Komaclasses such as scrbook do not define \sf anymore

[kiryph]

When using latexdiff for a file which uses as documentclass scrbook the compilation fails with following error:

Class scrbook Error: undefined old font command '\sf'.

This can be fixed when adding following to the preamble

\makeatletter
\DeclareOldFontCommand{\rm}{\normalfont\rmfamily}{\mathrm}
\DeclareOldFontCommand{\sf}{\normalfont\sffamily}{\mathsf}
\DeclareOldFontCommand{\tt}{\normalfont\ttfamily}{\mathtt}
\DeclareOldFontCommand{\bf}{\normalfont\bfseries}{\mathbf}
\DeclareOldFontCommand{\it}{\normalfont\itshape}{\mathit}
\DeclareOldFontCommand{\sl}{\normalfont\slshape}{\@nomath\sl}
\DeclareOldFontCommand{\sc}{\normalfont\scshape}{\@nomath\sc}
\makeatother

However, these style of commands are discouraged to use (see e.g.l2tabuen.pdf) and I also do not like to add code just for diffing latex files.

Can latexdiff itself be changed to handle these classes out-of-the-box?

[ftilmann]

Are you using -t CFONT option? The default markup style does not use \sf command. You can easily define your own markup commands by using --preamble option (start with show--preamble and simply add the command defining \sf from your post) . I cannot simply replace \sf by \sffamily because the same command needs to work both in text and math mode. I guess there is an argument for adding the line \DeclareOldFontCommand{\sf}{\normalfont\sffamily}{\mathsf}. I will probably do this. I don't think you need the \makeatletter and \makeatother commands.

[kiryph]

Yes, I was using CFONT. Since only \sf is missed by latexdiff, only \DeclareOldFontCommand{\sf}{\normalfont\sffamily}{\mathsf} has to be added.

Anyhow, I am no expert and can't judge about side-effects. However, supporting the komaclasses as they stand seems to be a good reason. This would definitely make latexdiff more newbie friendly.

I can imagine how difficult it is to maintain a tool such as latexdiff in an always changing latex world.
For instance, in order to use lualatex and a major mode with changebars following things have to be adjusted: pdftex driver has to be enabled manually for the package changebars and the package luatex85 must be loaded.

[ftilmann]

There does not seem to be any disadvantage to using \DeclareOldFontCommand so I added that to all the styles using \sf or \bf font commands, and will close this issue. For your comment on luatex please open a separate issue if required. In fact you can implement this your self even without knowing perl by introducing a new type. The preamble for the different markup types are defined near the end of latexdiff, and you could simply add one for luatex+changebar. If you do so please consider submitting a pull request.