contourIndex property Null safety

The zero-based index of the contour.

Path objects are made up of zero or more contours. The first contour is created once a drawing command (e.g. Path.lineTo) is issued. A Path.moveTo command after a drawing command may create a new contour, although it may not if optimizations are applied that determine the move command did not actually result in moving the pen.

This property is only valid with reference to its original iterator and the contours of the path at the time the path's metrics were computed. If additional contours were added or existing contours updated, this metric will be invalid for the current state of the path.