layout/generic/nsTextFrameUtils.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef NSTEXTFRAMEUTILS_H_
   7 #define NSTEXTFRAMEUTILS_H_
   8
   9 #include "gfxSkipChars.h"
  10 #include "nsBidiUtils.h"
  11 #include "nsUnicodeProperties.h"
  12
  13 class nsIContent;
  14 struct nsStyleText;
  15
  16 #define BIG_TEXT_NODE_SIZE 4096
  17
  18 #define CH_NBSP   160
  19 #define CH_SHY    173
  20 #define CH_CJKSP  12288 // U+3000 IDEOGRAPHIC SPACE (CJK Full-Width Space)
  21
  22 class nsTextFrameUtils {
  23 public:
  24   // These constants are used as textrun flags for textframe textruns.
  25   enum {
  26     // The following flags are set by TransformText
  27
  28     // the text has at least one untransformed tab character
  29     TEXT_HAS_TAB             = 0x010000,
  30     // the original text has at least one soft hyphen character
  31     TEXT_HAS_SHY             = 0x020000,
  32     TEXT_WAS_TRANSFORMED     = 0x040000,
  33     TEXT_UNUSED_FLAG         = 0x080000,
  34
  35     // The following flags are set by nsTextFrame
  36
  37     TEXT_IS_SIMPLE_FLOW      = 0x100000,
  38     TEXT_INCOMING_WHITESPACE = 0x200000,
  39     TEXT_TRAILING_WHITESPACE = 0x400000,
  40     TEXT_COMPRESSED_LEADING_WHITESPACE = 0x800000,
  41     TEXT_NO_BREAKS           = 0x1000000,
  42     TEXT_IS_TRANSFORMED      = 0x2000000,
  43     // This gets set if there's a break opportunity at the end of the textrun.
  44     // We normally don't use this break opportunity because the following text
  45     // will have a break opportunity at the start, but it's useful for line
  46     // layout to know about it in case the following content is not text
  47     TEXT_HAS_TRAILING_BREAK  = 0x4000000,
  48
  49     // This is set if the textrun was created for a textframe whose
  50     // NS_FRAME_IS_IN_SINGLE_CHAR_MI flag is set.  This occurs if the textframe
  51     // belongs to a MathML <mi> element whose embedded text consists of a
  52     // single character.
  53     TEXT_IS_SINGLE_CHAR_MI   = 0x8000000
  54
  55     // The following are defined by gfxTextRunWordCache rather than here,
  56     // so that it also has access to the _INCOMING flag
  57     // TEXT_TRAILING_ARABICCHAR
  58     // TEXT_INCOMING_ARABICCHAR
  59
  60     // This is defined in gfxTextRunFactory to allow access in gfxFont.
  61     // TEXT_USE_MATH_SCRIPT
  62   };
  63
  64   // These constants are used in TransformText to represent context information
  65   // from previous textruns.
  66   enum {
  67     INCOMING_NONE       = 0,
  68     INCOMING_WHITESPACE = 1,
  69     INCOMING_ARABICCHAR = 2
  70   };
  71
  72   /**
  73    * Returns true if aChars/aLength are something that make a space
  74    * character not be whitespace when they follow the space character
  75    * (combining mark or join control, ignoring intervening direction
  76    * controls).
  77    */
  78   static bool
  79   IsSpaceCombiningSequenceTail(const char16_t* aChars, int32_t aLength) {
  80     return aLength > 0 &&
  81       (mozilla::unicode::IsClusterExtender(aChars[0]) ||
  82        (IsBidiControl(aChars[0]) &&
  83         IsSpaceCombiningSequenceTail(aChars + 1, aLength - 1)
  84        )
  85       );
  86   }
  87
  88   enum CompressionMode {
  89     COMPRESS_NONE,
  90     COMPRESS_WHITESPACE,
  91     COMPRESS_WHITESPACE_NEWLINE,
  92     COMPRESS_NONE_TRANSFORM_TO_SPACE
  93   };
  94
  95   /**
  96    * Create a text run from a run of Unicode text. The text may have whitespace
  97    * compressed. A preformatted tab is sent to the text run as a single space.
  98    * (Tab spacing must be performed by textframe later.) Certain other
  99    * characters are discarded.
 100    *
 101    * @param aCompressWhitespace control what is compressed to a
 102    * single space character: no compression, compress spaces (not followed
 103    * by combining mark) and tabs, compress those plus newlines, or
 104    * no compression except newlines are discarded.
 105    * @param aIncomingFlags a flag indicating whether there was whitespace
 106    * or an Arabic character preceding this text. We set it to indicate if
 107    * there's an Arabic character or whitespace preceding the end of this text.
 108    */
 109   static char16_t* TransformText(const char16_t* aText, uint32_t aLength,
 110                                   char16_t* aOutput,
 111                                   CompressionMode aCompression,
 112                                   uint8_t * aIncomingFlags,
 113                                   gfxSkipChars* aSkipChars,
 114                                   uint32_t* aAnalysisFlags);
 115
 116   static uint8_t* TransformText(const uint8_t* aText, uint32_t aLength,
 117                                 uint8_t* aOutput,
 118                                 CompressionMode aCompression,
 119                                 uint8_t * aIncomingFlags,
 120                                 gfxSkipChars* aSkipChars,
 121                                 uint32_t* aAnalysisFlags);
 122
 123   static void
 124   AppendLineBreakOffset(nsTArray<uint32_t>* aArray, uint32_t aOffset)
 125   {
 126     if (aArray->Length() > 0 && (*aArray)[aArray->Length() - 1] == aOffset)
 127       return;
 128     aArray->AppendElement(aOffset);
 129   }
 130
 131   static uint32_t
 132   ComputeApproximateLengthWithWhitespaceCompression(nsIContent *aContent,
 133                                                     const nsStyleText
 134                                                       *aStyleText);
 135 };
 136
 137 class nsSkipCharsRunIterator {
 138 public:
 139   enum LengthMode {
 140     LENGTH_UNSKIPPED_ONLY   = false,
 141     LENGTH_INCLUDES_SKIPPED = true
 142   };
 143   nsSkipCharsRunIterator(const gfxSkipCharsIterator& aStart,
 144       LengthMode aLengthIncludesSkipped, uint32_t aLength)
 145     : mIterator(aStart), mRemainingLength(aLength), mRunLength(0),
 146       mVisitSkipped(false),
 147       mLengthIncludesSkipped(aLengthIncludesSkipped) {
 148   }
 149   void SetVisitSkipped() { mVisitSkipped = true; }
 150   void SetOriginalOffset(int32_t aOffset) {
 151     mIterator.SetOriginalOffset(aOffset);
 152   }
 153   void SetSkippedOffset(uint32_t aOffset) {
 154     mIterator.SetSkippedOffset(aOffset);
 155   }
 156
 157   // guaranteed to return only positive-length runs
 158   bool NextRun();
 159   bool IsSkipped() const { return mSkipped; }
 160   // Always returns something > 0
 161   int32_t GetRunLength() const { return mRunLength; }
 162   const gfxSkipCharsIterator& GetPos() const { return mIterator; }
 163   int32_t GetOriginalOffset() const { return mIterator.GetOriginalOffset(); }
 164   uint32_t GetSkippedOffset() const { return mIterator.GetSkippedOffset(); }
 165
 166 private:
 167   gfxSkipCharsIterator mIterator;
 168   int32_t              mRemainingLength;
 169   int32_t              mRunLength;
 170   bool                 mSkipped;
 171   bool                 mVisitSkipped;
 172   bool                 mLengthIncludesSkipped;
 173 };
 174
 175 #endif /*NSTEXTFRAMEUTILS_H_*/