Re: [Denemo-devel] Denemo Breakthrough

[R. Mattes]

On Sun, 24 Jul 2011 17:50:07 +0100, Richard Shann wrote
> On Sun, 2011-07-24 at 15:08 +0000, Ralf Mattes wrote:
> > 
> > Hello,
> > 
> > sorry if I seem to just complain,
> Not at all, I very much appreciate finding out how scheme/C should work
> together
> 
> >  but that's an extremely ugly interface.
> > You're introducing an ad-hoc markup language
> however, this is going a bit far, asking the scripters to put the
> parameters to the cairo_show_text() onto successive lines is no sort 
> of language at all; you cannot change font or size or anything 
> within the string you are printing. Curiously, cairo_show_text() is 
> described by the cairo folk as a "toy" interface, but it may be the 
> right thing to use here, as we are not seriously interested in text 
> (kerning, justification, spell-checking ...)
> 
> >  without need - have a look at
> > Gtk's (Pango's, to be more specific) markup language [1]. 
> > May I suggest a more "scheme-ish" way: 
> > 
> >  d-DirectivePut-standalone-graphic tag <spec>
> > 
> >  Where spec is either a string (backward-comaptible) or a list of the
> >  form (<type> &rest ...)  where type is a keyword and the rest args
> >  specify type specific information. A few examples:
> > 
> >   (d-DirectivePut-standalone-graphic tag (:graphic :file
> > "/home/wallace/cheese.svg"))
> 
> Did you mean 'graphic 'file etc here?

No, I meant ":graphic" and ":file" 
One of the first things I do in my guile projects is:

(read-set! keywords 'prefix)

so ":file" is the same as "#:file". Keywords are pretty nice 
for named parameters and "tags" since comarison is so cheap.
As a matter of fact, they can easily be used in C switch statements.
Being able to use keywords is one of the main reasons I wanted to have
some sort of central guile initialization place. Denemo can lookup the
SCM value for keywords during startup (with   scm_from_locale_keyword)
and store/remember the value for application lifetime (keywords are
guaranteed to stay constant).
 
> >  
> >   bbb
> > DOUBLE FLAT" :font "Lucida Bright"))
> 
> Did you have some sort of lookup for "MUSICAL SYMBOL DOUBLE FLAT" to
> find what utf8 value this was? I am not sure if there is stuff for that
> available.

No, I desing APIs by wishful thinking. If there's no way to map the unicode
character name -- too bad. Maybe we then need to code one. I'm just 
trying to point out a different approach. I'm not even shure about the
list parameter. I only picked it since it would make dispatch easier: if
the first parameter is a string do the old style, else do it the new way.
An alternative would be to leave out the list like this:
 (d-DirectivePut-standalone-graphic tag :glyph "CAPITAL A" ....)

> As always, the bottom line is having the manpower - I am confident 
> now about iterating through a scheme list in C (thanks to earlier comments
> by you), but testing symbols like 'glyph would take me some research 
> (in fact I haven't really got a solid model in my head for symbols 
> and the strings that are used to name them ...). Well, the very 
> bottom line is that scheme objects carry their type with them, so we 
> can always add extra parameter types to d-DirectivePut-standalone-
> graphic, for instance if we found we needed to use several fonts in 
> one display string.

Too bad I short on time right now. 

BTW, would it be possible to merge my load-path branch into main?
I'd love to use it for the midi input stuff (and that would then contain
code that does keyword lookup ... ;-)


Cheers, RalfD
 
> Thanks for your comments
> 
> Richard


--
R. Mattes -
Hochschule fuer Musik Freiburg
address@hidden