How to get hostcb from V..3 plug-in?

[azslow3]

Sorry if that is mentioned somewhere, Google was not my friend this time...

How to get REAPER hostcb from "V..3" compatible plug-in?
There is documentation how to do this from V..2, but ABI is completely different. Is there any interface UID for that?

PS. I do not want to mention related company name nor any trademarks of it, that is why I write a bit cryptic
I was almost ready to apply for a license, but I have started to read it carefully... Not only I have to do a lot of small things, I also HAVE TO update to any new version they decide to release within a year, and they CAN cancel the license without any explanation. Sorry, without me...

Since REAPER has no own processing plug-in format, I have to use "V.." compatible ABI. Just for fun, I have decided to check V..3 format. Works fine (from plain C, without any SDK), but I am stuck in getting REAPER pointer.

[Xenakios]

I got a C++ header file like this from Justin or Schwa at some point for using Reaper API functions from a VST3 plugin :

#pragma once

#include <pluginterfaces/base/funknown.h>

class IReaperHostApplication : public Steinberg::FUnknown // publicly-visible interface
{
public:
	// Gets a REAPER Extension API function by name, returns NULL is failed
	virtual void* PLUGIN_API getReaperApi(Steinberg::CStringA funcname) = 0;

	virtual void* PLUGIN_API getReaperParent(uint32 w) = 0; // get parent track(=1), take(=2), project(=3), fxdsp(=4), trackchan(=5)

															// Multi-purpose function, returns NULL if unsupported
	virtual void* PLUGIN_API reaperExtended(uint32 call, void *parm1, void *parm2, void *parm3) = 0;

	static const Steinberg::FUID iid;

};
DECLARE_CLASS_IID(IReaperHostApplication, 0x79655E36, 0x77EE4267, 0xA573FEF7, 0x4912C27C)
const ::Steinberg::FUID IReaperHostApplication::iid(IReaperHostApplication_iid);

I was able to use it for a C++ and Juce based VST3 plugin (on Windows and macOs) by doing some changes in the the Juce source code. I have no idea at all how that could work from plain C code.

[azslow3]

Thanks! That is exactly what I was looking for