Bi-directional text

Bi-directional texts are usually multilingual texts in which fonts are used with different writing direction. This is especially in the information and computer technology for the global exchange of data through the Internet represents a problem

Writings with different writing directions

Left side ( The text runs from left to right)

Different writing systems are used in different languages. In Europe and in European-influenced cultures are predominantly writings with a writing direction from left to right use, for example, in Latin, German or English. Others, especially Semitic writings, such as Hebrew, Arabic or Persian and it influenced writings such Thaana and Kharoshthi are written from right to left. There are also fonts that are both written from right to left and vice versa, as it is possible, for example, with Egyptian hieroglyphics or Chinese characters.

Bi-directional Texts in computer systems

Whether your browser the Hebrew text correctly on this page represents you can see here.

גן עדן

The text ( right) should be about as look like the picture ( left)

Bidirectional write support ( Bidirectional script support, BiDi or bidi ) is the ability to computer systems to write complex texts in different writing directions. In older systems usually was only one writing direction, often to the right, supported by the left. With the spread of computer technology over the entire world and across cultures text editors and other text processing systems must be able to process both directions of writing.

Some computer programs can not correctly display bidirectional text. Thus, the Hebrew term for the garden should be spelled Eden ( גן עדן ) from right to left ( gimel ( ג ), now ( ן ), ayin ( ע ), daleth ( ד ), now ( ן ) ).

Especially when mixed texts in which different typefaces are used within a paragraph, computer systems have display problems today.

Unicode

In Unicode several writing systems are presented, with each letter is assigned to write his direction; Punctuation, however, have no set writing direction. Characters with a fixed direction of writing called "strong characters"; Characters that can be used in different writing directions are called " weak characters". The Unicode Standard does not thereby determines how must be dealt with "weak characters", but there is the Unicode bidi algorithm that attempts to find a suitable writing direction for the punctuation.

An example of such an algorithm: If a "weak character" between two "strong characters" with the same direction of writing, so it inherits the writing direction. Is it, however, between two "strong characters" with a different writing direction, the major writing direction of the text is adopted. If a "weak character" between other "weak characters", an attempt is made to determine the writing direction of the nearest "strong characters". To change this behavior, there are among the bidirectional control characters, the "pseudo -strong characters" (U 200 E and U 200 F RTL LTR ), also called " marks". These characters are not printed, but behave as a corresponding " strong character " to determine the writing direction for a punctuation mark.