Deprecate canDispatchToEventManager?

[GavinJoyce]

From

ember.js/packages/ember-views/lib/system/event_dispatcher.js

Lines 105 to 133 in e24e403

	/**
	It enables events to be dispatched to the view's `eventManager.` When present,
	this object takes precedence over handling of events on the view itself.
	Note that most Ember applications do not use this feature. If your app also
	does not use it, consider setting this property to false to gain some performance
	improvement by allowing the EventDispatcher to skip the search for the
	`eventManager` on the view tree.
	```javascript
	let EventDispatcher = Em.EventDispatcher.extend({
	events: {
	click : 'click',
	focusin : 'focusIn',
	focusout : 'focusOut',
	change : 'change'
	},
	canDispatchToEventManager: false
	});
	container.register('event_dispatcher:main', EventDispatcher);
	```
	@property canDispatchToEventManager
	@type boolean
	@default 'true'
	@since 1.7.0
	@private
	*/
	canDispatchToEventManager: true,

:

Note that most Ember applications do not use this feature. If your app also
does not use it, consider setting this property to false to gain some performance
improvement by allowing the EventDispatcher to skip the search for the
`eventManager` on the view tree.

Some questions:

• Do many apps use this? If not, perhaps we can deprecate (with a RFC)
• If we can't deprecate, can we disable it by default and make it opt-in?
• What are the use cases for custom eventManagers? Can we suggest alternative solutions?

[rwjblue]

Do many apps use this?

I checked with @tomdale and apparently this was originally added to allow views to differentiate between certain types of touch input, however the addon that originally used this (ember-touch) has been deprecated in favor of Hammer.js.

If not, perhaps we can deprecate (with a RFC)

Yes, we should absolutely deprecate it.

If we can't deprecate, can we disable it by default and make it opt-in?

I think we can make it more "pay-go" either way, so that most apps don't have to pay the cost of the feature they never use...

[GavinJoyce]

TODOs:

• Make it pay-as-you-go : Disable costly eventManager support when unused. #14756 🍻 @rwjblue
• Create RFC to deprecate canDispatchToCustomEventManager @GavinJoyce : Deprecate component eventManager rfcs#194
• Deprecate canDispatchToEventManager