Re: Why do chords print below staff?

[Han-Wen Nienhuys]

Mats Bengtsson wrote:
> Of course, but your explanation does not say why the second ChordNames
> context appears below the Staff context. However, Han-Wen provided the
> missing piece of information, namely that the inner ChordNames context
> is treated as if it was created "after" the Staff context.
> So, the intuitive notion that contexts are ordered in the order they
> appear in the score is actually very tricky. The rules I have seen
> so far are:
> A) If two contexts are created at different (time) locations in the
>    piece, then the one created first is processed first.
> B) If two contexts are created at the same time location, then the
>    one that is created first within \score{...} (when reading from
>    top to bottom) is processed first.
> C) When interpreting rule A), Property settings within a context are
>    considered to happen after the creation of the score but before the
>    first note of the piece.
> In mathematical terms, these rules clearly define a partial order.
> However, it's not clear to me if they also define a complete order
> or if there's some more tricky special case to be considered.
> Thanks to Han-Wen who hinted to rule C), which I learnt today.

The actual rule is: they are put in the order that \new <contextName> 
expressions are opened for processing. "Opening" a music expression for 
processing means calling Music_iterator::construct_children for that 
expression.

When "opening" a Simultaneous expression

 <<
    \new Foo { x y z }
    \new Foo { p q r }
 >>

the two "\new Foo"s are processed in the order of specification, and 
then x and p are "opened" 
(Simultaneous_music_iterator::construct_children calls 
Music_iterator::construct_children for each of its child iterators).

Of course, if construct_children for x and p has no side effects, 
nothing else happens. Then, normal side-effects occur when processing 
Eg. x and p are typeset as notes, or the property settings are effected. 
If y is another "\new Foo", it is only opened after x is finished. It's 
perfectly logical that the new context appears below the 2 existing ones 
if x has non-zero duration; it's just the case when x has no duration 
that it could be confusing.

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