Re: An overview of the system

[Han-Wen Nienhuys]

Erik Sandberg wrote:
> > Each syntactic thing you can do for actual music entry---i.e. most of
> > what you type inside \score other than managing contexts---is
> > interpreted as a musical expression, much as 3+4 might be interpreted as
> > a mathematical expression.  As each expression is read in, it is
> > classified as an Event (atomic events, e.g. NoteEvent) or a Music (for
> > expressions composed of other expressions?).  This music expression is
> > then handed off to an engraver.
> > * what is a Music really?
>
>
> "Everything is Music". Events is a special case of Music (those that don't 
> happen to have child expressions). The most useful way to describe it is as a 

almost correct. Events don't have subtimings. An event causes an effect 
time=0 and time=length(event). 	NoteEvents does have children in the 
'articulations field (Probably, the latter should be renamed to 'elements)

> > The created grobs have properties that can be modified just as for
> > contexts, except with \override instead of \set---the idea is that the
> > engraver would calculate values for each grob property, but you might
> > want to override its choices by some offset amount.  Here, unlike with
> > \set, you *must* say which kind of object you're overriding for (and
> > possibly also which context it's in).  (\revert to delete change)  These
> > properties control exactly where and how an object is laid out.
> > * When a 'direction property is labelled "Up or down, left or right?",
> >  and its value is a number, this is confusing.
>
> -1 generally means down/left iirc (think time and octave)

Extra note: this is just a convention, based on the cartesian convention 
for 2D graphics (up / right = positive, down / left = negative). The 
point is that we can compute with directions, eg.

  for dir in left, right:
    x += dir * spanner->get_bound (dir)
                      ->extent (common, X_AXIS)[-direction]

puts the distance between inner edges of the bounds of SPANNER in X.


--
 Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen