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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef nsBidi_h__
#define nsBidi_h__
#include "unicode/ubidi.h"
#include "ICUUtils.h"
#include "nsIFrame.h" // for nsBidiLevel/nsBidiDirection declarations
// nsBidi implemented as a simple wrapper around the bidi reordering engine
// from ICU.
// We could eliminate this and let callers use the ICU functions directly
// once we no longer care about building without ICU available.
class nsBidi {
/** @brief Default constructor.
* The nsBidi object is initially empty. It is assigned
* the Bidi properties of a paragraph by <code>SetPara()</code>.
nsBidi() { mBiDi = ubidi_open(); }
/** @brief Destructor. */
~nsBidi() { ubidi_close(mBiDi); }
* Perform the Unicode Bidi algorithm.
* @param aText is a pointer to the single-paragraph text that the
* Bidi algorithm will be performed on
* (step (P1) of the algorithm is performed externally).
* <strong>The text must be (at least) <code>aLength</code> long.
* </strong>
* @param aLength is the length of the text; if <code>aLength==-1</code> then
* the text must be zero-terminated.
* @param aParaLevel specifies the default level for the paragraph;
* it is typically 0 (LTR) or 1 (RTL).
* If the function shall determine the paragraph level from the text,
* then <code>aParaLevel</code> can be set to
* either <code>NSBIDI_DEFAULT_LTR</code>
* or <code>NSBIDI_DEFAULT_RTL</code>;
* if there is no strongly typed character, then
* the desired default is used (0 for LTR or 1 for RTL).
* Any other value between 0 and <code>NSBIDI_MAX_EXPLICIT_LEVEL</code>
* is also valid, with odd levels indicating RTL.
nsresult SetPara(const char16_t* aText, int32_t aLength,
nsBidiLevel aParaLevel) {
UErrorCode error = U_ZERO_ERROR;
ubidi_setPara(mBiDi, reinterpret_cast<const UChar*>(aText), aLength,
aParaLevel, nullptr, &error);
return ICUUtils::UErrorToNsResult(error);
* Get the directionality of the text.
* @param aDirection receives a <code>NSBIDI_XXX</code> value that indicates
* if the entire text represented by this object is unidirectional,
* and which direction, or if it is mixed-directional.
* @see nsBidiDirection
nsBidiDirection GetDirection() {
return nsBidiDirection(ubidi_getDirection(mBiDi));
* Get the paragraph level of the text.
* @param aParaLevel receives a <code>NSBIDI_XXX</code> value indicating
* the paragraph level
* @see nsBidiLevel
nsBidiLevel GetParaLevel() { return ubidi_getParaLevel(mBiDi); }
* Get a logical run.
* This function returns information about a run and is used
* to retrieve runs in logical order.<p>
* This is especially useful for line-breaking on a paragraph.
* <code>CountRuns</code> should be called before this.
* before the runs are retrieved.
* @param aLogicalStart is the first character of the run.
* @param aLogicalLimit will receive the limit of the run.
* The l-value that you point to here may be the
* same expression (variable) as the one for
* <code>aLogicalStart</code>.
* This pointer cannot be <code>nullptr</code>.
* @param aLevel will receive the level of the run.
* This pointer cannot be <code>nullptr</code>.
void GetLogicalRun(int32_t aLogicalStart, int32_t* aLogicalLimit,
nsBidiLevel* aLevel);
* Get the number of runs.
* This function may invoke the actual reordering on the
* <code>nsBidi</code> object, after <code>SetPara</code>
* may have resolved only the levels of the text. Therefore,
* <code>CountRuns</code> may have to allocate memory,
* and may fail doing so.
* @param aRunCount will receive the number of runs.
nsresult CountRuns(int32_t* aRunCount);
* Get one run's logical start, length, and directionality,
* which can be 0 for LTR or 1 for RTL.
* In an RTL run, the character at the logical start is
* visually on the right of the displayed run.
* The length is the number of characters in the run.<p>
* <code>CountRuns</code> should be called
* before the runs are retrieved.
* @param aRunIndex is the number of the run in visual order, in the
* range <code>[0..CountRuns-1]</code>.
* @param aLogicalStart is the first logical character index in the text.
* The pointer may be <code>nullptr</code> if this index is not needed.
* @param aLength is the number of characters (at least one) in the run.
* The pointer may be <code>nullptr</code> if this is not needed.
* @returns the directionality of the run,
* <code>NSBIDI_LTR==0</code> or <code>NSBIDI_RTL==1</code>,
* never <code>NSBIDI_MIXED</code>.
* @see CountRuns<p>
* Example:
* @code
* int32_t i, count, logicalStart, visualIndex=0, length;
* nsBidiDirection dir;
* pBidi->CountRuns(&count);
* for(i=0; i<count; ++i) {
* dir = pBidi->GetVisualRun(i, &logicalStart, &length);
* if(NSBIDI_LTR==dir) {
* do { // LTR
* show_char(text[logicalStart++], visualIndex++);
* } while(--length>0);
* } else {
* logicalStart+=length; // logicalLimit
* do { // RTL
* show_char(text[--logicalStart], visualIndex++);
* } while(--length>0);
* }
* }
* @endcode
* Note that in right-to-left runs, code like this places
* modifier letters before base characters and second surrogates
* before first ones.
nsBidiDirection GetVisualRun(int32_t aRunIndex, int32_t* aLogicalStart,
int32_t* aLength) {
return nsBidiDirection(
ubidi_getVisualRun(mBiDi, aRunIndex, aLogicalStart, aLength));
* This is a convenience function that does not use a nsBidi object.
* It is intended to be used for when an application has determined the levels
* of objects (character sequences) and just needs to have them reordered
* (L2). This is equivalent to using <code>GetVisualMap</code> on a
* <code>nsBidi</code> object.
* @param aLevels is an array with <code>aLength</code> levels that have been
* determined by the application.
* @param aLength is the number of levels in the array, or, semantically,
* the number of objects to be reordered.
* It must be <code>aLength>0</code>.
* @param aIndexMap is a pointer to an array of <code>aLength</code>
* indexes which will reflect the reordering of the characters.
* The array does not need to be initialized.<p>
* The index map will result in
* <code>aIndexMap[aVisualIndex]==aLogicalIndex</code>.
static void ReorderVisual(const nsBidiLevel* aLevels, int32_t aLength,
int32_t* aIndexMap) {
ubidi_reorderVisual(aLevels, aLength, aIndexMap);
nsBidi(const nsBidi&) = delete;
void operator=(const nsBidi&) = delete;
UBiDi* mBiDi;
// The two fields below are updated when CountRuns is called.
const nsBidiLevel* mLevels = nullptr;
int32_t mLength = 0;
#endif // _nsBidi_h_