In 1.x, we used to be able to provide a custom background node to a XY chart that could be used for example either to set an image as a background or to highlight parts of the chart by displaying a marker line at a specific point of X or Y axis, etc.

This member has been removed from the 2.0 API so it is not possible to set some nodes behind the series anymore.

Additionnaly : the API needs to be expanded from 1.x to allow acces to the dimensions of the plot area. In 1.x it was possible to get the rectangular dimension of the plot are by projecting the upper and lower bounds of the X and Y axis of the chart but this felt more like a hack of some sort.