Source/bindings/v8/V8NodeFilterCondition.h

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#ifndef V8NodeFilterCondition_h
#define V8NodeFilterCondition_h

#include "bindings/v8/ScopedPersistent.h"
#include "core/dom/NodeFilterCondition.h"
#include <v8.h>
#include "wtf/PassRefPtr.h"

namespace WebCore {

class Node;
class ScriptState;

// V8NodeFilterCondition maintains a Javascript implemented callback for
// filtering Node returned by NodeIterator/TreeWalker.
// A NodeFilterCondition is referenced by a NodeFilter, and A NodeFilter is
// referenced by a NodeIterator/TreeWalker. As V8NodeFilterCondition maintains
// a Javascript callback which may reference Document, we need to avoid circular
// reference spanning V8/Blink object space.
// To address this issue, V8NodeFilterCondition holds a weak reference to
// |m_filter|, the Javascript value, and the whole reference is exposed to V8 to
// let V8 GC handle collection of |m_filter|.
// (DOM)
// NodeIterator  ----RefPtr----> NodeFilter ----RefPtr----> NodeFilterCondition
//   |   ^                        |   ^                        |
//  weak |                       weak |                ScopedPersistent(weak)
//   | RefPtr                     | RefPtr                     |
//   v   |                        v   |                        v
// NodeIterator  --HiddenValue--> NodeFilter --HiddenValue--> JS Callback
// (V8)
class V8NodeFilterCondition : public NodeFilterCondition {
public:
    static PassRefPtr<V8NodeFilterCondition> create(v8::Handle<v8::Value> filter, v8::Handle<v8::Object> owner, v8::Isolate* isolate)
    {
        return adoptRef(new V8NodeFilterCondition(filter, owner, isolate));
    }

    virtual ~V8NodeFilterCondition();

    virtual short acceptNode(ScriptState*, Node*) const;

private:
    // As the value |filter| is maintained by V8GC, the |owner| which references
    // V8NodeFilterCondition, usually a wrapper of NodeFilter, is specified here
    // to hold a strong reference to |filter|.
    V8NodeFilterCondition(v8::Handle<v8::Value> filter, v8::Handle<v8::Object> owner, v8::Isolate*);

    static void makeWeakCallback(v8::Isolate*, v8::Persistent<v8::Value>*, V8NodeFilterCondition*);

    ScopedPersistent<v8::Value> m_filter;
};

} // namespace WebCore

#endif // V8NodeFilterCondition_h