106 lines
2.8 KiB
JavaScript
106 lines
2.8 KiB
JavaScript
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/**
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* Copyright (c) 2013-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @typechecks
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*
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*/
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/**
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* Constants to represent text directionality
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*
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* Also defines a *global* direciton, to be used in bidi algorithms as a
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* default fallback direciton, when no better direction is found or provided.
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*
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* NOTE: Use `setGlobalDir()`, or update `initGlobalDir()`, to set the initial
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* global direction value based on the application.
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*
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* Part of the implementation of Unicode Bidirectional Algorithm (UBA)
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* Unicode Standard Annex #9 (UAX9)
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* http://www.unicode.org/reports/tr9/
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*/
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'use strict';
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var invariant = require('./invariant');
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var NEUTRAL = 'NEUTRAL'; // No strong direction
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var LTR = 'LTR'; // Left-to-Right direction
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var RTL = 'RTL'; // Right-to-Left direction
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var globalDir = null;
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// == Helpers ==
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/**
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* Check if a directionality value is a Strong one
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*/
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function isStrong(dir) {
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return dir === LTR || dir === RTL;
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}
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/**
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* Get string value to be used for `dir` HTML attribute or `direction` CSS
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* property.
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*/
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function getHTMLDir(dir) {
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!isStrong(dir) ? process.env.NODE_ENV !== 'production' ? invariant(false, '`dir` must be a strong direction to be converted to HTML Direction') : invariant(false) : void 0;
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return dir === LTR ? 'ltr' : 'rtl';
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}
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/**
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* Get string value to be used for `dir` HTML attribute or `direction` CSS
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* property, but returns null if `dir` has same value as `otherDir`.
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* `null`.
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*/
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function getHTMLDirIfDifferent(dir, otherDir) {
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!isStrong(dir) ? process.env.NODE_ENV !== 'production' ? invariant(false, '`dir` must be a strong direction to be converted to HTML Direction') : invariant(false) : void 0;
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!isStrong(otherDir) ? process.env.NODE_ENV !== 'production' ? invariant(false, '`otherDir` must be a strong direction to be converted to HTML Direction') : invariant(false) : void 0;
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return dir === otherDir ? null : getHTMLDir(dir);
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}
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// == Global Direction ==
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/**
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* Set the global direction.
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*/
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function setGlobalDir(dir) {
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globalDir = dir;
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}
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/**
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* Initialize the global direction
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*/
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function initGlobalDir() {
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setGlobalDir(LTR);
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}
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/**
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* Get the global direction
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*/
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function getGlobalDir() {
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if (!globalDir) {
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this.initGlobalDir();
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}
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!globalDir ? process.env.NODE_ENV !== 'production' ? invariant(false, 'Global direction not set.') : invariant(false) : void 0;
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return globalDir;
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}
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var UnicodeBidiDirection = {
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// Values
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NEUTRAL: NEUTRAL,
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LTR: LTR,
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RTL: RTL,
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// Helpers
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isStrong: isStrong,
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getHTMLDir: getHTMLDir,
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getHTMLDirIfDifferent: getHTMLDirIfDifferent,
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// Global Direction
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setGlobalDir: setGlobalDir,
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initGlobalDir: initGlobalDir,
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getGlobalDir: getGlobalDir
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};
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module.exports = UnicodeBidiDirection;
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