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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 14:29:10 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 14:29:10 +0000
commit2aa4a82499d4becd2284cdb482213d541b8804dd (patch)
treeb80bf8bf13c3766139fbacc530efd0dd9d54394c /layout/base/nsBidi.h
parentInitial commit. (diff)
downloadfirefox-2aa4a82499d4becd2284cdb482213d541b8804dd.tar.xz
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Adding upstream version 86.0.1.upstream/86.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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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 http://mozilla.org/MPL/2.0/. */
+
+#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 {
+ public:
+ /** @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);
+ }
+
+ private:
+ 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_