Svg.js: Extend the EventTarget Class with methods for event handling

[wout]

Just to be consistent I would like to replace the loaded callback on SVG.Image with a loaded event.

[Fuzzyma]

I agree with that. In the fx module we use events, too but kept the during()/after() method for not breaking the api. Maybe we could remove this methods, too?

[wout]

Yes, we should remove them everywhere.

[Fuzzyma]

The problem with events is, that they are awfully slow and that they only can be dispatched on nodes.
In the new fx module we dont have a node to dispatch. And creating a detached node only for dispatching events on it is highly memory intensive and leads to lots of garbage collections.

So my proposal is the following:

• extend the EventTarget class with the following methods:
  
  
  
  • addEventListener
  
  
  • removeEventListener
  
  
  • getEventDispatcher
  
  
  • dispatchEvent
  
  

This class should be completely able to remove and add events on its own.
However in case of SVG.Shapes we HAVE a node which we want to use. In that case getEventDispatcher returns a node and not this so that the events are bound and dispatched on the node instead of the object.

Note: Implementation has to be done on the 3.0 branch
For all questions head over to our gitter chat: https://gitter.im/svgdotjs/svg.js

[Fuzzyma]

This landed in 3.0 with 47fda3cf67cdc8ab20d3b1ba9d65a810adddf5ee in the following way:

EventTarget is a class that all classes can extend to get event handling.
It comes with the following interface:

• on() bind the event
• off() unbind event
• dispatch() dispatch an event on the object and return the event
• fire() same as dispatch but returns the object

When you need to use a special event target (e.g. a node), you need to implement the following methods:

• getEventTarget() returns the target
• getEventHolder() returns the object on which the events/listeners are saved

Additionally the target needs to implement:

• addEventListener()
• removeEventListener() and
• dispatchEvent()

The default is the EventTarget itself which implements all of these