I used all uppercase for constants so far (see app\htmlpreviewgenerator.cpp and app-static\snippets\jsonsnippettranslator.cpp). I would like to stick to a single code style as much as possible. I started a page in the wiki now: https://github.com/cloose/CuteMarkEd/wiki/Coding-Style

I also prefer the constants at the start of the source file.