Rust bindings for the REAPER C++ API.

Important note: If you want to use reaper-rs for your own project, please use the master branch for the time being, not the crates on crates.io! I push changes here pretty often, but I don't publish to crates.io at the moment, so my crates there are very outdated. Rationale: As long as I'm the only consumer of this library, this process is easier for me.

Here's the snippet:

reaper-medium = { git = "https://github.com/helgoboss/reaper-rs.git", branch = "master" }
reaper-low = { git = "https://github.com/helgoboss/reaper-rs.git", branch = "master" }
reaper-macros = { git = "https://github.com/helgoboss/reaper-rs.git", branch = "master" }

• Introduction
• Example
• Basics
• Usage
• Contribution
• Background

reaper-rs allows programmers to write plug-ins for the REAPER DAW (digital audio workstation) in the Rust programming language. It does so by providing raw Rust bindings for the REAPER C++ API and more convenient APIs on top of that. It also exposes the SWELL C++ API, which is provided by REAPER on Linux and macOS in order to enable developers to create cross-platform user interfaces with a subset of the Win32 API.

A minimal working extension project can be found here. Make sure you also read the basics though! It's important to understand the differences between the provided APIs and be aware that the high-level API shouldn't be used for anything else than bootstrapping the extension (because I don't keep it stable).

reaper-rs consists of the following production crates:

• reaper-macros
• reaper-low
• reaper-medium
• reaper-high (not yet published)
• reaper-rx (not yet published)

reaper-macros provides a simple attribute macro to simplify bootstrapping REAPER extension plug-ins.

reaper-low, reaper-medium and reaper-high represent the 3 different APIs of reaper-rs

The remaining crates are add-ons for the high-level API.

This API contains the raw bindings, nothing more. It's unsafe to a large extent and not intended to be used directly. However, it serves as foundation for all the other APIs and is easy to keep up-to-date because it's mostly auto-generated from reaper_plugin_functions.h. It also can serve as last resort if a function has not yet been implemented in the medium-level API (although I rather want to encourage to contribute to the medium-level API in such a case).

Status:

• crates.io: published
• API stability: approaching stable (quite polished already, breaking changes still possible)
• Completion: ~95% (some virtual function calls still missing)

Example:

unsafe {
    reaper.ShowConsoleMsg(c_str!("Hello world from reaper-rs low-level API!").as_ptr());
    let track = reaper.GetTrack(null_mut(), 0);
    reaper.DeleteTrack(track);
}

This API builds on top of the low-level API. It exposes the original REAPER C++ API functions almost one to one, but in an idiomatic and type-safe way. It's a big step forward from the raw bindings and far more convenient to use. Its focus is on stability rather than exploring new paradigms. Since the high-level API is still very unstable, this is the recommended API.

Status:

• crates.io: published
• API stability: approaching stable (quite polished already, breaking changes still possible)
• Completion: ~13% (solid foundation, roughly 100 of 800 functions implemented)

Basics:

reaper.show_console_msg("Hello world from reaper-rs medium-level API!");
let track = reaper.get_track(CurrentProject, 0).ok_or("no tracks")?;
unsafe { reaper.delete_track(track); }

Control surface:

#[derive(Debug)]
struct MyControlSurface;

impl ControlSurface for MyControlSurface {
    fn set_track_list_change(&self) {
        println!("Tracks changed");
    }
}

session.plugin_register_add_csurf_inst(MyControlSurface);

Audio hook:

struct MyOnAudioBuffer {
    counter: u64
}

impl OnAudioBuffer for MyOnAudioBuffer {
    fn call(&mut self, args: OnAudioBufferArgs) {
        if self.counter % 100 == 0 {
            println!("Audio hook callback counter: {}\n", self.counter);
        }
        self.counter += 1;
    }
}

session.audio_reg_hardware_hook_add(MyOnAudioBuffer { counter: 0 });

This API builds on top of the medium-level API. It makes a break with the "flat functions" nature of the original REAPER C++ API and replaces it with an API that uses object-oriented paradigms. This break makes it possible to provide an intuitive API which can be used completely without unsafe.

Status:

• crates.io: not published
• API stability: unstable (in a state of flux, but working)
• Completion: ~13% (roughly on par with the medium-level API)

Example:

reaper.show_console_msg("Hello world from reaper-rs high-level API!");
let project = reaper.current_project();
let track = project.track_by_index(0).ok_or("no tracks")?;
project.remove_track(&track);

reaper-rx adds reactive programming via rxRust to the mix.

Example:

rx.track_removed().subscribe(|t| println!("Track {:?} removed", t));

The procedure depends on the desired type of plug-in. In addition to writing REAPER extension plug-ins, reaper-rs can be used for developing VST plug-ins that use REAPER functions. No matter what you choose, the possibilities of interacting with REAPER are essentially the same. The difference between the two is the context in which your plug-in will run.

An extension plug-in is loaded when REAPER starts and remains active until REAPER quits, so it's perfectly suited to add some functions to REAPER which should be available globally. Popular examples are SWS and ReaPack (both written in C++).

A REAPER VST plug-in is loaded as track, take or monitoring FX as part of a particular REAPER project, just like any instrument or effect plug-in out there. That also means it can be instantiated multiple times. Examples are Playtime (written in C++) and ReaLearn (successfully ported to Rust).

In both cases you need to make a library crate of type cdylib.

Using the reaper_extension_plugin macro is the fastest way to get going.

Add this to your Cargo.toml:

[dependencies]
reaper-low = "0.1.0"
reaper-medium = "0.1.0"
reaper-macros = "0.1.0"

[lib]
name = "reaper_my_extension"
crate-type = ["cdylib"]

Then in your lib.rs:

use std::error::Error;
use reaper_macros::reaper_extension_plugin;
use reaper_low::PluginContext;
use reaper_medium::ReaperSession;

#[reaper_extension_plugin]
fn plugin_main(context: PluginContext) -> Result<(), Box<dyn Error>> {
    let session = ReaperSession::load(context);
    session.reaper().show_console_msg("Hello world from reaper-rs medium-level API!");
    Ok(())
}

Important: Compiled REAPER extension plug-ins (i.e. .dll files) must be prefixed with reaper_ in order for REAPER to load them during startup - even on Linux and macOS, where library file names usually start with lib. On Windows, it's enough to name the library reaper_my_extension in Cargo.toml and it will result in the compiled file being named reaper_my_extension, thus obeying this rule. On Linux and macOS, you still need to remove the lib prefix. In any case, make sure that the compiled file placed in REAPER_RESOURCE_PATH/UserPlugins is prefixed with reaper_ before attempting to test it!

The macro primarily exposes an extern "C" ReaperPluginEntry() function which calls reaper_low::bootstrap_extension_plugin(). So if for some reason you don't want to use that macro, have a look at the macro implementation. No magic there.

The following instructions should result in a functional extension, loaded into REAPER on start:

1. Run cargo new reaper-my-extension --lib to initialize the project
2. Run cargo build from within reaper-my-extension to generate the compiled plugin extension inside of the target/debug directory
3. Copy the extension plug-in to the REAPER/UserPlugins directory
   • You could do this manually, and overwrite the file after each build
   • Or, you could create a symbolic link from the target/debug file, to REAPER/UserPlugins so that they were synced

     • Note: Here it's explicitly necessary to give the link a name that starts with reaper_ (by default it will start with lib)

     • To do this, on unix-based systems, run ln -s ./target/debug/<name-of-the-compiled-extension-file> <path to REAPER/UserPlugins>
     • On Windows, you can use the same command if running Git Bash, else you can use mklink \D target\debug\<name-of-the-compiled-extension-file> %AppData%\REAPER\UserPlugins
4. Now start REAPER, and you should see the console message from the code appear!

A REAPER VST plug-in is nothing else than a normal VST plug-in which gets access to functions from the REAPER C++ API. Luckily, there is a Rust crate for creating VST plug-ins already: vst-rs. So all you need to do is write a VST plug-in via vst-rs and gain access to the REAPER functions by letting reaper-rs access the HostCallback function.

Add this to your Cargo.toml:

[dependencies]
reaper-low = "0.1.0"
reaper-medium = "0.1.0"
vst = "0.2.0"

[lib]
name = "my_reaper_vst_plugin"
crate-type = ["cdylib"]

Then in your lib.rs:

use vst::plugin::{Info, Plugin, HostCallback};
use reaper_low::{PluginContext, reaper_vst_plugin, static_plugin_context};
use reaper_medium::ReaperSession;

reaper_vst_plugin!();

#[derive(Default)]
struct MyReaperVstPlugin {
    host: HostCallback,
};

impl Plugin for MyReaperVstPlugin {
    fn new(host: HostCallback) -> Self {
        Self { host }
    }

    fn get_info(&self) -> Info {
        Info {
            name: "My REAPER VST plug-in".to_string(),
            unique_id: 6830,
            ..Default::default()
        }
    }

    fn init(&mut self) {
        if let Ok(context) = PluginContext::from_vst_plugin(&self.host, static_plugin_context()) {
            let session = ReaperSession::load(context);
            session
                .reaper()
                .show_console_msg("Hello world from reaper-rs medium-level API!");
        }
    }
}

vst::plugin_main!(MyReaperVstPlugin);

Contributions are very welcome! Especially to the medium-level API.

reaper-low has several generated files, namely bindings.rs, reaper.rs and swell.rs. These files are not generated with each build though. In order to decrease build time and improve IDE/debugging support, they are included in the Git repository like any other Rust source.

You can generate these files on demand (see build section), e.g. after you have adjusted reaper_plugin_functions.h. Right now this is enabled for Linux only. If we generated the files on Windows, bindings.rs would look very different (whereas reaper.rs should end up the same). The reason is that reaper_plugin.h includes windows.h on Windows, whereas on Linux and macOS, it uses swell.h (Simple Windows Emulation Layer) as a replacement. But even on macOS, the result looks different than on Linux.

Most parts of bindings.rs are used to generate reaper.rs and otherwise ignored, but a few structs, types and constants are published as part of the raw module. In order to have deterministic builds, for now the convention is to only commit files generated on Linux. Rationale: swell.h is a sort of subset of windows.h, so if things work with the subset, they also should work for the superset. The inverse isn't true.

Thanks to Cargo, building reaper-rs is not a big deal.

In the following you will find the complete instructions for Windows 10, including Rust setup. Points where you have to consider the target architecture (REAPER 32-bit vs. 64-bit) are marked with ⭐.

1. Setup "Build tools for Visual Studio 2019"
   • Rust uses native build toolchains. On Windows, it's necessary to use the MSVC (Microsoft Visual Studio C++) toolchain because REAPER plug-ins only work with that.
   • Visual Studio downloads → All downloads → Tools for Visual Studio 2019 → Build Tools for Visual Studio 2019
   • Start it and follow the installer instructions
   • Required components
     • Workloads tab
       • "C++ build tools" (large box on the left)
       • Make sure "Windows 10 SDK" is checked on the right side (usually it is)
     • Language packs
       • English
2. Setup Rust
   • Download and execute rustup-init.exe
   • Accept the defaults
   • Set the correct toolchain default (nightly toolchain is not necessary if you only want to build reaper-low, reaper-medium and reaper-high) ⭐

     rustup default stable-x86_64-pc-windows-msvc

3. Download and install Git for Windows
4. Clone the reaper-rs Git repository

   git clone --recurse-submodules https://github.com/helgoboss/reaper-rs.git`
   cd reaper-rs

5. Build reaper-rs

   cargo build

Regenerate the low-level API:

• See section "Docker".
• As an alternative to Docker, use the WSL (preferably Ubuntu) and follow the instruction in the "Linux" section.

Complete instructions to build reaper-rs from a fresh Ubuntu 18.04.3 LTS installation, including Rust setup:

# Install basic stuff
sudo apt update
sudo apt install curl git build-essential pkg-config libssl-dev liblzma-dev llvm-dev libclang-dev clang -y

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh # choose 1 (default)
source $HOME/.cargo/env
# Using nightly is not necessary if you want to build just the low-level, medium-level or high-level API!
rustup default stable-x86_64-unknown-linux-gnu

# Clone reaper-rs
cd Downloads
git clone --recurse-submodules https://github.com/helgoboss/reaper-rs.git
cd reaper-rs

# Build reaper-rs
cargo build

Make the test plug-ins available in REAPER:

1. Download REAPER for Linux and start it at least one time.
2. Create symbolic links

   mkdir -p $HOME/.config/REAPER/UserPlugins/FX
   ln -s $HOME/Downloads/reaper-rs/target/debug/libreaper_test_extension_plugin.so $HOME/.config/REAPER/UserPlugins/reaper_test_extension_plugin.so
   ln -s $HOME/Downloads/reaper-rs/target/debug/libreaper_test_vst_plugin.so $HOME/.config/REAPER/UserPlugins/FX/reaper_test_vst_plugin.so

Regenerate the low-level API:

cd main/low
cargo build --features generate
cargo fmt

In order to get the most deterministic results, use Docker (see section "Docker").

The following instructions include Rust setup. However, it's very well possible that some native toolchain setup instructions are missing, because I don't have a bare macOS installation at my disposal. The Rust installation script should provide you with the necessary instructions if something is missing.

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh # choose 1 (default)
source $HOME/.cargo/env
# Using nightly is not necessary if you want to build just the low-level, medium-level or high-level API!
rustup default stable-x86_64-apple-darwin

# Clone reaper-rs
cd Downloads
git clone --recurse-submodules https://github.com/helgoboss/reaper-rs.git
cd reaper-rs

# Build reaper-rs
cargo build

Regenerate the low-level API:

• See section "Docker".

Regenerating the low-level API should always be done on Linux. And for getting really deterministic results, it's best to always use the same distro and same environment, which is easy to achieve with Docker:

# Build image (official Rust image + LLVM and Clang)
docker build --tag rust-for-reaper-rs .

# Build reaper-low with feature "generate"
docker run --rm --user "$(id -u)":"$(id -g)" -v "$PWD":/usr/src/myapp -w /usr/src/myapp rust-for-reaper-rs cargo build --package reaper-low --features generate

# Format code
cargo fmt

When building the complete reaper-rs workspace, 3 test crates are produced:

• reaper-test
• reaper-test-extension-plugin
• reaper-test-vst-plugin

reaper-test provides an integration test that is supposed to be run in REAPER itself. This is the main testing mechanism for reaper-rs. reaper-test-extension-plugin and reaper-test-vst-plugin are both test plug-ins which register the integration test as REAPER action.

Running the integration test is not only a good way to find reaper-rs regression bugs, but can also help to expose subtle changes in the REAPER C++ API itself. Currently, the test assertions are very strict in order to reveal even the slightest deviations.

Attention: The test should be executed using a fresh reaper.ini. Some assertions assume that REAPER preferences are set to their defaults. Executing the test with modified preferences can lead to wrong test results!

On Linux and macOS, the REAPER integration test will be run automatically as Cargo integration test run_reaper_integration_test when invoking cargo test (downloads, unpacks and executes REAPER). This test is part of reaper-test-extension-plugin. It can be disabled by building that crate with --no-default-features.

reaper-rs has been born as part of the effort of porting the REAPER VST plug-in ReaLearn to Rust and publish it as open-source project. The high-level API is heavily inspired by ReaPlus, a C++ facade for the native REAPER C++ API, which is a basic building block of the original ReaLearn.