ble_midi_registry.hpp

Go to the documentation of this file.

#pragma once
 
// Process-wide registry that bridges a connected BLE-MIDI peripheral into the
// platform MidiSystem's port list.
//
// Why this exists: on Apple, CoreMIDI itself exposes an OS-paired BLE
// peripheral as a regular MIDI endpoint, so MidiSystem::enumerate_inputs()
// shows it for free. Off Apple there is no such OS bridge — ALSA-seq does NOT
// auto-create a port for a GATT notify stream. The BlueZ central therefore has
// to publish the connection somewhere the platform MidiSystem can see it, and
// the MidiSystem has to merge those published entries into its enumeration and
// route open() on a BLE port id to the registry instead of the raw transport.
//
// This registry is the smallest honest seam for that: the central
// register_input()/register_output() on connect (and unregister on
// disconnect); the MidiSystem queries list_inputs()/list_outputs() to merge,
// and attach_input_sink()/take_output_source() to wire delivery once a port is
// opened. The registry owns NO transport — it only forwards bytes between the
// central and the MidiInput/MidiOutput the host opened.
//
// All ids use the "ble-midi-in:<peripheral-id>" / "ble-midi-out:<peripheral-id>"
// convention also produced by the Apple backend, so a host can pre-select a BLE
// port via BleMidiCentral::midi_input_port_for() before it appears in
// enumerate_inputs().
//
// Cross-platform + Skia-free: compiled on every platform so the central and the
// MidiSystem link against one definition. On platforms whose central never
// registers anything (the stub central) the registry simply stays empty and the
// merge is a no-op.
 
#include <pulp/midi/device.hpp>
#include <pulp/midi/message.hpp>
 
#include <functional>
#include <string>
#include <vector>
 
namespace pulp::midi {

class BleMidiPortRegistry {
public:
    static BleMidiPortRegistry& instance();
 
    // ── Central side ────────────────────────────────────────────────────────

    void register_input(const std::string& port_id, const std::string& name);
    void register_output(const std::string& port_id, const std::string& name,
                         std::function<void(const std::vector<uint8_t>&)> sink);

    void unregister_input(const std::string& port_id);
    void unregister_output(const std::string& port_id);

    void deliver_message(const std::string& port_id,
                         const std::vector<uint8_t>& bytes, double timestamp_sec);
 
    // ── MidiSystem side ─────────────────────────────────────────────────────

    std::vector<MidiPortInfo> list_inputs() const;
    std::vector<MidiPortInfo> list_outputs() const;

    bool is_input(const std::string& port_id) const;
    bool is_output(const std::string& port_id) const;

    bool attach_input(const std::string& port_id, MidiInputCallback callback,
                      MidiSysexCallback sysex_callback);
    void detach_input(const std::string& port_id);

    std::function<void(const std::vector<uint8_t>&)> output_sink(
        const std::string& port_id) const;
 
private:
    BleMidiPortRegistry() = default;
 
    struct Impl;
    // Pimpl keeps <mutex>/<map> out of this widely-included header.
    Impl& impl() const;
};
 
}  // namespace pulp::midi