- From: Leif Arne Storset <lstorset@opera.com>
- Date: Fri, 20 Aug 2010 14:32:52 +0200
- To: "Anne van Kesteren" <annevk@opera.com>
As probably is known to members of this WG, hit testing for events is not the same across browsers. This is something we would like to have standardized. I hope this can be discussed at next week's F2F in Oslo. The demos at [0] contain a transparent, absolutely positioned box covering the entire viewport. There is an anchor underneath it, labelled "Click me". Attempting to click the link gives these results: * Gecko and WebKit hit the transparent box. * Trident (IE) and Presto (Opera) hit the link. (However, if you add an event listeners to the transparent box, Presto will hit it.) IE's behavior is analyzed at [1]. IE9 hits even transparent <svg> elements, but this is probably a bug. [2] We would like to see this behavior specified and converging on a specific behavior. Whether Gecko/WebKit adopt the more sophisticated behavior or IE and we (Opera) switch to the simpler behavior is not very important to us, although in general, simpler algorithms are preferred, of course. --- It may be that reviving the previous work on the 'pointer-events' CSS property [3,4] is a logical place to specify this. Currently, only WebKit and Gecko offer experimental (although non-prefixed) support for this property for CSS layout boxes. (For SVG, of course, we and probably IE9 support it.) If we do frame the hit testing issue this way, the main factor is the current behavior when 'pointer-events: auto' (which is the initial value) or not supported. I've updated Dean Jackson's 2008 proposal [5] with some notes from the discussion; this updated version can be found at [6]. Rephrasing the above in terms of pointer-events, * Gecko and WebKit behave as if 'pointer-events: all', and in WebKit's proposal this is specified as the 'auto' behavior [7]. (They don't support 'painted', only 'none' as an alternative. [8]) * Trident (IE) and Presto behave as if 'pointer-events: painted' (with the exception of transparent areas of embedded images and the Presto exception of event listeners). * Our preference is for 'auto' to mean 'pointer-events: all', the simpler option. But again, either value is better than nothing. Of course, there are still a number of issues to be resolved. See Dean Jackson's list at [5] and David Baron's reply at [9]. One possible issue is that referring to document language (SVG) has been strongly discouraged in the past; however, drafts such as CSSOM do this. [0] http://people.opera.com/lstorset/demos/pointer-events/pointer-events-auto.html [1] http://lists.w3.org/Archives/Public/www-style/2009Feb/0287.html (Hixie's notes on IE hit testing) [2] http://people.opera.com/lstorset/demos/pointer-events/painted/transparent.xhtml [3] http://wiki.csswg.org/ideas/pointer-events [4] https://wiki.mozilla.org/SVG:pointer-events [5] http://lists.w3.org/Archives/Public/www-style/2008Jul/0428.html (Dean Jackson's proposal) [6] http://people.opera.com/lstorset/TR/pointer-events/ED-pointer-events-20100820.html [7] http://webkit.org/specs/PointerEventsProperty.html [8] http://lists.w3.org/Archives/Public/www-style/2009Dec/0060.html (pointer-events in WebKit) [9] http://lists.w3.org/Archives/Public/www-style/2008Jul/0431.html (David Baron's reply) I'll see some of you on Monday! -- Leif Arne Storset Core Technology Developer, Opera Software Oslo, Norway
Received on Friday, 20 August 2010 14:49:53 UTC