This works on macOS, Wayland, and a few more esoteric platforms. X11
doesn't have a concept of DPI-awareness. Note that with this flag
SDL_GetWindowSize() isn't guaranteed to return the actual window size.
This prevents issues when calling std::abs with a float on some older
compilers. While it would normally be promoted to an int, std::abs is
special due to being overloaded despite being a C function. This can
cause errors due to the compiler being unable to find a float overload.
SDL_abs doesn't have this problem, since it's a normal C function.
leo60228