Mapping inside and outside of the element differently

[pjasiun]

It should be possible to map differently inside and outside of the model element into the view element.

Now to create such structure:

<div data-widget contenteditable="false">
    <div data-mask></div>
    <div data-label>Fixed label</div>
    <div contenteditable="true">Editable</div>
</div>

You need to have two separate model elements:

<widget>
    <editable>Editable</editable>
</widget>

And the mapping is:

<widget> <-> <div data-widget>
<editable> <-> <div contenteditable="true">

It should be possible to map <widget> outside (element) to <div data-widget> and <widget> inside (children) to <div contenteditable="true">, so the model would look like:

<widget>Editable<</widget>

And no additional element would be needed.

[pjasiun]

It should be also possible where attributes should be mapped.

[pjasiun]

Never mind. It does not make sense.

[scofalik]

We implemented different solution in ckeditor/ckeditor5-engine#584. Mapper uses callbacks for position mapping now, so it is possible to recognize special case scenario in them and modify how position is mapped.