I’ve a toolkit to draw sprites and things for games, it was working just fine with libSDL v2.0.8 for Mac OS X, and then a few months ago I updated to libSDL v2.0.12 but didn’t recompile until today.
I discovered to my great horror that right clicking in the mousepad doesn’t generate any right-button SDL_MOUSEBUTTONDOWN event like before. Only the left-button still generates events. I’m using Mac OS X El Capitan v10.11.6
So I reinstalled libSDL2 v2.0.8 from https://www.libsdl.org/release/ and it worked just fine. (^^)!
Out of curiosity also tried v2.0.9 and it works. Tried also v2.0.10 and from that version ithe right button of mouse ceased to work.
I know developers can take a lot of time to find the bug.