third_party/WebKit/Source/core/editing/VisiblePosition.h

/*
 * Copyright (C) 2004, 2008 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef VisiblePosition_h
#define VisiblePosition_h

#include "core/CoreExport.h"
#include "core/editing/PositionWithAffinity.h"
#include "core/editing/TextAffinity.h"
#include "platform/heap/Handle.h"

namespace blink {

// VisiblePosition default affinity is downstream because
// the callers do not really care (they just want the
// deep position without regard to line position), and this
// is cheaper than UPSTREAM
#define VP_DEFAULT_AFFINITY TextAffinity::Downstream

// Callers who do not know where on the line the position is,
// but would like UPSTREAM if at a line break or DOWNSTREAM
// otherwise, need a clear way to specify that.  The
// constructors auto-correct UPSTREAM to DOWNSTREAM if the
// position is not at a line break.
#define VP_UPSTREAM_IF_POSSIBLE TextAffinity::Upstream

class InlineBox;
class Range;

// |VisiblePosition| is an immutable object representing "canonical position"
// with affinity.
//
// "canonical position" is roughly equivalent to a position where we can place
// caret, see |canonicalPosition()| for actual definition.
//
// "affinity" represents a place of caret at wrapped line. UPSTREAM affinity
// means caret is placed at end of line. DOWNSTREAM affinity means caret is
// placed at start of line.
//
// Example of affinity:
//    abc^def where "^" represent |Position|
// When above text line wrapped after "abc"
//    abc|  UPSTREAM |VisiblePosition|
//    |def  DOWNSTREAM |VisiblePosition|
//
// NOTE: UPSTREAM affinity will be used only if pos is at end of a wrapped line,
// otherwise it will be converted to DOWNSTREAM.
template <typename Strategy>
class CORE_TEMPLATE_CLASS_EXPORT VisiblePositionTemplate final {
    DISALLOW_NEW();
public:
    VisiblePositionTemplate();

    // Node: Other than |createVisiblePosition()|, we should not use
    // |create()|.
    static VisiblePositionTemplate create(const PositionWithAffinityTemplate<Strategy>&);

    // Intentionally delete |operator==()| and |operator!=()| for reducing
    // compilation error message.
    // TODO(yosin) We'll have |equals()| when we have use cases of checking
    // equality of both position and affinity.
    bool operator==(const VisiblePositionTemplate&) const = delete;
    bool operator!=(const VisiblePositionTemplate&) const = delete;

    bool isNull() const { return m_positionWithAffinity.isNull(); }
    bool isNotNull() const { return m_positionWithAffinity.isNotNull(); }
    bool isOrphan() const { return deepEquivalent().isOrphan(); }

    PositionTemplate<Strategy> deepEquivalent() const { return m_positionWithAffinity.position(); }
    PositionTemplate<Strategy> toParentAnchoredPosition() const { return deepEquivalent().parentAnchoredEquivalent(); }
    PositionWithAffinityTemplate<Strategy> toPositionWithAffinity() const { return m_positionWithAffinity; }
    TextAffinity affinity() const { return m_positionWithAffinity.affinity(); }

    DEFINE_INLINE_TRACE()
    {
        visitor->trace(m_positionWithAffinity);
    }

#ifndef NDEBUG
    void debugPosition(const char* msg = "") const;
    void formatForDebugger(char* buffer, unsigned length) const;
    void showTreeForThis() const;
#endif

private:
    explicit VisiblePositionTemplate(const PositionWithAffinityTemplate<Strategy>&);

    PositionWithAffinityTemplate<Strategy> m_positionWithAffinity;
};

extern template class CORE_EXTERN_TEMPLATE_EXPORT VisiblePositionTemplate<EditingStrategy>;
extern template class CORE_EXTERN_TEMPLATE_EXPORT VisiblePositionTemplate<EditingInFlatTreeStrategy>;

using VisiblePosition = VisiblePositionTemplate<EditingStrategy>;
using VisiblePositionInFlatTree = VisiblePositionTemplate<EditingInFlatTreeStrategy>;

CORE_EXPORT VisiblePosition createVisiblePosition(const Position&, TextAffinity = VP_DEFAULT_AFFINITY);
CORE_EXPORT VisiblePosition createVisiblePosition(const PositionWithAffinity&);
CORE_EXPORT VisiblePositionInFlatTree createVisiblePosition(const PositionInFlatTree&, TextAffinity = VP_DEFAULT_AFFINITY);
CORE_EXPORT VisiblePositionInFlatTree createVisiblePosition(const PositionInFlatTreeWithAffinity&);

// TODO(yosin) Once we have flat tree version of VisibleUnits, we should not
// use |createVisiblePositionInDOMTree()|.
VisiblePosition createVisiblePositionInDOMTree(const Position&, TextAffinity = VP_DEFAULT_AFFINITY);
VisiblePosition createVisiblePositionInDOMTree(const PositionInFlatTree&, TextAffinity = VP_DEFAULT_AFFINITY);

} // namespace blink

#ifndef NDEBUG
// Outside the WebCore namespace for ease of invocation from gdb.
void showTree(const blink::VisiblePosition*);
void showTree(const blink::VisiblePosition&);
#endif

#endif // VisiblePosition_h