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      1 /*
      2  * Copyright (C) 2000 Lars Knoll (knoll (at) kde.org)
      3  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All right reserved.
      4  * Copyright (C) 2010 Google Inc. All rights reserved.
      5  * Copyright (C) 2014 Adobe Systems Inc.
      6  *
      7  * This library is free software; you can redistribute it and/or
      8  * modify it under the terms of the GNU Library General Public
      9  * License as published by the Free Software Foundation; either
     10  * version 2 of the License, or (at your option) any later version.
     11  *
     12  * This library is distributed in the hope that it will be useful,
     13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     15  * Library General Public License for more details.
     16  *
     17  * You should have received a copy of the GNU Library General Public License
     18  * along with this library; see the file COPYING.LIB.  If not, write to
     19  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     20  * Boston, MA 02110-1301, USA.
     21  *
     22  */
     23 
     24 #ifndef TrailingObjects_h
     25 #define TrailingObjects_h
     26 
     27 #include "wtf/Vector.h"
     28 
     29 namespace blink {
     30 
     31 class InlineIterator;
     32 class RenderObject;
     33 class RenderText;
     34 
     35 struct BidiRun;
     36 
     37 template <class Iterator, class Run> class BidiResolver;
     38 template <class Iterator> class MidpointState;
     39 typedef BidiResolver<InlineIterator, BidiRun> InlineBidiResolver;
     40 typedef MidpointState<InlineIterator> LineMidpointState;
     41 
     42 // This class allows us to ensure lineboxes are created in the right place on the line when
     43 // an out-of-flow positioned object or an empty inline is encountered between a trailing space
     44 // and subsequent spaces and we want to ignore (i.e. collapse) surplus whitespace. So for example:
     45 //   <div>X <span></span> Y</div>
     46 // or
     47 //   <div>X <div style="position: absolute"></div> Y</div>
     48 // In both of the above snippets the inline and the positioned object occur after a trailing space
     49 // and before a space that will cause our line breaking algorithm to start ignoring spaces. When it
     50 // does that we want to ensure that the inline/positioned object gets a linebox and that it is part
     51 // of the collapsed whitespace. So to achieve this we use appendObjectIfNeeded() to keep track of
     52 // objects encountered after a trailing whitespace and updateMidpointsForTrailingObjects() to put
     53 // them in the right place when we start ignoring surplus whitespace.
     54 
     55 class TrailingObjects {
     56 public:
     57     TrailingObjects()
     58         : m_whitespace(0)
     59     {
     60     }
     61 
     62     void setTrailingWhitespace(RenderText* whitespace)
     63     {
     64         ASSERT(whitespace);
     65         m_whitespace = whitespace;
     66     }
     67 
     68     void clear()
     69     {
     70         m_whitespace = 0;
     71         // Using resize(0) rather than clear() here saves 2% on
     72         // PerformanceTests/Layout/line-layout.html because we avoid freeing and
     73         // re-allocating the underlying buffer repeatedly.
     74         m_objects.resize(0);
     75     }
     76 
     77     void appendObjectIfNeeded(RenderObject* object)
     78     {
     79         if (m_whitespace)
     80             m_objects.append(object);
     81     }
     82 
     83     enum CollapseFirstSpaceOrNot { DoNotCollapseFirstSpace, CollapseFirstSpace };
     84 
     85     void updateMidpointsForTrailingObjects(LineMidpointState&, const InlineIterator& lBreak, CollapseFirstSpaceOrNot);
     86 
     87 private:
     88     RenderText* m_whitespace;
     89     Vector<RenderObject*, 4> m_objects;
     90 };
     91 
     92 }
     93 
     94 #endif // TrailingObjects_h
     95