flutter_flutter/sky/engine/platform/text/BidiContext.cpp

/*
 * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
 * Copyright (C) 2003, 2004, 2006, 2007, 2009, 2010 Apple Inc.
 * All right reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#include "flutter/sky/engine/platform/text/BidiContext.h"

#include "flutter/sky/engine/wtf/StdLibExtras.h"
#include "flutter/sky/engine/wtf/Vector.h"

namespace blink {

using namespace WTF::Unicode;

struct SameSizeAsBidiContext : public RefCounted<SameSizeAsBidiContext> {
  uint32_t bitfields : 16;
  void* parent;
};

COMPILE_ASSERT(sizeof(BidiContext) == sizeof(SameSizeAsBidiContext),
               BidiContext_should_stay_small);

inline PassRefPtr<BidiContext> BidiContext::createUncached(
    unsigned char level,
    Direction direction,
    bool override,
    BidiEmbeddingSource source,
    BidiContext* parent) {
  return adoptRef(new BidiContext(level, direction, override, source, parent));
}

PassRefPtr<BidiContext> BidiContext::create(unsigned char level,
                                            Direction direction,
                                            bool override,
                                            BidiEmbeddingSource source,
                                            BidiContext* parent) {
  ASSERT(direction == (level % 2 ? RightToLeft : LeftToRight));

  if (parent)
    return createUncached(level, direction, override, source, parent);

  ASSERT(level <= 1);
  if (!level) {
    if (!override) {
      DEFINE_STATIC_REF(
          BidiContext, ltrContext,
          (createUncached(0, LeftToRight, false, FromStyleOrDOM, 0)));
      return ltrContext;
    }

    DEFINE_STATIC_REF(
        BidiContext, ltrOverrideContext,
        (createUncached(0, LeftToRight, true, FromStyleOrDOM, 0)));
    return ltrOverrideContext;
  }

  if (!override) {
    DEFINE_STATIC_REF(
        BidiContext, rtlContext,
        (createUncached(1, RightToLeft, false, FromStyleOrDOM, 0)));
    return rtlContext;
  }

  DEFINE_STATIC_REF(BidiContext, rtlOverrideContext,
                    (createUncached(1, RightToLeft, true, FromStyleOrDOM, 0)));
  return rtlOverrideContext;
}

static inline PassRefPtr<BidiContext> copyContextAndRebaselineLevel(
    BidiContext* context,
    BidiContext* parent) {
  ASSERT(context);
  unsigned char newLevel = parent ? parent->level() : 0;
  if (context->dir() == RightToLeft)
    newLevel = nextGreaterOddLevel(newLevel);
  else if (parent)
    newLevel = nextGreaterEvenLevel(newLevel);

  return BidiContext::create(newLevel, context->dir(), context->override(),
                             context->source(), parent);
}

// The BidiContext stack must be immutable -- they're re-used for re-layout
// after DOM modification/editing -- so we copy all the non-unicode contexts,
// and recalculate their levels.
PassRefPtr<BidiContext>
BidiContext::copyStackRemovingUnicodeEmbeddingContexts() {
  Vector<BidiContext*, 64> contexts;
  for (BidiContext* iter = this; iter; iter = iter->parent()) {
    if (iter->source() != FromUnicode)
      contexts.append(iter);
  }
  ASSERT(contexts.size());

  RefPtr<BidiContext> topContext =
      copyContextAndRebaselineLevel(contexts.last(), 0);
  for (int i = contexts.size() - 1; i > 0; --i)
    topContext =
        copyContextAndRebaselineLevel(contexts[i - 1], topContext.get());

  return topContext.release();
}

bool operator==(const BidiContext& c1, const BidiContext& c2) {
  if (&c1 == &c2)
    return true;
  if (c1.level() != c2.level() || c1.override() != c2.override() ||
      c1.dir() != c2.dir() || c1.source() != c2.source())
    return false;
  if (!c1.parent())
    return !c2.parent();
  return c2.parent() && *c1.parent() == *c2.parent();
}

}  // namespace blink