mostly harmless is a minimal audio plugin framework for C++20. It's first and foremost a wrapper around the CLAP API, capable of building CLAP, VST3, Audio Unit and Standalone targets.

If you're compiling VST3 targets, the responsibility to ensure you're adhering to the Steinberg VST3 License agreement is firmly on you!

Documentation is built automatically, and hosted here. For convenience, it also includes the documentation for marvin.

While the framework itself doesn't provide anything in the way of audio helpers ala something like JUCE, it ships with our sibling dsp library marvin, should you need some convenience helpers and basic audio features.

The goal of the framework was to provide the bare minimum we (as in SLM Audio) need to write a plugin - and as such we don't provide any kind of gui framework of our own. We do, however, provide a thin wrapper around choc's WebView, and plan to implement similar minimal wrappers around a couple of other frameworks.
We also provide an interface with hooks for you to implement your framework of choice, in mostly_harmless::gui::IEffect.

Firstly, we'd recommend taking a look in the examples directory for a real-world use case, in the absence of actual tutorials (which are planned).
mostly harmless is built with CMake, and supports Windows and macOS (Linux support is on the roadmap). It can be consumed either as a git submodule, or as a FetchContent dependency.

include(FetchContent)
FetchContent_Declare(mostly_harmless
       GIT_REPOSITORY "https://github.com/SLM-Audio/mostly-harmless.git
GIT_TAG main 
GIT_SHALLOW ON)

FetchContent_MakeAvailable(mostly_harmless)

We provide a convenience function to set up your plugin targets, mostly_harmless_add_plugin. This function will create targets for the specified formats, and link them to the necessary dependencies. Note that if you specify the AU format, a few more arguments become neccessary - the arguments are detailed below.

mostly_harmless_add_plugin(YourTarget
       FORMATS CLAP # REQUIRED - At least one of: CLAP, VST3, AU or STANDALONE
       ID "com.whatever" # REQUIRED - The ID for your plugin
       FEATURES "audio-effect" # REQUIRED - The CLAP features your plugin uses. [1]
       VERSION "1.0.0" # OPTIONAL - Your plugin's verson.
       DESCRIPTION "We are trapped in the belly of this horrible machine" # OPTIONAL 
       #                                            - A description for your plugin
       URL "https://slm-audio.com" # OPTIONAL - A link to your website.
       MANUAL_URL "https://slm-audio.com/manual" # OPTIONAL - A link to your manual.
       SUPPORT_URL "https://slm-audio.com/hr" # OPTIONAL - A link to your support page.

       NEEDS_NOTE_IN_BUS FALSE # OPTIONAL, DEFAULTS TO FALSE - Whether your plugin accepts midi/note input.
       NEEDS_NOTE_OUT_BUS FALSE # OPTIONAL, DEFAULTS TO FALSE - Whether your plugin produces midi/note output.
       NEEDS_AUDIO_IN_BUS TRUE # OPTIONAL, DEFAULTS TO TRUE - Whether your plugin accepts audio input.
       NEEDS_AUDIO_OUT_BUS TRUE # OPTIONAL, DEFAULTS TO TRUE - Whether your plugin produces audio output.

       VENDOR "YourCompany" # REQUIRED FOR AU, OPTIONAL OTHERWISE - The name of your company.
       AU_BUNDLE_ID "com.yourcompany.plugin" # REQUIRED FOR AU, UNUSED OTHERWISE - A company id for the AU bundle.
       AU_BUNDLE_VERSION "1" # REQUIRED FOR AU, UNUSED OTHERWISE - A version for the AU bundle.
       MANUFACTURER_CODE "Brat" # REQUIRED FOR AU, UNUSED OTHERWISE - Your unique 4 character manufacturer code.
       SUBTYPE_CODE "Bpi1" # REQUIRED FOR AU, UNUSED OTHERWISE - A 4 character identifier for your plugin.
       AU_TYPE "aufx" # REQUIRED FOR AU, UNUSED OTHERWISE - The AU plugin type for your plugin. [2]
)

mostly_harmless_add_plugin will create several targets based on the arguments provided to the FORMATS field. Internally, we create a static library named based on the value you provide to the YourTarget argument, with linkage to the library dependencies, and then link our format targets to that - so after the call to mostly_harmless_add_plugin, the usual cmake rules and techniques apply to the shared target.
For example, to add some sources to the target:

target_sources(YourTarget PRIVATE
        ${CMAKE_CURRENT_SOURCE_DIR}/source/Plugin.cpp
        ${CMAKE_CURRENT_SOURCE_DIR}/source/PluginEditor.cpp
)

[1] - See here for a full list of available features.
[2] - These are the au specific 4 letter idents you get when you scan with auval - options are as follows:

    aufx - audio effect
    aufc - format converter
    augn - audio generator
    aumi - midi processor
    aumx - mixer 
    aumu - music device
    aumf - music effect
    auol - offline effect
    auou - output
    aupn - panner

We also provide a helper to embed assets into your binary, and a corresponding cmake function to call this, mostly_harmless_add_binary_data.

    mostly_harmless_add_binary_data(YourTarget
        BINARY_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/resources/VonDutch128.mp3
        ${CMAKE_CURRENT_SOURCE_DIR}/resources/JamesJoyceReads_TheJungleBook.wav
)

This will generate a static library internally called binary-data, compile your sources into cpp files, and link your target to said library. It also generates a header, BinaryData.h, and ensures it's on your plugin's include path.
The header contains extern declarations of type BinaryResource for the generated resources, within the binary_data namespace. The BinaryResource struct is as follows:

    struct BinaryResource {
        std::string originalFilename; // The original filename on disk (excluding the leading path, but including the extension).
        std::vector<char> data; // The raw bytes in the file.
    };

which is hopefully relatively self explanatory.
With our example call to mostly_harmless_add_binary_data from above, the generated header would be:

// This file is auto generated!
#ifndef BINARYDATA_H
#define BINARYDATA_H
#include <vector>
#include <string>
namespace binary_data {
    struct BinaryResource {
        std::string originalFilename;
        std::vector<char> data;
    };
    extern BinaryResource VonDutch128;
    extern BinaryResource JamesJoyceReads_TheJungleBook;
}
#endif

To access a some data from it from some imaginary class,

#include <BinaryData.h>
class ImaginaryClass final {
public: 
    ImaginaryClass() { 
        const auto& importantListening = binary_data::JamesJoyceReads_TheJungleBook; 
        // Access the data with importantListening.data()..
    }
    
};

We've included the boilerplate for various projects in the boilerplate directory - these should serve as a good starting point for your plugin sources. As previously mentioned, you can also check out the examples directory for more inspiration.

mostly harmless depends on the following libraries:

• marvin (and its dependencies)
• clap, clap-helpers, clap-wrapper
• choc
• fmtlib
• json
• catch2

This framework wouldn't exist without the advice, moral support and help of mthierman, Ben Vining, Signalsmith and the legions of incredible people in The Audio Programmer Discord.