unicode-bidi

Summary

The unicode-bidi CSS property together with the direction property relates to the handling of bidirectional text in a document. For example, if a block of text contains both left-to-right and right-to-left text then the user-agent uses a complex Unicode algorithm to decide how to display the text. This property overrides this algorithm and allows the developer to control the text embedding.

The unicode-bidi and direction properties are the two only properties that are not affected by the all shorthand.

Syntax

/* Keyword values */
unicode-bidi: normal;
unicode-bidi: embed;
unicode-bidi: isolate;
unicode-bidi: bidi-override;
unicode-bidi: isolate-override;
unicode-bidi: plaintext;

/* Global values */
unicode-bidi: inherit;
unicode-bidi: initial;
unicode-bidi: unset;

Values

normal

The element does not offer a additional level of embedding with respect to the bidirectional algorithm. For inline elements implicit reordering works across element boundaries.

embed

If the element is inline, this value opens an additional level of embedding with respect to the bidirectional algorithm. The direction of this embedding level is given by the direction property.

bidi-override

For inline elements this creates an override. For block container elements this creates an override for inline-level descendants not within another block container element. This means that inside the element, reordering is strictly in sequence according to the direction property; the implicit part of the bidirectional algorithm is ignored.

isolate

This keyword indicates that the element's container directionality should be calculated without considering the content of this element. The element is therefore isolated from its siblings. When applying its bidirectional-resolution algorithm, its container element treats it as one or several U+FFFC Object Replacement Character, i.e. like an image.

isolate-override

This keyword applies the isolation behavior of the isolate keyword to the surrounding content and the override behavior of the bidi-override keyword to the inner content.

plaintext

This keyword makes the elements directionality calculated without considering its parent bidirectional state or the value of the direction property. The directionality is calculated using the P2 and P3 rules of the Unicode Bidirectional Algorithm.
This value allows to display data which has already formatted using a tool following the Unicode Bidirectional Algorithm.

Formal syntax

normal | embed | isolate | bidi-override | isolate-override | plaintext

Examples

.bible-quote {
  direction: rtl;   
  unicode-bidi: embed;
} 

Specification

Browser compatibility

[1] Since Chrome 19, the syntax from a previous version of the spec, where the isolate keyword could be used together with bidi-override, is allowed.

[2] From Firefox 10 to Firefox 16 included, the old version of the spec, where the isolate keyword could be used together with bidi-override, was implemented. From Firefox 17, this is no longer possible: only one value is allowed and the previous isolate bidi-override can be described using the new isolate-override keyword.

[3] Up to Firefox 15, plaintext didn't do anything to an inline element. The specification changed and the implementation was fixed in Firefox 15.

[4] -webkit-isolate can lock up older versions of Safari (up to 9) and Chrome (up to 47) and is best avoided in favor of the unprefixed version.

[5] Before Firefox 50, the plaintext value was ignored for vertical writing modes (bug 1302734).

See also

• direction