// Copyright 2014 The Flutter Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. /// Constants for useful Unicode characters. /// /// Currently, these characters are all related to bidirectional text. /// /// See also: /// /// * <http://unicode.org/reports/tr9/>, which describes the Unicode /// bidirectional text algorithm. class Unicode { // This class is not meant to be instantiated or extended; this constructor // prevents instantiation and extension. Unicode._(); /// `U+202A LEFT-TO-RIGHT EMBEDDING` /// /// Treat the following text as embedded left-to-right. /// /// Use [PDF] to end the embedding. static const String LRE = '\u202A'; /// `U+202B RIGHT-TO-LEFT EMBEDDING` /// /// Treat the following text as embedded right-to-left. /// /// Use [PDF] to end the embedding. static const String RLE = '\u202B'; /// `U+202C POP DIRECTIONAL FORMATTING` /// /// End the scope of the last [LRE], [RLE], [RLO], or [LRO]. static const String PDF = '\u202C'; /// `U+202A LEFT-TO-RIGHT OVERRIDE` /// /// Force following characters to be treated as strong left-to-right characters. /// /// For example, this causes Hebrew text to render backwards. /// /// Use [PDF] to end the override. static const String LRO = '\u202D'; /// `U+202B RIGHT-TO-LEFT OVERRIDE` /// /// Force following characters to be treated as strong right-to-left characters. /// /// For example, this causes English text to render backwards. /// /// Use [PDF] to end the override. static const String RLO = '\u202E'; /// `U+2066 LEFT-TO-RIGHT ISOLATE` /// /// Treat the following text as isolated and left-to-right. /// /// Use [PDI] to end the isolated scope. static const String LRI = '\u2066'; /// `U+2067 RIGHT-TO-LEFT ISOLATE` /// /// Treat the following text as isolated and right-to-left. /// /// Use [PDI] to end the isolated scope. static const String RLI = '\u2067'; /// `U+2068 FIRST STRONG ISOLATE` /// /// Treat the following text as isolated and in the direction of its first /// strong directional character that is not inside a nested isolate. /// /// This essentially "auto-detects" the directionality of the text. It is not /// 100% reliable. For example, Arabic text that starts with an English quote /// will be detected as LTR, not RTL, which will lead to the text being in a /// weird order. /// /// Use [PDI] to end the isolated scope. static const String FSI = '\u2068'; /// `U+2069 POP DIRECTIONAL ISOLATE` /// /// End the scope of the last [LRI], [RLI], or [FSI]. static const String PDI = '\u2069'; /// `U+200E LEFT-TO-RIGHT MARK` /// /// Left-to-right zero-width character. static const String LRM = '\u200E'; /// `U+200F RIGHT-TO-LEFT MARK` /// /// Right-to-left zero-width non-Arabic character. static const String RLM = '\u200F'; /// `U+061C ARABIC LETTER MARK` /// /// Right-to-left zero-width Arabic character. static const String ALM = '\u061C'; }