-/** If "data" is valid, the length represented by it is
- stored into "result", if that is not 0. */
+/** Test whether \p data represents a valid length.
+ *
+ * \returns whether \p data is a valid length
+ * \param data Length in LyX format. Since the only difference between LyX
+ * and LaTeX format is the representation of length variables as units (e.g.
+ * \c text% vs. \c \\textwidth) you can actually use this function as well
+ * for testing LaTeX lengths as long as they only contain real units like pt.
+ * \param result Pointer to a LyXLength variable. If \p result is not 0 and
+ * \p data is valid, the length represented by it is stored into \p result.
+ */