Thanks,
Adam


On Wed, Aug 14, 2019 at 10:57 AM Hans Hagen <j.hagen at xs4all.nl> wrote:

> Hi,
>
> In the process of providing an additional (more abstract) interface to
> some of the old and also new MetaFun code we wonder what kind of
> features users would like to see.
>
> http://www.pragma-ade.com/general/magazines/mag-1104-mkiv.pdf
>
> As a teaser I uploaded a MyWay document that shows some of what is
> coming. All is experimental but it shows the direction. We're talking
> ConTeXt LMTX here. For instance,
>
>      draw lmt_outline [
>          content       = "hello",
>          kind          = "reverse",
>          fillcolor     = "darkred",
>          drawcolor     = "darkblue",
>          rulethickness = 1/2,
>      ] ysized h shifted (3.75h,-1.25h) ;
>
> Wraps all the outline drawing in one macro with a set of options (there
> will be xml interface definitions for that). Or take:
>
>      draw lmt_followtext [
>          content = "How well does it work {\bf 1}! ",
>          path    = (fullcircle scaled 4cm),
>          trace   = true,
>          spread  = true,
>      ] ysized 5cm ;
>
> which is an easier interface to text along a curve. Arrows can be drawn
> with
>
>      draw lmt_arrow [
>          kind        = "draw",
>          location    = "middle",
>          alternative = "curved",
>          path        = fullcircle
>              scaled  3cm
>              shifted (3.5cm,0cm),
>      ] withcolor "darkblue" ;
>
> but of course the low level interface with its many variables for
> tweaking stays around. Other examples are shown in the mentioned document.
>
> So the question is: What do you miss in metapost support? Of course it
> should fit within the concept, so 'artistic freehand drawings' is not
> something that is likely to get interfaced. We are particularly
> interested in educational applications, if only because ConTeXt started
> out that way.
>
> Hans
>
>
>
> -----------------------------------------------------------------
>                                            Hans Hagen | PRAGMA ADE
>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>         tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
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