add willHandleNewline hook

[eguitarz]

• It addresses feature: Able to match newline in onTextInput handler #481
• I was planning to handle newline base on callback return value. But current callback structure omits the return values. Instead, I passed a parameter into willHandleNewline and handle newline base on its value is changed or not.

[bantic]

@eguitarz Instead of using this ad hoc options hash, let's use a synthetic event object that has a preventDefault method on it. In user code, the developer can call the preventDefault method on it, e.g.:

editor.willHandleNewline((event) => {
  if (shouldPreventDefault) {
    event.preventDefault();
  }
});

[eguitarz]

@bantic Please check if this version is what you preferred. Unfortunately we have to do some workarounds to support custom events in IE, the code is a bit longer than I thought.

[bantic]

@eguitarz Thanks for doing all this work! I think I inadvertently led you astray, I apologize. I just meant passing a basic event-like object with a preventDefault method on it:

let defaultPrevented = false;
const event = { preventDefault() { defaultPrevented = true; };
this.runCallbacks(CALLBACK_QUEUES.WILL_HANDLE_NEWLINE, [event]);
if (defaultPrevented) { ...

I'd prefer that to using a true CustomEvent because of the inconsistencies between browsers.
If you can make that one change this will be good to go and I'd be happy to merge. Sorry about the back-and-forth.

[eguitarz]

@bantic No problem. I enjoyed in this back-and-forth convo, so don't worry about it. Now, it should be the version you preferred.

[bantic]

@eguitarz 👍 thank you for the hard work!

[bantic]

released in v0.10.10.