gecko/layout/generic/nsTextFrameUtils.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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 *   robert@ocallahan.org
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#include "nsTextFrameUtils.h"

#include "nsContentUtils.h"
#include "nsIWordBreaker.h"
#include "gfxFont.h"
#include "nsUnicharUtils.h"
#include "nsBidiUtils.h"

// XXX TODO implement transform of backslash to yen that nsTextTransform does
// when requested by PresContext->LanguageSpecificTransformType(). Do it with
// a new factory type that just munges the input stream. But first, check
// that we really still need this, it's only enabled via a hidden pref
// which defaults false...

#define UNICODE_ZWSP 0x200B
  
static PRBool IsDiscardable(PRUnichar ch, PRUint32* aFlags)
{
  // Unlike IS_DISCARDABLE, we don't discard \r. \r will be ignored by gfxTextRun
  // and discarding it would force us to copy text in many cases of preformatted
  // text containing \r\n.
  if (ch == CH_SHY) {
    *aFlags |= nsTextFrameUtils::TEXT_HAS_SHY;
    return PR_TRUE;
  }
  if ((ch & 0xFF00) != 0x2000) {
    // Not a Bidi control character
    return PR_FALSE;
  }
  return IS_BIDI_CONTROL_CHAR(ch);
}

static PRBool IsDiscardable(PRUint8 ch, PRUint32* aFlags)
{
  if (ch == CH_SHY) {
    *aFlags |= nsTextFrameUtils::TEXT_HAS_SHY;
    return PR_TRUE;
  }
  return PR_FALSE;
}

PRUnichar*
nsTextFrameUtils::TransformText(const PRUnichar* aText, PRUint32 aLength,
                                PRUnichar* aOutput,
                                CompressionMode aCompression,
                                PRPackedBool* aIncomingWhitespace,
                                gfxSkipCharsBuilder* aSkipChars,
                                PRUint32* aAnalysisFlags)
{
  PRUint32 flags = 0;
  PRUnichar* outputStart = aOutput;

  if (aCompression == COMPRESS_NONE) {
    // Skip discardables.
    PRUint32 i;
    for (i = 0; i < aLength; ++i) {
      PRUnichar ch = *aText++;
      if (IsDiscardable(ch, &flags)) {
        aSkipChars->SkipChar();
      } else {
        aSkipChars->KeepChar();
        if (ch == '\t') {
          flags |= TEXT_HAS_TAB;
        }
        *aOutput++ = ch;
      }
    }
    *aIncomingWhitespace = PR_FALSE;
  } else {
    PRBool inWhitespace = *aIncomingWhitespace;
    PRUint32 i;
    for (i = 0; i < aLength; ++i) {
      PRUnichar ch = *aText++;
      PRBool nowInWhitespace;
      if (ch == ' ' &&
          (i + 1 >= aLength ||
           !IsSpaceCombiningSequenceTail(aText, aLength - (i + 1)))) {
        nowInWhitespace = PR_TRUE;
      } else if (ch == '\n' && aCompression == COMPRESS_WHITESPACE_NEWLINE) {
        if (i > 0 && IS_CJ_CHAR(aText[-1]) &&
            i + 1 < aLength && IS_CJ_CHAR(aText[1])) {
          // Discard newlines between CJK chars.
          // XXX this really requires more context to get right!
          aSkipChars->SkipChar();
          continue;
        }
        nowInWhitespace = PR_TRUE;
      } else {
        nowInWhitespace = ch == '\t';
      }

      if (!nowInWhitespace) {
        if (IsDiscardable(ch, &flags)) {
          aSkipChars->SkipChar();
          nowInWhitespace = inWhitespace;
        } else {
          *aOutput++ = ch;
          aSkipChars->KeepChar();
        }
      } else {
        if (inWhitespace) {
          aSkipChars->SkipChar();
        } else {
          if (ch != ' ') {
            flags |= TEXT_WAS_TRANSFORMED;
          }
          *aOutput++ = ' ';
          aSkipChars->KeepChar();
        }
      }
      inWhitespace = nowInWhitespace;
    }
    *aIncomingWhitespace = inWhitespace;
  }

  if (outputStart + aLength != aOutput) {
    flags |= TEXT_WAS_TRANSFORMED;
  }
  *aAnalysisFlags = flags;
  return aOutput;
}

PRUint8*
nsTextFrameUtils::TransformText(const PRUint8* aText, PRUint32 aLength,
                                PRUint8* aOutput,
                                CompressionMode aCompression,
                                PRPackedBool* aIncomingWhitespace,
                                gfxSkipCharsBuilder* aSkipChars,
                                PRUint32* aAnalysisFlags)
{
  PRUint32 flags = 0;
  PRUint8* outputStart = aOutput;

  if (aCompression == COMPRESS_NONE) {
    // Skip discardables.
    PRUint32 i;
    for (i = 0; i < aLength; ++i) {
      PRUint8 ch = *aText++;
      if (IsDiscardable(ch, &flags)) {
        aSkipChars->SkipChar();
      } else {
        aSkipChars->KeepChar();
        if (ch == '\t') {
          flags |= TEXT_HAS_TAB;
        }
        *aOutput++ = ch;
      }
    }
    *aIncomingWhitespace = PR_FALSE;
  } else {
    PRBool inWhitespace = *aIncomingWhitespace;
    PRUint32 i;
    for (i = 0; i < aLength; ++i) {
      PRUint8 ch = *aText++;
      PRBool nowInWhitespace = ch == ' ' || ch == '\t' ||
        (ch == '\n' && aCompression == COMPRESS_WHITESPACE_NEWLINE);
      if (!nowInWhitespace) {
        if (IsDiscardable(ch, &flags)) {
          aSkipChars->SkipChar();
          nowInWhitespace = inWhitespace;
        } else {
          *aOutput++ = ch;
          aSkipChars->KeepChar();
        }
      } else {
        if (inWhitespace) {
          aSkipChars->SkipChar();
        } else {
          if (ch != ' ') {
            flags |= TEXT_WAS_TRANSFORMED;
          }
          *aOutput++ = ' ';
          aSkipChars->KeepChar();
        }
      }
      inWhitespace = nowInWhitespace;
    }
    *aIncomingWhitespace = inWhitespace;
  }

  if (outputStart + aLength != aOutput) {
    flags |= TEXT_WAS_TRANSFORMED;
  }
  *aAnalysisFlags = flags;
  return aOutput;
}

PRBool nsSkipCharsRunIterator::NextRun() {
  do {
    if (mRunLength) {
      mIterator.AdvanceOriginal(mRunLength);
      NS_ASSERTION(mRunLength > 0, "No characters in run (initial length too large?)");
      if (!mSkipped || mLengthIncludesSkipped) {
        mRemainingLength -= mRunLength;
      }
    }
    if (!mRemainingLength)
      return PR_FALSE;
    PRInt32 length;
    mSkipped = mIterator.IsOriginalCharSkipped(&length);
    mRunLength = PR_MIN(length, mRemainingLength);
  } while (!mVisitSkipped && mSkipped);

  return PR_TRUE;
}