Re: Determining what parameters exist for an item

[Thomas Morley]

2016-01-25 21:00 GMT+01:00 David Nalesnik <address@hidden>:
>
>
> On Mon, Jan 25, 2016 at 1:47 PM, Kieren MacMillan
> <address@hidden> wrote:
>>
>> Hi Harm,
>>
>> > if a property is settable, this does not mean your setting takes any
>> > effect.
>> > I don't speak of user-errors in syntax, missing context, etc, but
>> > sometimes an engraver does not listen to a certain property, maybe
>> > because it's hard-coded or not really needed or for other good reasons.
>>
>> Excellent point. I’m sure it’s a pie-in-the-sky thought… but…
>>
>> Is there a way, in your [wonderful] list of _all_ properties, to have Lily
>> automatically say which will have an effect?

No.

To illustrate:
TextScript has 'font-name as a property, but setting it will not
always have an effect!!

'font-name in musicglyph-markup-command is hardcoded to #f, otherwise
LilyPond would try to take it from "TeX Gyre Chorus" in the example
below, with little chance for nice output, I'd say ...

{
  \override TextScript.font-name = "TeX Gyre Chorus"
  a'1-\markup { "This is a clef:  " \musicglyph #"clefs.G" }
}

This is only one single example (there are other markup-commands doing
similar) for one single grob...

>> Or is that as simple as “adjusting a property will have an effect if and
>> only if it’s listed on the grob’s ‘homepage’ in the IR”?

Again, no.
See, David's explanation, below.

>
>
> Just because a grob supports a certain interface doesn't guarantee that
> there's code written to handle all of the interface's properties for that
> particular grob.  Also, an overridable property doesn't necessarily have a
> default value listed in the IR: 'color, for example.
>
> DN

Sorry,
  Harm