Greater control of execution loop

[Kevinpgalligan]

Summarising a brainstorming session between me and @Gleefre.

• It would be nice if the user had greater control of sketch's "game loop".
• This includes controlling the frame rate.
• Also, there could be a separate update-state method, allowing the user to decouple their physics simulation/whatever from the drawing loop, with a separate FPS.
• Idle render will have to have a flag to disable it if the user is controlling the render themselves.
• sdl2kit contains its own implementation of a game loop, but it's not decomposed into reusable parts. We could either submit a pull request there or copy the parts we need.

Example of how this might work:

(defsketch my-sketch ...)
(defun main ()
  (let ((sketch (make-instance 'my-sketch :idle-render nil)))
      (loop (handle-events sketch)
                (render sketch)
                (update-state sketch))))

[Kevinpgalligan]

Useful article on timing stuff in SDL2: https://thenumb.at/cpp-course/sdl2/08/08.html