Richard Heck wrote:

> If we support the added style, then users who both use that style and
> use an older version of the package will have non-compilable documents.
> So you could have a document that worked perfectly well, you make one
> change---use the new style---and now it won't compile. What follows is a
> frustrated message to the user list.

Good point, I did not think too much about that. However, it would be no 
problem IMHO if there was an error message explaining that the compilation 
did not work because of an outdated package. Then the user could easily 
either update his TeX installation or refrain from using this style. This 
would be similar to the error you get when the package is completely 
missing. We could extend the layout file syntax so that a style can list its 
minimum required package version, and then LyX could determine for each 
installed package the version in chkconfig.ltx (if this is technically 
possible, I did not check). Then LyX could give a meaningful error message.

> But even if we do that, then I think we should require that the new
> layout to include preamble code that makes the output with an old
> package equivalent to that with the new one, at least as far as the new
> style is concerned. E.g.:
>      \ifundefined\phone{
>          \newcommand\phone{
>              % code borrowed from the new version....
>          }
>      }
> There's a \providecommand, too, that is equivalent to this, right? Ugly
> preamble stuff, to be sure, but useful, nonetheless, I think.

I would not do that. This would require to check the license of that code 
which is often incompatible to the LyX license.


Georg


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