Fix input flow event logic (flutter/engine#24526)

engine/src/flutter/shell/common/animator.cc

@@ -80,6 +80,7 @@ void Animator::EnqueueTraceFlowId(uint64_t trace_flow_id) {
           return;
         }
         self->trace_flow_ids_.push_back(trace_flow_id);
+        self->ScheduleMaybeClearTraceFlowIds();
       });
 }
 
@@ -249,8 +250,27 @@ void Animator::AwaitVSync() {
   delegate_.OnAnimatorNotifyIdle(dart_frame_deadline_);
 }
 
-void Animator::ScheduleSecondaryVsyncCallback(const fml::closure& callback) {
-  waiter_->ScheduleSecondaryCallback(callback);
+void Animator::ScheduleSecondaryVsyncCallback(uintptr_t id,
+                                              const fml::closure& callback) {
+  waiter_->ScheduleSecondaryCallback(id, callback);
+}
+
+void Animator::ScheduleMaybeClearTraceFlowIds() {
+  waiter_->ScheduleSecondaryCallback(
+      reinterpret_cast<uintptr_t>(this), [self = weak_factory_.GetWeakPtr()] {
+        if (!self) {
+          return;
+        }
+        if (!self->frame_scheduled_ && !self->trace_flow_ids_.empty()) {
+          TRACE_EVENT0("flutter",
+                       "Animator::ScheduleMaybeClearTraceFlowIds - callback");
+          while (!self->trace_flow_ids_.empty()) {
+            auto flow_id = self->trace_flow_ids_.front();
+            TRACE_FLOW_END("flutter", "PointerEvent", flow_id);
+            self->trace_flow_ids_.pop_front();
+          }
+        }
+      });
 }
 
 }  // namespace flutter

engine/src/flutter/shell/common/animator.h

@@ -63,10 +63,11 @@ class Animator final {
   ///           secondary callback will still be executed at vsync.
   ///
   ///           This callback is used to provide the vsync signal needed by
-  ///           `SmoothPointerDataDispatcher`.
+  ///           `SmoothPointerDataDispatcher`, and for our own flow events.
   ///
   /// @see      `PointerDataDispatcher::ScheduleSecondaryVsyncCallback`.
-  void ScheduleSecondaryVsyncCallback(const fml::closure& callback);
+  void ScheduleSecondaryVsyncCallback(uintptr_t id,
+                                      const fml::closure& callback);
 
   void Start();
 
@@ -74,8 +75,9 @@ class Animator final {
 
   void SetDimensionChangePending();
 
-  // Enqueue |trace_flow_id| into |trace_flow_ids_|.  The corresponding flow
-  // will be ended during the next |BeginFrame|.
+  // Enqueue |trace_flow_id| into |trace_flow_ids_|.  The flow event will be
+  // ended at either the next frame, or the next vsync interval with no active
+  // active rendering.
   void EnqueueTraceFlowId(uint64_t trace_flow_id);
 
  private:
@@ -91,6 +93,9 @@ class Animator final {
 
   const char* FrameParity();
 
+  // Clear |trace_flow_ids_| if |frame_scheduled_| is false.
+  void ScheduleMaybeClearTraceFlowIds();
+
   Delegate& delegate_;
   TaskRunners task_runners_;
   std::shared_ptr<VsyncWaiter> waiter_;

engine/src/flutter/shell/common/engine.cc

@@ -515,8 +515,9 @@ void Engine::DoDispatchPacket(std::unique_ptr<PointerDataPacket> packet,
   }
 }
 
-void Engine::ScheduleSecondaryVsyncCallback(const fml::closure& callback) {
-  animator_->ScheduleSecondaryVsyncCallback(callback);
+void Engine::ScheduleSecondaryVsyncCallback(uintptr_t id,
+                                            const fml::closure& callback) {
+  animator_->ScheduleSecondaryVsyncCallback(id, callback);
 }
 
 void Engine::HandleAssetPlatformMessage(fml::RefPtr<PlatformMessage> message) {

engine/src/flutter/shell/common/engine.h

@@ -804,7 +804,8 @@ class Engine final : public RuntimeDelegate,
                         uint64_t trace_flow_id) override;
 
   // |PointerDataDispatcher::Delegate|
-  void ScheduleSecondaryVsyncCallback(const fml::closure& callback) override;
+  void ScheduleSecondaryVsyncCallback(uintptr_t id,
+                                      const fml::closure& callback) override;
 
   //----------------------------------------------------------------------------
   /// @brief      Get the last Entrypoint that was used in the RunConfiguration

engine/src/flutter/shell/common/pointer_data_dispatcher.cc

@@ -4,6 +4,8 @@
 
 #include "flutter/shell/common/pointer_data_dispatcher.h"
 
+#include "flutter/fml/trace_event.h"
+
 namespace flutter {
 
 PointerDataDispatcher::~PointerDataDispatcher() = default;
@@ -16,12 +18,17 @@ SmoothPointerDataDispatcher::~SmoothPointerDataDispatcher() = default;
 void DefaultPointerDataDispatcher::DispatchPacket(
     std::unique_ptr<PointerDataPacket> packet,
     uint64_t trace_flow_id) {
+  TRACE_EVENT0("flutter", "DefaultPointerDataDispatcher::DispatchPacket");
+  TRACE_FLOW_STEP("flutter", "PointerEvent", trace_flow_id);
   delegate_.DoDispatchPacket(std::move(packet), trace_flow_id);
 }
 
 void SmoothPointerDataDispatcher::DispatchPacket(
     std::unique_ptr<PointerDataPacket> packet,
     uint64_t trace_flow_id) {
+  TRACE_EVENT0("flutter", "SmoothPointerDataDispatcher::DispatchPacket");
+  TRACE_FLOW_STEP("flutter", "PointerEvent", trace_flow_id);
+
   if (is_pointer_data_in_progress_) {
     if (pending_packet_ != nullptr) {
       DispatchPendingPacket();
@@ -39,6 +46,7 @@ void SmoothPointerDataDispatcher::DispatchPacket(
 
 void SmoothPointerDataDispatcher::ScheduleSecondaryVsyncCallback() {
   delegate_.ScheduleSecondaryVsyncCallback(
+      reinterpret_cast<uintptr_t>(this),
       [dispatcher = weak_factory_.GetWeakPtr()]() {
         if (dispatcher && dispatcher->is_pointer_data_in_progress_) {
           if (dispatcher->pending_packet_ != nullptr) {

engine/src/flutter/shell/common/pointer_data_dispatcher.h

@@ -53,14 +53,16 @@ class PointerDataDispatcher {
     ///           by `Animator::RequestFrame`).
     ///
     ///           Like the callback in `AsyncWaitForVsync`, this callback is
-    ///           only scheduled to be called once, and it will be called in the
-    ///           UI thread. If there is no AsyncWaitForVsync callback
-    ///           (`Animator::RequestFrame` is not called), this secondary
-    ///           callback will still be executed at vsync.
+    ///           only scheduled to be called once per |id|, and it will be
+    ///           called in the UI thread. If there is no AsyncWaitForVsync
+    ///           callback (`Animator::RequestFrame` is not called), this
+    ///           secondary callback will still be executed at vsync.
     ///
     ///           This callback is used to provide the vsync signal needed by
-    ///           `SmoothPointerDataDispatcher`.
+    ///           `SmoothPointerDataDispatcher`, and for `Animator` input flow
+    ///           events.
     virtual void ScheduleSecondaryVsyncCallback(
+        uintptr_t id,
         const fml::closure& callback) = 0;
   };
 

engine/src/flutter/shell/common/vsync_waiter.cc

@@ -52,7 +52,7 @@ void VsyncWaiter::AsyncWaitForVsync(const Callback& callback) {
       return;
     }
     callback_ = std::move(callback);
-    if (secondary_callback_) {
+    if (!secondary_callbacks_.empty()) {
       // Return directly as `AwaitVSync` is already called by
       // `ScheduleSecondaryCallback`.
       return;
@@ -61,7 +61,8 @@ void VsyncWaiter::AsyncWaitForVsync(const Callback& callback) {
   AwaitVSync();
 }
 
-void VsyncWaiter::ScheduleSecondaryCallback(const fml::closure& callback) {
+void VsyncWaiter::ScheduleSecondaryCallback(uintptr_t id,
+                                            const fml::closure& callback) {
   FML_DCHECK(task_runners_.GetUITaskRunner()->RunsTasksOnCurrentThread());
 
   if (!callback) {
@@ -72,13 +73,13 @@ void VsyncWaiter::ScheduleSecondaryCallback(const fml::closure& callback) {
 
   {
     std::scoped_lock lock(callback_mutex_);
-    if (secondary_callback_) {
+    auto [_, inserted] = secondary_callbacks_.emplace(id, std::move(callback));
+    if (!inserted) {
       // Multiple schedules must result in a single callback per frame interval.
       TRACE_EVENT_INSTANT0("flutter",
                            "MultipleCallsToSecondaryVsyncInFrameInterval");
       return;
     }
-    secondary_callback_ = std::move(callback);
     if (callback_) {
       // Return directly as `AwaitVSync` is already called by
       // `AsyncWaitForVsync`.
@@ -91,15 +92,18 @@ void VsyncWaiter::ScheduleSecondaryCallback(const fml::closure& callback) {
 void VsyncWaiter::FireCallback(fml::TimePoint frame_start_time,
                                fml::TimePoint frame_target_time) {
   Callback callback;
-  fml::closure secondary_callback;
+  std::vector<fml::closure> secondary_callbacks;
 
   {
     std::scoped_lock lock(callback_mutex_);
     callback = std::move(callback_);
-    secondary_callback = std::move(secondary_callback_);
+    for (auto& pair : secondary_callbacks_) {
+      secondary_callbacks.push_back(std::move(pair.second));
+    }
+    secondary_callbacks_.clear();
   }
 
-  if (!callback && !secondary_callback) {
+  if (!callback && secondary_callbacks.empty()) {
     // This means that the vsync waiter implementation fired a callback for a
     // request we did not make. This is a paranoid check but we still want to
     // make sure we catch misbehaving vsync implementations.
@@ -128,7 +132,7 @@ void VsyncWaiter::FireCallback(fml::TimePoint frame_start_time,
         frame_start_time);
   }
 
-  if (secondary_callback) {
+  for (auto& secondary_callback : secondary_callbacks) {
     task_runners_.GetUITaskRunner()->PostTaskForTime(
         std::move(secondary_callback), frame_start_time);
   }

engine/src/flutter/shell/common/vsync_waiter.h

@@ -8,6 +8,7 @@
 #include <functional>
 #include <memory>
 #include <mutex>
+#include <unordered_map>
 
 #include "flutter/common/task_runners.h"
 #include "flutter/fml/time/time_point.h"
@@ -25,10 +26,11 @@ class VsyncWaiter : public std::enable_shared_from_this<VsyncWaiter> {
 
   void AsyncWaitForVsync(const Callback& callback);
 
-  /// Add a secondary callback for the next vsync.
+  /// Add a secondary callback for key |id| for the next vsync.
   ///
-  /// See also |PointerDataDispatcher::ScheduleSecondaryVsyncCallback|.
-  void ScheduleSecondaryCallback(const fml::closure& callback);
+  /// See also |PointerDataDispatcher::ScheduleSecondaryVsyncCallback| and
+  /// |Animator::ScheduleMaybeClearTraceFlowIds|.
+  void ScheduleSecondaryCallback(uintptr_t id, const fml::closure& callback);
 
  protected:
   // On some backends, the |FireCallback| needs to be made from a static C
@@ -52,9 +54,7 @@ class VsyncWaiter : public std::enable_shared_from_this<VsyncWaiter> {
  private:
   std::mutex callback_mutex_;
   Callback callback_;
-
-  std::mutex secondary_callback_mutex_;
-  fml::closure secondary_callback_;
+  std::unordered_map<uintptr_t, fml::closure> secondary_callbacks_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(VsyncWaiter);
 };