Doc: improve documentation of Bézier curves (2858) (issue 6561064)

[k-ohara5a5a]

Maybe just dump the waste of time that was
   \override 'control-points


http://codereview.appspot.com/6561064/diff/1/Documentation/notation/changing-defaults.itely
File Documentation/notation/changing-defaults.itely (right):

http://codereview.appspot.com/6561064/diff/1/Documentation/notation/changing-defaults.itely#newcode3953
Documentation/notation/changing-defaults.itely:3953: values are then
found by trial and error.
.. and trial and error again if you change anything, or if the
line-breaking changes, or if you need to switch between A4 and US letter
paper ...

http://codereview.appspot.com/6561064/diff/1/Documentation/notation/changing-defaults.itely#newcode3977
Documentation/notation/changing-defaults.itely:3977: If cubic-shaped
curve is required the control points must be set
A curve shaped like a cube ?
You mean S-shaped, or sigmoidal, or 'curve with inflection' or 'curve
that changes the direction of its bend'?

http://codereview.appspot.com/6561064/diff/1/Documentation/notation/changing-defaults.itely#newcode3988
Documentation/notation/changing-defaults.itely:3988: { c4 e, f' d }
A tiny bit ugly.

\relative c'' {
    c8( e b-> f d' a e-> g)
    \shape Slur #'((0 . 0) (5.5 . 0) (-5.5 . -10) (0 . -6))
    c8( e b-> f d' a e-> g)
  }

Accents make the point that the newly-shaped Slur is integrated into the
usual collision-avoidance (distinct from other hand-tweaks like rotation
and extra-offset).

http://codereview.appspot.com/6561064/diff/1/Documentation/notation/changing-defaults.itely#newcode3996
Documentation/notation/changing-defaults.itely:3996: the ones calculated
automatically, remembering that a translation of
You can probably skip the "remembering that.."
Discussions of Bezier curves always mention this, but it seems implicit
in having the curves parametrized by "control points".

http://codereview.appspot.com/6561064/