#reaper #midi #api-bindings #daw #plugin


Bindings for the REAPER C++ API - low-level API

3 releases

0.1.31 Mar 31, 2024
0.1.2 Dec 26, 2022
0.1.1 Dec 26, 2022

#261 in Audio

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Used in 4 crates

MIT license

174K SLoC

C 81K SLoC // 0.2% comments C++ 59K SLoC // 0.0% comments Rust 16K SLoC // 0.0% comments Objective-C++ 15K SLoC // 0.0% comments Assembly 892 SLoC // 0.0% comments PHP 750 SLoC // 0.0% comments Visual Studio Project 484 SLoC Happy 341 SLoC Vim Script 332 SLoC // 0.1% comments Visual Studio Solution 56 SLoC Shell 13 SLoC // 0.1% comments Objective-C 10 SLoC // 0.6% comments

Contains (Mach-o exe, 7KB) lib/WDL/WDL/eel2/asm-nseel-x64-macho.o


linux windows macos

Easy to use ReaScript API. While reaper-rs is full-implemented at low-level, and, partially implemented at medium-level, on top of it (mostly, on top of low-level) this crate builds API that is pleasure to use. Actually, for the moment it is the better version of Reapy project.

See the docs

The main skeleton of this API is cloned from the Reapy, but reimplemented in a more "rusty" way. Also, a bunch of new functions are added to Track, Item and Take, as well as a good new implementation for ExtState and midi was made. I would say, that currently wrapped ~95% of Track, Take, Item, AudioAccessor and FX original functions; about of 70% for Envelope and Source. And the rest is probably, less, then 50%. It should also be possible to use from VST Plugin, but this has not yet been tested at all.

Until there is no new version of reaper-rs which differs from the current master branch a lot, this is the dependency list I highly recommend:

These are the dependencies:

rea-rs = "0.1.3"
rea-rs-low = "0.1.3" # optional
rea-rs-macros = "0.1.3"

But, actually, all medium- and low-level functionality is still existing in the Reaper object. Just use Reaper::low, Reaper::medium and Reaper::medium_session. The Common entry point should look like this:

use rea_rs::{errors::ReaperResult, ActionKind, Reaper, PluginContext};
use rea_rs_macros::reaper_extension_plugin;
use std::error::Error;

fn plugin_main(context: PluginContext) -> Result<(), Box<dyn Error>> {
    let reaper = Reaper::get_mut();
    let message = "Hello from small extension";

Since, there are not many things to be done at the start time of Reaper, there are two common ways to invoke the code: Actions and Timer.

use rea_rs::{PluginContext, Reaper, RegisteredAccel, Timer};
use rea_rs_macros::reaper_extension_plugin;
use std::error::Error;

struct Listener {
    action: RegisteredAccel,

// Full list of function larger.
impl Timer for Listener {
    fn run(&mut self) -> Result<(), Box<dyn Error>> {
        Reaper::get().perform_action(self.action.command_id, 0, None);
    fn id_string(&self) -> String {"test listener".to_string()}

fn my_action_func(_flag: i32) -> Result<(), Box<dyn Error>> {

fn plugin_main(context: PluginContext) -> Result<(), Box<dyn Error>> {
    let reaper = Reaper::get_mut();

    let action = reaper.register_action(
        // This will be capitalized and used as action ID in action window
        // This is the line user searches action for
        // Only type currently supported


There are float values in API. I recommend to use float_eq crate.

API structure

Most of the time, API is used hierarchically: Reaper holds top-level functions and can return Project, Item etc. While Project can manipulate by Track, Item, Take. The key point of the hierarchical structure — to be sure safe as long as possible. Since Project is alive, it is safe to refer from track to it. The same with other children. By the same reason, it's almost impossible to mutate two object at a time. If one track is mutable, it responses for the whole underlying objects. And we can be almost sure, that the rest of tracks consist of objects, we left them before. The most part of API is covered by tests, and they are a good set of usage examples.

use rea_rs::Reaper;
use std::collections::HashMap;
let rpr = Reaper::get();
let captions =
vec!["age(18)", "name(user)", "leave blank", "fate(atheist)"];
let mut answers = HashMap::new();
answers.insert(String::from("age(18)"), String::from("18"));
answers.insert(String::from("name(user)"), String::from("user"));
answers.insert(String::from("leave blank"), String::from(""));
answers.insert(String::from("fate(atheist)"), String::from("atheist"));
let result = rpr.get_user_inputs(
    "Fill values as asked in fields",
assert_eq!(result, answers);

Better to know about

For the moment, downsides of API are:

  • top-level functionality: I'm not sure, that at least a half of little reaper functions is wrapped. Like all windowing and theming stuff.
  • GUI. As well as with reapy, GUI is an issue. I've started reaper-imgui crate, that makes possible to use ReaImGui extension from rust. But it waits for being properly wrapped by rea-rs.
  • Thread-safety. It's important to know, that almost nothing of Reaper should left the main thread. There are some functions, that are designed for audio thread, and some, that are safe to execute from any thread. But, basically, here is a rule: if you make a listener, gui or socket communication — Reaper lives in main thread, and else made by std::sync::mpsc. Enjoy the coding!