The Tor Browser / file revision

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* 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 "nsString.h"

 #include "nsTArray.h"

 #include "nsILineBreaker.h"

 class nsIAtom;

 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 nsILineBreaker

  * 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 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) ||

            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 nsILineBreaker. We pass a whitespace-

   // delimited word to nsILineBreaker 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(nsIAtom* 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(nsIAtom* 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 nsILineBreaker::kWordBreak_* value.

    */

   void SetWordBreak(uint8_t aMode) { mWordBreak = aMode; }

 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(nsIAtom *aHyphenationLanguage);

   void FindHyphenationPoints(nsHyphenator *aHyphenator,

                              const char16_t *aTextStart,

                              const char16_t *aTextLimit,

                              uint8_t *aBreakState);

   nsAutoTArray<char16_t,100> mCurrentWord;

   // All the items that contribute to mCurrentWord

   nsAutoTArray<TextItem,2>    mTextItems;

   nsIAtom*                    mCurrentWordLanguage;

   bool                        mCurrentWordContainsMixedLang;

   bool                        mCurrentWordContainsComplexChar;

   // 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

   uint8_t                     mWordBreak;

 };

 #endif /*NSLINEBREAKER_H_*/