Bug 83688 – File API does not support DOM events (like addEventListener)

• Component: UI Events
• Status: RESOLVED FIXED

The specifications of e.g. FileReader and FileWriter require that events are handled in the manner of DOM events. See:

http://www.w3.org/TR/FileAPI/#fire-a-progress-event
http://dev.w3.org/2009/dap/file-system/file-writer.html#dfn-fire-a-progress-event

Currently it's not possible to actually use functions such as addEventListener on file readers or file writers. It's merely possible to assign a function like:

someFileWriter.onwriteend = func;

It should be possible to do the following as well:

someFileWriter.addEventListener("writeend", func, false);

[Alexey Proskuryakov]

Could you please attach a test case?

This is known to work in WebKit - we even have a regression test verifying that: <http://trac.webkit.org/browser/trunk/LayoutTests/fast/files/file-reader-event-listener.html>.

Created attachment 136745 [details]
Test case

I've attached a test case. I can reproduce on Google Chrome 20.0.1097.0 canary.

[Alexey Proskuryakov]

The test is about FileSystem and FireWriter, maybe these are different somehow.

[Alexey Proskuryakov]

FileWriter.idl has EventTarget attribute though, and had it for a very long time, so it's unclear what's going on.

[Jian Li]

I think we need to expose EventTarget interface methods in FileWriter.idl, like what I did for FileReader:

http://trac.webkit.org/changeset/104180/trunk/Source/WebCore/fileapi/FileReader.idl

[Erik Arvidsson]

It is not enough to include EventTarget as an extended attribute in the interface section. We also have to include the methods from the EventTarget interface.

For example, look at Node.idl and XMLHttpRequest.idl. They both include addEventListener, removeEventListener and dispatchEvent.

Here are the IDL files that are missing the implementation.

http://code.google.com/p/chromium/source/search?q=file%3A%5C.idl+%5CbEventTarget%28%2C%7C%5Cn%29+-addEventListener&origq=file%3A%5C.idl+%5CbEventTarget%28%2C%7C%5Cn%29+-addEventListener&btnG=Search+Trunk

The short fix is to add these 3 methods to the 3 incomplete idl files above. The long term, better solution is to implicitly add these method when we have an EventTarget.

[Erik Arvidsson]

(In reply to comment #6)
> It is not enough to include EventTarget as an extended attribute in the interface section. We also have to include the methods from the EventTarget interface.
> 
> For example, look at Node.idl and XMLHttpRequest.idl. They both include addEventListener, removeEventListener and dispatchEvent.
> 
> Here are the IDL files that are missing the implementation.
> 
> http://code.google.com/p/chromium/source/search?q=file%3A%5C.idl+%5CbEventTarget%28%2C%7C%5Cn%29+-addEventListener&origq=file%3A%5C.idl+%5CbEventTarget%28%2C%7C%5Cn%29+-addEventListener&btnG=Search+Trunk
> 
> The short fix is to add these 3 methods to the 3 incomplete idl files above. The long term, better solution is to implicitly add these method when we have an EventTarget.

Sorry, the long term solution is to follow the spec and make interfaces extend the EventTarget interface instead of implementing it.

[Erik Arvidsson]

The long term fix is covered by bug 67312. Short term fix coming in a minute.

[Erik Arvidsson]

Created attachment 136773 [details]
Patch

[WebKit Review Bot]

Attachment 136773 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/fast..." exit_code: 1
Source/WebCore/ChangeLog:10:  You should remove the 'No new tests' and either add and list tests, or explain why no new tests were possible.  [changelog/nonewtests] [5]
Total errors found: 1 in 7 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Adam Barth]

Comment on attachment 136773 [details]
Patch

Please fixenate the stylebot's complaint before landing.

[Erik Arvidsson]

Committed r113924: <http://trac.webkit.org/changeset/113924>

[Alexey Proskuryakov]

Comment on attachment 136773 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=136773&action=review

> Source/WebCore/ChangeLog:3
> +        File API does not support DOM events (like addEventListener)

In the future, please take care to rename a bug and update title in patch when scope of an issue becomes more clear. Here, we didn't have an issue with FileReader, but the fix changes a number of non-File APIs.