In order to use the swapchain, we have to start by acquiring an image. This is done with the
let (image_num, acquire_future) = swapchain::acquire_next_image(swapchain.clone(), None).unwrap();
This function call returns a tuple. The first element is a
usize corresponding to the index of
the image within the
images array of the image which is now available to us. The second element
of the tuple is a future that represents the moment when the image will be acquired by the GPU.
acquire_next_image function will block until an image is available. This can happen depending
on the present mode.
To be finished - check the Triangle example for now.
To be finished