screen_rss/background.html

<script src="js/cache_manager.js"></script>
<script src="js/common.js"></script>
<script src="js/urls.js"></script>
<script type="text/javascript" src="https://www.google.com/jsapi"></script>
<script>
  var defaultOptions = JSON.stringify({
    'articleRefresh' : 8,
    'displayMode' : 'newest',
    'lunchScreensaverAfter' : 0,
    'rssSource' : urlGoogleTopNews
  });

  localStorage['temporaryOptions'] =
    localStorage['temporaryOptions'] || defaultOptions;
  localStorage['permanentOptions'] =
    localStorage['permanentOptions'] || defaultOptions;

  var screensaverAddress = 'screensaver.html';
  var screensaverPreviewAddress = 'screensaver.html?preview';
  var screensaverWindowId = -1;
  var toBeOpened = '';
  var launchAfterM; // Time in seconds after which screensaver will be launched.
  // This hack is currently needed because of bug in tabs API - chromium:95617
  var lastActiveWindowId = -1; // Last focused window before screensaver opened.
  var windowLastClosed = 0; // Time when screen saver window was last closed.
  var cacheManager = new CacheManager();
  var previewWindowOpened = false;
  var launchScreensaverAfterUncalculated;
 /*
  * Two functions below are made so that there's only one screensaver window
  * open at the time and they are as "atomic", as javascript allows.
  */

  function maybeOpenWindow(whatWindow) {
    if (screensaverWindowId == -1) {
      screensaverWindowId = -2; // operation pending.
      chrome.windows.getLastFocused(function(window) {
        lastActiveWindowId = window.id;
      });
      chrome.windows.create({
        'url' : whatWindow,
        'focused' : true,
      }, function(screensaverWindow) {
        screensaverWindowId = screensaverWindow.id;
      });
    }
  }

  function maybeCloseWindow() {
    if (screensaverWindowId >= 0) {
      var toBeClosed = screensaverWindowId;
      screensaverWindowId = -1;
      var now = new Date();
      windowLastClosed = now.getTime();
      chrome.windows.remove(toBeClosed, function() {
        if(toBeOpened != '') {
          if (lastActiveWindowId != -1) {
            chrome.tabs.create({
              'windowId' : lastActiveWindowId,
              'url' : toBeOpened
            });
          } else {
            console.log('Could not establish last active window.');
          }
          toBeOpened = '';
        }
      });
    }
  }

  chrome.extension.onRequest.addListener(function(request, sender, sendResp) {
    if (request.method) {
      if (request.method == 'openTab') {
        toBeOpened = request.url;
      } else if (request.method == 'openPreview') {
        previewWindowOpened = true;
        maybeOpenWindow(screensaverPreviewAddress);
      } else if (request.method == 'closeScreensaver') {
        // usually issued by screensaver itself after detecting activity.
        if (previewWindowOpened)
          previewWindowOpened = false;
        maybeCloseWindow();
      } else if (request.method == 'updateOptions') {
        launchScreensaverAfterUncalculated = JSON.parse(
            localStorage['permanentOptions']).lunchScreensaverAfter;
        launchAfterM =
            silderValueToMinutes(launchScreensaverAfterUncalculated);
        cacheManager.updateOptions();
      } else if (request.method == 'getFeed') {
        cacheManager.getFeed(request.options, function(result) {
          sendResp(result);
        });
      }
    }
  });

  chrome.windows.onRemoved.addListener(function(windowId) {
    if (windowId == screensaverWindowId) {
      screensaverWindowId = -1;
      if (previewWindowOpened)
        previewWindowOpened = false;
    }
  });

  function checkState() {
    if (launchAfterM != MAX_LAUNCH_DELAY_M && !previewWindowOpened) {
      chrome.idle.queryState(launchAfterM * 60, function(state) {
        if (state == 'idle') {
          var now = new Date();
          if(now - windowLastClosed > IDLE_API_INTERVAL_MS)
            maybeOpenWindow(screensaverAddress);
        } else { // active or unknown
          maybeCloseWindow();
        }
      });
    }
  }

  launchScreensaverAfterUncalculated = JSON.parse(
      localStorage['permanentOptions']).lunchScreensaverAfter;
  launchAfterM = silderValueToMinutes(launchScreensaverAfterUncalculated);

  window.setInterval(checkState, 1000);
</script>