I'm trying to get rid of the 9% cost of pango_default_break() for
measuring text.  I'd like to lazily calculate the logical attributes
(bug 123646 but don't bother).  I have some hacks that work but I need
some advice.

  Of the 11 logical attributes, only three are used in pango:

  is_cursor_position
    -- used for public APIs like line_to_x and move_cursor_visually,
       and also for ellipsizing

  is_char_break
    -- used by pango-layout.c:can_break_at for PANGO_WRAP_CHAR

  is_line_break
    -- used by pango-layout.c:can_break_at for PANGO_WORD_WRAP

  is_line_break is the most important.  PANGO_WORD_WRAP is the
default, and process_line calls can_break_at to determine whether there
is any break point in the line.

  I'm wondering there is a high-level algorithmic way to avoid using
is_line_break.  I can understand the lower-level stuff, but the
pango-layout.c:process_line code is getting up there.

  Any thoughts or pointers?

  -Billy