code: def set_default_viewport(self):
          
          # The expected height with the current viewport width
          expected_height = int(self.buffer_width / self.aspect_ratio)
  
          # How much positive or negative y padding
          blank_space = self.buffer_height - expected_height
          self.fbo.viewport = (0, blank_space // 2, self.buffer_width, expected_height)
docs: Calculates the viewport based on the configured aspect ratio in settings.
          Will add black borders if the window do not match the viewport.