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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_ACCESSIBILITY_AX_TREE_UPDATE_H_
#define UI_ACCESSIBILITY_AX_TREE_UPDATE_H_
#include <vector>
#include "ui/accessibility/ax_node_data.h"
namespace ui {
// An AXTreeUpdate is a serialized representation of an atomic change
// to an AXTree. The sender and receiver must be in sync; the update
// is only meant to bring the tree from a specific previous state into
// its next state. Trying to apply it to the wrong tree should immediately
// die with a fatal assertion.
//
// An AXTreeUpdate consists of an optional node id to clear (meaning
// that all of that node's children and their descendants are deleted),
// followed by an ordered vector of AXNodeData structures to be applied
// to the tree in order.
//
// Suppose that the next AXNodeData to be applied is |node|. The following
// invariants must hold:
// 1. Either |node.id| is already in the tree, or else the tree is empty,
// |node| is the new root of the tree, and
// |node.role| == WebAXRoleRootWebArea.
// 2. Every child id in |node.child_ids| must either be already a child
// of this node, or a new id not previously in the tree. It is not
// allowed to "reparent" a child to this node without first removing
// that child from its previous parent.
// 3. When a new id appears in |node.child_ids|, the tree should create a
// new uninitialized placeholder node for it immediately. That
// placeholder must be updated within the same AXTreeUpdate, otherwise
// it's a fatal error. This guarantees the tree is always complete
// before or after an AXTreeUpdate.
struct AX_EXPORT AXTreeUpdate {
AXTreeUpdate();
~AXTreeUpdate();
// The id of a node to clear, before applying any updates,
// or 0 if no nodes should be cleared. Clearing a node means deleting
// all of its children and their descendants, but leaving that node in
// the tree. It's an error to clear a node but not subsequently update it
// as part of the tree update.
int node_id_to_clear;
// A vector of nodes to update, according to the rules above.
std::vector<AXNodeData> nodes;
// TODO(dmazzoni): location changes
};
} // namespace ui
#endif // UI_ACCESSIBILITY_AX_TREE_UPDATE_H_
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