[Bug 18912] [Shadow]: ShadowRoot needs to support elementFromPoint

https://www.w3.org/Bugs/Public/show_bug.cgi?id=18912

--- Comment #5 from dfreedm@chromium.org 2012-09-24 19:09:47 UTC ---
The primary use case I see for elementFromPoint is inside of an event handler.
Since one cannot trust the projected children inside of ShadowRoot, it makes
sense that one should not try to add an event listener to a ShadowRoot's
projected children.
In that case, the most logical spot to add an event listener would be in the
ShadowRoot that contains the element, which would then have the correct scope
for an elementFromPoint call.

Now, there is a larger problem here involving touch events. In the
implementation of touch events, touchmove does not change target.
This means that while the finger is moving on the screen, the same element that
received the touchstart event will receive all the touchmoves (and touchend).
In this environment, if a finger is placed outside of a ShadowRoot and moved
into it, the ShadowRoot will never receive the touchmove event, and cannot call
its version of elementFromPoint.

This is a major problem for any polyfilled event systems (like PointerEvents:
https://github.com/toolkitchen/PointerEvents).

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Received on Monday, 24 September 2012 19:09:48 UTC