Although this does not affect any benchmarks because of event handlers' performance issue, I guess that this may affect quickness of user operation. https://searchfox.org/mozilla-central/search?q=nsIDOM.*Event%3E.*%5Cn%3F.*do_QueryInterface&case=false&regexp=true&path= I think that if all of them can use Widget*Event instead, they should use it. Otherwise, I think that mozilla::dom::*Event classes should have |As*Event()| virtual methods like Widget*Event.

Probably yes, though need to be careful with this. What if we want to handle also events named foo when those aren't dispatched using WidgetFooEvent, but generic WidgetEvent. In that case event's message would be the generic one.

I believe the patches landed for bug 1455055 pretty much fix this. Masayuki-san, do you agree?

(In reply to Boris Zbarsky [:bz] (no decent commit message means r-) from comment #2) > I believe the patches landed for bug 1455055 pretty much fix this. > Masayuki-san, do you agree? Yes, I do! Really thank you for your work!!