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Agenda Request: Real X/Y (was: [cssom-view] Extensions to the MouseEvent Interface)

From: Doug Schepers <schepers@w3.org>
Date: Sun, 27 Sep 2009 00:03:45 -0700
Message-ID: <4ABF0E51.1030301@w3.org>
To: SVG WG <public-svg-wg@w3.org>
Hi, Folks-

I'd like to talk about this at the F2F.

-------- Original Message --------
Subject: [cssom-view] Extensions to the MouseEvent Interface
Resent-Date: Sat, 19 Sep 2009 18:43:01 +0000
Resent-From: www-style@w3.org
Date: Sat, 19 Sep 2009 14:42:44 -0400
From: Doug Schepers <schepers@w3.org>
To: www-style CSS <www-style@w3.org>, www-svg <www-svg@w3.org>, 
"www-dom@w3.org" <www-dom@w3.org>

Hi, CSS WG-

I'm editing the DOM3 Events specification in the WebApps WG, and I was
recently made aware that the CSSOM View Module extends the MouseEvent
interface, which seems to raise some issues.  Here are some high-level
comments I would appreciate your considering.

CSSOM currently references DOM3 Events.  Since DOM3 Events is closing in
on Last Call, I think it's safe to reference DOM3 Events instead of DOM2
Events.

CSSOM's extension of the MouseEvent interface [1] redefines screenX,
screenY, clientX, and clientY, which are already defined in DOM3 Events
(and DOM2 Events).  Though the wording is slightly different, there
doesn't appear to be a significant change.  It would be better to simply
reference the definitions in the DOM Events spec rather than redefining
these attributes, so that the definitions don't need to be maintained in
two places.  I'm happy to work with you to improve the definitions in
the DOM3 Events spec if that's needed.

CSSOM also defines several new attributes:

[[
The pageX attribute, on getting, must return the horizontal coordinate
of the position where the event occurred relative to the origin of the
initial containing block.

The pageY attribute, on getting, must return the y-coordinate of the
position where the event occurred relative to the origin of the initial
containing block.

The x  attribute, on getting, must return the value of clientX.

The y attribute, on getting, must return the value of clientY.

The offsetX attribute, on getting, must return the x-coordinate of the
position where the event occurred relative to the origin of the padding
edge of the target node.

The offsetY attribute, on getting, must return the y-coordinate of the
position where the event occurred relative to the origin of the padding
edge of the target node.
]]

However, it doesn't also extend the initMouseEvent() method to allow the
author to initialize these attributes.  Depending on discussions in the
WebApps WG regarding a generic initialization method, this may be moot,
but for now at least, it's something that needs discussion.

I do like the authoring convenience of providing x and y attributes, but
I'm not convinced that simply reflecting the clientX/clientY attributes
provides the most benefit to authors.  The SVG WG has suggested that
DOM3 Events offers a way to resolve the mouse coordinates with respect
to transformations and viewbox adjustments, rather than forcing authors
to do this in Javascript; if the CSS WG also adds transformations to
CSS, this is something that will be needed for CSS+HTML as well.  Thus,
it is best defined in the DOM3 Events spec than in the SVG spec.  The
most obvious names for these attributes are x and y.  I understand that
this part of the CSSOM spec is already implemented, but this need not
cause a problem... in the absence of any coordinate transformations, x/y
would be identical to clientX/clientY, so we could simply extend that
definition.

The offsetX/offsetY attributes seem like they might also be useful in an
SVG context, if they were defined in terms of the bounding box, rather
than the padding edge.

Since I'm actively editing the DOM3 Events specification, I'd like to
work with you to update that specification so you don't need to extend
the interfaces defined there.


[1] http://www.w3.org/TR/cssom-view/#extensions-to-the-mouseevent-interface

Regards-
-Doug Schepers
W3C Team Contact, SVG and WebApps WGs
Received on Sunday, 27 September 2009 07:04:04 UTC

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