WheelEvent's deltaX/deltaY sign is wrong

WheelEvent's deltaX/deltaY sign is wrong

According to the specification, if a user agent scrolls as the default action
of the wheel event then the sign of the delta should be given by a right-hand
coordinate system where positive X, Y, and Z axes are directed towards the
right-most edge, bottom-most edge, and farthest depth (away from the user) of
the document, respectively:
http://www.w3.org/TR/DOM-Level-3-Events/#events-wheelevents

This signs for deltaX/deltaY are the inversed compared to the legacy
wheelDeltaX/wheelDeltaY. r156404 added support for DOM3 WheelEvent but used
the same sign for deltaX/deltaY and wheelDeltaX/wheelDeltaY.

Firefox 23 and IE10 uses the right sign according to the specification.

BUG=227454
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=156478

[arv (Not doing code reviews), 2013-08-21 14:19:23]

LGTM

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
File Source/core/dom/WheelEvent.cpp (right):

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
Source/core/dom/WheelEvent.cpp:36: return 0;
Is it worth special casing 0? Are you concerned about -0?

[do-not-use, 2013-08-21 14:31:09]

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
File Source/core/dom/WheelEvent.cpp (right):

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
Source/core/dom/WheelEvent.cpp:36: return 0;
On 2013/08/21 14:19:23, arv wrote:
> Is it worth special casing 0? Are you concerned about -0?

I had an issue with a test failing because a shouldBe check that would say "got
-0 but expected 0".

shouldBe() is extremely strict:
function isResultCorrect(_actual, _expected)
{
    if (_expected === 0)
        return _actual === _expected && (1/_actual) === (1/_expected);
...
}

1/0 !== 1/-0 even though 0 === -0.

[arv (Not doing code reviews), 2013-08-21 14:52:30]

Still LGTM

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
File Source/core/dom/WheelEvent.cpp (right):

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
Source/core/dom/WheelEvent.cpp:36: return 0;
On 2013/08/21 14:31:10, Christophe Dumez wrote:
> On 2013/08/21 14:19:23, arv wrote:
> > Is it worth special casing 0? Are you concerned about -0?
> 
> I had an issue with a test failing because a shouldBe check that would say
"got
> -0 but expected 0".
> 
> shouldBe() is extremely strict:
> function isResultCorrect(_actual, _expected)
> {
>     if (_expected === 0)
>         return _actual === _expected && (1/_actual) === (1/_expected);
> ...
> }
> 
> 1/0 !== 1/-0 even though 0 === -0.

Makes sense. I think we should normalize -0 here.

Maybe a comment would be useful?

[do-not-use, 2013-08-21 15:00:36]

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
File Source/core/dom/WheelEvent.cpp (right):

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
Source/core/dom/WheelEvent.cpp:36: return 0;
On 2013/08/21 14:52:30, arv wrote:
> On 2013/08/21 14:31:10, Christophe Dumez wrote:
> > On 2013/08/21 14:19:23, arv wrote:
> > > Is it worth special casing 0? Are you concerned about -0?
> > 
> > I had an issue with a test failing because a shouldBe check that would say
> "got
> > -0 but expected 0".
> > 
> > shouldBe() is extremely strict:
> > function isResultCorrect(_actual, _expected)
> > {
> >     if (_expected === 0)
> >         return _actual === _expected && (1/_actual) === (1/_expected);
> > ...
> > }
> > 
> > 1/0 !== 1/-0 even though 0 === -0.
> 
> Makes sense. I think we should normalize -0 here.
> 
> Maybe a comment would be useful?

Done.

[arv (Not doing code reviews), 2013-08-21 15:02:53]

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
File Source/core/dom/WheelEvent.cpp (right):

https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
Source/core/dom/WheelEvent.cpp:36: return 0;
On 2013/08/21 15:00:36, Christophe Dumez wrote:
> On 2013/08/21 14:52:30, arv wrote:
> > On 2013/08/21 14:31:10, Christophe Dumez wrote:
> > > On 2013/08/21 14:19:23, arv wrote:
> > > > Is it worth special casing 0? Are you concerned about -0?
> > > 
> > > I had an issue with a test failing because a shouldBe check that would say
> > "got
> > > -0 but expected 0".
> > > 
> > > shouldBe() is extremely strict:
> > > function isResultCorrect(_actual, _expected)
> > > {
> > >     if (_expected === 0)
> > >         return _actual === _expected && (1/_actual) === (1/_expected);
> > > ...
> > > }
> > > 
> > > 1/0 !== 1/-0 even though 0 === -0.
> > 
> > Makes sense. I think we should normalize -0 here.
> > 
> > Maybe a comment would be useful?
> 
> Done.

That comment is not very nice. How about:

// Make sure we use +0 for all zeros.

[do-not-use, 2013-08-21 15:05:10]

On 2013/08/21 15:02:53, arv wrote:
>
https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
> File Source/core/dom/WheelEvent.cpp (right):
> 
>
https://codereview.chromium.org/22888005/diff/4001/Source/core/dom/WheelEvent...
> Source/core/dom/WheelEvent.cpp:36: return 0;
> On 2013/08/21 15:00:36, Christophe Dumez wrote:
> > On 2013/08/21 14:52:30, arv wrote:
> > > On 2013/08/21 14:31:10, Christophe Dumez wrote:
> > > > On 2013/08/21 14:19:23, arv wrote:
> > > > > Is it worth special casing 0? Are you concerned about -0?
> > > > 
> > > > I had an issue with a test failing because a shouldBe check that would
say
> > > "got
> > > > -0 but expected 0".
> > > > 
> > > > shouldBe() is extremely strict:
> > > > function isResultCorrect(_actual, _expected)
> > > > {
> > > >     if (_expected === 0)
> > > >         return _actual === _expected && (1/_actual) === (1/_expected);
> > > > ...
> > > > }
> > > > 
> > > > 1/0 !== 1/-0 even though 0 === -0.
> > > 
> > > Makes sense. I think we should normalize -0 here.
> > > 
> > > Maybe a comment would be useful?
> > 
> > Done.
> 
> That comment is not very nice. How about:
> 
> // Make sure we use +0 for all zeros.

Ok :)  Done.

[commit-bot: I haz the power, 2013-08-21 15:21:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@sisa.samsung.com/22888005/18001

[commit-bot: I haz the power, 2013-08-21 17:03:05]

Change committed as 156478