Bidirectional Control

Bidirectional Control is a character property that designates specific formatting codes used to manage text direction in mixed-language contexts, such as combining left-to-right and right-to-left scripts. These control characters, including LRM, RLM, LRE, RLE, PDF, LRO, RLO, and ALM, override the automatic bidirectional algorithm that normally determines character ordering. Their purpose is to ensure correct visual display when default directionality fails, for example in nested quotes, parentheses, or embedded Hebrew or Arabic within English text. The property strictly classifies these characters as having explicit directional control, meaning they do not represent visible glyphs but instead influence how neighboring characters are ordered. This allows software to handle complex layouts predictably, though misuse can cause confusing "bidi spoofing" in security contexts. As such, the property is essential for proper rendering of multilingual documents and user interfaces.