`sorting` - the sorting type to use when rendering the views in this paper (i.e. In what order should the views be rendered?).

The SVG 1.1 format does not have built-in z-index functionality, so JointJS implements it programmatically. You can set the z-index directly using using regular Backbone `set('z')`/`get('z')` methods or through `element.toFront()`/`element.toBack()`/`link.toFront()`/`link.toBack()` methods. See the element Z documentation for more information.

The Paper object exposes a `sorting` object with three values that may be used as values of this option:

- `joint.dia.Paper.sorting.EXACT` - (default) render views in exactly the same order as reported by `graph.getCells()` (views with different z-values are rendered in order, and views with the same z-value are rendered in the order in which they were added). This is by far the slowest option, present mainly for backwards compatibility.
- `joint.dia.Paper.sorting.APPROX` - render views according to their z-values. Views with different z-value are rendered in order, but the ordering of views with the same z-value is indeterminate. Similar in functionality to the `EXACT` option, but much faster.
- `joint.dia.Paper.sorting.NONE` - render views in an indeterminate order. (Note that this setting disables all `toFront`/`toBack` functions mentioned above.)