[7.27]CLAP: Invalid State Transiton on request_restart()

[Reaktor:[Dave]]

A CLAP plugin changing its parameter count at runtime loaded in REAPER will trigger a misbehaving host check when using the clap-helpers. These helpers include some checks enforcing the correct interaction between a CLAP plugin and a CLAP host.

Most of the time, it goes like this:

1. (during clapProcess) plugin calls host->request_restart
2. (host calls) clapStopProcessing
3. (host calls) clapStartProcessing (weird?)
4. (host calls) clapDeactivate
5. (during clapDeactivate) plugin applies parameter changes and calls paramsExtension->rescan()
6. (host calls) clapActivate
7. (host calls) clapStartProcessing (self._isProcessing is already true due to 'weird?', triggers hostMisbehaving)

That will trigger this check to fail: https://github.com/free-audio/clap-h...lugin.hxx#L392

The first clapStartProcessing is called on a different thread than the second clapStartProcessing call.

Sometimes the check in "clapProcess()" at check "!self._isActive" fails: https://github.com/free-audio/clap-h...lugin.hxx#L449
When that happens in the debugger, the _isActive state is already at true, which shouldn't have triggered the check. This is likely due to the clapStartProcessing calls happening on different threads, but I'm guessing.

I'd expect REAPER to not call clapStartProcessing before clapDeactivate and also not to call that twice. I'm also not sure why the two clapStartProcessing calls happen on different threads. This is happening on Windows 10 with REAPER v7.27.

[Justin]

ah, I think I see why this would be, fixing!

[Reaktor:[Dave]]

Can confirm v7.28 fixes this. Thanks a lot!