+ * - tune the page breaking algorithm to impose penalties on
+ * various things
+ * * breaking in the middle of a code paragraph
+ * * breaking one line from the start or end of a paragraph
+ * * breaking immediately after a heading of any kind (or
+ * indeed within one)
+ * * we may also need to impose a limit on the amount by which
+ * we can _stretch_ a page; after a certain point we may
+ * prefer just to unapologetically leave space at the bottom.
+ *
+ * - implement some simple graphics
+ * * I had an underline below chapter headings in the original
+ * Perl version, and I thought it looked rather nice
+ * * also we need para_Rule.
+ *