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      1 /*
      2  * Copyright (C) 2000 Lars Knoll (knoll (at) kde.org)
      3  * Copyright (C) 2003, 2004, 2006, 2007, 2009, 2010 Apple Inc. All right reserved.
      4  *
      5  * This library is free software; you can redistribute it and/or
      6  * modify it under the terms of the GNU Library General Public
      7  * License as published by the Free Software Foundation; either
      8  * version 2 of the License, or (at your option) any later version.
      9  *
     10  * This library is distributed in the hope that it will be useful,
     11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     13  * Library General Public License for more details.
     14  *
     15  * You should have received a copy of the GNU Library General Public License
     16  * along with this library; see the file COPYING.LIB.  If not, write to
     17  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     18  * Boston, MA 02110-1301, USA.
     19  *
     20  */
     21 
     22 #include "config.h"
     23 #include "platform/text/BidiContext.h"
     24 
     25 #include "wtf/StdLibExtras.h"
     26 #include "wtf/Vector.h"
     27 
     28 namespace WebCore {
     29 
     30 using namespace WTF::Unicode;
     31 
     32 struct SameSizeAsBidiContext : public RefCounted<SameSizeAsBidiContext> {
     33     uint32_t bitfields : 16;
     34     void* parent;
     35 };
     36 
     37 COMPILE_ASSERT(sizeof(BidiContext) == sizeof(SameSizeAsBidiContext), BidiContext_should_stay_small);
     38 
     39 inline PassRefPtr<BidiContext> BidiContext::createUncached(unsigned char level, Direction direction, bool override, BidiEmbeddingSource source, BidiContext* parent)
     40 {
     41     return adoptRef(new BidiContext(level, direction, override, source, parent));
     42 }
     43 
     44 PassRefPtr<BidiContext> BidiContext::create(unsigned char level, Direction direction, bool override, BidiEmbeddingSource source, BidiContext* parent)
     45 {
     46     ASSERT(direction == (level % 2 ? RightToLeft : LeftToRight));
     47 
     48     if (parent)
     49         return createUncached(level, direction, override, source, parent);
     50 
     51     ASSERT(level <= 1);
     52     if (!level) {
     53         if (!override) {
     54             DEFINE_STATIC_REF(BidiContext, ltrContext, (createUncached(0, LeftToRight, false, FromStyleOrDOM, 0)));
     55             return ltrContext;
     56         }
     57 
     58         DEFINE_STATIC_REF(BidiContext, ltrOverrideContext, (createUncached(0, LeftToRight, true, FromStyleOrDOM, 0)));
     59         return ltrOverrideContext;
     60     }
     61 
     62     if (!override) {
     63         DEFINE_STATIC_REF(BidiContext, rtlContext, (createUncached(1, RightToLeft, false, FromStyleOrDOM, 0)));
     64         return rtlContext;
     65     }
     66 
     67     DEFINE_STATIC_REF(BidiContext, rtlOverrideContext, (createUncached(1, RightToLeft, true, FromStyleOrDOM, 0)));
     68     return rtlOverrideContext;
     69 }
     70 
     71 static inline PassRefPtr<BidiContext> copyContextAndRebaselineLevel(BidiContext* context, BidiContext* parent)
     72 {
     73     ASSERT(context);
     74     unsigned char newLevel = parent ? parent->level() : 0;
     75     if (context->dir() == RightToLeft)
     76         newLevel = nextGreaterOddLevel(newLevel);
     77     else if (parent)
     78         newLevel = nextGreaterEvenLevel(newLevel);
     79 
     80     return BidiContext::create(newLevel, context->dir(), context->override(), context->source(), parent);
     81 }
     82 
     83 // The BidiContext stack must be immutable -- they're re-used for re-layout after
     84 // DOM modification/editing -- so we copy all the non-unicode contexts, and
     85 // recalculate their levels.
     86 PassRefPtr<BidiContext> BidiContext::copyStackRemovingUnicodeEmbeddingContexts()
     87 {
     88     Vector<BidiContext*, 64> contexts;
     89     for (BidiContext* iter = this; iter; iter = iter->parent()) {
     90         if (iter->source() != FromUnicode)
     91             contexts.append(iter);
     92     }
     93     ASSERT(contexts.size());
     94 
     95     RefPtr<BidiContext> topContext = copyContextAndRebaselineLevel(contexts.last(), 0);
     96     for (int i = contexts.size() - 1; i > 0; --i)
     97         topContext = copyContextAndRebaselineLevel(contexts[i - 1], topContext.get());
     98 
     99     return topContext.release();
    100 }
    101 
    102 bool operator==(const BidiContext& c1, const BidiContext& c2)
    103 {
    104     if (&c1 == &c2)
    105         return true;
    106     if (c1.level() != c2.level() || c1.override() != c2.override() || c1.dir() != c2.dir() || c1.source() != c2.source())
    107         return false;
    108     if (!c1.parent())
    109         return !c2.parent();
    110     return c2.parent() && *c1.parent() == *c2.parent();
    111 }
    112 
    113 } // namespace WebCore
    114