Re: Bug in lmt_arrow

[Hans Hagen via ntg-context <ntg-context@ntg.nl>]

On 11/14/2021 4:33 AM, Aditya Mahajan via ntg-context wrote:
> Hi,
> 
> There is a bug in lmt_arrow. If given a "non-cycle" path, lmt_arrow completes the cycle.
> 
>      \starttext
> 
>      \startMPcode
>        newpath p;
>        ahfactor := 5;
>        p := origin .. (1cm, 1cm) .. (2cm, 0);
>        draw lmt_arrow
>             [
>               path = p,
>               location = "percentage",
>               percentage = 50,
>               alternative = "curved",
>             ]
>             withpen pencircle scaled 1bp;
>      \stopMPcode
>      \stoptext
> 
> With 2021.11.11, I get the attached file. Note that lmt_arrow has drawn the "cycle" version of the path, even though p does not have a cycle.
> 
> I have looked at the code and cannot figure out why this is happening.

it happens in the 'direct' variant (metapost.registerdirect) where a 
boolean is passed as signal and that boolean then is also picked up by 
the (shared) path injector as (old school) signal that a path is closed 
while it should instead consutl the closed field in a path table (sounds 
more complex than it is)

so in the end it is a nasty side effect of the fast inject code path 
(shared function with different stack values; i'll probably have to 
ditch a "low level backward compatibility feature no one uses anyway" 
some day)

i uploaded a fix that you can test when the bins are compiled at

	https://build.contextgarden.net/#/waterfall?tags=c.luametatex

new bins then in:

	https://dl.contextgarden.net/build/luametatex/

(fyi: in the mp code you see that the path p is 'get' from the lua end 
where it got passed to by parameter)

(interesting that it didn't show up sooner, maybe most users have closed 
paths and/or most lmt_ features used closed paths)

Hans

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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