When the attribute returned from this function is attached to a dom node, the attribute tracks the visible region of the node in the browser.

E.g. when the node is visible fully, min_x = min_y = 0, and max_x = node's width, max_y = node's height.

The bounds is conservative; it may over-estimate the size, but will never underestimate the size. Over-estimation can occur when a parent of the tracked node has a more restrictive size than the tracked node such that a scrollbar is present.

This is mostly useful for large nodes, to implement some custom scrolling behaviour - if your browser has height 500px, and you have a node with height 1000px, the y bounds will be (0, 500) if scrolled to the top (so that the top of the node visible), than (50, 550) as you scroll 50 pixels down, etc.