[LV2] Feature request: DSP write_function() ?

[Rui Nuno Capela]

On 12/20/20 10:49 AM, Sven Jaehnichen wrote:
> Hi,
> 
> the old problem: control ports are READ_ONLY in LV2. Me and other plugin 
> programmers struggle about it. I know it has been discussed here before 
> and I know the workarounds (like parameters) and their limitations.
> 
> Actually I read in unfa's software chat that the Surge programmers team 
> are struggling about this problem too:
> 
>> |We made this choice because parts of the current LV2 spec and Surge 
>> are incompatible in a couple of ways, most importantly in the LV2 
>> assumption that plugins never modify their control input port. Actions 
>> like ‘changing parameter types when an effect changes’ or ‘patch 
>> changes’ are not compatible with this design constraint. As a result, 
>> the LV2 - especially in Ardour - unreliably saves and restores state. 
>> The solution - which we are working on - is to use new LV2 APIs that 
>> allow current Surge behavior (and match what other plugin specs like 
>> AU and VST do).|||
> 
> 
> My request: LV2 UI can call the host to change control port via the 
> write_function(). I don't see such an option for the DSP instance. Why? 
> It would be nice to have it. Or are there restrictions why it's 
> impossible or problematic to implement?
> 

hi,

fyi. there's this proposal that's since then implemented on qtractor 
(host) and the vee-ones (plugins):
https://github.com/lv2/lv2/pull/42

cheers
-- 
rncbc aka. Rui Nuno Capela
rncbc at rncbc.org