twitter_yahoo_placemaker.user.js

// ==UserScript==
// @name           Twitter + Yahoo Placemaker
// @namespace      http://aspietribe.com/
// @description    Automatically adds a geo location to your tweet.
// @include        http://twitter.com/
// ==/UserScript==

var appidE = 'your-appid-for-wherein.yahooapis.com';

document.getElementById('tweeting_button').parentNode.addEventListener('click', function(e) {
  post();
  e.preventDefault();
  e.stopPropagation();
}, true);

function post() {
  var tweet = document.getElementById('status').value;
  var query = [], params = {
    appid: appidE,
    inputLanguage: 'ja-JP',
    documentType: 'text/plain',
    documentContent: tweet,
  };
  for(var i in params) query.push(i + '=' + encodeURIComponent(params[i]));
  var url = 'http://wherein.yahooapis.com/v1/document';
  GM_xmlhttpRequest({
    method : 'POST',
    url: url,
    data: query.join('&'),
    headers: {"Content-Type": "application/x-www-form-urlencoded"},
    onload: function(res) {
      var lat, lng;
      var x = new DOMParser().parseFromString(res.responseText, 'text/xml');
      var e = x.getElementsByTagName('place') || x.getElementsByTagName('geographicScope');
      if(e && e.length) {
        lat = e[0].getElementsByTagName('latitude')[0].textContent;
        lng = e[0].getElementsByTagName('longitude')[0].textContent;
      }
      if(lat && lng) {
        document.getElementById('lat').value = lat;
        document.getElementById('lon').value = lng;
        document.getElementById('display_coordinates').value = true;
      }
      var form = document.getElementById('status_update_form');
      var evt = document.createEvent('HTMLEvents');
      evt.initEvent('submit', true, true);
      evt.element = function (){ return evt.target; };
      form.dispatchEvent(evt);
      
      document.getElementById('lat').value = document.getElementById('lon').value = '';
      document.getElementById('display_coordinates').value = false;
    }
  });
}