Web MIDI API gets HotPlug Feature from Chrome M43(for Mac)

日本語

Web MIDI API on Chrome gets new feature from M43(You can try with Canary from today!!). That feature is Hot-Plug. So, the Chrome immediately recognizes MIDI device’s connection or disconnection. The connection/disconnection of MIDI device is informed by event. Before M43, Chrome does not recognize the MIDI devices are connected after requestMIDIAccess() is used. I think to add this feature is a big progress!! In the spec, Hot-Plug feature is written as “onstatechage” in MIDIAccess Interface and MIDI Port Interface. Let’s take a look at how to write code.

navigator.requestMIDIAccess({"sysex":true}).then(successCallback, errorCallback);
function successCallback(access) {
      access.onstatechange=function(event){
          console.log(event);
          // event.port に 接続/切断 されたMIDI機器が入っています。
      }
}
function errorCallback(msg) {
      console.log("[ERROR] ", msg);
}

The device information(MIDIPort) which is connected/disconnected is set in port. And its status is coming into port.state. port.state has 3 status in below.

  • disconnected: the device, which is connected , is disconnected
  • connected: the device is connected, but does NOT accept data transfer
  • opened: the device is connected, and ready to transfer data
    For MIDIPort, code and state are exactly same with MIDIAccess. When the event is attached to MIDIPort, connection/disconnection will be detected and informeb by event.

    This update would help lots of application which is using Web MIDI API and improve user experience!!!

Sonic Boom! (Google I/O'19)

Published on May 15, 2019

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