// Copyright 2015 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.

[DartPackage="mojo_services"]
module mojo.gfx.composition;

import "mojo/services/geometry/interfaces/geometry.mojom";
import "mojo/services/gfx/composition/interfaces/scene_token.mojom";

// Indicates that hit testing is not needed for a given node.
const uint32 kHitIdNone = 0;

// Provides information about the point of intersection of a hit test with
// a node in a scene graph.
struct Hit {
  // The scene token of the scene which was hit.
  SceneToken scene_token;

  // The version of the scene which was consulted as part of evaluating the
  // hit test.
  uint32 scene_version;

  // The node id of the node which was hit.
  uint32 node_id;

  // The hit test id of the node which was hit.
  uint32 hit_id;

  // The coordinates of the hit within the node's content space.
  mojo.Point intersection;
};

// The result of a hit test operation.
struct HitTestResult {
  // A sorted list of hits in dispatch order from the top-most hit node
  // to the nodes underneath it and containing it, or an empty array if none.
  // Omits nodes for which the hit_id was |kHitIdNone|.
  array<Hit> hits;
};

// A hit testing service for scene graphs.
interface HitTester {
  // Performs a hit test on the specified point.
  //
  // TODO(jeffbrown): Specify a timestamp to allow for hit-tests of geometry
  // as it appeared in the recent past.
  HitTest(mojo.Point point) => (HitTestResult result);
};