Our published [OF code style](https://github.com/openframeworks/openFrameworks/wiki/oF-code-style#indentation) to the rescue ;-)
> Use tabs for indentation and set your tab width to 4 spaces. Keep in mind the Github source code viewer uses a tab width of 8 spaces.

The latter is why these errors are visible in the PR view, when people are mixing tabs and spaces in a file.