EventFromHost

Table of contents

1. Description
2. 1. Checking if available
3. 2. Identify the type of event
4. 3. Accessing the information
5. Example

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Description

As mentioned before the data received from the host are provided in a per-buffer basis. For each buffer multiple information can be available:

1. DAW Status at the start of the buffer: Play, Stop, Record, Loop, Tempo, Time Signature, Buffer Position
2. MIDI Events within the buffer: Note On, Note Off …

These data received from the host are wrapped in the EventFromHost data type and are provided to you in the ITP thread.

In ITP_Deploy.cpp, these events are passed on to you sequentially (whenever available) using the new_event_from_host variable of the Deploy() method.

As mentioned before, you can specify which of these events you want to receive in the ITP thread

To do so, you need to specify the event_communication_settings in the settings.json file. To learn more about this process, visit [this page]((/docs/V2_1_0/DeploymentStages/ITP/HostEvents)

1. Checking if available

The new_event_from_host variable is an optional variable, as a result before using it, you should always check if it is available

if (new_event_from_host->has_value()) {
    // ... 
}

2. Identify the type of event

There are different types available in the EventFromHost data type.

Event Type	Check Method	Description
FirstBufferEvent	new_event_from_host->isFirstBufferEvent()	Sent at the beginning of the host start.
PlaybackStoppedEvent	new_event_from_host->isPlaybackStoppedEvent()	Sent when the host stops the playback.
NewBufferEvent	new_event_from_host->isNewBufferEvent()	Sent at the beginning of every new buffer or when qpm, meter, etc. changes.
NewBarEvent	new_event_from_host->isNewBarEvent()	Sent at the beginning of every new bar.
NewTimeShiftEvent	new_event_from_host->isNewTimeShiftEvent()	Sent every N QuarterNotes (as specified in the settings.json file
NoteOnEvent	new_event_from_host->isNoteOnEvent()	Sent when a note is played.
NoteOffEvent	new_event_from_host->isNoteOffEvent()	Sent when a note is stopped.
CCEvent	new_event_from_host->isCCEvent()	Sent for Control Change events.

3. Accessing the information

Regardless of the type, the following information is always available within the received event:

Information	Access Method
Event Time (Various Units)	new_event_from_host->Time().inSeconds(), new_event_from_host->Time().inSamples(), new_event_from_host->Time().inQuarterNotes()
QPM (Tempo)	new_event_from_host->qpm()
Time Signature	new_event_from_host->numerator(), new_event_from_host->denominator()
Playback Status	new_event_from_host->isPlaying(), new_event_from_host->isRecording()
Buffer Start Time	new_event_from_host->BufferStartTime().inSeconds()
Buffer End Time (Seconds)	new_event_from_host->BufferEndTime().inSamples()
Buffer End Time (Quarter Notes)	new_event_from_host->BufferEndTime().inQuarterNotes()
Looping Status	new_event_from_host->isLooping()
Loop Start and End Times (Quarter Notes)	new_event_from_host->loopStart(), new_event_from_host->loopEnd()
Number of Bars Elapsed	new_event_from_host->barCount()
Last Bar Position	new_event_from_host->lastBarPos().inSeconds(), new_event_from_host->lastBarPos().inSamples(), new_event_from_host->lastBarPos().inQuarterNotes(),

The following information is available for NoteOnEvent and NoteOffEvent:

Information	Access Method
Note Number	new_event_from_host->getNoteNumber()
Velocity	new_event_from_host->getVelocity()
Channel	new_event_from_host->getChannel()

The following information is available for CCEvent:

Information	Access Method
CC Number	new_event_from_host->getCCNumber()
Value	new_event_from_host->getCCValue()
Channel	new_event_from_host->getChannel()

Example

   if (new_event_from_host.has_value()) {

        if (new_event_from_host->isFirstBufferEvent()) {

        } else if (new_event_from_host->isPlaybackStoppedEvent()) {

        } else if (new_event_from_host->isNewBufferEvent()) {

        } else if (new_event_from_host->isNewBarEvent()) {

        } else if (new_event_from_host->isNewTimeShiftEvent()) {

        } else if (new_event_from_host->isNoteOnEvent()) {
            auto note_n = new_event_from_host->getNoteNumber();
            auto vel =new_event_from_host->getVelocity();
            auto channel = new_event_from_host->getChannel();
            auto time = new_event_from_host->Time().inSeconds();
        } else if (new_event_from_host->isNoteOffEvent()) {
            auto note_n = new_event_from_host->getNoteNumber();
            auto vel =new_event_from_host->getVelocity();
            auto channel = new_event_from_host->getChannel();
        } else if (new_event_from_host->isCCEvent()) {
        }
    }