Make event-targeting asynchronous in window server.

services/ui/ws/window_manager_state.cc

Index: services/ui/ws/window_manager_state.cc
diff --git a/services/ui/ws/window_manager_state.cc b/services/ui/ws/window_manager_state.cc
index 6657f1500c52b9d070a88b1ef07e96d2023a9ba1..5bf4a0a79cab8d52b555c86dfd7b8315445abe28 100644
--- a/services/ui/ws/window_manager_state.cc
+++ b/services/ui/ws/window_manager_state.cc
@@ -72,7 +72,7 @@ const ServerWindow* GetEmbedRoot(const ServerWindow* window) {
 
 }  // namespace
 
-WindowManagerState::InFlightEventDetails::InFlightEventDetails(
+WindowManagerState::InFlightEventDispatchDetails::InFlightEventDispatchDetails(
     WindowManagerState* window_manager_state,
     WindowTree* tree,
     int64_t display_id,
@@ -84,7 +84,8 @@ WindowManagerState::InFlightEventDetails::InFlightEventDetails(
       phase(phase),
       weak_factory(window_manager_state) {}
 
-WindowManagerState::InFlightEventDetails::~InFlightEventDetails() {}
+WindowManagerState::InFlightEventDispatchDetails::
+    ~InFlightEventDispatchDetails() {}
 
 class WindowManagerState::ProcessedEventTarget {
  public:
@@ -192,10 +193,11 @@ void WindowManagerState::SetDragDropSourceWindow(
     const std::unordered_map<std::string, std::vector<uint8_t>>& drag_data,
     uint32_t drag_operation) {
   int32_t drag_pointer = MouseEvent::kMousePointerId;
-  if (in_flight_event_details_ &&
-      in_flight_event_details_->event->IsPointerEvent()) {
-    drag_pointer =
-        in_flight_event_details_->event->AsPointerEvent()->pointer_details().id;
+  if (in_flight_event_dispatch_details_ &&
+      in_flight_event_dispatch_details_->event->IsPointerEvent()) {
+    drag_pointer = in_flight_event_dispatch_details_->event->AsPointerEvent()
+                       ->pointer_details()
+                       .id;
   } else {
     NOTIMPLEMENTED() << "Set drag drop set up during something other than a "
                      << "pointer event; rejecting drag.";
@@ -250,13 +252,14 @@ const UserId& WindowManagerState::user_id() const {
 void WindowManagerState::OnWillDestroyTree(WindowTree* tree) {
   event_dispatcher_.OnWillDestroyDragTargetConnection(tree);
 
-  if (!in_flight_event_details_ || in_flight_event_details_->tree != tree)
+  if (!in_flight_event_dispatch_details_ ||
+      in_flight_event_dispatch_details_->tree != tree)
     return;
 
   // The WindowTree is dying. So it's not going to ack the event.
   // If the dying tree matches the root |tree_| mark as handled so we don't
   // notify it of accelerators.
-  OnEventAck(in_flight_event_details_->tree,
+  OnEventAck(in_flight_event_dispatch_details_->tree,
              tree == window_tree_ ? mojom::EventResult::HANDLED
                                   : mojom::EventResult::UNHANDLED);
 }
@@ -292,7 +295,8 @@ void WindowManagerState::ProcessEvent(const ui::Event& event,
                                       int64_t display_id) {
   // If this is still waiting for an ack from a previously sent event, then
   // queue up the event to be dispatched once the ack is received.
-  if (in_flight_event_details_) {
+  if (event_dispatcher_.IsHitTestInFlight() ||
+      in_flight_event_dispatch_details_) {
     if (!event_queue_.empty() && !event_queue_.back()->processed_target &&
         EventsCanBeCoalesced(*event_queue_.back()->event, event)) {
       event_queue_.back()->event = CoalesceEvents(
@@ -310,12 +314,12 @@ void WindowManagerState::ProcessEvent(const ui::Event& event,
 void WindowManagerState::OnAcceleratorAck(
     mojom::EventResult result,
     const std::unordered_map<std::string, std::vector<uint8_t>>& properties) {
-  DCHECK(in_flight_event_details_);
+  DCHECK(in_flight_event_dispatch_details_);
   DCHECK_EQ(EventDispatchPhase::PRE_TARGET_ACCELERATOR,
-            in_flight_event_details_->phase);
+            in_flight_event_dispatch_details_->phase);
 
-  std::unique_ptr<InFlightEventDetails> details =
-      std::move(in_flight_event_details_);
+  std::unique_ptr<InFlightEventDispatchDetails> details =
+      std::move(in_flight_event_dispatch_details_);
 
   if (result == mojom::EventResult::UNHANDLED) {
     DCHECK(details->event->IsKeyEvent());
@@ -389,9 +393,9 @@ ServerWindow* WindowManagerState::GetWindowManagerRootForDisplayRoot(
 
 void WindowManagerState::OnEventAck(mojom::WindowTree* tree,
                                     mojom::EventResult result) {
-  DCHECK(in_flight_event_details_);
-  std::unique_ptr<InFlightEventDetails> details =
-      std::move(in_flight_event_details_);
+  DCHECK(in_flight_event_dispatch_details_);
+  std::unique_ptr<InFlightEventDispatchDetails> details =
+      std::move(in_flight_event_dispatch_details_);
 
   if (result == mojom::EventResult::UNHANDLED &&
       details->post_target_accelerator) {
@@ -406,16 +410,19 @@ void WindowManagerState::OnEventAckTimeout(ClientSpecificId client_id) {
   WindowTree* hung_tree = window_server()->GetTreeWithId(client_id);
   if (hung_tree && !hung_tree->janky())
     window_tree_->ClientJankinessChanged(hung_tree);
-  if (in_flight_event_details_->phase ==
+  if (in_flight_event_dispatch_details_->phase ==
       EventDispatchPhase::PRE_TARGET_ACCELERATOR) {
     OnAcceleratorAck(mojom::EventResult::UNHANDLED, KeyEvent::Properties());
   } else {
-    OnEventAck(in_flight_event_details_->tree, mojom::EventResult::UNHANDLED);
+    OnEventAck(in_flight_event_dispatch_details_->tree,
+               mojom::EventResult::UNHANDLED);
   }
 }
 
 void WindowManagerState::ProcessEventImpl(const ui::Event& event,
                                           int64_t display_id) {
+  DCHECK(!in_flight_event_dispatch_details_ &&
+         !event_dispatcher_.IsHitTestInFlight());
   // Debug accelerators are always checked and don't interfere with processing.
   ProcessDebugAccelerator(event);
   event_processing_display_id_ = display_id;
@@ -434,31 +441,14 @@ void WindowManagerState::QueueEvent(
   event_queue_.push(std::move(queued_event));
 }
 
-void WindowManagerState::ProcessNextEventFromQueue() {
-  // Loop through |event_queue_| stopping after dispatching the first valid
-  // event.
-  while (!event_queue_.empty()) {
-    std::unique_ptr<QueuedEvent> queued_event = std::move(event_queue_.front());
-    event_queue_.pop();
-    if (!queued_event->processed_target) {
-      ProcessEventImpl(*queued_event->event, queued_event->display_id);
-      return;
-    }
-    if (queued_event->processed_target->IsValid()) {
-      DispatchInputEventToWindowImpl(
-          queued_event->processed_target->window(),
-          queued_event->processed_target->client_id(), *queued_event->event,
-          queued_event->processed_target->accelerator());
-      return;
-    }
-  }
-}
-
+// TODO(riajiang): We might want to do event targeting for the next event while
+// waiting for the current event to be dispatched. crbug.com/724521
 void WindowManagerState::DispatchInputEventToWindowImpl(
     ServerWindow* target,
     ClientSpecificId client_id,
     const ui::Event& event,
     base::WeakPtr<Accelerator> accelerator) {
+  DCHECK(!in_flight_event_dispatch_details_);
   DCHECK(target);
   if (target->parent() == nullptr)
     target = GetWindowManagerRootForDisplayRoot(target);
@@ -471,17 +461,18 @@ void WindowManagerState::DispatchInputEventToWindowImpl(
   WindowTree* tree = window_server()->GetTreeWithId(client_id);
   DCHECK(tree);
   ScheduleInputEventTimeout(tree, target, event, EventDispatchPhase::TARGET);
-  in_flight_event_details_->post_target_accelerator = accelerator;
+  in_flight_event_dispatch_details_->post_target_accelerator = accelerator;
 
   // Ignore |tree| because it will receive the event via normal dispatch.
-  window_server()->SendToPointerWatchers(event, user_id(), target, tree,
-                                         in_flight_event_details_->display_id);
+  window_server()->SendToPointerWatchers(
+      event, user_id(), target, tree,
+      in_flight_event_dispatch_details_->display_id);
 
   tree->DispatchInputEvent(
       target, event,
-      base::BindOnce(&WindowManagerState::OnEventAck,
-                     in_flight_event_details_->weak_factory.GetWeakPtr(),
-                     tree));
+      base::BindOnce(
+          &WindowManagerState::OnEventAck,
+          in_flight_event_dispatch_details_->weak_factory.GetWeakPtr(), tree));
 }
 
 void WindowManagerState::AddDebugAccelerators() {
@@ -525,8 +516,8 @@ void WindowManagerState::ScheduleInputEventTimeout(WindowTree* tree,
                                                    ServerWindow* target,
                                                    const Event& event,
                                                    EventDispatchPhase phase) {
-  std::unique_ptr<InFlightEventDetails> details =
-      base::MakeUnique<InFlightEventDetails>(
+  std::unique_ptr<InFlightEventDispatchDetails> details =
+      base::MakeUnique<InFlightEventDispatchDetails>(
           this, tree, event_processing_display_id_, event, phase);
 
   // TOOD(sad): Adjust this delay, possibly make this dynamic.
@@ -537,7 +528,7 @@ void WindowManagerState::ScheduleInputEventTimeout(WindowTree* tree,
       FROM_HERE, max_delay,
       base::Bind(&WindowManagerState::OnEventAckTimeout,
                  details->weak_factory.GetWeakPtr(), tree->id()));
-  in_flight_event_details_ = std::move(details);
+  in_flight_event_dispatch_details_ = std::move(details);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -550,12 +541,12 @@ void WindowManagerState::OnAccelerator(uint32_t accelerator_id,
   const bool needs_ack = phase == AcceleratorPhase::PRE;
   WindowTree::AcceleratorCallback ack_callback;
   if (needs_ack) {
-    DCHECK(!in_flight_event_details_);
+    DCHECK(!in_flight_event_dispatch_details_);
     ScheduleInputEventTimeout(window_tree_, nullptr, event,
                               EventDispatchPhase::PRE_TARGET_ACCELERATOR);
-    ack_callback =
-        base::BindOnce(&WindowManagerState::OnAcceleratorAck,
-                       in_flight_event_details_->weak_factory.GetWeakPtr());
+    ack_callback = base::BindOnce(
+        &WindowManagerState::OnAcceleratorAck,
+        in_flight_event_dispatch_details_->weak_factory.GetWeakPtr());
   }
   window_tree_->OnAccelerator(accelerator_id, event, std::move(ack_callback));
 }
@@ -625,7 +616,7 @@ void WindowManagerState::DispatchInputEventToWindow(ServerWindow* target,
   DCHECK(IsActive());
   // TODO(sky): this needs to see if another wms has capture and if so forward
   // to it.
-  if (in_flight_event_details_) {
+  if (in_flight_event_dispatch_details_) {
     std::unique_ptr<ProcessedEventTarget> processed_event_target(
         new ProcessedEventTarget(target, client_id, accelerator));
     QueueEvent(event, std::move(processed_event_target),
@@ -639,6 +630,33 @@ void WindowManagerState::DispatchInputEventToWindow(ServerWindow* target,
   DispatchInputEventToWindowImpl(target, client_id, event, weak_accelerator);
 }
 
+void WindowManagerState::ProcessNextEventFromQueue() {
+  // Loop through |event_queue_| stopping after dispatching the first valid
+  // event.
+  while (!event_queue_.empty()) {
+    if (in_flight_event_dispatch_details_)
+      return;
+
+    if (!event_queue_.front()->processed_target &&
+        event_dispatcher_.IsHitTestInFlight())
+      return;
+
+    std::unique_ptr<QueuedEvent> queued_event = std::move(event_queue_.front());
+    event_queue_.pop();
+    if (!queued_event->processed_target) {
+      ProcessEventImpl(*queued_event->event, queued_event->display_id);
+      return;
+    }
+    if (queued_event->processed_target->IsValid()) {
+      DispatchInputEventToWindowImpl(
+          queued_event->processed_target->window(),
+          queued_event->processed_target->client_id(), *queued_event->event,
+          queued_event->processed_target->accelerator());
+      return;
+    }
+  }
+}
+
 ClientSpecificId WindowManagerState::GetEventTargetClientId(
     const ServerWindow* window,
     bool in_nonclient_area) {