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
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