MetaPost label direction prefix

MetaPost label direction prefix

[Marco Patzer]

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Hi,

what is the reason the label direction prefix variables (rt, bot,
llft, etc.) are prefixed with mpfun_ in MkIV (mp-mlib.mpiv)? When
new directional prefixes are being defined it fails when mplib is
used unless the mpfun_ prefix is added. And likewise, code using the
mpfun_ prefix fails on traditional MetaPost.

Is this prefix required? It breaks old code and required a branch in
every new project. And I don't really see a reason for this
incompatibility. Here is an example defining a new direction “foo”:

\starttext
  \startMPcode
    label("first", origin);

    %% MkIV
    %% pair mfun_laboff.foo ; mfun_laboff.foo := (.5,-1) ;
    %% mfun_labxf.foo := mfun_labyf.foo := 1 ;

    %% MkII
    pair laboff.foo ; laboff.foo := (.5,-1) ;
    labxf.foo := labyf.foo := 1 ;

    label.foo("second", origin);
  \stopMPcode
\stoptext

Marco

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Re: MetaPost label direction prefix

[Hans Hagen]

On 8/23/2013 11:42 AM, Marco Patzer wrote:
> Hi,
>
> what is the reason the label direction prefix variables (rt, bot,
> llft, etc.) are prefixed with mpfun_ in MkIV (mp-mlib.mpiv)? When
> new directional prefixes are being defined it fails when mplib is
> used unless the mpfun_ prefix is added. And likewise, code using the
> mpfun_ prefix fails on traditional MetaPost.

So is anyone using mkiv still using MkII?

> Is this prefix required? It breaks old code and required a branch in
> every new project. And I don't really see a reason for this
> incompatibility. Here is an example defining a new direction “foo”:

The MpIV code has namespace protection. Why run traditional in MkIV?

> \starttext
>    \startMPcode
>      label("first", origin);
>
>      %% MkIV
>      %% pair mfun_laboff.foo ; mfun_laboff.foo := (.5,-1) ;
>      %% mfun_labxf.foo := mfun_labyf.foo := 1 ;
>
>      %% MkII
>      pair laboff.foo ; laboff.foo := (.5,-1) ;
>      labxf.foo := labyf.foo := 1 ;
>
>      label.foo("second", origin);
>    \stopMPcode
> \stoptext

I wasn't aware of users defining extra ones. I'll add this:

\starttext
   \startMPcode
     label("first", origin);

     if known mfun_laboff :

         vardef installlabel@\# (expr type, x, y, offset) =
             numeric mfun_labtype @\# ; mfun_labtype @\# := type ;
             pair    mfun_laboff  @\# ; mfun_laboff  @\# := offset ;
             numeric mfun_labxf   @\# ; mfun_labxf   @\# := x ;
             numeric mfun_labyf   @\# ; mfun_labyf   @\# := y ;
         enddef ;

     else :

         vardef installlabel@\# (expr type, x, y, offset) =
             numeric labtype @\# ; labtype @\# := type ;
             pair    laboff  @\# ; laboff  @\# := offset ;
             numeric labxf   @\# ; labxf   @\# := x ;
             numeric labyf   @\# ; labyf   @\# := y ;
         enddef ;

     fi ;

     installlabel.foo ( 0, 1, 1, (.5,-1) ) ;

     label.foo("second", origin);
   \stopMPcode
\stoptext


-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
     tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
-----------------------------------------------------------------
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___________________________________________________________________________________

Re: MetaPost label direction prefix

[Marco Patzer]

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On 2013–08–23 Hans Hagen wrote:

> >Is this prefix required? It breaks old code and required a branch in
> >every new project. And I don't really see a reason for this
> >incompatibility. Here is an example defining a new direction “foo”:
> 
> The MpIV code has namespace protection. Why run traditional in MkIV?
>
> 
> >\starttext
> >   \startMPcode
> >     label("first", origin);
> >
> >     %% MkIV
> >     %% pair mfun_laboff.foo ; mfun_laboff.foo := (.5,-1) ;
> >     %% mfun_labxf.foo := mfun_labyf.foo := 1 ;
> >
> >     %% MkII
> >     pair laboff.foo ; laboff.foo := (.5,-1) ;
> >     labxf.foo := labyf.foo := 1 ;
> >
> >     label.foo("second", origin);
> >   \stopMPcode
> >\stoptext
> 
> I wasn't aware of users defining extra ones. I'll add this:

Probably not many users will tinker with custom label directions,
but MetaPost package authors do. Some packages like piechartmp¹
internally use laboff.foo and the mpfun_ prefix breaks those
packages. They work in traditional MetaPost, plain TeX, LaTeX and
ConTeXt MkII, but since mplib uses the mpfun_ prefix, those packages
are broken in MkIV.

> […]
>     installlabel.foo ( 0, 1, 1, (.5,-1) ) ;

This does not fix the problem since it only *defines* the correct
variant, it doesn't help *using* those values. If the label values
are being changed in the package one still has to branch out to
support both variants. And even if there was an abstraction
assisting to *use* the laboff values, all MetaPost packages
tinkering with laboff would need to be adjusted. I can't imagine
that to happen. Here's what the piechartmp package is doing, for
instance:

  if laboff.@# = (-3,-3): % auto justification

  […]
    laboff.auto := ((cosd l),(sind l)) ;
    labxf.auto  := ((cosd l) - 1) / -2 ;
    labyf.auto  := ((sind l) - 1) / -2 ;

  […]

This code is being executed every time a label is typeset.

Marco

¹ http://mirrors.ctan.org/graphics/metapost/contrib/macros/piechartmp/piechartmp.mp

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Re: MetaPost label direction prefix

[Hans Hagen]

On 8/23/2013 3:14 PM, Marco Patzer wrote:
> On 2013–08–23 Hans Hagen wrote:
>
>>> Is this prefix required? It breaks old code and required a branch in
>>> every new project. And I don't really see a reason for this
>>> incompatibility. Here is an example defining a new direction “foo”:
>>
>> The MpIV code has namespace protection. Why run traditional in MkIV?
>>
>>
>>> \starttext
>>>    \startMPcode
>>>      label("first", origin);
>>>
>>>      %% MkIV
>>>      %% pair mfun_laboff.foo ; mfun_laboff.foo := (.5,-1) ;
>>>      %% mfun_labxf.foo := mfun_labyf.foo := 1 ;
>>>
>>>      %% MkII
>>>      pair laboff.foo ; laboff.foo := (.5,-1) ;
>>>      labxf.foo := labyf.foo := 1 ;
>>>
>>>      label.foo("second", origin);
>>>    \stopMPcode
>>> \stoptext
>>
>> I wasn't aware of users defining extra ones. I'll add this:
>
> Probably not many users will tinker with custom label directions,
> but MetaPost package authors do. Some packages like piechartmp¹
> internally use laboff.foo and the mpfun_ prefix breaks those
> packages. They work in traditional MetaPost, plain TeX, LaTeX and
> ConTeXt MkII, but since mplib uses the mpfun_ prefix, those packages
> are broken in MkIV.

that kind of tinkering can also result in overloading context 'extensions'

>> […]
>>      installlabel.foo ( 0, 1, 1, (.5,-1) ) ;
>
> This does not fix the problem since it only *defines* the correct
> variant, it doesn't help *using* those values. If the label values
> are being changed in the package one still has to branch out to
> support both variants. And even if there was an abstraction
> assisting to *use* the laboff values, all MetaPost packages
> tinkering with laboff would need to be adjusted. I can't imagine
> that to happen. Here's what the piechartmp package is doing, for
> instance:

I'll provide:

\starttext
   \startMPcode

     startplaincompatibity ;

         label("first", origin);

         pair laboff.foo ; laboff.foo := (.5,-1) ;
         labxf.foo := labyf.foo := 1 ;

         label.foo("second", origin);

     stopplaincompatibity ;

   \stopMPcode
\stoptext

As I wouldn't be surprised if there were more differences we need to 
handle.

Hans

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
     tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
-----------------------------------------------------------------
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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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___________________________________________________________________________________

Re: MetaPost label direction prefix

[Marco Patzer]

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On 2013–08–24 Hans Hagen wrote:

>     startplaincompatibity ;
> 
>         label("first", origin);
> 
>         pair laboff.foo ; laboff.foo := (.5,-1) ;
>         labxf.foo := labyf.foo := 1 ;
> 
>         label.foo("second", origin);
> 
>     stopplaincompatibity ;

Brilliant! Thanks a lot. A few things:

1) Can you replace

  def useplainlabels =
    let label    = plain_label ;
    let thelabel = plain_thelabel ;
  enddef ;

with

  def useplainlabels =
    def label    = plain_label    enddef ;
    def thelabel = plain_thelabel enddef ;
  enddef ;

The minimal example works with your version, but the old MetaPost
code does not. The def variant works fine with both.

2) Replace

  startplaincompatibity  →  startplaincompatibility
   stopplaincompatibity  →  stopplaincompatibility

3) This one is truly optional and just a suggestion for a better
interface. Although it's nice to have the grouping in
start-stopplaincompatibility, it's not required here, since the
entire MetaPost instance runs in plain compatibility mode. It would
be nice to either have a non-grouped command:

  def plaincompatibility =
    scantokens plain_compatibity_data ;
  enddef ;

Or maybe even a higher-level switch:

  \defineMPinstance
    [fun-with-old-MP]
    [metafun]
    [compatibility=plain] %% default* | plain

> As I wouldn't be surprised if there were more differences we need
> to handle.

We will find out if things break.

Marco

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___________________________________________________________________________________

Re: MetaPost label direction prefix

[Hans Hagen]

On 8/24/2013 2:31 PM, Marco Patzer wrote:
> On 2013–08–24 Hans Hagen wrote:
>
>>      startplaincompatibity ;
>>
>>          label("first", origin);
>>
>>          pair laboff.foo ; laboff.foo := (.5,-1) ;
>>          labxf.foo := labyf.foo := 1 ;
>>
>>          label.foo("second", origin);
>>
>>      stopplaincompatibity ;
>
> Brilliant! Thanks a lot. A few things:
>
> 1) Can you replace
>
>    def useplainlabels =
>      let label    = plain_label ;
>      let thelabel = plain_thelabel ;
>    enddef ;
>
> with
>
>    def useplainlabels =
>      def label    = plain_label    enddef ;
>      def thelabel = plain_thelabel enddef ;
>    enddef ;
>
> The minimal example works with your version, but the old MetaPost
> code does not. The def variant works fine with both.

ok

> 2) Replace
>
>    startplaincompatibity  →  startplaincompatibility
>     stopplaincompatibity  →  stopplaincompatibility

ok, best check the next beta well (i might have missed some)

> 3) This one is truly optional and just a suggestion for a better
> interface. Although it's nice to have the grouping in
> start-stopplaincompatibility, it's not required here, since the
> entire MetaPost instance runs in plain compatibility mode. It would
> be nice to either have a non-grouped command:
>
>    def plaincompatibility =
>      scantokens plain_compatibity_data ;
>    enddef ;

due to the way grouping works in mp it doesn't hurt to have it and by 
using it we can avoid a push/pop stack after all in the end we want to 
go back to the metafun labels

> Or maybe even a higher-level switch:
>
>    \defineMPinstance
>      [fun-with-old-MP]
>      [metafun]
>      [compatibility=plain] %% default* | plain
>
>> As I wouldn't be surprised if there were more differences we need
>> to handle.

maybe later

> We will find out if things break.

indeed

Hans

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
     tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
-----------------------------------------------------------------
___________________________________________________________________________________
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/
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___________________________________________________________________________________