[LV2] RFC: ui:requestParameter feature

[Hanspeter Portner]

On 16.02.20 21:57, David Robillard wrote:
> Hi all,
> 
> Quite some time ago myself, falktx, and rgareus prototyped a feature to
> allow a plugin UI to request a parameter value from a host.  The main
> incentive here is to avoid needing to implement file selector dialogs
> in plugins, though you could conceptually use it for whatever else, and
> it has some other potential advantages like integrating with embedded
> host content/browsers and the like.
> 
> I just cleaned this up a bit and would like to make it a real thing for
> the next release, so if anyone wants to weigh in, or better yet
> implement it:
> 
> https://gitlab.com/drobilla/jalv/-/commits/ui-request-parameter
> https://gitlab.com/lv2/lv2/-/commit/540268fb05b6d42ecfaec118ab7dde0febcddde3
> 
> This is the simplest possible thing that gets the job done.  I'm
> pondering whether it's a bit too simplistic, e.g. adding an optional
> subject and type parameter would remove the requirement that the host
> knows all about the parameter and allow the plugin to request a value
> for any property (set via a message) which could be quite useful for
> more advanced plugins.  Nothing else comes to mind.

This feature seems very useful, indeed.

The option to specify the type would be mandatory for hidden/dynamic parameters,
though.

E.g in moony I'll only be able to use this feature (and I desperately want to
get rid of its crappy file dialog) if I can specify a type,
because moony's dynamic ui parameters (which can be of arbitrary type:
atom:String, atom:Chunk, atom:Float, ...) are internal to the plugin only and
thus hidden from the host.

Another issue: Say the plugin ui requests an atom:String (representing code of
some kind), would it make sense to be able to tell the host what kind of widget
it should open ?

* open a file dialog and send the chosen file's content ?
* open (and keep open) an editor window and send the editor's content whenever
  user saves content ?

Or is it up to the host to decide ?