mus: Add EventObserver to allow passively listening to UI events

components/mus/ws/window_tree_unittest.cc

 // Copyright 2014 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.
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 313 matching lines @@
   ASSERT_EQ(1u, wm_client()->tracker()->changes()->size());
   EXPECT_EQ("Focused id=2,1",
             ChangesToDescription1(*wm_client()->tracker()->changes())[0]);
   ASSERT_EQ(2u, embed_connection->tracker()->changes()->size());
   EXPECT_EQ("Focused id=2,1",
             ChangesToDescription1(*embed_connection->tracker()->changes())[0]);
   EXPECT_EQ("InputEvent window=2,1 event_action=4",
             ChangesToDescription1(*embed_connection->tracker()->changes())[1]);
 }
 
+// Tests that a client can observe events outside its bounds.
+TEST_F(WindowTreeTest, SetEventObserver) {
+  // Create an embedded client.
+  TestWindowTreeClient* client = nullptr;
+  WindowTree* tree = nullptr;
+  ServerWindow* window = nullptr;
+  EXPECT_NO_FATAL_FAILURE(SetupEventTargeting(&client, &tree, &window));
+
+  // Create an event outside the bounds of the client.
+  ui::PointerEvent pointer_down = CreatePointerDownEvent(5, 5);
+
+  // Events are not observed before setting an observer.
+  DispatchEventAndAckImmediately(pointer_down);
+  ASSERT_EQ(0u, client->tracker()->changes()->size());
+
+  // Create an observer for pointer-down events.
+  mojom::EventMatcherPtr matcher = mojom::EventMatcher::New();
+  matcher->type_matcher = mojom::EventTypeMatcher::New();
+  matcher->type_matcher->type = mojom::EventType::POINTER_DOWN;
+  WindowTreeTestApi(tree).SetEventObserver(std::move(matcher));
+
+  // Pointer-down events are sent to the client.
+  DispatchEventAndAckImmediately(pointer_down);
+  ASSERT_EQ(1u, client->tracker()->changes()->size());
+  EXPECT_EQ("EventObserved event_action=4",
+            ChangesToDescription1(*client->tracker()->changes())[0]);
+  client->tracker()->changes()->clear();
+
+  // Clearing the observer stops sending events to the client.
+  WindowTreeTestApi(tree).ClearEventObserver();
+  DispatchEventAndAckImmediately(pointer_down);
+  ASSERT_EQ(0u, client->tracker()->changes()->size());
+}
+
+// Tests that a client using an event observer does not receive events that
+// don't match the EventMatcher spec.
+TEST_F(WindowTreeTest, SetEventObserverNonMatching) {
+  // Create an embedded client.
+  TestWindowTreeClient* client = nullptr;
+  WindowTree* tree = nullptr;
+  ServerWindow* window = nullptr;
+  EXPECT_NO_FATAL_FAILURE(SetupEventTargeting(&client, &tree, &window));
+
+  // Create an observer for pointer-down events.
+  mojom::EventMatcherPtr matcher = mojom::EventMatcher::New();
+  matcher->type_matcher = mojom::EventTypeMatcher::New();
+  matcher->type_matcher->type = mojom::EventType::POINTER_DOWN;
+  WindowTreeTestApi(tree).SetEventObserver(std::move(matcher));
+
+  // Pointer-up events are not sent to the client, since they don't match.
+  DispatchEventAndAckImmediately(CreatePointerUpEvent(5, 5));
+  ASSERT_EQ(0u, client->tracker()->changes()->size());
+}
+
 TEST_F(WindowTreeTest, CursorChangesWhenMouseOverWindowAndWindowSetsCursor) {
   TestWindowTreeClient* embed_connection = nullptr;
   WindowTree* tree = nullptr;
   ServerWindow* window = nullptr;
   EXPECT_NO_FATAL_FAILURE(
       SetupEventTargeting(&embed_connection, &tree, &window));
 
   // Like in BasicInputEventTarget, we send a pointer down event to be
   // dispatched. This is only to place the mouse cursor over that window though.
   DispatchEventAndAckImmediately(CreateMouseMoveEvent(21, 22));
@@ skipping 528 matching lines @@
   ASSERT_NE(new_opacity, unknown_window.opacity());
 
   EXPECT_FALSE(tree->SetWindowOpacity(
       ClientWindowId(WindowIdToTransportId(window_id)), new_opacity));
   EXPECT_NE(new_opacity, unknown_window.opacity());
 }
 
 }  // namespace test
 }  // namespace ws
 }  // namespace mus