[Windows] Expose channel buffers 'resize' and 'overflow' control commands exposed by the control channel. (#47158)

## Description

This PR adds two helper functions to invoke the 'resize' and 'overflow' commands exposed by the control channel.
See:

https://github.com/flutter/engine/blob/93e8901490e78c7ba7e319cce4470d9c6478c6dc/lib/ui/channel_buffers.dart#L302-L309

Implementation based on the discussion from #46998.

## Related Issue

Windows implementation for flutter/flutter#132386

## Tests

Adds 4 tests.

Author: bleroux

shell/platform/common/client_wrapper/basic_message_channel_unittests.cc

@@ -9,6 +9,7 @@
 
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/binary_messenger.h"
 #include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_message_codec.h"
+#include "flutter/shell/platform/common/client_wrapper/include/flutter/standard_method_codec.h"
 #include "gtest/gtest.h"
 
 namespace flutter {
@@ -20,23 +21,34 @@ class TestBinaryMessenger : public BinaryMessenger {
   void Send(const std::string& channel,
             const uint8_t* message,
             const size_t message_size,
-            BinaryReply reply) const override {}
+            BinaryReply reply) const override {
+    send_called_ = true;
+    int length = static_cast<int>(message_size);
+    last_message_ =
+        std::vector<uint8_t>(message, message + length * sizeof(uint8_t));
+  }
 
   void SetMessageHandler(const std::string& channel,
                          BinaryMessageHandler handler) override {
     last_message_handler_channel_ = channel;
     last_message_handler_ = handler;
   }
 
+  bool send_called() { return send_called_; }
+
   std::string last_message_handler_channel() {
     return last_message_handler_channel_;
   }
 
   BinaryMessageHandler last_message_handler() { return last_message_handler_; }
 
+  std::vector<uint8_t> last_message() { return last_message_; }
+
  private:
+  mutable bool send_called_ = false;
   std::string last_message_handler_channel_;
   BinaryMessageHandler last_message_handler_;
+  mutable std::vector<uint8_t> last_message_;
 };
 
 }  // namespace
@@ -86,4 +98,68 @@ TEST(BasicMessageChannelTest, Unregistration) {
   EXPECT_EQ(messenger.last_message_handler(), nullptr);
 }
 
+// Tests that calling Resize generates the binary message expected by the Dart
+// implementation.
+TEST(BasicMessageChannelTest, Resize) {
+  TestBinaryMessenger messenger;
+  const std::string channel_name("flutter/test");
+  BasicMessageChannel channel(&messenger, channel_name,
+                              &flutter::StandardMessageCodec::GetInstance());
+
+  channel.Resize(3);
+
+  // Because the Dart implementation for the control channel implements its own
+  // custom deserialization logic, this test compares the generated bytes array
+  // to the expected one (for instance, the deserialization logic expects the
+  // size parameter of the resize method call to be an uint32).
+  //
+  // The expected content was created from the following Dart code:
+  //   MethodCall call = MethodCall('resize', ['flutter/test',3]);
+  //   StandardMethodCodec().encodeMethodCall(call).buffer.asUint8List();
+  const int expected_message_size = 29;
+
+  EXPECT_EQ(messenger.send_called(), true);
+  EXPECT_EQ(static_cast<int>(messenger.last_message().size()),
+            expected_message_size);
+
+  int expected[expected_message_size] = {
+      7,   6,   114, 101, 115, 105, 122, 101, 12,  2, 7, 12, 102, 108, 117,
+      116, 116, 101, 114, 47,  116, 101, 115, 116, 3, 3, 0,  0,   0};
+  for (int i = 0; i < expected_message_size; i++) {
+    EXPECT_EQ(messenger.last_message()[i], expected[i]);
+  }
+}
+
+// Tests that calling SetWarnsOnOverflow generates the binary message expected
+// by the Dart implementation.
+TEST(BasicMessageChannelTest, SetWarnsOnOverflow) {
+  TestBinaryMessenger messenger;
+
+  const std::string channel_name("flutter/test");
+  BasicMessageChannel channel(&messenger, channel_name,
+                              &flutter::StandardMessageCodec::GetInstance());
+
+  channel.SetWarnsOnOverflow(false);
+
+  // Because the Dart implementation for the control channel implements its own
+  // custom deserialization logic, this test compares the generated bytes array
+  // to the expected one.
+  //
+  // The expected content was created from the following Dart code:
+  //   MethodCall call = MethodCall('overflow',['flutter/test', true]);
+  //   StandardMethodCodec().encodeMethodCall(call).buffer.asUint8List();
+  const int expected_message_size = 27;
+
+  EXPECT_EQ(messenger.send_called(), true);
+  EXPECT_EQ(static_cast<int>(messenger.last_message().size()),
+            expected_message_size);
+
+  int expected[expected_message_size] = {
+      7,   8,   111, 118, 101, 114, 102, 108, 111, 119, 12,  2,   7, 12,
+      102, 108, 117, 116, 116, 101, 114, 47,  116, 101, 115, 116, 1};
+  for (int i = 0; i < expected_message_size; i++) {
+    EXPECT_EQ(messenger.last_message()[i], expected[i]);
+  }
+}
+
 }  // namespace flutter

shell/platform/common/client_wrapper/core_implementations.cc

@@ -19,6 +19,8 @@
 
 #include "binary_messenger_impl.h"
 #include "include/flutter/engine_method_result.h"
+#include "include/flutter/method_channel.h"
+#include "include/flutter/standard_method_codec.h"
 #include "texture_registrar_impl.h"
 
 namespace flutter {
@@ -164,6 +166,46 @@ void ReplyManager::SendResponseData(const std::vector<uint8_t>* data) {
 
 }  // namespace internal
 
+// ========== method_channel.h ==========
+
+namespace {
+
+constexpr char kControlChannelName[] = "dev.flutter/channel-buffers";
+constexpr char kResizeMethod[] = "resize";
+constexpr char kOverflowMethod[] = "overflow";
+
+}  // namespace
+
+namespace internal {
+
+void ResizeChannel(BinaryMessenger* messenger, std::string name, int new_size) {
+  auto control_channel = std::make_unique<MethodChannel<EncodableValue>>(
+      messenger, kControlChannelName, &StandardMethodCodec::GetInstance());
+
+  // The deserialization logic handles only 32 bits values, see
+  // https://github.com/flutter/engine/blob/93e8901490e78c7ba7e319cce4470d9c6478c6dc/lib/ui/channel_buffers.dart#L495.
+  control_channel->InvokeMethod(
+      kResizeMethod, std::make_unique<EncodableValue>(EncodableList{
+                         EncodableValue(name),
+                         EncodableValue(static_cast<int32_t>(new_size)),
+                     }));
+}
+
+void SetChannelWarnsOnOverflow(BinaryMessenger* messenger,
+                               std::string name,
+                               bool warns) {
+  auto control_channel = std::make_unique<MethodChannel<EncodableValue>>(
+      messenger, kControlChannelName, &StandardMethodCodec::GetInstance());
+
+  control_channel->InvokeMethod(kOverflowMethod,
+                                std::make_unique<EncodableValue>(EncodableList{
+                                    EncodableValue(name),
+                                    EncodableValue(!warns),
+                                }));
+}
+
+}  // namespace internal
+
 // ========== texture_registrar_impl.h ==========
 
 TextureRegistrarImpl::TextureRegistrarImpl(

shell/platform/common/client_wrapper/include/flutter/basic_message_channel.h

@@ -14,6 +14,26 @@
 
 namespace flutter {
 
+namespace internal {
+// Internal helper functions used by BasicMessageChannel and MethodChannel.
+
+// Adjusts the number of messages that will get buffered when sending messages
+// to channels that aren't fully set up yet. For example, the engine isn't
+// running yet or the channel's message handler isn't set up on the Dart side
+// yet.
+void ResizeChannel(BinaryMessenger* messenger, std::string name, int new_size);
+
+// Defines whether the channel should show warning messages when discarding
+// messages due to overflow.
+//
+// When |warns| is false, the channel is expected to overflow and warning
+// messages will not be shown.
+void SetChannelWarnsOnOverflow(BinaryMessenger* messenger,
+                               std::string name,
+                               bool warns);
+
+}  // namespace internal
+
 class EncodableValue;
 
 // A message reply callback.
@@ -101,6 +121,23 @@ class BasicMessageChannel {
     messenger_->SetMessageHandler(name_, std::move(binary_handler));
   }
 
+  // Adjusts the number of messages that will get buffered when sending messages
+  // to channels that aren't fully set up yet. For example, the engine isn't
+  // running yet or the channel's message handler isn't set up on the Dart side
+  // yet.
+  void Resize(int new_size) {
+    internal::ResizeChannel(messenger_, name_, new_size);
+  }
+
+  // Defines whether the channel should show warning messages when discarding
+  // messages due to overflow.
+  //
+  // When |warns| is false, the channel is expected to overflow and warning
+  // messages will not be shown.
+  void SetWarnsOnOverflow(bool warns) {
+    internal::SetChannelWarnsOnOverflow(messenger_, name_, warns);
+  }
+
  private:
   BinaryMessenger* messenger_;
   std::string name_;

shell/platform/common/client_wrapper/include/flutter/method_channel.h

@@ -8,6 +8,7 @@
 #include <iostream>
 #include <string>
 
+#include "basic_message_channel.h"
 #include "binary_messenger.h"
 #include "engine_method_result.h"
 #include "method_call.h"
@@ -122,6 +123,23 @@ class MethodChannel {
     messenger_->SetMessageHandler(name_, std::move(binary_handler));
   }
 
+  // Adjusts the number of messages that will get buffered when sending messages
+  // to channels that aren't fully set up yet. For example, the engine isn't
+  // running yet or the channel's message handler isn't set up on the Dart side
+  // yet.
+  void Resize(int new_size) {
+    internal::ResizeChannel(messenger_, name_, new_size);
+  }
+
+  // Defines whether the channel should show warning messages when discarding
+  // messages due to overflow.
+  //
+  // When |warns| is false, the channel is expected to overflow and warning
+  // messages will not be shown.
+  void SetWarnsOnOverflow(bool warns) {
+    internal::SetChannelWarnsOnOverflow(messenger_, name_, warns);
+  }
+
  private:
   BinaryMessenger* messenger_;
   std::string name_;

shell/platform/common/client_wrapper/method_channel_unittests.cc

@@ -24,6 +24,9 @@ class TestBinaryMessenger : public BinaryMessenger {
             BinaryReply reply) const override {
     send_called_ = true;
     last_reply_handler_ = reply;
+    int length = static_cast<int>(message_size);
+    last_message_ =
+        std::vector<uint8_t>(message, message + length * sizeof(uint8_t));
   }
 
   void SetMessageHandler(const std::string& channel,
@@ -42,11 +45,14 @@ class TestBinaryMessenger : public BinaryMessenger {
 
   BinaryMessageHandler last_message_handler() { return last_message_handler_; }
 
+  std::vector<uint8_t> last_message() { return last_message_; }
+
  private:
   mutable bool send_called_ = false;
   mutable BinaryReply last_reply_handler_;
   std::string last_message_handler_channel_;
   BinaryMessageHandler last_message_handler_;
+  mutable std::vector<uint8_t> last_message_;
 };
 
 }  // namespace
@@ -156,4 +162,64 @@ TEST(MethodChannelTest, InvokeNotImplemented) {
   EXPECT_TRUE(received_not_implemented);
 }
 
+// Tests that calling Resize generates the binary message expected by the Dart
+// implementation.
+TEST(MethodChannelTest, Resize) {
+  TestBinaryMessenger messenger;
+  const std::string channel_name("flutter/test");
+  MethodChannel channel(&messenger, channel_name,
+                        &StandardMethodCodec::GetInstance());
+
+  channel.Resize(3);
+
+  // Because the Dart implementation for the control channel implements its own
+  // custom deserialization logic, this test compares the generated bytes array
+  // to the expected one (for instance, the deserialization logic expects the
+  // size parameter of the resize method call to be an uint32).
+  //
+  // The expected content was created from the following Dart code:
+  //   MethodCall call = MethodCall('resize', ['flutter/test',3]);
+  //   StandardMethodCodec().encodeMethodCall(call).buffer.asUint8List();
+  const int expected_message_size = 29;
+
+  EXPECT_EQ(messenger.send_called(), true);
+  EXPECT_EQ(static_cast<int>(messenger.last_message().size()),
+            expected_message_size);
+
+  int expected[expected_message_size] = {
+      7,   6,   114, 101, 115, 105, 122, 101, 12,  2, 7, 12, 102, 108, 117,
+      116, 116, 101, 114, 47,  116, 101, 115, 116, 3, 3, 0,  0,   0};
+  for (int i = 0; i < expected_message_size; i++) {
+    EXPECT_EQ(messenger.last_message()[i], expected[i]);
+  }
+}
+
+// Tests that calling SetWarnsOnOverflow generates the binary message expected
+// by the Dart implementation.
+TEST(MethodChannelTest, SetWarnsOnOverflow) {
+  TestBinaryMessenger messenger;
+
+  const std::string channel_name("flutter/test");
+  MethodChannel channel(&messenger, channel_name,
+                        &StandardMethodCodec::GetInstance());
+
+  channel.SetWarnsOnOverflow(false);
+
+  // The expected content was created from the following Dart code:
+  //   MethodCall call = MethodCall('overflow',['flutter/test', true]);
+  //   StandardMethodCodec().encodeMethodCall(call).buffer.asUint8List();
+  const int expected_message_size = 27;
+
+  EXPECT_EQ(messenger.send_called(), true);
+  EXPECT_EQ(static_cast<int>(messenger.last_message().size()),
+            expected_message_size);
+
+  int expected[expected_message_size] = {
+      7,   8,   111, 118, 101, 114, 102, 108, 111, 119, 12,  2,   7, 12,
+      102, 108, 117, 116, 116, 101, 114, 47,  116, 101, 115, 116, 1};
+  for (int i = 0; i < expected_message_size; i++) {
+    EXPECT_EQ(messenger.last_message()[i], expected[i]);
+  }
+}
+
 }  // namespace flutter