Email 在Thunderbird扩展中获取邮件发件人

我正在开发一个非常简单的Thunderbird扩展，它应该在邮件发送时提醒发件人的姓名和收件人的姓名。问题是在下面的代码段中，gMsgCompose.compFields.from字段为空。to字段按预期工作，用于处理compose send message事件。我错过了什么

function send_event_handler( evt ) {
var msgcomposeWindow = document.getElementById( "msgcomposeWindow" );
var msg_type = msgcomposeWindow.getAttribute( "msgtype" );

// do not continue unless this is an actual send event
if( !(msg_type == nsIMsgCompDeliverMode.Now || msg_type == nsIMsgCompDeliverMode.Later) )
  return;

var promptService = Components.classes["@mozilla.org/embedcomp/prompt-service;1"].getService(Components.interfaces.nsIPromptService);
promptService.alert(window, "From", gMsgCompose.compFields.from);
promptService.alert(window, "To", gMsgCompose.compFields.to);
}

window.addEventListener( "compose-send-message", send_event_handler, true );

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您可以通过msgIdentity小部件获取发送标识：

var identityWidget = document.getElementById('msgIdentity');
var fromIdentityKey= self.identityWidget.value;

然后，使用帐户管理器查找身份信息：

var acctMgr = Components.classes["@mozilla.org/messenger/account-manager;1"]
                      .getService(Components.interfaces.nsIMsgAccountManager);
var accounts = acctMgr.accounts;
for (var i = 0; i < accounts.Count(); i++) {
  var account = accounts.QueryElementAt(i, Components.interfaces.nsIMsgAccount);

  var accountIdentities = account.identities;

  for(var identCount = 0; identCount < accountIdentities.Count(); identCount++) {
    var identity = accountIdentities.QueryElementAt(identCount,
                                                 Components.interfaces.nsIMsgIdentity);

    if(identity.key == fromIdentityKey) {
       // Identity found
       alert(identity.email);
    }
  }
}

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或者在TB 7.0+中更方便&简单地说：

alert(gCurrentIdentity.email);

不需要获取服务和迭代，它已经由TB设置，请参阅