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