[LV2] RFC: ui:requestParameter feature

[David Robillard]

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.

Cheers,

-- 
dr