sdk/fidl/fuchsia.ui.accessibility.view/accessibility_view_registry.fidl

// Copyright 2021 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.ui.accessibility.view;

using fuchsia.ui.views;

/// Registry allows a privileged client to create an accessibility ViewHolder
/// as a child of the root view in the scene graph.
[Discoverable]
protocol Registry {
    /// Creates a new accessibility `ViewHolder` as a child of the root view
    /// in the scene graph. The created ViewHolder holds an accessibility view.
    /// The accessibility view does not render any content; it's only used to
    /// vend capabilities to the accessibility manager that a view confers, e.g.
    /// ability to request focus, consume and respond to input events, annotate
    /// underlying views, and apply coordinate transforms to its subtree.
    ///
    /// Additionally, the a11y_view_ref can be used to inject input into the the
    /// accessibility view's subgraph.
    ///
    /// Note that the caller must create a view using |a11y_view_ref| BEFORE
    /// calling CreateAccessibilityViewHolder().
    ///
    /// The protocol returns a client ViewHolderToken, which the caller MUST use
    /// to attach the corresponding client view holder as a child of the
    /// accessibility view it created.
    ///
    /// Since creating a ViewHolder modifies the SceneGraph, this function won't
    /// take effect until we schedule a new frame by calling Present() on any
    /// Session.
    ///
    /// EPITAPH
    ///
    /// This method may return the following epitaphs:
    ///
    /// - ZX_ERR_INVALID_ARGS, if the provided `ViewRef` is invalid.
    /// - ZX_ERR_PEER_CLOSED, if Scenic fails creating the accessibility `ViewHolder`.
    ///
    CreateAccessibilityViewHolder(fuchsia.ui.views.ViewRef a11y_view_ref,
                                  fuchsia.ui.views.ViewHolderToken a11y_view_token)
        -> (fuchsia.ui.views.ViewHolderToken client_view_holder_token);
};