Atto has no mechanism for creating a span of right to left running text in a left to right running paragraph or vice versa. You would need this if you were quoting another language inline or referencing the title of a book published in another language.
TinyMCE does this properly.
- Enable the rtl button by adding rtl to the toolbar config list in Site Admin > Plugins > Text Editors > Atto HTML Editor > Atto Toolbar Settings
- Write some text in an Atto editor
- Highlight part of a sentence
- Click the RTL button
Expect: The highlighted text should be wrapped in a span with dir=rtl
Returns: Paragraph tag of the entire sentence is set to dir=rtl