Thanks for the patch!

What do you think about a small redesign:

• a method Klaus.should_highlight(filename, data) -> bool that is passed the filename + the contents
• in highlight_or_render, rename render_markup to enable_markup
• add enable_highlight : bool to the highlight_or_render function (not as a function but a boolean)

Also, in your current implementation, highlight_enabled can also be used to disable markup rendering. If this is intended, then the name should be changed to reflect this behaviour. If not the logic should be changed accordingly.

As a last step we would have to add a new argument to make_app that allows you to give your own Klaus subclass, i.e. make_app(app_class=MyKlaus).