[glfw] Implement clipboard support from GLFW api (flutter/engine#9361)

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -917,6 +917,8 @@ FILE: ../../../flutter/shell/platform/glfw/flutter_glfw.cc
 FILE: ../../../flutter/shell/platform/glfw/key_event_handler.cc
 FILE: ../../../flutter/shell/platform/glfw/key_event_handler.h
 FILE: ../../../flutter/shell/platform/glfw/keyboard_hook_handler.h
+FILE: ../../../flutter/shell/platform/glfw/platform_handler.cc
+FILE: ../../../flutter/shell/platform/glfw/platform_handler.h
 FILE: ../../../flutter/shell/platform/glfw/public/flutter_glfw.h
 FILE: ../../../flutter/shell/platform/glfw/text_input_plugin.cc
 FILE: ../../../flutter/shell/platform/glfw/text_input_plugin.h

engine/src/flutter/shell/platform/glfw/BUILD.gn

@@ -36,6 +36,8 @@ source_set("flutter_glfw") {
     "key_event_handler.cc",
     "key_event_handler.h",
     "keyboard_hook_handler.h",
+    "platform_handler.cc",
+    "platform_handler.h",
     "text_input_plugin.cc",
     "text_input_plugin.h",
   ]

engine/src/flutter/shell/platform/glfw/flutter_glfw.cc

@@ -17,6 +17,7 @@
 #include "flutter/shell/platform/embedder/embedder.h"
 #include "flutter/shell/platform/glfw/key_event_handler.h"
 #include "flutter/shell/platform/glfw/keyboard_hook_handler.h"
+#include "flutter/shell/platform/glfw/platform_handler.h"
 #include "flutter/shell/platform/glfw/text_input_plugin.h"
 
 // For compatibility with GTK-based plugins, special message loop setup is
@@ -75,6 +76,9 @@ struct FlutterDesktopWindowControllerState {
   std::vector<std::unique_ptr<flutter::KeyboardHookHandler>>
       keyboard_hook_handlers;
 
+  // Handler for the flutter/platform channel.
+  std::unique_ptr<flutter::PlatformHandler> platform_handler;
+
   // Whether or not the pointer has been added (or if tracking is enabled, has
   // been added since it was last removed).
   bool pointer_currently_added = false;
@@ -606,6 +610,8 @@ FlutterDesktopWindowControllerRef FlutterDesktopCreateWindow(
       std::make_unique<flutter::KeyEventHandler>(internal_plugin_messenger));
   state->keyboard_hook_handlers.push_back(
       std::make_unique<flutter::TextInputPlugin>(internal_plugin_messenger));
+  state->platform_handler = std::make_unique<flutter::PlatformHandler>(
+      internal_plugin_messenger, state->window.get());
 
   // Trigger an initial size callback to send size information to Flutter.
   state->monitor_screen_coordinates_per_inch = GetScreenCoordinatesPerInch();

engine/src/flutter/shell/platform/glfw/platform_handler.cc

@@ -0,0 +1,80 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/glfw/platform_handler.h"
+
+#include <iostream>
+
+#include "flutter/shell/platform/common/cpp/client_wrapper/include/flutter/json_method_codec.h"
+
+static constexpr char kChannelName[] = "flutter/platform";
+
+static constexpr char kGetClipboardDataMethod[] = "Clipboard.getData";
+static constexpr char kSetClipboardDataMethod[] = "Clipboard.setData";
+
+static constexpr char kTextPlainFormat[] = "text/plain";
+static constexpr char kTextKey[] = "text";
+
+static constexpr char kUnknownClipboardFormatError[] =
+    "Unknown clipboard format error";
+
+namespace flutter {
+
+PlatformHandler::PlatformHandler(flutter::BinaryMessenger* messenger,
+                                 GLFWwindow* window)
+    : channel_(std::make_unique<flutter::MethodChannel<rapidjson::Document>>(
+          messenger,
+          kChannelName,
+          &flutter::JsonMethodCodec::GetInstance())),
+      window_(window) {
+  channel_->SetMethodCallHandler(
+      [this](
+          const flutter::MethodCall<rapidjson::Document>& call,
+          std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result) {
+        HandleMethodCall(call, std::move(result));
+      });
+}
+
+void PlatformHandler::HandleMethodCall(
+    const flutter::MethodCall<rapidjson::Document>& method_call,
+    std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result) {
+  const std::string& method = method_call.method_name();
+
+  if (method.compare(kGetClipboardDataMethod) == 0) {
+    // Only one string argument is expected.
+    const rapidjson::Value& format = method_call.arguments()[0];
+
+    if (strcmp(format.GetString(), kTextPlainFormat) != 0) {
+      result->Error(kUnknownClipboardFormatError,
+                    "GLFW clipboard API only supports text.");
+      return;
+    }
+
+    const char* clipboardData = glfwGetClipboardString(window_);
+    if (clipboardData == nullptr) {
+      result->Error(kUnknownClipboardFormatError,
+                    "Failed to retrieve clipboard data from GLFW api.");
+      return;
+    }
+    rapidjson::Document document;
+    document.SetObject();
+    rapidjson::Document::AllocatorType& allocator = document.GetAllocator();
+    document.AddMember(rapidjson::Value(kTextKey, allocator),
+                       rapidjson::Value(clipboardData, allocator), allocator);
+    result->Success(&document);
+  } else if (method.compare(kSetClipboardDataMethod) == 0) {
+    const rapidjson::Value& document = *method_call.arguments();
+    rapidjson::Value::ConstMemberIterator itr = document.FindMember(kTextKey);
+    if (itr == document.MemberEnd()) {
+      result->Error(kUnknownClipboardFormatError,
+                    "Missing text to store on clipboard.");
+      return;
+    }
+    glfwSetClipboardString(window_, itr->value.GetString());
+    result->Success();
+  } else {
+    result->NotImplemented();
+  }
+}
+}  // namespace flutter

engine/src/flutter/shell/platform/glfw/platform_handler.h

@@ -0,0 +1,38 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_GLFW_PLATFORM_HANDLER_H_
+#define FLUTTER_SHELL_PLATFORM_GLFW_PLATFORM_HANDLER_H_
+
+#include <GLFW/glfw3.h>
+
+#include "flutter/shell/platform/common/cpp/client_wrapper/include/flutter/binary_messenger.h"
+#include "flutter/shell/platform/common/cpp/client_wrapper/include/flutter/method_channel.h"
+#include "flutter/shell/platform/glfw/public/flutter_glfw.h"
+#include "rapidjson/document.h"
+
+namespace flutter {
+
+// Handler for internal system channels.
+class PlatformHandler {
+ public:
+  explicit PlatformHandler(flutter::BinaryMessenger* messenger,
+                           GLFWwindow* window);
+
+ private:
+  // Called when a method is called on |channel_|;
+  void HandleMethodCall(
+      const flutter::MethodCall<rapidjson::Document>& method_call,
+      std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result);
+
+  // The MethodChannel used for communication with the Flutter engine.
+  std::unique_ptr<flutter::MethodChannel<rapidjson::Document>> channel_;
+
+  // A reference to the GLFW window.
+  GLFWwindow* window_;
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_GLFW_PLATFORM_HANDLER_H_