This makes it possible to move windows by their title bar, even if they're in
relative mode, if you click the title bar when the window does not have focus.
Bug: https://bugzilla.libsdl.org/show_bug.cgi?id=2396
Alex Szpakowski
On my Mac OS X system (10.9.1), the SDL_MOUSEWHEEL event reports negative X values when my trackpad scrolls to the right, and positive X values when my trackpad scrolls to the left. This is backwards from what I'd expect, and I don't think it matches the Windows wheel events.
The vertical scroll values are what I'd expect though, and are consistent what gets reported on Windows (positive Y for scrolling up, negative Y for scrolling down.)
This is with "scroll direction: natural" disabled in the OS X trackpad settings (i.e. my scroll direction in non-SDL OS X programs matches what happens in Windows and Linux.)
I also tested with the horizontal scroll on a real mouse (Logitech G500 without custom drivers), and the horizontal scroll values in SDL are still flipped.
I "solved" the issue for myself by changing this line in the Cocoa_HandleMouseWheel function:
float x = [event deltaX];
to this:
float x = -[event deltaX];
I believe it should work fine with that change - I found something similar in another codebase while looking online for my issue - but I haven't tested on anything below Mac OS 10.8.
