gtk:widget-compute-transform (widget target transform)

widget -- a gtk:widget object
target -- a gtk:widget object for the target widget that the matrix will transform to
transform -- a graphene:matrix-t instance for the final transformation

The graphene:matrix-t instance with the transformation, or nil if transform could not be computed, for example, when widget and target do not share a common ancestor. In that case transform gets set to the identity matrix.

Computes a matrix suitable to describe a transformation from the coordinate system of widget into the coordinate system of target.