[LyX/master] Implement properly \limits and \nolimits

[Jean-Marc Lasgouttes]

Le 09/09/2020 à 11:00, Enrico Forestieri a écrit :
>> Do you have a concrete case in mind where deriving requirements from the
>> contents of the macro goes wrong? Note that in this case, we could decide
>> that the requirements given to the macro override whatever is decided from
>> its contents.
> 
> The point is that the macros defined in the symbols file are only used
> for on-screen representation. Their definition will never appear in the
> output. So, if \int is defined in the symbols file as
> 
> \def\int{\intop\nolimits}	esint|amsmath
> 
> meaning that it requires either esint or masmath, the requirements for
> \intop should not be taken into account because \intop will never
> appear in the latex file. 

But \intop can appear in a LaTeX file, and it should work. So we have to 
set the requirements of \intop anyway.

> Here, the definition of \int is only used
> for representing it on the screen. For example, if you define
> 
> \def\int{\vcentcolon}		esint|amsmath
> 
> because you like to see \vcentcolon instead of \int on screen, then
> you would get the package mathtools as a requirement. But \vcentcolon
> does not really appear in the output and that requirement is bogus.

I understand that but:

1/ we do not want to do such bogus things in symbols file, unless you
    have a better use case in mind.

2/ this is why I proposed that in the case where requirements are given
    for the macro, the requirements induced by the definition are
    skipped.

The proposal 2/ is of course not 100% precise, since it is difficult to 
make a difference between "no requirement needed" and "no requirement 
given".

But in practice it seems easier in terms of maintenance to let LyX infer 
the requirements.

JMarc