David,
On Thu, Feb 25, 2016 at 9:28 AM, David Kastrup [via Lilypond] <
ml-node+s1069038n187720...@n5.nabble.com> wrote:
> Abraham Lee <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=187720&i=0>> writes:
>
> > All,
> >
> > In the docs are numerous sections that discuss how to modify context
> > properties. This is not complicated. However, a handful of recent
> threads
> > on the user list have got me wondering about the correct way(s) of
> > _accessing_ these properties within, for example, a music function. The
> > music function may or may not modify the same or another context
> property.
> > If music functions are NOT the way to go, then what is preferred?
> >
> > Thanks, in advance, for all insights and instruction.
>
> I have no idea what you want. Music functions are called when parsing
> LilyPond source code. At that time, there are no contexts and no
> context properties. Consequently, music functions have no way
> whatsoever to read or modify context properties. All they can do is
> create music expressions (typically overrides or applyContext calls,
> possibly as context modifications) that contain callbacks of some form
> that, when ultimately called during iteration of the music expression,
> will be able to access actual properties.
>
> So for your actual question, there is little insight and instruction to
> be had.
Thanks for your response. That helps knowing that music functions cannot
read or modify context properties.
Let me give some examples of what I might want to do:
1. Determine the currentBarNumber in order to print a custom stencil
2. Access the System or Staff's vertical position on the page in order to
change it
3. Determine which page I'm on so I can print a particular stencil on that
page only
4. Determine the current time signature so I can create a MMR of the exact
size needed to fill a measure
etc.
These are just examples and I'm not even asking for specifics on how to do
these (as they've partially been discussed in other threads). What approach
would I want to follow in order to access the properties so I could make a
change elsewhere?
Thanks,
Abraham
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