\c void (*draw_update)(void *handle, int x, int y, int w, int h);
-This function behaves exactly like the back end \cw{draw_text()}
+This function behaves exactly like the back end \cw{draw_update()}
function; see \k{drawing-draw-text}.
An implementation of this API which only supports printing is
Similarly, \c{ym} and \c{yc} specify the vertical position of the
puzzle as a function of the page height: the page height times
-\c{xm}, plus \c{xc} millimetres, equals the desired distance from
+\c{ym}, plus \c{yc} millimetres, equals the desired distance from
the top of the page to the top of the puzzle.
(This unwieldy mechanism is required because not all printing