// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module viz.mojom;

import "third_party/blink/public/mojom/tokens/tokens.mojom";

// An identifier for a texture representing the content of a shared element. The
// id is created in the renderer process and used to embed this content in
// CompositorFrames. Viz scopes the access to this resource to the renderer
// process which created it.
//
// This ID is created by the renderer process and shared with the Viz process
// in CompositorFrames. Its usage is scoped to a single CompositorFrameSink IPC
// interface. This means that the ID is created and used by a single renderer
// process. The content cached for one renderer process can not, in general, be
// embedded in frames generated by a different renderer process. The only
// exception to this is when a view transition is occurring across documents,
// where the documents are required to be same-origin, and the documents are in
// separate processes. This can happen, for example, when navigating to a
// prerendered document.
//
// The ID is composed of a `transition_token` which identifies a specific view
// transition. The `local_id` identifies a specific snapshot resource and is
// unique only with respect to a given `transition_token`.
struct ViewTransitionElementResourceId {
  blink.mojom.ViewTransitionToken? transition_token;
  uint32 local_id;

  // A special "scope snapshot" is used for non-document transitions as well as
  // same-site iframe document transitions in order to pause rendering during
  // the callback. These need to be treated as distinct from the shared elements
  // that render the transition's participants.
  bool for_scope_snapshot;
};