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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 <stddef.h>
- #include <stdint.h>
- #include <string>
- #include <vector>
- #include "ui/accessibility/ax_base_export.h"
- #include "ui/accessibility/ax_enums.mojom.h"
- #include "ui/accessibility/ax_event_intent.h"
- #include "ui/accessibility/ax_node_data.h"
- #include "ui/accessibility/ax_tree_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 zero or more AXNodeData structures to
- // be applied to the tree in order. An update may also include an optional
- // update to the AXTreeData structure that applies to the tree as a whole.
- //
- // Suppose that the next AXNodeData to be applied is |node|. The following
- // invariants must hold:
- // 1. Either
- // a) |node.id| is already in the tree, or
- // b) the tree is empty, and
- // |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_BASE_EXPORT AXTreeUpdate {
- AXTreeUpdate();
- AXTreeUpdate(const AXTreeUpdate& other);
- ~AXTreeUpdate();
- // If |has_tree_data| is true, the value of |tree_data| should be used
- // to update the tree data, otherwise it should be ignored.
- bool has_tree_data = false;
- AXTreeData tree_data;
- // 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.
- AXNodeID node_id_to_clear = kInvalidAXNodeID;
- // The id of the root of the tree, if the root is changing. This is
- // required to be set if the root of the tree is changing or Unserialize
- // will fail. If the root of the tree is not changing this is optional
- // and it is allowed to pass 0.
- AXNodeID root_id = kInvalidAXNodeID;
- // A vector of nodes to update, according to the rules above.
- std::vector<AXNodeData> nodes;
- // The source of the event which generated this tree update.
- ax::mojom::EventFrom event_from = ax::mojom::EventFrom::kNone;
- // The accessibility action that caused this tree update.
- ax::mojom::Action event_from_action = ax::mojom::Action::kNone;
- // The event intents associated with this tree update.
- std::vector<AXEventIntent> event_intents;
- // Return a multi-line indented string representation, for logging.
- std::string ToString() const;
- };
- // Two tree updates can be merged into one if the second one
- // doesn't clear a subtree, doesn't have new tree data, and
- // doesn't have a new root id - in other words the second tree
- // update consists of only changes to nodes.
- bool AX_BASE_EXPORT TreeUpdatesCanBeMerged(const AXTreeUpdate& u1,
- const AXTreeUpdate& u2);
- } // namespace ui
- #endif // UI_ACCESSIBILITY_AX_TREE_UPDATE_H_
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