events.h

#pragma once

#include "private/std.h"
#include "fixedpoint.h"
#include "id.h"

#ifdef __cplusplus
extern "C" {
#endif

// event header
// must be the first attribute of the event
typedef struct clap_event_header {
   uint32_t size;     // event size including this header, eg: sizeof (clap_event_note)
   uint32_t time;     // sample offset within the buffer for this event
   uint16_t space_id; // event space, see clap_host_event_registry
   uint16_t type;     // event type
   uint32_t flags;    // see clap_event_flags
} clap_event_header_t;

// The clap core event space
static const CLAP_CONSTEXPR uint16_t CLAP_CORE_EVENT_SPACE_ID = 0;

enum clap_event_flags {
   // Indicate a live user event, for example a user turning a physical knob
   // or playing a physical key.
   CLAP_EVENT_IS_LIVE = 1 << 0,

   // Indicate that the event should not be recorded.
   // For example this is useful when a parameter changes because of a MIDI CC,
   // because if the host records both the MIDI CC automation and the parameter
   // automation there will be a conflict.
   CLAP_EVENT_DONT_RECORD = 1 << 1,
};

// Some of the following events overlap, a note on can be expressed with:
// - CLAP_EVENT_NOTE_ON
// - CLAP_EVENT_MIDI
// - CLAP_EVENT_MIDI2
//
// The preferred way of sending a note event is to use CLAP_EVENT_NOTE_*.
//
// The same event must not be sent twice: it is forbidden to send a the same note on
// encoded with both CLAP_EVENT_NOTE_ON and CLAP_EVENT_MIDI.
//
// The plugins are encouraged to be able to handle note events encoded as raw midi or midi2,
// or implement clap_plugin_event_filter and reject raw midi and midi2 events.
enum {
   // NOTE_ON and NOTE_OFF represent a key pressed and key released event, respectively.
   // A NOTE_ON with a velocity of 0 is valid and should not be interpreted as a NOTE_OFF.
   //
   // NOTE_CHOKE is meant to choke the voice(s), like in a drum machine when a closed hihat
   // chokes an open hihat. This event can be sent by the host to the plugin. Here are two use
   // cases:
   // - a plugin is inside a drum pad in Bitwig Studio's drum machine, and this pad is choked by
   //   another one
   // - the user double-clicks the DAW's stop button in the transport which then stops the sound on
   //   every track
   //
   // NOTE_END is sent by the plugin to the host. The port, channel, key and note_id are those given
   // by the host in the NOTE_ON event. In other words, this event is matched against the
   // plugin's note input port.
   // NOTE_END is useful to help the host to match the plugin's voice life time.
   //
   // When using polyphonic modulations, the host has to allocate and release voices for its
   // polyphonic modulator. Yet only the plugin effectively knows when the host should terminate
   // a voice. NOTE_END solves that issue in a non-intrusive and cooperative way.
   //
   // CLAP assumes that the host will allocate a unique voice on NOTE_ON event for a given port,
   // channel and key. This voice will run until the plugin will instruct the host to terminate
   // it by sending a NOTE_END event.
   //
   // Consider the following sequence:
   // - process()
   //    Host->Plugin NoteOn(port:0, channel:0, key:16, time:t0)
   //    Host->Plugin NoteOn(port:0, channel:0, key:64, time:t0)
   //    Host->Plugin NoteOff(port:0, channel:0, key:16, t1)
   //    Host->Plugin NoteOff(port:0, channel:0, key:64, t1)
   //    # on t2, both notes did terminate
   //    Host->Plugin NoteOn(port:0, channel:0, key:64, t3)
   //    # Here the plugin finished processing all the frames and will tell the host
   //    # to terminate the voice on key 16 but not 64, because a note has been started at t3
   //    Plugin->Host NoteEnd(port:0, channel:0, key:16, time:ignored)
   //
   // These four events use clap_event_note.
   CLAP_EVENT_NOTE_ON = 0,
   CLAP_EVENT_NOTE_OFF = 1,
   CLAP_EVENT_NOTE_CHOKE = 2,
   CLAP_EVENT_NOTE_END = 3,

   // Represents a note expression.
   // Uses clap_event_note_expression.
   CLAP_EVENT_NOTE_EXPRESSION = 4,

   // PARAM_VALUE sets the parameter's value; uses clap_event_param_value.
   // PARAM_MOD sets the parameter's modulation amount; uses clap_event_param_mod.
   //
   // The value heard is: param_value + param_mod.
   //
   // In case of a concurrent global value/modulation versus a polyphonic one,
   // the voice should only use the polyphonic one and the polyphonic modulation
   // amount will already include the monophonic signal.
   CLAP_EVENT_PARAM_VALUE = 5,
   CLAP_EVENT_PARAM_MOD = 6,

   // Indicates that the user started or finished adjusting a knob.
   // This is not mandatory to wrap parameter changes with gesture events, but this improves
   // the user experience a lot when recording automation or overriding automation playback.
   // Uses clap_event_param_gesture.
   CLAP_EVENT_PARAM_GESTURE_BEGIN = 7,
   CLAP_EVENT_PARAM_GESTURE_END = 8,

   CLAP_EVENT_TRANSPORT = 9,   // update the transport info; clap_event_transport
   CLAP_EVENT_MIDI = 10,       // raw midi event; clap_event_midi
   CLAP_EVENT_MIDI_SYSEX = 11, // raw midi sysex event; clap_event_midi_sysex
   CLAP_EVENT_MIDI2 = 12,      // raw midi 2 event; clap_event_midi2
};

// Note on, off, end and choke events.
//
// Clap addresses notes and voices using the 4-value tuple
// (port, channel, key, note_id). Note on/off/end/choke
// events and parameter modulation messages are delivered with
// these values populated.
//
// Values in a note and voice address are either >= 0 if they
// are specified, or -1 to indicate a wildcard. A wildcard
// means a voice with any value in that part of the tuple
// matches the message.
//
// For instance, a (PCKN) of (0, 3, -1, -1) will match all voices
// on channel 3 of port 0. And a PCKN of (-1, 0, 60, -1) will match
// all channel 0 key 60 voices, independent of port or note id.
//
// Especially in the case of note-on note-off pairs, and in the
// absence of voice stacking or polyphonic modulation, a host may
// choose to issue a note id only at note on. So you may see a
// message stream like
//
// CLAP_EVENT_NOTE_ON  [0,0,60,184]
// CLAP_EVENT_NOTE_OFF [0,0,60,-1]
//
// and the host will expect the first voice to be released.
// Well constructed plugins will search for voices and notes using
// the entire tuple.
//
// In the case of note on events:
// - The port, channel and key must be specified with a value >= 0
// - A note-on event with a '-1' for port, channel or key is invalid and
//   can be rejected or ignored by a plugin or host.
// - A host which does not support note ids should set the note id to -1.
//
// In the case of note choke or end events:
// - the velocity is ignored.
// - key and channel are used to match active notes
// - note_id is optionally provided by the host
typedef struct clap_event_note {
   clap_event_header_t header;

   int32_t note_id; // host provided note id >= 0, or -1 if unspecified or wildcard
   int16_t port_index; // port index from ext/note-ports; -1 for wildcard
   int16_t channel;  // 0..15, same as MIDI1 Channel Number, -1 for wildcard
   int16_t key;      // 0..127, same as MIDI1 Key Number (60==Middle C), -1 for wildcard
   double  velocity; // 0..1
} clap_event_note_t;

// Note Expressions are well named modifications of a voice targeted to
// voices using the same wildcard rules described above. Note Expressions are delivered
// as sample accurate events and should be applied at the sample when received.
//
// Note expressions are a statement of value, not cumulative. A PAN event of 0 followed by 1
// followed by 0.5 would pan hard left, hard right, and center. They are intended as
// an offset from the non-note-expression voice default. A voice which had a volume of
// -20db absent note expressions which received a +4db note expression would move the
// voice to -16db.
//
// A plugin which receives a note expression at the same sample as a NOTE_ON event
// should apply that expression to all generated samples. A plugin which receives
// a note expression after a NOTE_ON event should initiate the voice with default
// values and then apply the note expression when received. A plugin may make a choice
// to smooth note expression streams.
enum {
   // with 0 < x <= 4, plain = 20 * log(x)
   CLAP_NOTE_EXPRESSION_VOLUME = 0,

   // pan, 0 left, 0.5 center, 1 right
   CLAP_NOTE_EXPRESSION_PAN = 1,

   // Relative tuning in semitones, from -120 to +120. Semitones are in
   // equal temperament and are doubles; the resulting note would be
   // retuned by `100 * evt->value` cents.
   CLAP_NOTE_EXPRESSION_TUNING = 2,

   // 0..1
   CLAP_NOTE_EXPRESSION_VIBRATO = 3,
   CLAP_NOTE_EXPRESSION_EXPRESSION = 4,
   CLAP_NOTE_EXPRESSION_BRIGHTNESS = 5,
   CLAP_NOTE_EXPRESSION_PRESSURE = 6,
};
typedef int32_t clap_note_expression;

typedef struct clap_event_note_expression {
   clap_event_header_t header;

   clap_note_expression expression_id;

   // target a specific note_id, port, key and channel, with
   // -1 meaning wildcard, per the wildcard discussion above
   int32_t note_id;
   int16_t port_index;
   int16_t channel;
   int16_t key;

   double value; // see expression for the range
} clap_event_note_expression_t;

typedef struct clap_event_param_value {
   clap_event_header_t header;

   // target parameter
   clap_id param_id; // @ref clap_param_info.id
   void   *cookie;   // @ref clap_param_info.cookie

   // target a specific note_id, port, key and channel, with
   // -1 meaning wildcard, per the wildcard discussion above
   int32_t note_id;
   int16_t port_index;
   int16_t channel;
   int16_t key;

   double value;
} clap_event_param_value_t;

typedef struct clap_event_param_mod {
   clap_event_header_t header;

   // target parameter
   clap_id param_id; // @ref clap_param_info.id
   void   *cookie;   // @ref clap_param_info.cookie

   // target a specific note_id, port, key and channel, with
   // -1 meaning wildcard, per the wildcard discussion above
   int32_t note_id;
   int16_t port_index;
   int16_t channel;
   int16_t key;

   double amount; // modulation amount
} clap_event_param_mod_t;

typedef struct clap_event_param_gesture {
   clap_event_header_t header;

   // target parameter
   clap_id param_id; // @ref clap_param_info.id
} clap_event_param_gesture_t;

enum clap_transport_flags {
   CLAP_TRANSPORT_HAS_TEMPO = 1 << 0,
   CLAP_TRANSPORT_HAS_BEATS_TIMELINE = 1 << 1,
   CLAP_TRANSPORT_HAS_SECONDS_TIMELINE = 1 << 2,
   CLAP_TRANSPORT_HAS_TIME_SIGNATURE = 1 << 3,
   CLAP_TRANSPORT_IS_PLAYING = 1 << 4,
   CLAP_TRANSPORT_IS_RECORDING = 1 << 5,
   CLAP_TRANSPORT_IS_LOOP_ACTIVE = 1 << 6,
   CLAP_TRANSPORT_IS_WITHIN_PRE_ROLL = 1 << 7,
};

typedef struct clap_event_transport {
   clap_event_header_t header;

   uint32_t flags; // see clap_transport_flags

   clap_beattime song_pos_beats;   // position in beats
   clap_sectime  song_pos_seconds; // position in seconds

   double tempo;     // in bpm
   double tempo_inc; // tempo increment for each sample and until the next
                     // time info event

   clap_beattime loop_start_beats;
   clap_beattime loop_end_beats;
   clap_sectime  loop_start_seconds;
   clap_sectime  loop_end_seconds;

   clap_beattime bar_start;  // start pos of the current bar
   int32_t       bar_number; // bar at song pos 0 has the number 0

   uint16_t tsig_num;   // time signature numerator
   uint16_t tsig_denom; // time signature denominator
} clap_event_transport_t;

typedef struct clap_event_midi {
   clap_event_header_t header;

   uint16_t port_index;
   uint8_t  data[3];
} clap_event_midi_t;

typedef struct clap_event_midi_sysex {
   clap_event_header_t header;

   uint16_t       port_index;
   const uint8_t *buffer; // midi buffer
   uint32_t       size;
} clap_event_midi_sysex_t;

// While it is possible to use a series of midi2 event to send a sysex,
// prefer clap_event_midi_sysex if possible for efficiency.
typedef struct clap_event_midi2 {
   clap_event_header_t header;

   uint16_t port_index;
   uint32_t data[4];
} clap_event_midi2_t;

// Input event list. The host will deliver these sorted in sample order.
typedef struct clap_input_events {
   void *ctx; // reserved pointer for the list

   // returns the number of events in the list
   uint32_t(CLAP_ABI *size)(const struct clap_input_events *list);

   // Don't free the returned event, it belongs to the list
   const clap_event_header_t *(CLAP_ABI *get)(const struct clap_input_events *list, uint32_t index);
} clap_input_events_t;

// Output event list. The plugin must insert events in sample sorted order when inserting events
typedef struct clap_output_events {
   void *ctx; // reserved pointer for the list

   // Pushes a copy of the event
   // returns false if the event could not be pushed to the queue (out of memory?)
   bool(CLAP_ABI *try_push)(const struct clap_output_events *list,
                            const clap_event_header_t       *event);
} clap_output_events_t;

#ifdef __cplusplus
}
#endif