From 2a55af809a256196fb14740ea951fed3d8546806 Mon Sep 17 00:00:00 2001
From: chunhtai <47866232+chunhtai@users.noreply.github.com>
Date: Tue, 7 Apr 2020 11:24:11 -0700
Subject: [PATCH] always forward move event (flutter/engine#17541)

flutter/flutter#54022

The original issue is the _MotionEventsDispatcher depends on all down pointers to send out their own move events. If the third pointer has the movement of zero, it will get filter out by the PointerDataPacketConverter. This result with only two pointer move events been sent to RenderAndroidView, and they both get ignored because it is waiting for the third one.

This pr fixes it by always forward the move event
---
 .../window/pointer_data_packet_converter.cc   |  8 ++--
 ...pointer_data_packet_converter_unittests.cc | 37 +++++++++++++++++++
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/engine/src/flutter/lib/ui/window/pointer_data_packet_converter.cc b/engine/src/flutter/lib/ui/window/pointer_data_packet_converter.cc
index c7f643f2541..b945e7b1463 100644
--- a/engine/src/flutter/lib/ui/window/pointer_data_packet_converter.cc
+++ b/engine/src/flutter/lib/ui/window/pointer_data_packet_converter.cc
@@ -169,11 +169,9 @@ void PointerDataPacketConverter::ConvertPointerData(
         PointerState state = iter->second;
         FML_DCHECK(state.isDown);
 
-        if (LocationNeedsUpdate(pointer_data, state)) {
-          UpdatePointerIdentifier(pointer_data, state, false);
-          UpdateDeltaAndState(pointer_data, state);
-          converted_pointers.push_back(pointer_data);
-        }
+        UpdatePointerIdentifier(pointer_data, state, false);
+        UpdateDeltaAndState(pointer_data, state);
+        converted_pointers.push_back(pointer_data);
         break;
       }
       case PointerData::Change::kUp: {
diff --git a/engine/src/flutter/lib/ui/window/pointer_data_packet_converter_unittests.cc b/engine/src/flutter/lib/ui/window/pointer_data_packet_converter_unittests.cc
index d18b7f3e474..926637244f8 100644
--- a/engine/src/flutter/lib/ui/window/pointer_data_packet_converter_unittests.cc
+++ b/engine/src/flutter/lib/ui/window/pointer_data_packet_converter_unittests.cc
@@ -244,6 +244,43 @@ TEST(PointerDataPacketConverterTest, CanUpdatePointerIdentifier) {
   ASSERT_EQ(result[6].synthesized, 0);
 }
 
+TEST(PointerDataPacketConverterTest, AlwaysForwardMoveEvent) {
+  PointerDataPacketConverter converter;
+  auto packet = std::make_unique<PointerDataPacket>(4);
+  PointerData data;
+  CreateSimulatedPointerData(data, PointerData::Change::kAdd, 0, 0.0, 0.0);
+  packet->SetPointerData(0, data);
+  CreateSimulatedPointerData(data, PointerData::Change::kDown, 0, 0.0, 0.0);
+  packet->SetPointerData(1, data);
+  // Creates a move event without a location change.
+  CreateSimulatedPointerData(data, PointerData::Change::kMove, 0, 0.0, 0.0);
+  packet->SetPointerData(2, data);
+  CreateSimulatedPointerData(data, PointerData::Change::kUp, 0, 0.0, 0.0);
+  packet->SetPointerData(3, data);
+
+  auto converted_packet = converter.Convert(std::move(packet));
+
+  std::vector<PointerData> result;
+  UnpackPointerPacket(result, std::move(converted_packet));
+
+  ASSERT_EQ(result.size(), (size_t)4);
+  ASSERT_EQ(result[0].change, PointerData::Change::kAdd);
+  ASSERT_EQ(result[0].synthesized, 0);
+
+  ASSERT_EQ(result[1].change, PointerData::Change::kDown);
+  ASSERT_EQ(result[1].pointer_identifier, 1);
+  ASSERT_EQ(result[1].synthesized, 0);
+
+  // Does not filter out the move event.
+  ASSERT_EQ(result[2].change, PointerData::Change::kMove);
+  ASSERT_EQ(result[2].pointer_identifier, 1);
+  ASSERT_EQ(result[2].synthesized, 0);
+
+  ASSERT_EQ(result[3].change, PointerData::Change::kUp);
+  ASSERT_EQ(result[3].pointer_identifier, 1);
+  ASSERT_EQ(result[3].synthesized, 0);
+}
+
 TEST(PointerDataPacketConverterTest, CanWorkWithDifferentDevices) {
   PointerDataPacketConverter converter;
   auto packet = std::make_unique<PointerDataPacket>(12);