[federated_plugin] adds support for Windows (#533)

experimental/federated_plugin/federated_plugin_windows/windows/.gitignore

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+flutter/
+
+# Visual Studio user-specific files.
+*.suo
+*.user
+*.userosscache
+*.sln.docstates
+
+# Visual Studio build-related files.
+x64/
+x86/
+
+# Visual Studio cache files
+# files ending in .cache can be ignored
+*.[Cc]ache
+# but keep track of directories ending in .cache
+!*.[Cc]ache/

experimental/federated_plugin/federated_plugin_windows/windows/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.15)
+set(PROJECT_NAME "federated_plugin_windows")
+project(${PROJECT_NAME} LANGUAGES CXX)
+
+set(PLUGIN_NAME "${PROJECT_NAME}_plugin")
+
+add_library(${PLUGIN_NAME} SHARED
+  "${PLUGIN_NAME}.cpp"
+)
+apply_standard_settings(${PLUGIN_NAME})
+set_target_properties(${PLUGIN_NAME} PROPERTIES
+  CXX_VISIBILITY_PRESET hidden)
+target_compile_definitions(${PLUGIN_NAME} PRIVATE FLUTTER_PLUGIN_IMPL)
+target_include_directories(${PLUGIN_NAME} INTERFACE
+  "${CMAKE_CURRENT_SOURCE_DIR}/include")
+target_link_libraries(${PLUGIN_NAME} PRIVATE flutter flutter_wrapper_plugin)
+
+# List of absolute paths to libraries that should be bundled with the plugin
+set(federated_plugin_windows_bundled_libraries
+  ""
+  PARENT_SCOPE
+)

experimental/federated_plugin/federated_plugin_windows/windows/federated_plugin_windows_plugin.cpp

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+// Copyright 2020 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "include/federated_plugin_windows/federated_plugin_windows_plugin.h"
+
+#include <windows.h>
+
+#include <flutter/method_channel.h>
+#include <flutter/plugin_registrar_windows.h>
+#include <flutter/standard_method_codec.h>
+
+#include <map>
+#include <memory>
+
+namespace {
+
+	class FederatedPluginWindowsPlugin : public flutter::Plugin {
+	public:
+		static void RegisterWithRegistrar(flutter::PluginRegistrarWindows* registrar);
+
+		FederatedPluginWindowsPlugin();
+
+		virtual ~FederatedPluginWindowsPlugin();
+
+	private:
+		// Called when a method is called on this plugin's channel from Dart.
+		void HandleMethodCall(
+			const flutter::MethodCall<flutter::EncodableValue>& method_call,
+			std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>> result);
+	};
+
+	void FederatedPluginWindowsPlugin::RegisterWithRegistrar(
+		flutter::PluginRegistrarWindows* registrar) {
+		auto channel =
+			std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
+				registrar->messenger(), "battery",
+				&flutter::StandardMethodCodec::GetInstance());
+
+		auto plugin = std::make_unique<FederatedPluginWindowsPlugin>();
+
+		channel->SetMethodCallHandler(
+			[plugin_pointer = plugin.get()](const auto& call, auto result) {
+			plugin_pointer->HandleMethodCall(call, std::move(result));
+		});
+
+		registrar->AddPlugin(std::move(plugin));
+	}
+
+	FederatedPluginWindowsPlugin::FederatedPluginWindowsPlugin() {}
+
+	FederatedPluginWindowsPlugin::~FederatedPluginWindowsPlugin() {}
+
+	void FederatedPluginWindowsPlugin::HandleMethodCall(
+		const flutter::MethodCall<flutter::EncodableValue>& method_call,
+		std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>> result) {
+		if (method_call.method_name().compare("getBatteryLevel") == 0) {
+			SYSTEM_POWER_STATUS systemPower;
+			// GetSystemPowerStatus will retrieve the power status of the system.
+			if (GetSystemPowerStatus(&systemPower)) {
+				int batteryLevel = systemPower.BatteryLifePercent;
+				// The batteryLevel value in the range 0 to 100, or 255 if status is unknown.
+				if (batteryLevel != 255) {
+					flutter::EncodableValue response(batteryLevel);
+					result->Success(&response);
+				}
+				else {
+					result->Error("STATUS_UNAVAILABLE", "Not able to determine battery level.");
+				}
+			}
+			else {
+				result->Error("STATUS_UNAVAILABLE", "Not able to determine battery level.");
+			}
+		}
+		else {
+			result->NotImplemented();
+		}
+	}
+
+}
+
+void FederatedPluginWindowsPluginRegisterWithRegistrar(
+	FlutterDesktopPluginRegistrarRef registrar) {
+	FederatedPluginWindowsPlugin::RegisterWithRegistrar(
+		flutter::PluginRegistrarManager::GetInstance()
+		->GetRegistrar<flutter::PluginRegistrarWindows>(registrar));
+}

experimental/federated_plugin/federated_plugin_windows/windows/include/federated_plugin_windows/federated_plugin_windows_plugin.h

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+#ifndef FLUTTER_PLUGIN_FEDERATED_PLUGIN_WINDOWS_PLUGIN_H_
+#define FLUTTER_PLUGIN_FEDERATED_PLUGIN_WINDOWS_PLUGIN_H_
+
+#include <flutter_plugin_registrar.h>
+
+#ifdef FLUTTER_PLUGIN_IMPL
+#define FLUTTER_PLUGIN_EXPORT __declspec(dllexport)
+#else
+#define FLUTTER_PLUGIN_EXPORT __declspec(dllimport)
+#endif
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+FLUTTER_PLUGIN_EXPORT void FederatedPluginWindowsPluginRegisterWithRegistrar(
+    FlutterDesktopPluginRegistrarRef registrar);
+
+#if defined(__cplusplus)
+}  // extern "C"
+#endif
+
+#endif  // FLUTTER_PLUGIN_FEDERATED_PLUGIN_WINDOWS_PLUGIN_H_