W3C home > Mailing lists > Public > www-svg@w3.org > December 2005

SVGT 1.2: lack of capture phase for event handling

From: Maciej Stachowiak <mjs@apple.com>
Date: Mon, 26 Dec 2005 23:29:28 -0700
Message-Id: <5FAE7917-AFBA-48B5-971E-474ABEFAC53F@apple.com>
To: www-svg@w3c.org


The lack of capture phase is a serious compatibility problem for CDF  
UAs, full DOM implementations, and upward compatibility with SVG 1.2  
Full, which is supposed to be a strict superset.

uDOM specifies the following exception for all EventTarget methods:

DOMException NOT_SUPPORTED_ERR: Raised if useCapture is true since  
capture phase is not required in SVG Tiny and implementations may not  
support registering listeners for the capture phase.

And the scripting section has no capture phase.

This causes the following issues:

1) The EventTarget methods all mandate an exception in a case where  
the DOM spec forbids an exception. Thus, full DOM implementations  
could not simultaneously implement the uDOM interface on the same  
objects.

2) In CDF implementations, is it forbidden to have capturing event  
handlers wrapped around SVG content? If they are present would they  
be ignored? If you get full DOM access to an SVG 1.2 Tiny document  
externally, may you add a capturing event handler? this sows serious  
confusion.

3) If SVG 1.2 Full is to be a strict superset, it would have to also  
forbid capturing event handlers, wouldn't it?

I recommend either mandating the capture phase, or making it  
optional. Furthermore, if capture remains optional, then for the  
EventTarget methods, I recommend removing the exception even in the  
case where capture is not supported, instead the listener should be  
added but silently ignored since no capture phase occurs.

Regards,
Maciej
Received on Tuesday, 27 December 2005 06:30:56 GMT

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