[whatwg] <video> feedback

Jonas Sicking jonas at sicking.cc
Wed Feb 10 11:56:49 PST 2010

On Wed, Feb 10, 2010 at 11:29 AM, Boris Zbarsky <bzbarsky at mit.edu> wrote:
> On 2/10/10 2:19 PM, Brian Campbell wrote:
>> Do browsers fire events for which there are no listeners?
> It varies.  Gecko, for example, fires image load events not matter what but
> only fires mutation events if there are listeners.

However checking for listeners has a non-trivial cost. You have to
walk the full parentNode chain and see if any of the parents has a
listener. This applies to both bubbling and non-bubbling events due to
the capture phase.

Also, feature which requires implementations to optimize for the
feature not being used seems like a questionable feature to me. We
want people to use the stuff we're creating, there's little point

/ Jonas

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