BubblingEmitterMixin

[niegowski]

Suggested merge commit message (convention)

Feature (engine): Introducing BubblingEmitterMixin and ArrowKeysObserver. Closes #8640.

Fix (utils): The EmitterMixin#listenTo() method is split into listener and emitter parts. The ObservableMixin decorated methods reverted to the original method while destroying an observable.

Other (typing): The TwoStepCaretMovement is now using bubbling events. Closes #7437.

BREAKING CHANGE: We introduced bubbling of view.Document events, similar to how bubbling works in the DOM. That allowed us to reprioritize many listeners that previously had to rely on priority. However, it means that existing listeners that use priorities may now be executed in a wrong moment. The listeners to such events should be reviewed in terms of when they should be executed (in what context/element/phase). You can find more information regarding bubbling in the documentation: [TODO].

Internal (widget): The enter, delete and arrow key events handling moved to the usage of the bubbling observer.

Internal (block-quote): The enter and delete events handling moved to the usage of the bubbling observer.

Internal (code-block): The enter event handling moved to the usage of the bubbling observer.

Internal (list): The enter and delete events handling moved to the usage of the bubbling observer.

Internal (table): The arrow keys handling moved to the usage of the bubbling observer.

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Additional information

[niegowski]

Notes from F2F talk with @Reinmar:

• We don't want to generalize the solution because currently we don't see another usage for it (we could change it in the future)
• The name is ok because it's inside the view part of the engine code (we already have document, node, element in both view and model parts of the engine)
• We could use dedicated BubblingEventInfo while triggering the event so we could provide a custom "start position" for the bubbling so it could start bubbling from the click position instead of the current selection
• We will add eventPhase and currentContext to the BubblingEventInfo (as mentioned in the TODOs in code)

[Reinmar]

Please align it a bit to match other observers' docs.

[Reinmar]

Update the name :d

[Reinmar]

I'd keep this. We listened on low to make sure that if someone didn't pass any priority (and want to override this), that they don't have to do anything else.

Same in: shift enter, delete and perhaps somewhere else.

[Reinmar]

Same here.

[Reinmar]

Clarify that the use cases is in the tests.

[Reinmar]

Clarify that the use cases is in the tests.

[Reinmar]

BREAKING CHANGE: We introduced bubbling of view.Document events, similar to how bubbling works in the DOM. That allowed us to reprioritize many listeners that previously had to rely on priority. However, it means that existing listeners that use priorities may now be executed in a wrong moment. The listeners to such events should be reviewed in terms of when they should be executed (in what context/element/phase). You can find more information regarding bubbling in the documentation: [TODO].

[niegowski]

@ckeditor/qa-team could you please test it? This is a massive change in event handling. Please focus on the custom enter/delete/delete forward/arrow keys handling in the context of blockquotes, lists, to-do lists, block widgets (widget type around), tables, links (2 step caret movement)

[Reinmar]

@ckeditor/qa-team could you please test it? This is a massive change in event handling. Please focus on the custom enter/delete/delete forward/arrow keys handling in the context of blockquotes, lists, to-do lists, block widgets (widget type around), tables, links (2 step caret movement)

I'd add that it's a lot about nesting. Nesting things inside other things. Like blockquotes in tables, images in block quotes, etc. Those are the most tricky cases. But the PR could've affected also more typical ones with flat structures.

[Mgsy]

I've tested it and haven't noticed any weird behaviours. It seems to be fine 👍