flutter_flutter/shell/platform/windows/text_input_plugin.cc

// 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/windows/text_input_plugin.h"

#include <windows.h>

#include <cstdint>
#include <iostream>

#include "flutter/shell/platform/common/cpp/json_method_codec.h"

static constexpr char kSetEditingStateMethod[] = "TextInput.setEditingState";
static constexpr char kClearClientMethod[] = "TextInput.clearClient";
static constexpr char kSetClientMethod[] = "TextInput.setClient";
static constexpr char kShowMethod[] = "TextInput.show";
static constexpr char kHideMethod[] = "TextInput.hide";

static constexpr char kMultilineInputType[] = "TextInputType.multiline";

static constexpr char kUpdateEditingStateMethod[] =
    "TextInputClient.updateEditingState";
static constexpr char kPerformActionMethod[] = "TextInputClient.performAction";

static constexpr char kTextInputAction[] = "inputAction";
static constexpr char kTextInputType[] = "inputType";
static constexpr char kTextInputTypeName[] = "name";
static constexpr char kComposingBaseKey[] = "composingBase";
static constexpr char kComposingExtentKey[] = "composingExtent";
static constexpr char kSelectionAffinityKey[] = "selectionAffinity";
static constexpr char kAffinityDownstream[] = "TextAffinity.downstream";
static constexpr char kSelectionBaseKey[] = "selectionBase";
static constexpr char kSelectionExtentKey[] = "selectionExtent";
static constexpr char kSelectionIsDirectionalKey[] = "selectionIsDirectional";
static constexpr char kTextKey[] = "text";

static constexpr char kChannelName[] = "flutter/textinput";

static constexpr char kBadArgumentError[] = "Bad Arguments";
static constexpr char kInternalConsistencyError[] =
    "Internal Consistency Error";

namespace flutter {

void TextInputPlugin::TextHook(FlutterWindowsView* view,
                               const std::u16string& text) {
  if (active_model_ == nullptr) {
    return;
  }
  active_model_->AddText(text);
  SendStateUpdate(*active_model_);
}

void TextInputPlugin::KeyboardHook(FlutterWindowsView* view,
                                   int key,
                                   int scancode,
                                   int action,
                                   char32_t character) {
  if (active_model_ == nullptr) {
    return;
  }
  if (action == WM_KEYDOWN) {
    switch (key) {
      case VK_LEFT:
        if (active_model_->MoveCursorBack()) {
          SendStateUpdate(*active_model_);
        }
        break;
      case VK_RIGHT:
        if (active_model_->MoveCursorForward()) {
          SendStateUpdate(*active_model_);
        }
        break;
      case VK_END:
        active_model_->MoveCursorToEnd();
        SendStateUpdate(*active_model_);
        break;
      case VK_HOME:
        active_model_->MoveCursorToBeginning();
        SendStateUpdate(*active_model_);
        break;
      case VK_BACK:
        if (active_model_->Backspace()) {
          SendStateUpdate(*active_model_);
        }
        break;
      case VK_DELETE:
        if (active_model_->Delete()) {
          SendStateUpdate(*active_model_);
        }
        break;
      case VK_RETURN:
        EnterPressed(active_model_.get());
        break;
      default:
        break;
    }
  }
}

TextInputPlugin::TextInputPlugin(flutter::BinaryMessenger* messenger)
    : channel_(std::make_unique<flutter::MethodChannel<rapidjson::Document>>(
          messenger,
          kChannelName,
          &flutter::JsonMethodCodec::GetInstance())),
      active_model_(nullptr) {
  channel_->SetMethodCallHandler(
      [this](
          const flutter::MethodCall<rapidjson::Document>& call,
          std::unique_ptr<flutter::MethodResult<rapidjson::Document>> result) {
        HandleMethodCall(call, std::move(result));
      });
}

TextInputPlugin::~TextInputPlugin() = default;

void TextInputPlugin::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(kShowMethod) == 0 || method.compare(kHideMethod) == 0) {
    // These methods are no-ops.
  } else if (method.compare(kClearClientMethod) == 0) {
    active_model_ = nullptr;
  } else if (method.compare(kSetClientMethod) == 0) {
    if (!method_call.arguments() || method_call.arguments()->IsNull()) {
      result->Error(kBadArgumentError, "Method invoked without args");
      return;
    }
    const rapidjson::Document& args = *method_call.arguments();

    const rapidjson::Value& client_id_json = args[0];
    const rapidjson::Value& client_config = args[1];
    if (client_id_json.IsNull()) {
      result->Error(kBadArgumentError, "Could not set client, ID is null.");
      return;
    }
    if (client_config.IsNull()) {
      result->Error(kBadArgumentError,
                    "Could not set client, missing arguments.");
      return;
    }
    client_id_ = client_id_json.GetInt();
    input_action_ = "";
    auto input_action_json = client_config.FindMember(kTextInputAction);
    if (input_action_json != client_config.MemberEnd() &&
        input_action_json->value.IsString()) {
      input_action_ = input_action_json->value.GetString();
    }
    input_type_ = "";
    auto input_type_info_json = client_config.FindMember(kTextInputType);
    if (input_type_info_json != client_config.MemberEnd() &&
        input_type_info_json->value.IsObject()) {
      auto input_type_json =
          input_type_info_json->value.FindMember(kTextInputTypeName);
      if (input_type_json != input_type_info_json->value.MemberEnd() &&
          input_type_json->value.IsString()) {
        input_type_ = input_type_json->value.GetString();
      }
    }
    active_model_ = std::make_unique<TextInputModel>();
  } else if (method.compare(kSetEditingStateMethod) == 0) {
    if (!method_call.arguments() || method_call.arguments()->IsNull()) {
      result->Error(kBadArgumentError, "Method invoked without args");
      return;
    }
    const rapidjson::Document& args = *method_call.arguments();

    if (active_model_ == nullptr) {
      result->Error(
          kInternalConsistencyError,
          "Set editing state has been invoked, but no client is set.");
      return;
    }
    auto text = args.FindMember(kTextKey);
    if (text == args.MemberEnd() || text->value.IsNull()) {
      result->Error(kBadArgumentError,
                    "Set editing state has been invoked, but without text.");
      return;
    }
    auto selection_base = args.FindMember(kSelectionBaseKey);
    auto selection_extent = args.FindMember(kSelectionExtentKey);
    if (selection_base == args.MemberEnd() || selection_base->value.IsNull() ||
        selection_extent == args.MemberEnd() ||
        selection_extent->value.IsNull()) {
      result->Error(kInternalConsistencyError,
                    "Selection base/extent values invalid.");
      return;
    }
    // Flutter uses -1/-1 for invalid; translate that to 0/0 for the model.
    int base = selection_base->value.GetInt();
    int extent = selection_extent->value.GetInt();
    if (base == -1 && extent == -1) {
      base = extent = 0;
    }
    active_model_->SetEditingState(base, extent, text->value.GetString());
  } else {
    result->NotImplemented();
    return;
  }
  // All error conditions return early, so if nothing has gone wrong indicate
  // success.
  result->Success();
}

void TextInputPlugin::SendStateUpdate(const TextInputModel& model) {
  auto args = std::make_unique<rapidjson::Document>(rapidjson::kArrayType);
  auto& allocator = args->GetAllocator();
  args->PushBack(client_id_, allocator);

  rapidjson::Value editing_state(rapidjson::kObjectType);
  editing_state.AddMember(kComposingBaseKey, -1, allocator);
  editing_state.AddMember(kComposingExtentKey, -1, allocator);
  editing_state.AddMember(kSelectionAffinityKey, kAffinityDownstream,
                          allocator);
  editing_state.AddMember(kSelectionBaseKey, model.selection_base(), allocator);
  editing_state.AddMember(kSelectionExtentKey, model.selection_extent(),
                          allocator);
  editing_state.AddMember(kSelectionIsDirectionalKey, false, allocator);
  editing_state.AddMember(
      kTextKey, rapidjson::Value(model.GetText(), allocator).Move(), allocator);
  args->PushBack(editing_state, allocator);

  channel_->InvokeMethod(kUpdateEditingStateMethod, std::move(args));
}

void TextInputPlugin::EnterPressed(TextInputModel* model) {
  if (input_type_ == kMultilineInputType) {
    model->AddText(std::u16string({u'\n'}));
    SendStateUpdate(*model);
  }
  auto args = std::make_unique<rapidjson::Document>(rapidjson::kArrayType);
  auto& allocator = args->GetAllocator();
  args->PushBack(client_id_, allocator);
  args->PushBack(rapidjson::Value(input_action_, allocator).Move(), allocator);

  channel_->InvokeMethod(kPerformActionMethod, std::move(args));
}

}  // namespace flutter