Source/WebCore/accessibility/isolatedtree/AXIsolatedTree.h

/*
 * Copyright (C) 2019 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 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 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
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#if ENABLE(ACCESSIBILITY_ISOLATED_TREE)

#include "AccessibilityObjectInterface.h"
#include "PageIdentifier.h"
#include <wtf/HashMap.h>
#include <wtf/RefPtr.h>
#include <wtf/ThreadSafeRefCounted.h>

namespace WTF {
class TextStream;
}

namespace WebCore {

class AXIsolatedObject;
class AXObjectCache;
class Page;

typedef unsigned AXIsolatedTreeID;

class AXIsolatedTree : public ThreadSafeRefCounted<AXIsolatedTree> {
    WTF_MAKE_NONCOPYABLE(AXIsolatedTree); WTF_MAKE_FAST_ALLOCATED;
    friend WTF::TextStream& operator<<(WTF::TextStream&, AXIsolatedTree&);
public:
    static Ref<AXIsolatedTree> create();
    virtual ~AXIsolatedTree();

    static Ref<AXIsolatedTree> createTreeForPageID(PageIdentifier);
    static void removeTreeForPageID(PageIdentifier);

    static RefPtr<AXIsolatedTree> treeForPageID(PageIdentifier);
    static RefPtr<AXIsolatedTree> treeForID(AXIsolatedTreeID);
    AXObjectCache* axObjectCache() const { return m_axObjectCache; }
    void setAXObjectCache(AXObjectCache* axObjectCache) { m_axObjectCache = axObjectCache; }

    RefPtr<AXIsolatedObject> rootNode();
    RefPtr<AXIsolatedObject> focusedNode();
    RefPtr<AXIsolatedObject> nodeForID(AXID) const;
    Vector<RefPtr<AXCoreObject>> objectsForIDs(Vector<AXID>) const;

    struct NodeChange {
        Ref<AXIsolatedObject> m_isolatedObject;
        RetainPtr<AccessibilityObjectWrapper> m_wrapper;
        NodeChange(AXIsolatedObject&, AccessibilityObjectWrapper*);
        NodeChange(const NodeChange&);
    };

    void generateSubtree(AXCoreObject&, AXCoreObject*, bool attachWrapper);
    void updateNode(AXCoreObject&);
    void updateSubtree(AXCoreObject&);
    void updateChildren(AXCoreObject&);

    // Removes the given node leaving all descendants alone.
    void removeNode(AXID);
    // Removes the given node and all its descendants.
    void removeSubtree(AXID);

    // Both setRootNodeID and setFocusedNodeID are called during the generation
    // of the IsolatedTree.
    // Focused node updates in AXObjectCache use setFocusNodeID.
    void setRootNode(AXIsolatedObject*);
    void setFocusedNodeID(AXID);

    // Called on AX thread from WebAccessibilityObjectWrapper methods.
    // During layout tests, it is called on the main thread.
    void applyPendingChanges();

    AXIsolatedTreeID treeID() const { return m_treeID; }

private:
    AXIsolatedTree();
    void clear();

    static HashMap<AXIsolatedTreeID, Ref<AXIsolatedTree>>& treeIDCache();
    static HashMap<PageIdentifier, Ref<AXIsolatedTree>>& treePageCache();

    // Call on main thread
    Ref<AXIsolatedObject> createSubtree(AXCoreObject&, AXID parentID, bool attachWrapper, Vector<NodeChange>&);
    // Queues all pending additions to the tree as the result of a subtree generation.
    void appendNodeChanges(Vector<NodeChange>&&);
    // Called on main thread to update both m_nodeMap and m_pendingChildrenUpdates.
    void updateChildrenIDs(AXID parentID, Vector<AXID>&& childrenIDs);

    AXIsolatedTreeID m_treeID;
    AXObjectCache* m_axObjectCache { nullptr };

    // Only accessed on main thread.
    HashMap<AXID, Vector<AXID>> m_nodeMap;
    // Only accessed on AX thread requesting data.
    HashMap<AXID, Ref<AXIsolatedObject>> m_readerThreadNodeMap;

    // Written to by main thread under lock, accessed and applied by AX thread.
    RefPtr<AXIsolatedObject> m_rootNode;
    Vector<NodeChange> m_pendingAppends; // Nodes to be added to the tree and platform-wrapped.
    Vector<AXID> m_pendingNodeRemovals; // Nodes to be removed from the tree.
    Vector<AXID> m_pendingSubtreeRemovals; // Nodes whose subtrees are to be removed from the tree.
    Vector<std::pair<AXID, Vector<AXID>>> m_pendingChildrenUpdates;
    AXID m_pendingFocusedNodeID { InvalidAXID };
    AXID m_focusedNodeID { InvalidAXID };
    Lock m_changeLogLock;
};

} // namespace WebCore

#endif