Presets

Presets are full-state snapshots. A saved preset captures the current engine state (LFO settings, audio routing, MIDI mappings, input/output config) plus your effect's State struct.

Saving and loading

Use the Presets tab in the control window. Presets are stored as JSON files in:

~/.config/rustjay/<app-name>/presets/

Each effect's presets are isolated by app_name(). Running template and delta from the same machine gives them separate preset banks.

Quick-slots

Eight quick-slot buttons appear at the top of the Presets tab. Press Shift+F1–Shift+F8 on the output window to recall them instantly, without switching to the control window.

Save a preset to a quick-slot: right-click the slot button and choose Save here, or drag-and-drop from the preset list.

Including plugin state

By default, presets only save engine state (LFO, audio, MIDI, etc.). To save your effect's own state — extra textures, ring-buffer configuration, anything beyond EngineState — implement three preset hooks:

#![allow(unused)]
fn main() {
impl EffectPlugin for MyEffect {
    // ...

    fn serialize_preset_state(&self, state: &MyState) -> Option<String> {
        // Return a JSON string, or None to skip
        serde_json::to_string(state).ok()
    }

    fn deserialize_preset_state(&self, data: &str, state: &mut MyState) {
        if let Ok(loaded) = serde_json::from_str::<MyState>(data) {
            *state = loaded;
        }
    }

    fn on_preset_applied(&self, state: &mut MyState, engine: &mut EngineState) {
        // Called after both engine state and plugin state are restored.
        // Use to push any required commands back to the engine.
        // e.g. engine.input_commands.push(InputCommand::SetDevice(...));
    }
}
}

Because State already derives serde::Serialize + DeserializeOwned, serde_json::to_string / from_str are the standard approach.

State initialisation vs presets

Preset loading calls deserialize_preset_state() and then on_preset_applied(). The initial state at launch comes from default_state(). These are separate paths — don't rely on on_preset_applied() for startup initialisation.

File format

Preset files are plain JSON. You can hand-edit them, version-control them, or share them. The top-level keys are:

{
  "engine": { /* EngineState fields */ },
  "plugin": "{ /* your serialized State as a JSON string */ }"
}