Periodic refresh instead of every iteration in manifest worker.

frontend/src/js/component/wb-collection-content.js

@@ -23,6 +23,10 @@ function endsWith(what, endings) {
   throw Error('Expected second argument to be either a string or an array');
 }
 
+function maskRows(rows) {
+  return rows.map(r => r.map(c => '-'));
+}
+
 class WBCollectionContent extends Component {
   constructor(...args) {
     super(...args);
@@ -74,16 +78,29 @@ class WBCollectionContent extends Component {
         return manifestWorker.postMessage([ 'precreatePaths', paths ]);
       });
 
+      let lastListingTimestamp = new Date(0);
+
       for (let i = 0; i < streams.length; i++) {
         prom_1 = prom_1.then(() => manifestWorker.postMessage([ 'parseStream', streams[i] ]));
 
-        prom_1 = prom_1.then(() => manifestWorker.postMessage([
-          'listDirectory', '.' + this.props.collectionPath, true
-        ]));
+        prom_1 = prom_1.then(() => {
+          if (new Date() - lastListingTimestamp < 1000)
+            return;
+
+          lastListingTimestamp = new Date();
 
-        prom_1 = prom_1.then(e => {
-          this.prepareRows(e.data[1]);
-          this.setState({ 'parsedStreams': (i + 1) });
+          let prom_2 = new Promise(accept => accept());
+
+          prom_2 = prom_2.then(() => manifestWorker.postMessage([
+            'listDirectory', '.' + this.props.collectionPath, true
+          ]));
+
+          prom_2 = prom_2.then(e => {
+            this.prepareRows(e.data[1]);
+            this.setState({ 'parsedStreams': (i + 1) });
+          });
+
+          return prom_2;
         });
       }
 
@@ -102,6 +119,8 @@ class WBCollectionContent extends Component {
   componentWillReceiveProps(nextProps) {
     this.props = nextProps;
 
+    this.setState({ rows: maskRows(this.state.rows) });
+
     const { manifestWorker, mode } = this.state;
     const { collectionPath } = this.props;