ISSUE-111 (mouse z): Add z attribute to mouse events? [DOM3 Events]

ISSUE-111 (mouse z): Add z attribute to mouse events? [DOM3 Events]

http://www.w3.org/2008/webapps/track/issues/111

Raised by: Doug Schepers
On product: DOM3 Events

With CSS and SVG both adding 3D (2.5D) transformations to the language, with a position on the z-axis, there may well be cause to add z/tz/clientZ attributes to mouse events along with the traditional x and y attributes.  This would return the element's z-position, with a default of 0, in case there are any z transforms applied to the element.

Note that the z-axis position is different than z-index.