t/1151: Implemented the right–to–left (RTL) languages support for the UI and the content

[oleq]

Suggested merge commit message (convention)

Feature: Implemented the right–to–left (RTL) languages support for the UI and the content (see #1151).

---

Additional information

This is also a constellation branch. Other PRs in the constellation:

• T/ckeditor5/1151: Implemented the conifg.contentLanguage configuration ckeditor5-core#187
• T/ckeditor5/1151: The InlineEditorUIView should display on different sides of editable depending on the direction of the UI language.  ckeditor5-editor-inline#61
• T/ckeditor5/1151: Adjusted InsertTableView for better compatibility with right–to–left (RTL) languages ckeditor5-table#196
• T/ckeditor5/1151: Brought support for right–to–left (RTL) UI to various components' styles ckeditor5-theme-lark#238
• T/ckeditor5/1151: Brought support for right–to–left (RTL) languages to various UI components ckeditor5-ui#520
• T/ckeditor5/1151: Allowed passing the content language to Locale constructor ckeditor5-utils#296
• T/ckeditor5/1151: Adjusted blockquote content styles for better compatibility with RTL languages ckeditor5-block-quote#38
• t/ckeditor5/1151: Added a manual test for widget selection handler in different UI language directions ckeditor5-widget#96
• T/ckeditor5/1151: Integrated the text alignment feature with different editor content directions ckeditor5-alignment#43
• T/ckeditor5/1151: Integrated the indent block feature with different editor content directions ckeditor5-indent#16
• t/ckeditor5/1151: Made the undo and redo button icons match the editor UI language direction ckeditor5-undo#99
• T/ckeditor5/1151: Brought support for RTL content in the bindTwoStepCaretToAttribute() helper ckeditor5-engine#1769
• t/ckeditor5/1151: Passed editor content direction to the bindTwoStepCaretToAttribute() helper in the LinkEditing plugin ckeditor5-link#244
• t/ckeditor5/1151: Aligned the CKFinderCommand to the latest Locale API ckeditor5-ckfinder#47

[Reinmar]

All fine in this PR.

[Reinmar]

OK, I finished reviewing other PRs. There are some R-es but mostly due to implementation details and API. The whole thing works fine.

Two things that I found but which are not blocking:

1. The keyboard navigation around widgets is broken.
2. I miss RTL tests for all features. Where did you actually test them? The best way I found was to override the language in Locale() and build all manual tests.

[Reinmar]

And there's also #1151 (comment) which should be fairly easy to resolve.

[oleq]

• The keyboard navigation around widgets is broken.

https://github.com/ckeditor/ckeditor5-widget/issues/97

And there's also #1151 (comment) which should be fairly easy to resolve.

https://github.com/ckeditor/ckeditor5-table/issues/200

2. I miss RTL tests for all features. Where did you actually test them? The best way I found was to override the language in Locale() and build all manual tests.

Those features that are affected by UI language/content language and RTL in an obvious way (indent, alignment, editor-inline) got their new rtl.js manual tests.

Other features that have very little (block quote) or nothing (font) to do with RTL can be checked in docs (UI language guide) or in the locale.js manual test (ckeditor5-utils).

I don't see any good reason for creating an RTL test for each feature (as a rule of thumb).