juicysfplugin/modules/juce_audio_plugin_client/VST/juce_VSTCallbackHandler.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 5 End-User License
   Agreement and JUCE 5 Privacy Policy (both updated and effective as of the
   27th April 2017).

   End User License Agreement: www.juce.com/juce-5-licence
   Privacy Policy: www.juce.com/juce-5-privacy-policy

   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

/** An interface to allow an AudioProcessor to send and receive VST specific calls from
    the host.

    @tags{Audio}
*/
struct VSTCallbackHandler
{
    virtual ~VSTCallbackHandler() = default;

    /** This is called by the VST plug-in wrapper when it receives unhandled
        plug-in "can do" calls from the host.
    */
    virtual pointer_sized_int handleVstPluginCanDo (int32 index,
                                                    pointer_sized_int value,
                                                    void* ptr,
                                                    float opt)
    {
        ignoreUnused (index, value, ptr, opt);
        return 0;
    }

    /** This is called by the VST plug-in wrapper when it receives unhandled
        vendor specific calls from the host.
    */
    virtual pointer_sized_int handleVstManufacturerSpecific (int32 index,
                                                             pointer_sized_int value,
                                                             void* ptr,
                                                             float opt) = 0;

    // Note: VS2013 prevents a "using" declaration here
    /** The host callback function type. */
    typedef pointer_sized_int (VstHostCallbackType) (int32 opcode,
                                                     int32 index,
                                                     pointer_sized_int value,
                                                     void* ptr,
                                                     float opt);

    /** This is called once by the VST plug-in wrapper after its constructor.
        You can use the supplied function to query the VST host.
    */
    virtual void handleVstHostCallbackAvailable (std::function<VstHostCallbackType>&& callback)
    {
        ignoreUnused (callback);
    }
};

} // namespace juce