Re: Lyrics break estimation of vertical spacing

[Boris Shingarov]

> Replace constrained-breaking.cc:461 by
 >
 > Interval begin_extent = sys->begin_of_line_extent (start, end);
 > Interval rest_extent = sys->rest_of_line_extent (start, end);
 
Ok, experimenting with this, I am inclined to *add* instead of
*replacing*.  The extent_ member of Line_details is touched in
many other places, not just Page_breaking (e.g. the spacer also
uses it).  I wanted to replace it everywhere first, but now I
think it's probably too intrusive.  All I need is access to the
two Intervals in Page_breaking::min_page_count().
 
> Interval
> System::begin_of_line_pure_height(Grob *me, vsize start, vsize end)
 > {
 > System *sys = dynamic_cast<System*> (me);
 
This I have been always wondering about, it's happening
throughout all the Grob code.  Why not just take "this" as the
argument?  I *am* in class System to bgin with, so why the
dynamic_cast?  (or maybe my mind is corrupted by 15  years
of Smalltalk, and this is a standard C   quirk?)