屏幕

//init must be called once during startup, before any function to nw.Screen can be called
nw.Screen.Init();

var screenCB = {
  onDisplayBoundsChanged: function(screen) {
    console.log('displayBoundsChanged', screen);
  },

  onDisplayAdded: function(screen) {
    console.log('displayAdded', screen);
  },

  onDisplayRemoved: function(screen) {
    console.log('displayRemoved', screen)
  }
};

// listen to screen events
nw.Screen.on('displayBoundsChanged', screenCB.onDisplayBoundsChanged);
nw.Screen.on('displayAdded', screenCB.onDisplayAdded);
nw.Screen.on('displayRemoved', screenCB.onDisplayRemoved);

screen {
// unique id for a screen
  id: int,

// physical screen resolution, can be negative, not necessarily start from 0,depending on screen arrangement
  bounds: {
    x: int,
    y: int,
    width: int,
    height: int
  },

// useable area within the screen bound
  work_area: {
    x: int,
    y: int,
    width: int,
    height: int
  },

  scaleFactor: float,
  isBuiltIn: bool,
  rotation: int,
  touchSupport: int
}

nw.Screen.Init(); // you only need to call this once
nw.Screen.chooseDesktopMedia(["window","screen"], 
  function(streamId) {
    var vid_constraint = {
      mandatory: {
        chromeMediaSource: 'desktop', 
        chromeMediaSourceId: streamId, 
        maxWidth: 1920, 
        maxHeight: 1080
      }, 
      optional: []
    };
    navigator.webkitGetUserMedia({audio: false, video: vid_constraint}, success_func, fallback_func);
  }
);

var dcm = nw.Screen.DesktopCaptureMonitor;
nw.Screen.Init();
dcm.on("added", function (id, name, order, type) {
   //select first stream and shutdown
   var constraints = {
      audio: {
         mandatory: {
             chromeMediaSource: "system",
             chromeMediaSourceId: dcm.registerStream(id)
          }
      },
      video: {
         mandatory: {
             chromeMediaSource: 'desktop',
             chromeMediaSourceId: dcm.registerStream(id)
         }
      }
  };

  // TODO: call getUserMedia with contraints

  dcm.stop();
});

dcm.on("removed", function (id) { });
dcm.on("orderchanged", function (id, new_order, old_order) { });
dcm.on("namechanged", function (id, name) { });
dcm.on("thumbnailchanged", function (id, thumbnail) { });
dcm.start(true, true);