PlanarFigures can currently only be selected in the render window by clicking on one of their control points. Clicking on any other part of the PlanarFigure has no effect.
It should be possible to pick (and thus select) PlanarFigures with the mouse by clicking anywhere on their contour.
Also, when "hovering" with the mouse over a PlanarFigure, it should be highlighted to indicate that picking is possible.