1 // Copyright 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef UI_ACCESSIBILITY_AX_TREE_UPDATE_H_ 6 #define UI_ACCESSIBILITY_AX_TREE_UPDATE_H_ 7 8 #include <vector> 9 10 #include "ui/accessibility/ax_node_data.h" 11 12 namespace ui { 13 14 // An AXTreeUpdate is a serialized representation of an atomic change 15 // to an AXTree. The sender and receiver must be in sync; the update 16 // is only meant to bring the tree from a specific previous state into 17 // its next state. Trying to apply it to the wrong tree should immediately 18 // die with a fatal assertion. 19 // 20 // An AXTreeUpdate consists of an optional node id to clear (meaning 21 // that all of that node's children and their descendants are deleted), 22 // followed by an ordered vector of AXNodeData structures to be applied 23 // to the tree in order. 24 // 25 // Suppose that the next AXNodeData to be applied is |node|. The following 26 // invariants must hold: 27 // 1. Either |node.id| is already in the tree, or else the tree is empty, 28 // |node| is the new root of the tree, and 29 // |node.role| == WebAXRoleRootWebArea. 30 // 2. Every child id in |node.child_ids| must either be already a child 31 // of this node, or a new id not previously in the tree. It is not 32 // allowed to "reparent" a child to this node without first removing 33 // that child from its previous parent. 34 // 3. When a new id appears in |node.child_ids|, the tree should create a 35 // new uninitialized placeholder node for it immediately. That 36 // placeholder must be updated within the same AXTreeUpdate, otherwise 37 // it's a fatal error. This guarantees the tree is always complete 38 // before or after an AXTreeUpdate. 39 struct AX_EXPORT AXTreeUpdate { 40 AXTreeUpdate(); 41 ~AXTreeUpdate(); 42 43 // The id of a node to clear, before applying any updates, 44 // or 0 if no nodes should be cleared. Clearing a node means deleting 45 // all of its children and their descendants, but leaving that node in 46 // the tree. It's an error to clear a node but not subsequently update it 47 // as part of the tree update. 48 int node_id_to_clear; 49 50 // A vector of nodes to update, according to the rules above. 51 std::vector<AXNodeData> nodes; 52 53 // Return a multi-line indented string representation, for logging. 54 std::string ToString() const; 55 56 // TODO(dmazzoni): location changes 57 }; 58 59 } // namespace ui 60 61 #endif // UI_ACCESSIBILITY_AX_TREE_UPDATE_H_ 62