[Clipboard] setData and getData implementations added (flutter#76)

* [Clipboard] setData and getData implementations added

and also removed code for hasStrings, as this API is not present in documentation.

[Before] Clipboard.setData and Clipboard.getData feature was not implemented

[After] Naive implementation of clipboard shared only inside Flutter application
and only via Clipboard API. Such decision was done because of supporting partial
functionality on all profiles. CBHM API is supported only on mobile and currently
it is not possible to support it in other way.

Dart code below is able to set/get internal clipboard data:
      ClipboardData cd = ClipboardData(text: 'some text');
      Clipboard.setData(cd);

      Future<ClipboardData?> d = Clipboard.getData(Clipboard.kTextPlain);
      void dataCallback(ClipboardData? d) {
        if (d != null) {
          String? text = d.text;
          if(text != null) {
            print("Clipboard data $text");
          }
        }
      }
      d.then(dataCallback);

* [Clipboard] Fixes after review

* Removed unnecessary mutex
* Cleaned temporary logs

shell/platform/tizen/channels/platform_channel.cc

@@ -214,11 +214,9 @@ void PlatformChannel::HandleMethodCall(
 
     result->Error(error_cause, error_message);
   } else if (method == "Clipboard.getData") {
-    result->NotImplemented();
+    Clipboard::GetData(call, std::move(result));
   } else if (method == "Clipboard.setData") {
-    result->NotImplemented();
-  } else if (method == "Clipboard.hasStrings") {
-    result->NotImplemented();
+    Clipboard::SetData(call, std::move(result));
   } else if (method == "SystemChrome.setPreferredOrientations") {
     if (renderer_) {
       static const std::string kPortraitUp = "DeviceOrientation.portraitUp";
@@ -268,3 +266,53 @@ void PlatformChannel::HandleMethodCall(
     result->NotImplemented();
   }
 }
+
+// Clipboard constants and variables
+namespace Clipboard {
+
+// naive implementation using std::string as a container of internal clipboard
+// data
+std::string string_clipboard = "";
+
+static constexpr char kTextKey[] = "text";
+static constexpr char kTextPlainFormat[] = "text/plain";
+static constexpr char kUnknownClipboardFormatError[] =
+    "Unknown clipboard format error";
+static constexpr char kUnknownClipboardError[] =
+    "Unknown error during clipboard data retrieval";
+
+void GetData(
+    const flutter::MethodCall<rapidjson::Document>& call,
+    std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result) {
+  const rapidjson::Value& format = call.arguments()[0];
+
+  // https://api.flutter.dev/flutter/services/Clipboard/kTextPlain-constant.html
+  // API supports only kTextPlain format
+  if (strcmp(format.GetString(), kTextPlainFormat) != 0) {
+    result->Error(kUnknownClipboardFormatError,
+                  "Clipboard API only supports text.");
+    return;
+  }
+
+  rapidjson::Document document;
+  document.SetObject();
+  rapidjson::Document::AllocatorType& allocator = document.GetAllocator();
+  document.AddMember(rapidjson::Value(kTextKey, allocator),
+                      rapidjson::Value(string_clipboard, allocator),
+                      allocator);
+  result->Success(document);
+}
+
+void SetData(
+    const flutter::MethodCall<rapidjson::Document>& call,
+    std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result) {
+  const rapidjson::Value& document = *call.arguments();
+  rapidjson::Value::ConstMemberIterator itr = document.FindMember(kTextKey);
+  if (itr == document.MemberEnd()) {
+    result->Error(kUnknownClipboardError, "Invalid message format");
+    return;
+  }
+  string_clipboard = itr->value.GetString();
+  result->Success();
+}
+}  // namespace Clipboard

shell/platform/tizen/channels/platform_channel.h

@@ -28,4 +28,13 @@ class PlatformChannel {
   TizenRenderer* renderer_;
 };
 
+namespace Clipboard {
+void GetData(
+    const flutter::MethodCall<rapidjson::Document>& call,
+    std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result);
+void SetData(
+    const flutter::MethodCall<rapidjson::Document>& call,
+    std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result);
+};
+
 #endif  //  EMBEDDER_PLATFORM_CHANNEL_H_