+ * \param rtl is true for right-to-left layout
+ * \param ws is the amount of extra inter-word space applied text justication.
+ */
+ virtual int x2pos(docstring const & s, int & x, bool rtl, double ws) const = 0;
+ /**
+ * Break string at width at most x.
+ * \return true if successful
+ * \param rtl is true for right-to-left layout
+ * \param force is false for breaking at word separator, true for
+ * arbitrary position.