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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 */
#include "mozilla/intl/LineBreaker.h"
#include "mozilla/intl/Segmenter.h"
#include "nsString.h"
#include "nsTArray.h"
class nsAtom;
class nsHyphenator;
* A receiver of line break data.
class nsILineBreakSink {
* Sets the break data for a substring of the associated text chunk.
* One or more of these calls will be performed; the union of all substrings
* will cover the entire text chunk. Substrings may overlap (i.e., we may
* set the break-before state of a character more than once).
* @param aBreakBefore the break-before states for the characters in the
* substring. These are enum values from gfxTextRun::CompressedGlyph:
* FLAG_BREAK_TYPE_NONE - no linebreak is allowed here
* FLAG_BREAK_TYPE_NORMAL - a normal (whitespace) linebreak
* FLAG_BREAK_TYPE_HYPHEN - a hyphenation point
virtual void SetBreaks(uint32_t aStart, uint32_t aLength,
uint8_t* aBreakBefore) = 0;
* Indicates which characters should be capitalized. Only called if
virtual void SetCapitalization(uint32_t aStart, uint32_t aLength,
bool* aCapitalize) = 0;
* A line-breaking state machine. You feed text into it via AppendText calls
* and it computes the possible line breaks. Because break decisions can
* require a lot of context, the breaks for a piece of text are sometimes not
* known until later text has been seen (or all text ends). So breaks are
* returned via a call to SetBreaks on the nsILineBreakSink object passed
* with each text chunk, which might happen during the corresponding AppendText
* call, or might happen during a later AppendText call or even a Reset()
* call.
* The linebreak results MUST NOT depend on how the text is broken up
* into AppendText calls.
* The current strategy is that we break the overall text into
* whitespace-delimited "words". Then those words are passed to the LineBreaker
* for deeper analysis if they might contain breakable characters.
* This class also handles detection of which characters should be capitalized
* for text-transform:capitalize. This is a good place to handle that because
* we have all the context we need.
class nsLineBreaker {
static inline bool IsSpace(char16_t u) {
return mozilla::intl::NS_IsSpace(u);
// Break opportunities exist at the end of each run of breakable whitespace
// (see IsSpace above). Break opportunities can also exist between pairs of
// non-whitespace characters, as determined by mozilla::intl::LineBreaker.
// We pass a whitespace-
// delimited word to LineBreaker if it contains at least one character
// that has breakable line breaking classes.
// We provide flags to control on a per-chunk basis where breaks are allowed.
// At any character boundary, exactly one text chunk governs whether a
// break is allowed at that boundary.
// We operate on text after whitespace processing has been applied, so
// other characters (e.g. tabs and newlines) may have been converted to
// spaces.
* Flags passed with each chunk of text.
enum {
* Do not introduce a break opportunity at the start of this chunk of text.
* Do not introduce a break opportunity in the interior of this chunk of
* text. Also, whitespace in this chunk is treated as non-breakable.
* The sink currently is already set up to have no breaks in it;
* if no breaks are possible, nsLineBreaker does not need to call
* SetBreaks on it. This is useful when handling large quantities of
* preformatted text; the textruns will never have any breaks set on them,
* and there is no need to ever actually scan the text for breaks, except
* at the end of textruns in case context is needed for following breakable
* text.
* We need to be notified of characters that should be capitalized
* (as in text-transform:capitalize) in this chunk of text.
* Auto-hyphenation is enabled, so we need to get a hyphenator
* (if available) and use it to find breakpoints.
* Append "invisible whitespace". This acts like whitespace, but there is
* no actual text associated with it. Only the BREAK_SUPPRESS_INSIDE flag
* is relevant here.
nsresult AppendInvisibleWhitespace(uint32_t aFlags);
* Feed Unicode text into the linebreaker for analysis. aLength must be
* nonzero.
* @param aSink can be null if the breaks are not actually needed (we may
* still be setting up state for later breaks)
nsresult AppendText(nsAtom* aHyphenationLanguage, const char16_t* aText,
uint32_t aLength, uint32_t aFlags,
nsILineBreakSink* aSink);
* Feed 8-bit text into the linebreaker for analysis. aLength must be nonzero.
* @param aSink can be null if the breaks are not actually needed (we may
* still be setting up state for later breaks)
nsresult AppendText(nsAtom* aHyphenationLanguage, const uint8_t* aText,
uint32_t aLength, uint32_t aFlags,
nsILineBreakSink* aSink);
* Reset all state. This means the current run has ended; any outstanding
* calls through nsILineBreakSink are made, and all outstanding references to
* nsILineBreakSink objects are dropped.
* After this call, this linebreaker can be reused.
* This must be called at least once between any call to AppendText() and
* destroying the object.
* @param aTrailingBreak this is set to true when there is a break opportunity
* at the end of the text. This will normally only be declared true when there
* is breakable whitespace at the end.
nsresult Reset(bool* aTrailingBreak);
* Set word-break mode for line breaker. This is set by word-break property.
void SetWordBreak(mozilla::intl::WordBreakRule aMode) {
// If current word is non-empty and mode is changing, flush the breaker.
if (aMode != mWordBreak && !mCurrentWord.IsEmpty()) {
nsresult rv = FlushCurrentWord();
if (NS_FAILED(rv)) {
NS_WARNING("FlushCurrentWord failed, line-breaks may be wrong");
// If previous mode was break-all, we should allow a break here.
// XXX (jfkthame) css-text spec seems unclear on this, raised question in
if (mWordBreak == mozilla::intl::WordBreakRule::BreakAll) {
mBreakHere = true;
mWordBreak = aMode;
* Set line-break rule strictness mode for line breaker. This is set by the
* line-break property.
void SetStrictness(mozilla::intl::LineBreakRule aMode) {
if (aMode != mLineBreak && !mCurrentWord.IsEmpty()) {
nsresult rv = FlushCurrentWord();
if (NS_FAILED(rv)) {
NS_WARNING("FlushCurrentWord failed, line-breaks may be wrong");
// If previous mode was anywhere, we should allow a break here.
if (mLineBreak == mozilla::intl::LineBreakRule::Anywhere) {
mBreakHere = true;
mLineBreak = aMode;
* Return whether the line-breaker has a buffered "current word" that may
* be extended with additional word-forming characters.
bool InWord() const { return !mCurrentWord.IsEmpty(); }
* Set the word-continuation state, which will suppress capitalization of
* the next letter that might otherwise apply.
void SetWordContinuation(bool aContinuation) {
mWordContinuation = aContinuation;
// This is a list of text sources that make up the "current word" (i.e.,
// run of text which does not contain any whitespace). All the mLengths
// are are nonzero, these cannot overlap.
struct TextItem {
TextItem(nsILineBreakSink* aSink, uint32_t aSinkOffset, uint32_t aLength,
uint32_t aFlags)
: mSink(aSink),
mFlags(aFlags) {}
nsILineBreakSink* mSink;
uint32_t mSinkOffset;
uint32_t mLength;
uint32_t mFlags;
// State for the nonwhitespace "word" that started in previous text and hasn't
// finished yet.
// When the current word ends, this computes the linebreak opportunities
// *inside* the word (excluding either end) and sets them through the
// appropriate sink(s). Then we clear the current word state.
nsresult FlushCurrentWord();
void UpdateCurrentWordLanguage(nsAtom* aHyphenationLanguage);
void FindHyphenationPoints(nsHyphenator* aHyphenator,
const char16_t* aTextStart,
const char16_t* aTextLimit, uint8_t* aBreakState);
inline constexpr bool IsSegmentSpace(char16_t u) const {
if (mLegacyBehavior) {
return nsLineBreaker::IsSpace(u);
return u == 0x0020 || // SPACE u
u == 0x0009 || // CHARACTER TABULATION
u == 0x000D; // CARRIAGE RETURN
AutoTArray<char16_t, 100> mCurrentWord;
// All the items that contribute to mCurrentWord
AutoTArray<TextItem, 2> mTextItems;
nsAtom* mCurrentWordLanguage;
bool mCurrentWordContainsMixedLang;
bool mCurrentWordMightBeBreakable = false;
bool mScriptIsChineseOrJapanese;
// True if the previous character was breakable whitespace
bool mAfterBreakableSpace;
// True if a break must be allowed at the current position because
// a run of breakable whitespace ends here
bool mBreakHere;
// Break rules for letters from the "word-break" property.
mozilla::intl::WordBreakRule mWordBreak;
// Line breaking strictness from the "line-break" property.
mozilla::intl::LineBreakRule mLineBreak;
// Should the text be treated as continuing a word-in-progress (for purposes
// of initial capitalization)? Normally this is set to false whenever we
// start using a linebreaker, but it may be set to true if the line-breaker
// has been explicitly flushed mid-word.
bool mWordContinuation;
// True if using old line segmenter.
const bool mLegacyBehavior;