Scroll inertia cancel for Win32 (#34452)

Author: moffatman

shell/platform/windows/direct_manipulation.cc

@@ -4,6 +4,8 @@
 
 #include "flutter/fml/logging.h"
 
+#include <algorithm>
+
 #include "flutter/shell/platform/windows/direct_manipulation.h"
 #include "flutter/shell/platform/windows/window.h"
 #include "flutter/shell/platform/windows/window_binding_handler_delegate.h"
@@ -24,6 +26,10 @@
 
 namespace flutter {
 
+int32_t DirectManipulationEventHandler::GetDeviceId() {
+  return (int32_t) reinterpret_cast<int64_t>(this);
+}
+
 STDMETHODIMP DirectManipulationEventHandler::QueryInterface(REFIID iid,
                                                             void** ppv) {
   if ((iid == IID_IUnknown) ||
@@ -43,26 +49,39 @@ HRESULT DirectManipulationEventHandler::OnViewportStatusChanged(
     IDirectManipulationViewport* viewport,
     DIRECTMANIPULATION_STATUS current,
     DIRECTMANIPULATION_STATUS previous) {
+  during_inertia_ = current == DIRECTMANIPULATION_INERTIA;
   if (during_synthesized_reset_ && previous == DIRECTMANIPULATION_RUNNING) {
     during_synthesized_reset_ = false;
   } else if (current == DIRECTMANIPULATION_RUNNING) {
     if (!during_synthesized_reset_) {
       // Not a false event.
       if (owner_->binding_handler_delegate) {
-        owner_->binding_handler_delegate->OnPointerPanZoomStart(
-            (int32_t) reinterpret_cast<int64_t>(this));
+        owner_->binding_handler_delegate->OnPointerPanZoomStart(GetDeviceId());
       }
     }
-  } else if (previous == DIRECTMANIPULATION_RUNNING) {
+  }
+  if (previous == DIRECTMANIPULATION_RUNNING) {
+    // Reset deltas to ensure only inertia values will be compared later.
+    last_pan_delta_x_ = 0.0;
+    last_pan_delta_y_ = 0.0;
     if (owner_->binding_handler_delegate) {
-      owner_->binding_handler_delegate->OnPointerPanZoomEnd(
-          (int32_t) reinterpret_cast<int64_t>(this));
+      owner_->binding_handler_delegate->OnPointerPanZoomEnd(GetDeviceId());
+    }
+  } else if (previous == DIRECTMANIPULATION_INERTIA) {
+    if (owner_->binding_handler_delegate &&
+        (std::max)(std::abs(last_pan_delta_x_), std::abs(last_pan_delta_y_)) >
+            0.01) {
+      owner_->binding_handler_delegate->OnScrollInertiaCancel(GetDeviceId());
     }
     // Need to reset the content transform to its original position
     // so that we are ready for the next gesture.
     // Use during_synthesized_reset_ flag to prevent sending reset also to the
     // framework.
     during_synthesized_reset_ = true;
+    last_pan_x_ = 0.0;
+    last_pan_y_ = 0.0;
+    last_pan_delta_x_ = 0.0;
+    last_pan_delta_y_ = 0.0;
     RECT rect;
     HRESULT hr = viewport->GetViewportRect(&rect);
     if (FAILED(hr)) {
@@ -104,9 +123,13 @@ HRESULT DirectManipulationEventHandler::OnContentUpdated(
     float scale = c - (c - transform[0]);
     float pan_x = transform[4];
     float pan_y = transform[5];
-    if (owner_->binding_handler_delegate) {
+    last_pan_delta_x_ = pan_x - last_pan_x_;
+    last_pan_delta_y_ = pan_y - last_pan_y_;
+    last_pan_x_ = pan_x;
+    last_pan_y_ = pan_y;
+    if (owner_->binding_handler_delegate && !during_inertia_) {
       owner_->binding_handler_delegate->OnPointerPanZoomUpdate(
-          (int32_t) reinterpret_cast<int64_t>(this), pan_x, pan_y, scale, 0);
+          GetDeviceId(), pan_x, pan_y, scale, 0);
     }
   }
   return S_OK;
@@ -144,7 +167,8 @@ int DirectManipulationOwner::Init(unsigned int width, unsigned int height) {
       DIRECTMANIPULATION_CONFIGURATION_INTERACTION |
       DIRECTMANIPULATION_CONFIGURATION_TRANSLATION_X |
       DIRECTMANIPULATION_CONFIGURATION_TRANSLATION_Y |
-      DIRECTMANIPULATION_CONFIGURATION_SCALING;
+      DIRECTMANIPULATION_CONFIGURATION_SCALING |
+      DIRECTMANIPULATION_CONFIGURATION_TRANSLATION_INERTIA;
   RETURN_IF_FAILED(viewport_->ActivateConfiguration(configuration));
   RETURN_IF_FAILED(viewport_->SetViewportOptions(
       DIRECTMANIPULATION_VIEWPORT_OPTIONS_MANUALUPDATE));

shell/platform/windows/direct_manipulation.h

@@ -106,12 +106,23 @@ class DirectManipulationEventHandler
                 DIRECTMANIPULATION_INTERACTION_TYPE interaction) override;
 
  private:
+  // Unique identifier to associate with all gesture event updates.
+  int32_t GetDeviceId();
   // Parent object, used to store the target for gesture event updates.
   DirectManipulationOwner* owner_;
   // We need to reset some parts of DirectManipulation after each gesture
   // A flag is needed to ensure that false events created as the reset occurs
   // are not sent to the flutter framework.
   bool during_synthesized_reset_ = false;
+  // Store whether current events are from synthetic inertia rather than user
+  // input.
+  bool during_inertia_ = false;
+  // Store the difference between the last pan offsets to determine if inertia
+  // has been cancelled in the middle of an animation.
+  float last_pan_x_ = 0.0;
+  float last_pan_y_ = 0.0;
+  float last_pan_delta_x_ = 0.0;
+  float last_pan_delta_y_ = 0.0;
 };
 
 }  // namespace flutter

shell/platform/windows/direct_manipulation_unittests.cc

@@ -259,5 +259,110 @@ TEST(DirectManipulationTest, TestRounding) {
                                    DIRECTMANIPULATION_INERTIA);
 }
 
+TEST(DirectManipulationTest, TestInertiaCancelSentForUserCancel) {
+  MockIDirectManipulationContent content;
+  MockWindowBindingHandlerDelegate delegate;
+  MockIDirectManipulationViewport viewport;
+  const int DISPLAY_WIDTH = 800;
+  const int DISPLAY_HEIGHT = 600;
+  auto owner = std::make_unique<DirectManipulationOwner>(nullptr);
+  owner->SetBindingHandlerDelegate(&delegate);
+  auto handler =
+      fml::MakeRefCounted<DirectManipulationEventHandler>(owner.get());
+  int32_t device_id = (int32_t) reinterpret_cast<int64_t>(handler.get());
+  // No need to mock the actual gesture, just start at the end.
+  EXPECT_CALL(viewport, GetViewportRect(_))
+      .WillOnce(::testing::Invoke([DISPLAY_WIDTH, DISPLAY_HEIGHT](RECT* rect) {
+        rect->left = 0;
+        rect->top = 0;
+        rect->right = DISPLAY_WIDTH;
+        rect->bottom = DISPLAY_HEIGHT;
+        return S_OK;
+      }));
+  EXPECT_CALL(viewport, ZoomToRect(0, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT, false))
+      .WillOnce(::testing::Return(S_OK));
+  EXPECT_CALL(delegate, OnPointerPanZoomEnd(device_id));
+  handler->OnViewportStatusChanged((IDirectManipulationViewport*)&viewport,
+                                   DIRECTMANIPULATION_INERTIA,
+                                   DIRECTMANIPULATION_RUNNING);
+  // Have pan_y change by 10 between inertia updates.
+  EXPECT_CALL(content, GetContentTransform(_, 6))
+      .WillOnce(::testing::Invoke([](float* transform, DWORD size) {
+        transform[0] = 1;
+        transform[4] = 0;
+        transform[5] = 100;
+        return S_OK;
+      }));
+  handler->OnContentUpdated((IDirectManipulationViewport*)&viewport,
+                            (IDirectManipulationContent*)&content);
+  EXPECT_CALL(content, GetContentTransform(_, 6))
+      .WillOnce(::testing::Invoke([](float* transform, DWORD size) {
+        transform[0] = 1;
+        transform[4] = 0;
+        transform[5] = 110;
+        return S_OK;
+      }));
+  handler->OnContentUpdated((IDirectManipulationViewport*)&viewport,
+                            (IDirectManipulationContent*)&content);
+  // This looks like an interruption in the middle of synthetic inertia because
+  // of user input.
+  EXPECT_CALL(delegate, OnScrollInertiaCancel(device_id));
+  handler->OnViewportStatusChanged((IDirectManipulationViewport*)&viewport,
+                                   DIRECTMANIPULATION_READY,
+                                   DIRECTMANIPULATION_INERTIA);
+}
+
+TEST(DirectManipulationTest, TestInertiaCamcelNotSentAtInertiaEnd) {
+  MockIDirectManipulationContent content;
+  MockWindowBindingHandlerDelegate delegate;
+  MockIDirectManipulationViewport viewport;
+  const int DISPLAY_WIDTH = 800;
+  const int DISPLAY_HEIGHT = 600;
+  auto owner = std::make_unique<DirectManipulationOwner>(nullptr);
+  owner->SetBindingHandlerDelegate(&delegate);
+  auto handler =
+      fml::MakeRefCounted<DirectManipulationEventHandler>(owner.get());
+  int32_t device_id = (int32_t) reinterpret_cast<int64_t>(handler.get());
+  // No need to mock the actual gesture, just start at the end.
+  EXPECT_CALL(viewport, GetViewportRect(_))
+      .WillOnce(::testing::Invoke([DISPLAY_WIDTH, DISPLAY_HEIGHT](RECT* rect) {
+        rect->left = 0;
+        rect->top = 0;
+        rect->right = DISPLAY_WIDTH;
+        rect->bottom = DISPLAY_HEIGHT;
+        return S_OK;
+      }));
+  EXPECT_CALL(viewport, ZoomToRect(0, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT, false))
+      .WillOnce(::testing::Return(S_OK));
+  EXPECT_CALL(delegate, OnPointerPanZoomEnd(device_id));
+  handler->OnViewportStatusChanged((IDirectManipulationViewport*)&viewport,
+                                   DIRECTMANIPULATION_INERTIA,
+                                   DIRECTMANIPULATION_RUNNING);
+  // Have no change in pan between events.
+  EXPECT_CALL(content, GetContentTransform(_, 6))
+      .WillOnce(::testing::Invoke([](float* transform, DWORD size) {
+        transform[0] = 1;
+        transform[4] = 0;
+        transform[5] = 140;
+        return S_OK;
+      }));
+  handler->OnContentUpdated((IDirectManipulationViewport*)&viewport,
+                            (IDirectManipulationContent*)&content);
+  EXPECT_CALL(content, GetContentTransform(_, 6))
+      .WillOnce(::testing::Invoke([](float* transform, DWORD size) {
+        transform[0] = 1;
+        transform[4] = 0;
+        transform[5] = 140;
+        return S_OK;
+      }));
+  handler->OnContentUpdated((IDirectManipulationViewport*)&viewport,
+                            (IDirectManipulationContent*)&content);
+  // OnScrollInertiaCancel should not be called.
+  EXPECT_CALL(delegate, OnScrollInertiaCancel(device_id)).Times(0);
+  handler->OnViewportStatusChanged((IDirectManipulationViewport*)&viewport,
+                                   DIRECTMANIPULATION_READY,
+                                   DIRECTMANIPULATION_INERTIA);
+}
+
 }  // namespace testing
 }  // namespace flutter

shell/platform/windows/flutter_windows_view.cc

@@ -264,6 +264,11 @@ void FlutterWindowsView::OnScroll(double x,
              device_id);
 }
 
+void FlutterWindowsView::OnScrollInertiaCancel(int32_t device_id) {
+  PointerLocation point = binding_handler_->GetPrimaryPointerLocation();
+  SendScrollInertiaCancel(device_id, point.x, point.y);
+}
+
 void FlutterWindowsView::OnUpdateSemanticsEnabled(bool enabled) {
   engine_->UpdateSemanticsEnabled(enabled);
 }
@@ -500,6 +505,21 @@ void FlutterWindowsView::SendScroll(double x,
   SendPointerEventWithData(event, state);
 }
 
+void FlutterWindowsView::SendScrollInertiaCancel(int32_t device_id,
+                                                 double x,
+                                                 double y) {
+  auto state =
+      GetOrCreatePointerState(kFlutterPointerDeviceKindTrackpad, device_id);
+
+  FlutterPointerEvent event = {};
+  event.x = x;
+  event.y = y;
+  event.signal_kind =
+      FlutterPointerSignalKind::kFlutterPointerSignalKindScrollInertiaCancel;
+  SetEventPhaseFromCursorButtonState(&event, state);
+  SendPointerEventWithData(event, state);
+}
+
 void FlutterWindowsView::SendPointerEventWithData(
     const FlutterPointerEvent& event_data,
     PointerState* state) {

shell/platform/windows/flutter_windows_view.h

@@ -180,6 +180,9 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate,
                 FlutterPointerDeviceKind device_kind,
                 int32_t device_id) override;
 
+  // |WindowBindingHandlerDelegate|
+  void OnScrollInertiaCancel(int32_t device_id) override;
+
   // |WindowBindingHandlerDelegate|
   virtual void OnUpdateSemanticsEnabled(bool enabled) override;
 
@@ -331,6 +334,9 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate,
                   FlutterPointerDeviceKind device_kind,
                   int32_t device_id);
 
+  // Reports scroll inertia cancel events to Flutter engine.
+  void SendScrollInertiaCancel(int32_t device_id, double x, double y);
+
   // Creates a PointerState object unless it already exists.
   PointerState* GetOrCreatePointerState(FlutterPointerDeviceKind device_kind,
                                         int32_t device_id);

shell/platform/windows/testing/mock_window_binding_handler_delegate.h

@@ -60,6 +60,7 @@ class MockWindowBindingHandlerDelegate : public WindowBindingHandlerDelegate {
                     int,
                     FlutterPointerDeviceKind,
                     int32_t));
+  MOCK_METHOD1(OnScrollInertiaCancel, void(int32_t));
   MOCK_METHOD0(OnPlatformBrightnessChanged, void());
   MOCK_METHOD1(UpdateHighContrastEnabled, void(bool enabled));
 };

shell/platform/windows/window_binding_handler_delegate.h

@@ -122,6 +122,10 @@ class WindowBindingHandlerDelegate {
                         FlutterPointerDeviceKind device_kind,
                         int32_t device_id) = 0;
 
+  // Notifies delegate that scroll inertia should be cancelled.
+  // Typically called by DirectManipulationEventHandler
+  virtual void OnScrollInertiaCancel(int32_t device_id) = 0;
+
   // Notifies delegate that the Flutter semantics tree should be enabled or
   // disabled.
   virtual void OnUpdateSemanticsEnabled(bool enabled) = 0;