Files.app: Introduce AsyncUtil.ConcurrentQueue

ui/file_manager/file_manager/foreground/js/directory_contents.js

Index: ui/file_manager/file_manager/foreground/js/directory_contents.js
diff --git a/ui/file_manager/file_manager/foreground/js/directory_contents.js b/ui/file_manager/file_manager/foreground/js/directory_contents.js
index 37125baca64c38ffd42017111f17722897a799bb..350ecc22b81cf60bf12b1ad9111b2a03d0bf2228 100644
--- a/ui/file_manager/file_manager/foreground/js/directory_contents.js
+++ b/ui/file_manager/file_manager/foreground/js/directory_contents.js
@@ -566,7 +566,10 @@ DirectoryContents.prototype.cancelScan = function() {
 
   this.onScanFinished_();
 
+  // Cancels the current prefetchMetadata queue and replaces it with new one.
   this.prefetchMetadataQueue_.cancel();
+  this.prefetchMetadataQueue_ = new AsyncUtil.Queue();

[hirono, 2014/05/26 09:19:42]

Does it really need to reassign a new queue?
It looks this.scanCancelled_ does not turn back to false.

[yoshiki, 2014/05/26 09:36:33]

That's right. Removed.

+
   cr.dispatchSimpleEvent(this, 'scan-cancelled');
 };
 
@@ -579,7 +582,10 @@ DirectoryContents.prototype.cancelScan = function() {
 DirectoryContents.prototype.onScanFinished_ = function() {
   this.scanner_ = null;
 
-  this.prefetchMetadataQueue_.run(function(callback) {
+  this.prefetchMetadataQueue_.run(function(callback, cancelled) {
+    if (cancelled)
+      return callback();
+
     // TODO(yoshiki): Here we should fire the update event of changed
     // items. Currently we have a method this.fileList_.updateIndex() to
     // fire an event, but this method takes only 1 argument and invokes sort
@@ -603,11 +609,12 @@ DirectoryContents.prototype.onScanCompleted_ = function() {
   if (this.scanCancelled_)
     return;
 
-  this.prefetchMetadataQueue_.run(function(callback) {
+  this.prefetchMetadataQueue_.run(function(callback, cancelled) {

[hirono, 2014/05/26 09:19:42]

What is difference between this.scanCancelled_ and the cancelled argument passed
via Queue?

[yoshiki, 2014/05/26 09:36:33]

In this case, they are same. But in general, the callback function should need
to know if the task is cancelled to handle the cancel, and passing the status to
the callback is better than passing queue's instance using closure.

[hirono, 2014/05/26 09:41:04]

How about removing this.scanCancelled_ and using
this.prefetchMetadataQueue_.isCancelled() instead?
We can avoid having two names for the same thing.

     // Call callback first, so isScanning() returns false in the event handlers.
     callback();
 
-    cr.dispatchSimpleEvent(this, 'scan-completed');
+    if (!cancelled)
+      cr.dispatchSimpleEvent(this, 'scan-completed');
   }.bind(this));
 };
 
@@ -619,10 +626,12 @@ DirectoryContents.prototype.onScanError_ = function() {
   if (this.scanCancelled_)
     return;
 
-  this.prefetchMetadataQueue_.run(function(callback) {
+  this.prefetchMetadataQueue_.run(function(callback, cancelled) {
     // Call callback first, so isScanning() returns false in the event handlers.
     callback();
-    cr.dispatchSimpleEvent(this, 'scan-failed');
+
+    if (!cancelled)
+      cr.dispatchSimpleEvent(this, 'scan-failed');
   }.bind(this));
 };
 
@@ -655,7 +664,10 @@ DirectoryContents.prototype.onNewEntries_ = function(entries) {
   var MAX_CHUNK_SIZE = 50;
   for (var i = 0; i < entriesFiltered.length; i += MAX_CHUNK_SIZE) {
     var chunk = entriesFiltered.slice(i, i + MAX_CHUNK_SIZE);
-    this.prefetchMetadataQueue_.run(function(chunk, callback) {
+    this.prefetchMetadataQueue_.run(function(chunk, callback, cancelled) {
+      if (cancelled)
+        return callback();

[hirono, 2014/05/26 09:19:42]

Maybe "callback(); return;" is more free from misreadings.

[yoshiki, 2014/05/26 09:36:33]

Done.

+
       this.prefetchMetadata(chunk, function() {
         if (this.scanCancelled_) {
           // Do nothing if the scanning is cancelled.