SDL functionality have globals variable, so it cannot be really thread-safe if is misused. or at least might behave incorrectly due to SDL interaction. #124
still functions like drawing points in windows might be required to have a mutex
to avoid weird situation if drawing a point and changing color in another thread.
[ ] consider to make Window class thread-safe when accessing SDL functions, using a "sdl" mutex.
still functions like drawing points in windows might be required to have a mutex to avoid weird situation if drawing a point and changing color in another thread.