public interface EdgeSizes
defaultSize will map to
the default edge size or offset for the canvas (Canvas.edgeSize,
or Canvas.edgeOffset and top, left,
right and bottom will map to the edgeTop/edgeOffsetTop, edgeLeft/edgeOffsetLeft, edgeRight/edgeOffsetRight, and edgeBottom/edgeOffsetBottom attributes on the paneContainer
respectively. Note that not all these properties have to be set - if unset standard edge sizing rules will apply.