Bug 151158 – Stop passing a PassRefPtr to dispatchEvent()

• Component: DOM
• Status: RESOLVED FIXED

[Chris Dumez]

Stop passing a PassRefPtr to dispatchEvent() because:
1. PassRefPtr is legacy and should no longer be used
2. We don't actually transfer ownership of the Event to the callee

Pass a C++ reference instead.

[Chris Dumez]

Created attachment 265323 [details]
Patch

[Chris Dumez]

Created attachment 265325 [details]
Patch

[Chris Dumez]

Created attachment 265326 [details]
Patch

[Chris Dumez]

Created attachment 265328 [details]
Patch

[Chris Dumez]

Created attachment 265354 [details]
Patch

[Alex Christensen]

Comment on attachment 265354 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=265354&action=review

r=me with comments.  This is a huge code improvement and reduces ref thrashing.  I just have a few questions.  Good luck landing this.

> Source/WebCore/Modules/mediastream/MediaStream.cpp:306
> -        dispatchEvent(event.release());
> +        dispatchEvent(*event);

I don't like adding unchecked dereferencing of pointers.  Could we make events a Vector<Ref<Event>>?

> Source/WebCore/Modules/mediastream/RTCDTMFSender.cpp:165
> +        dispatchEvent(*event);

ditto

> Source/WebCore/Modules/mediastream/RTCDataChannel.cpp:324
> +        dispatchEvent(*event);

ditto

> Source/WebCore/Modules/mediastream/RTCPeerConnection.cpp:745
> +        dispatchEvent(*event);

ditto

> Source/WebCore/css/FontLoader.cpp:191
> +        dispatchEvent(*pendingEvents[index]);

ditto

> Source/WebCore/dom/EventTarget.h:127
> +    bool dispatchEvent(Event*, ExceptionCode&); // DOM API

Why is this comment here?

> Source/WebCore/dom/MessagePort.cpp:-165
> -        dispatchEvent(evt.release(), ASSERT_NO_EXCEPTION);

Should we completely remove IgnorableExceptionCode?

> Source/WebCore/editing/Editor.cpp:-855
> -    target->dispatchEvent(event, IGNORE_EXCEPTION);

Same with IGNORE_EXCEPTION.  Why are we getting rid of this?

> Source/WebCore/xml/XMLHttpRequestProgressEventThrottle.cpp:153
> -        dispatchEvent(WTF::move(deferredProgressEvent));
> +        dispatchEvent(*deferredProgressEvent);

Ditto

[Chris Dumez]

Created attachment 265361 [details]
Patch

[Chris Dumez]

Comment on attachment 265354 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=265354&action=review

>> Source/WebCore/Modules/mediastream/MediaStream.cpp:306
>> +        dispatchEvent(*event);
> 
> I don't like adding unchecked dereferencing of pointers.  Could we make events a Vector<Ref<Event>>?

Sure. Will do.

>> Source/WebCore/dom/EventTarget.h:127
>> +    bool dispatchEvent(Event*, ExceptionCode&); // DOM API
> 
> Why is this comment here?

Because this is supposed to be called from JS.

>> Source/WebCore/dom/MessagePort.cpp:-165
>> -        dispatchEvent(evt.release(), ASSERT_NO_EXCEPTION);
> 
> Should we completely remove IgnorableExceptionCode?

I am pretty sure there is still a lot of code that uses it.

>> Source/WebCore/editing/Editor.cpp:-855
>> -    target->dispatchEvent(event, IGNORE_EXCEPTION);
> 
> Same with IGNORE_EXCEPTION.  Why are we getting rid of this?

There are 2 dispatchEvent() overloads:
1. dispatchEvent(Event*, ExceptionCode&)
-> Meant to be used by JS bindings. Because the event comes from JS, we do some additional checks on the event and throw an exception if those checks fail. The checks are: null pointer, event is not initialized, event is already being dispatched.
2. dispatchEvent(Event&)
-> Meant to be called by C++ code. It cannot throw as we expect the event argument to be valid.

Previously, some of our C++ code was unnecessarily calling the overload that is meant to be used by JS so I fixed that. I will also add assertions in dispatchEvent(Event&) to make sure the event is initialized and not already being dispatched.

>> Source/WebCore/xml/XMLHttpRequestProgressEventThrottle.cpp:153
>> +        dispatchEvent(*deferredProgressEvent);
> 
> Ditto

Well, this one has a null check.

[Chris Dumez]

Created attachment 265362 [details]
Patch

[Chris Dumez]

Created attachment 265363 [details]
Patch

[Chris Dumez]

Created attachment 265364 [details]
Patch

[Chris Dumez]

Comment on attachment 265364 [details]
Patch

Clearing flags on attachment: 265364

Committed r192354: <http://trac.webkit.org/changeset/192354>

[Chris Dumez]

All reviewed patches have been landed.  Closing bug.