Those three files have to be "filtered" with `<Filter>addons\ofxGui\src</Filter>`.
Also, `ofParameters` in line [48](https://github.com/tgfrerer/openFrameworks/blob/c8ebd67a4c0a2316c8a9e73d691f274003eecf2f/apps/devApps/projectGenerator/projectGenerator.vcxproj.filters#L48) for example doesn't exist anymore.