Renderer does not re-render spaces in text nodes correctly

[scofalik]

There are (at least) two cases when spaces are not correctly from view text nodes to dom text nodes after a change.

Those errors are caused by the fact, that during re-render only the changed dom text node is updated. ckeditor/ckeditor5-engine#1083 changes the way spaces are converter to  . Now, changing to   bases on the data of the previous text node. This means that whenever a text node is changed, next touching text node has to be re-rendered, etc.

Mentioned cases:

Case 1:

1. DOM is <p>x<strong> y</strong></p>.
2. Type space after x.
3. DOM becomes <p>x <strong> y</strong></p>.
4. Only one space is rendered.

Case 2:

1. DOM is <p><strong>&nbsp;y</strong></p>.
2. Put caret before   and turn off bold.
3. Type x.
4. DOM becomes <p>x<strong>&nbsp;y</strong></p>.
5. Incorrect   stays in DOM.

We know that there is a "bug" in DomConverter.viewChildrenToDom. View elements mapped to DOM elements are not re-rendered. Those elements might have text nodes that need refreshing and this is the moment when the bug occurs. Unfortunately if we want to change viewChildrenToDom behavior, we will do a bit more processing. Hopefuly, this won't have negative impact on editor.

PS.
@Reinmar told me to hide those tests in case we need them: https://gist.github.com/scofalik/7d33adb45b82722bf5f6ca59ae8439d8

[Reinmar]

The second part of this issue (the viewChildrenToDom()'s poor behaviour) is caused by https://github.com/ckeditor/ckeditor5-engine/issues/1125.

[Reinmar]

You said @scofalik that you've been working on this. Or am I wrong?

[scofalik]

Yes, there should be branch pushed with proposed changes, but I'll have to take a look at it as it was week or more time ago and there are couple related tickets.

[scofalik]

https://github.com/ckeditor/ckeditor5-engine/issues/1125#issuecomment-332791847