#6432: Introduced SchemaItemDefinition#isSelectable and SchemaItemDefinition#isContent.

[oleq]

Suggested merge commit message (convention)

Feature (engine): Introduced the SchemaItemDefinition#isSelectable property. Closes #6432.

Feature (engine): Introduced the SchemaItemDefinition#isContent property. Closes #7631.

Other (table): The tableCell model element brought by the TableEditing plugin is no longer an object (SchemaItemDefinition#isObject) in the Schema but a selectable (SchemaItemDefinition#isSelectable) (see #6432).

Internal (ui): Aligned the BalloonToolbar plugin behavior to the new  SchemaItemDefinition#isSelectable property (see #6432).

Docs (engine): Extended the "Schema" deep dive guide with the new properties and methods (see #6432, #7631).

Tests (image): Aligned tests to the fact that the tableCell model element is no longer an object but a selectable in the schema (see #6432).

Tests (horizontal-line): Aligned tests to the fact that the tableCell model element is no longer an object but a selectable in the schema (see #6432).

MINOR BREAKING CHANGE (table): The tableCell model element brought by the TableEditing plugin is no longer an object (SchemaItemDefinition#isObject) in the Schema but a selectable (SchemaItemDefinition#isSelectable). Please update your integration code accordingly (see #6432).

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Additional information

• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-engine/src/model/utils/insertcontent.js#L243-L244 -> isSelectable()?

• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-engine/src/model/utils/modifyselection.js#L108 -> isSelectable()?

• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-engine/src/model/utils/selection-post-fixer.js#L181-L184 -> isSelectable()?

•  https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-horizontal-line/src/horizontallinecommand.js#L97 -> isSelectable()?

  On one hand, it makes sense because it would disable the command when a single table cell is selected (enabled ATM in this PR).

  OTOH, what if in the future we allow selecting some containers from the outside and converting them into a horizontal line when they are selected makes perfectly sense?

  •  https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-heading/src/headingcommand.js#L95 same as above, except for headings.
  • https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-image/src/image/utils.js#L150 same as above, except for images.
  • https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-list/src/listcommand.js#L310 same as above, except for lists.
  • https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-page-break/src/pagebreakcommand.js#L97 same as above, except for page breaks
  • https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-paragraph/src/paragraphcommand.js#L72 ...and paragraphs,

[oleq]

F2F call summary:

https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-engine/src/model/utils/insertcontent.js#L243-L244 -> isSelectable()?

waiting for confirmation from @Reinmar 

https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-engine/src/model/utils/modifyselection.js#L108 -> isSelectable()?

Yes.

https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-engine/src/model/utils/selection-post-fixer.js#L181-L184 -> isSelectable()?

Yes.

https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-horizontal-line/src/horizontallinecommand.js#L97 -> isSelectable()?
On one hand, it makes sense because it would disable the command when a single table cell is selected (enabled ATM in this PR).
OTOH, what if in the future we allow selecting some containers from the outside and converting them into a horizontal line when they are selected makes perfectly sense?

• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-heading/src/headingcommand.js#L95 same as above, except for headings.
• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-image/src/image/utils.js#L150 same as above, except for images.
• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-list/src/listcommand.js#L310 same as above, except for lists.
• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-page-break/src/pagebreakcommand.js#L97 same as above, except for page breaks
• https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-paragraph/src/paragraphcommand.js#L72 ...and paragraphs,

No.

[Reinmar]

https://github.com/ckeditor/ckeditor5/blob/i/6432-schema-is-selectable/packages/ckeditor5-engine/src/model/utils/insertcontent.js#L243-L244 -> isSelectable()?

waiting for confirmation from @Reinmar 

This one is tricky. We actually want to check if it's:

• a content, as if it's not content itself it could be ignored and only its children inserted in that place – as in _handleDisallowedNode,
• a limit, as it also defines that the element cannot be split (or otherwise ignored),
• selectable, asc we'll most likely try to select it.

Therefore, the current isObject() check is good. WITH ONE condition – that isObject() works this way:

isObject( item ) {
    const def = this.getDefinition( item );
    
    return def.isObject || ( def.isLimit && def.isSelectable && def.isContent );
}

You may remember that I already mentioned that isObject() should also return true if you set the 3 granular options to true. It'd definitely be safer in this case if we did that.

[oleq]

Let's have another round of review then.