sdk/fidl/fuchsia.accessibility.semantics/node.fidl

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.accessibility.semantics;

using fuchsia.ui.gfx;

/// Represents actions that can be applied to Nodes. In progress.
enum Action {
    // The default action associated with the role of an element.
    DEFAULT = 1;
};

/// Represents a role of an element on an UI. In progress.
enum Role {
    // Role used to represent elements which role is not currently supported.
    unknown = 1;
};

/// An attribute is an essential property to describe an element. Unlike states,
/// attributes define the nature of an element, and a change in one of them
/// changes the nature of the element itself.
/// Example: a button with a label attribute 'ok', could have its label changed
/// to 'cancel', which would alter drastically this element.  In progress.
table  Attributes {
    // The label for an element.
    1: string label;
};

///  A state is a dynamic property of an element that may change in response to
/// user action or automated processes. Thus, they are different from attributes
/// in an important point, which is frequency of change.
/// Example: a checkbox can be checked / unchecked, and this state can be
/// altered via user input. In progress.
table States {
    // Whether the element is checked.
    1: bool checked;
};

/// Node: data structure to represent semantic information about an UI element.
///
/// The Node represents a semantic element on an interface. This may
/// be a button, a text field, a checkbox or any element that has a relevant
/// semantic meaning so that assistive technology can understand the current UI.
table Node {
    // Unique ID that represents the node in a particular UI.
    // Zero is assumed to be the root node and the only entry point to the tree.
    // No forest is allowed.
    1: uint32 node_id;

    // Role of this element, e.g. button, checkbox, etc.
    2: Role role;

    // A list of states of this object, e.g. checked, editable, etc.
    3: States states;

    // A list of attributes of this node.
    4: Attributes attributes;

    // List of actions that can be performed on this node.
    5: vector<Action> actions;

    // The ordered list of children IDs  of this node.
    // It is assumed that runtimes supplying semantic tree information will not
    // create cycles inside the tree.
    // It is also assumed that each node can have only one parent.
    6: vector<uint32> child_ids;

    // Local bounding box of this element.
    7: fuchsia.ui.gfx.BoundingBox location;

    // Transform from parent coordinate space to local space.
    8: fuchsia.ui.gfx.mat4 transform;
};