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Diffstat (limited to 'dom/base/nsLineBreaker.h')
| -rw-r--r-- | dom/base/nsLineBreaker.h | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/dom/base/nsLineBreaker.h b/dom/base/nsLineBreaker.h new file mode 100644 index 0000000000..8b902a70c2 --- /dev/null +++ b/dom/base/nsLineBreaker.h @@ -0,0 +1,286 @@ +/* -*- 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 NSLINEBREAKER_H_ +#define NSLINEBREAKER_H_ + +#include "mozilla/intl/LineBreaker.h" +#include "nsString.h" +#include "nsTArray.h" + +class nsAtom; +class nsHyphenator; + +/** + * A receiver of line break data. + */ +class nsILineBreakSink { + public: + /** + * 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 + * BREAK_NEED_CAPITALIZATION was requested. + */ + 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 + * service for deeper analysis if they contain a "complex" character as + * described below. + * + * 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 { + public: + nsLineBreaker(); + ~nsLineBreaker(); + + static inline bool IsSpace(char16_t u) { + return mozilla::intl::NS_IsSpace(u); + } + + static inline bool IsComplexASCIIChar(char16_t u) { + return !((0x0030 <= u && u <= 0x0039) || (0x0041 <= u && u <= 0x005A) || + (0x0061 <= u && u <= 0x007A) || (0x000a == u)); + } + + static inline bool IsComplexChar(char16_t u) { + return IsComplexASCIIChar(u) || + mozilla::intl::NS_NeedsPlatformNativeHandling(u) || + (0x1100 <= u && u <= 0x11ff) || // Hangul Jamo + (0x2000 <= u && u <= 0x21ff) || // Punctuations and Symbols + (0x2e80 <= u && u <= 0xd7ff) || // several CJK blocks + (0xf900 <= u && u <= 0xfaff) || // CJK Compatibility Idographs + (0xff00 <= u && u <= 0xffef); // Halfwidth and Fullwidth Forms + } + + // 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 + // matching IsComplexChar. + // 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. + */ + BREAK_SUPPRESS_INITIAL = 0x01, + /** + * Do not introduce a break opportunity in the interior of this chunk of + * text. Also, whitespace in this chunk is treated as non-breakable. + */ + BREAK_SUPPRESS_INSIDE = 0x02, + /** + * 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. + */ + BREAK_SKIP_SETTING_NO_BREAKS = 0x04, + /** + * We need to be notified of characters that should be capitalized + * (as in text-transform:capitalize) in this chunk of text. + */ + BREAK_NEED_CAPITALIZATION = 0x08, + /** + * Auto-hyphenation is enabled, so we need to get a hyphenator + * (if available) and use it to find breakpoints. + */ + BREAK_USE_AUTO_HYPHENATION = 0x10 + }; + + /** + * 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 linebreaker. This is set by word-break property. + * @param aMode is LineBreaker::WordBreak::* value. + */ + void SetWordBreak(mozilla::intl::LineBreaker::WordBreak 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 + // https://github.com/w3c/csswg-drafts/issues/3897 + if (mWordBreak == mozilla::intl::LineBreaker::WordBreak::BreakAll) { + mBreakHere = true; + } + } + mWordBreak = aMode; + } + + /* + * Set line-break rule strictness mode for linebreaker. This is set by the + * line-break property. + * @param aMode is LineBreaker::Strictness::* value. + */ + void SetStrictness(mozilla::intl::LineBreaker::Strictness aMode) { + if (aMode != mStrictness && !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 (mStrictness == mozilla::intl::LineBreaker::Strictness::Anywhere) { + mBreakHere = true; + } + } + mStrictness = 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; + } + + private: + // 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), + mSinkOffset(aSinkOffset), + mLength(aLength), + 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); + + AutoTArray<char16_t, 100> mCurrentWord; + // All the items that contribute to mCurrentWord + AutoTArray<TextItem, 2> mTextItems; + nsAtom* mCurrentWordLanguage; + bool mCurrentWordContainsMixedLang; + bool mCurrentWordContainsComplexChar; + 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; + // line break mode by "word-break" style + mozilla::intl::LineBreaker::WordBreak mWordBreak; + // strictness of break rules, from line-break property + mozilla::intl::LineBreaker::Strictness mStrictness; + // 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; +}; + +#endif /*NSLINEBREAKER_H_*/ |