...

5 files changed, 463 insertions, 517 deletions

diff --git a/src/ui/CMakeLists.txt b/src/ui/CMakeLists.txt
index 28200eb5..d1c1e830 100644
--- a/src/ui/CMakeLists.txt
+++ b/src/ui/CMakeLists.txt
@@ -20,7 +20,7 @@ add_library(cru_ui STATIC
 	controls/StackLayout.cpp
 	controls/TextBlock.cpp
 	controls/TextBox.cpp
-	controls/TextControlService.hpp
+	controls/TextHostControlService.cpp
 	controls/Window.cpp
 	events/UiEvent.cpp
 	helper/BorderStyle.cpp
@@ -60,8 +60,9 @@ target_sources(cru_ui PUBLIC
 	${CRU_UI_INCLUDE_DIR}/controls/Popup.hpp
 	${CRU_UI_INCLUDE_DIR}/controls/RootControl.hpp
 	${CRU_UI_INCLUDE_DIR}/controls/StackLayout.hpp
-	${CRU_UI_INCLUDE_DIR}/controls/TextBox.hpp
 	${CRU_UI_INCLUDE_DIR}/controls/TextBlock.hpp
+	${CRU_UI_INCLUDE_DIR}/controls/TextBox.hpp
+	${CRU_UI_INCLUDE_DIR}/controls/TextHostControlService.hpp
 	${CRU_UI_INCLUDE_DIR}/controls/Window.hpp
 	${CRU_UI_INCLUDE_DIR}/events/UiEvent.hpp
 	${CRU_UI_INCLUDE_DIR}/helper/ClickDetector.hpp
diff --git a/src/ui/controls/TextBlock.cpp b/src/ui/controls/TextBlock.cpp
index 1a432582..0724edcf 100644
--- a/src/ui/controls/TextBlock.cpp
+++ b/src/ui/controls/TextBlock.cpp
@@ -1,6 +1,5 @@
 #include "cru/ui/controls/TextBlock.hpp"
 
-#include "TextControlService.hpp"
 #include "cru/ui/UiManager.hpp"
 #include "cru/ui/render/CanvasRenderObject.hpp"
 #include "cru/ui/render/StackLayoutRenderObject.hpp"
@@ -27,7 +26,7 @@ TextBlock::TextBlock() {
 
   text_render_object_->SetAttachedControl(this);
 
-  service_ = std::make_unique<TextControlService<TextBlock>>(this);
+  service_ = std::make_unique<TextHostControlService>(this);
 
   service_->SetEnabled(false);
   service_->SetEditable(false);
diff --git a/src/ui/controls/TextBox.cpp b/src/ui/controls/TextBox.cpp
index d8317a8c..e1acaee0 100644
--- a/src/ui/controls/TextBox.cpp
+++ b/src/ui/controls/TextBox.cpp
@@ -1,6 +1,5 @@
 #include "cru/ui/controls/TextBox.hpp"
 
-#include "TextControlService.hpp"
 #include "cru/ui/UiManager.hpp"
 #include "cru/ui/render/BorderRenderObject.hpp"
 #include "cru/ui/render/CanvasRenderObject.hpp"
@@ -30,7 +29,7 @@ TextBox::TextBox()
   text_render_object_->SetAttachedControl(this);
   text_render_object_->SetMinSize(Size{100, 24});
 
-  service_ = std::make_unique<TextControlService<TextBox>>(this);
+  service_ = std::make_unique<TextHostControlService>(this);
   service_->SetEnabled(true);
   service_->SetEditable(true);
 
diff --git a/src/ui/controls/TextControlService.hpp b/src/ui/controls/TextControlService.hpp
deleted file mode 100644
index c535512f..00000000
--- a/src/ui/controls/TextControlService.hpp
+++ /dev/null
@@ -1,511 +0,0 @@
-#pragma once
-#include "../Helper.hpp"
-#include "cru/common/Logger.hpp"
-#include "cru/common/StringUtil.hpp"
-#include "cru/platform/graphics/Font.hpp"
-#include "cru/platform/graphics/Painter.hpp"
-#include "cru/platform/gui/Cursor.hpp"
-#include "cru/platform/gui/InputMethod.hpp"
-#include "cru/platform/gui/UiApplication.hpp"
-#include "cru/platform/gui/Window.hpp"
-#include "cru/ui/Base.hpp"
-#include "cru/ui/DebugFlags.hpp"
-#include "cru/ui/controls/Control.hpp"
-#include "cru/ui/events/UiEvent.hpp"
-#include "cru/ui/helper/ShortcutHub.hpp"
-#include "cru/ui/host/WindowHost.hpp"
-#include "cru/ui/render/CanvasRenderObject.hpp"
-#include "cru/ui/render/ScrollRenderObject.hpp"
-#include "cru/ui/render/TextRenderObject.hpp"
-
-#include <string>
-
-namespace cru::ui::controls {
-constexpr int k_default_caret_blink_duration = 500;
-
-// TControl should inherits `Control` and has following methods:
-// ```
-// gsl::not_null<render::TextRenderObject*> GetTextRenderObject();
-// render::ScrollRenderObject* GetScrollRenderObject();
-// ```
-template <typename TControl>
-class TextControlService : public Object {
-  CRU_DEFINE_CLASS_LOG_TAG(u"cru::ui::controls::TextControlService")
-
- public:
-  TextControlService(gsl::not_null<TControl*> control) : control_(control) {}
-
-  CRU_DELETE_COPY(TextControlService)
-  CRU_DELETE_MOVE(TextControlService)
-
-  ~TextControlService() = default;
-
- public:
-  bool IsEnabled() { return enable_; }
-
-  void SetEnabled(bool enable) {
-    if (enable == this->enable_) return;
-    this->enable_ = enable;
-    if (enable) {
-      this->SetUpHandlers();
-      if (this->caret_visible_) {
-        this->SetupCaret();
-      }
-      this->control_->SetCursor(
-          GetUiApplication()->GetCursorManager()->GetSystemCursor(
-              platform::gui::SystemCursorType::IBeam));
-    } else {
-      this->AbortSelection();
-      this->TearDownHandlers();
-      this->TearDownCaret();
-      this->control_->SetCursor(nullptr);
-    }
-  }
-
-  bool IsEditable() { return this->editable_; }
-
-  void SetEditable(bool editable) {
-    this->editable_ = editable;
-    if (!editable) CancelComposition();
-  }
-
-  std::u16string GetText() { return this->text_; }
-  std::u16string_view GetTextView() { return this->text_; }
-  void SetText(std::u16string text, bool stop_composition = false) {
-    this->text_ = std::move(text);
-    CoerceSelection();
-    if (stop_composition) {
-      CancelComposition();
-    }
-    SyncTextRenderObject();
-  }
-
-  void InsertText(gsl::index position, std::u16string_view text,
-                  bool stop_composition = false) {
-    if (!Utf16IsValidInsertPosition(this->text_, position)) {
-      log::TagError(log_tag, u"Invalid text insert position.");
-      return;
-    }
-    this->text_.insert(this->text_.cbegin() + position, text.begin(),
-                       text.end());
-    if (stop_composition) {
-      CancelComposition();
-    }
-    SyncTextRenderObject();
-  }
-
-  void DeleteChar(gsl::index position, bool stop_composition = false) {
-    if (!Utf16IsValidInsertPosition(this->text_, position)) {
-      log::TagError(log_tag, u"Invalid text delete position.");
-      return;
-    }
-    if (position == static_cast<gsl::index>(this->text_.size())) return;
-    Index next;
-    Utf16NextCodePoint(this->text_, position, &next);
-    this->DeleteText(TextRange::FromTwoSides(position, next), stop_composition);
-  }
-
-  // Return the position of deleted character.
-  gsl::index DeleteCharPrevious(gsl::index position,
-                                bool stop_composition = false) {
-    if (!Utf16IsValidInsertPosition(this->text_, position)) {
-      log::TagError(log_tag, u"Invalid text delete position.");
-      return 0;
-    }
-    if (position == 0) return 0;
-    Index previous;
-    Utf16PreviousCodePoint(this->text_, position, &previous);
-    this->DeleteText(TextRange::FromTwoSides(previous, position),
-                     stop_composition);
-    return previous;
-  }
-
-  void DeleteText(TextRange range, bool stop_composition = false) {
-    if (range.count == 0) return;
-    range = range.Normalize();
-    if (!Utf16IsValidInsertPosition(this->text_, range.GetStart())) {
-      log::TagError(log_tag, u"Invalid text delete start position.");
-      return;
-    }
-    if (!Utf16IsValidInsertPosition(this->text_, range.GetStart())) {
-      log::TagError(log_tag, u"Invalid text delete end position.");
-      return;
-    }
-    this->text_.erase(this->text_.cbegin() + range.GetStart(),
-                      this->text_.cbegin() + range.GetEnd());
-    this->CoerceSelection();
-    if (stop_composition) {
-      CancelComposition();
-    }
-    this->SyncTextRenderObject();
-  }
-
-  platform::gui::IInputMethodContext* GetInputMethodContext() {
-    host::WindowHost* host = this->control_->GetWindowHost();
-    if (!host) return nullptr;
-    platform::gui::INativeWindow* native_window = host->GetNativeWindow();
-    if (!native_window) return nullptr;
-    return native_window->GetInputMethodContext();
-  }
-
-  void CancelComposition() {
-    auto input_method_context = GetInputMethodContext();
-    if (input_method_context == nullptr) return;
-    input_method_context->CancelComposition();
-  }
-
-  std::optional<platform::gui::CompositionText> GetCompositionInfo() {
-    auto input_method_context = GetInputMethodContext();
-    if (input_method_context == nullptr) return std::nullopt;
-    auto composition_info = input_method_context->GetCompositionText();
-    if (composition_info.text.empty()) return std::nullopt;
-    return composition_info;
-  }
-
-  bool IsCaretVisible() { return caret_visible_; }
-
-  void SetCaretVisible(bool visible) {
-    if (visible == this->caret_visible_) return;
-
-    this->caret_visible_ = visible;
-
-    if (this->enable_) {
-      if (visible) {
-        this->SetupCaret();
-      } else {
-        this->TearDownCaret();
-      }
-    }
-  }
-
-  int GetCaretBlinkDuration() { return caret_blink_duration_; }
-
-  void SetCaretBlinkDuration(int milliseconds) {
-    if (this->caret_blink_duration_ == milliseconds) return;
-
-    if (this->enable_ && this->caret_visible_) {
-      this->TearDownCaret();
-      this->SetupCaret();
-    }
-  }
-
-  gsl::not_null<render::TextRenderObject*> GetTextRenderObject() {
-    return this->control_->GetTextRenderObject();
-  }
-
-  render::ScrollRenderObject* GetScrollRenderObject() {
-    return this->control_->GetScrollRenderObject();
-  }
-
-  gsl::index GetCaretPosition() { return selection_.GetEnd(); }
-
-  TextRange GetSelection() { return selection_; }
-
-  void SetSelection(gsl::index caret_position) {
-    this->SetSelection(TextRange{caret_position, 0});
-  }
-
-  void SetSelection(TextRange selection, bool scroll_to_caret = true) {
-    this->selection_ = selection;
-    CoerceSelection();
-    SyncTextRenderObject();
-    if (scroll_to_caret) {
-      this->ScrollToCaret();
-    }
-  }
-
-  void DeleteSelectedText() {
-    this->DeleteText(GetSelection());
-    SetSelection(GetSelection().Normalize().GetStart());
-  }
-
-  // If some text is selected, then they are deleted first. Then insert text
-  // into caret position.
-  void ReplaceSelectedText(std::u16string_view text) {
-    DeleteSelectedText();
-    InsertText(GetSelection().GetStart(), text);
-    SetSelection(GetSelection().GetStart() + text.size());
-  }
-
-  void ScrollToCaret() {
-    if (const auto scroll_render_object = this->GetScrollRenderObject()) {
-      this->control_->GetWindowHost()->RunAfterLayoutStable(
-          [this, scroll_render_object]() {
-            const auto caret_rect = this->GetTextRenderObject()->GetCaretRect();
-            scroll_render_object->ScrollToContain(caret_rect, Thickness{5.f});
-          });
-    }
-  }
-
- private:
-  void CoerceSelection() {
-    this->selection_ = this->selection_.CoerceInto(0, text_.size());
-  }
-
-  void AbortSelection() {
-    if (this->select_down_button_.has_value()) {
-      this->control_->ReleaseMouse();
-      this->select_down_button_ = std::nullopt;
-    }
-    this->GetTextRenderObject()->SetSelectionRange(std::nullopt);
-  }
-
-  void SetupCaret() {
-    const auto application = GetUiApplication();
-    this->GetTextRenderObject()->SetDrawCaret(true);
-    this->caret_timer_canceler_.Reset(application->SetInterval(
-        std::chrono::milliseconds(this->caret_blink_duration_),
-        [this] { this->GetTextRenderObject()->ToggleDrawCaret(); }));
-  }
-
-  void TearDownCaret() {
-    this->caret_timer_canceler_.Reset();
-    this->GetTextRenderObject()->SetDrawCaret(false);
-  }
-
-  void SyncTextRenderObject() {
-    const auto text_render_object = this->GetTextRenderObject();
-    const auto composition_info = this->GetCompositionInfo();
-    if (composition_info) {
-      const auto caret_position = GetCaretPosition();
-      auto text = this->text_;
-      text.insert(caret_position, composition_info->text);
-      text_render_object->SetText(text);
-      text_render_object->SetCaretPosition(
-          caret_position + composition_info->selection.GetEnd());
-      auto selection = composition_info->selection;
-      selection.position += caret_position;
-      text_render_object->SetSelectionRange(selection);
-    } else {
-      text_render_object->SetText(this->text_);
-      text_render_object->SetCaretPosition(this->GetCaretPosition());
-      text_render_object->SetSelectionRange(this->GetSelection());
-    }
-  }
-
-  void StartSelection(Index start) {
-    SetSelection(start);
-    if constexpr (debug_flags::text_service)
-      log::TagDebug(log_tag, u"Text selection started, position: {}.", start);
-  }
-
-  void UpdateSelection(Index new_end) {
-    auto selection = GetSelection();
-    selection.AdjustEnd(new_end);
-    this->SetSelection(selection);
-    if constexpr (debug_flags::text_service)
-      log::TagDebug(log_tag, u"Text selection updated, range: {}, {}.",
-                    selection.GetStart(), selection.GetEnd());
-  }
-
-  void UpdateInputMethodPosition() {
-    if (auto input_method_context = this->GetInputMethodContext()) {
-      Point right_bottom =
-          this->GetTextRenderObject()->GetTotalOffset() +
-          this->GetTextRenderObject()->GetCaretRect().GetRightBottom();
-      right_bottom.x += 5;
-      right_bottom.y += 5;
-
-      if constexpr (debug_flags::text_service) {
-        log::TagDebug(log_tag,
-                      u"Calculate input method candidate window position: {}.",
-                      right_bottom.ToDebugString());
-      }
-
-      input_method_context->SetCandidateWindowPosition(right_bottom);
-    }
-  }
-
-  template <typename TArgs>
-  void SetupOneHandler(event::RoutedEvent<TArgs>* (Control::*event)(),
-                       void (TextControlService::*handler)(
-                           typename event::RoutedEvent<TArgs>::EventArgs)) {
-    this->event_guard_ += (this->control_->*event)()->Direct()->AddHandler(
-        std::bind(handler, this, std::placeholders::_1));
-  }
-
-  void SetUpHandlers() {
-    Expects(event_guard_.IsEmpty());
-
-    SetupOneHandler(&Control::MouseMoveEvent,
-                    &TextControlService::MouseMoveHandler);
-    SetupOneHandler(&Control::MouseDownEvent,
-                    &TextControlService::MouseDownHandler);
-    SetupOneHandler(&Control::MouseUpEvent,
-                    &TextControlService::MouseUpHandler);
-    SetupOneHandler(&Control::KeyDownEvent,
-                    &TextControlService::KeyDownHandler);
-    SetupOneHandler(&Control::GainFocusEvent,
-                    &TextControlService::GainFocusHandler);
-    SetupOneHandler(&Control::LoseFocusEvent,
-                    &TextControlService::LoseFocusHandler);
-
-    shortcut_hub_.Install(control_);
-  }
-
-  void TearDownHandlers() {
-    event_guard_.Clear();
-    shortcut_hub_.Uninstall();
-  }
-
-  void MouseMoveHandler(event::MouseEventArgs& args) {
-    if (this->select_down_button_.has_value()) {
-      const auto text_render_object = this->GetTextRenderObject();
-      const auto result = text_render_object->TextHitTest(
-          args.GetPointToContent(text_render_object));
-      const auto position = result.position + (result.trailing ? 1 : 0);
-      UpdateSelection(position);
-    }
-  }
-
-  void MouseDownHandler(event::MouseButtonEventArgs& args) {
-    if (this->select_down_button_.has_value()) {
-      return;
-    } else {
-      this->control_->SetFocus();
-      if (!this->control_->CaptureMouse()) return;
-      const auto text_render_object = this->GetTextRenderObject();
-      this->select_down_button_ = args.GetButton();
-      const auto result = text_render_object->TextHitTest(
-          args.GetPointToContent(text_render_object));
-      const auto position = result.position + (result.trailing ? 1 : 0);
-      StartSelection(position);
-    }
-  }
-
-  void MouseUpHandler(event::MouseButtonEventArgs& args) {
-    if (this->select_down_button_.has_value() &&
-        this->select_down_button_.value() == args.GetButton()) {
-      this->control_->ReleaseMouse();
-      this->select_down_button_ = std::nullopt;
-    }
-  }
-
-  void KeyDownHandler(event::KeyEventArgs& args) {
-    const auto key_code = args.GetKeyCode();
-    using cru::platform::gui::KeyCode;
-    using cru::platform::gui::KeyModifiers;
-
-    switch (key_code) {
-      case KeyCode::Backspace: {
-        if (!IsEditable()) return;
-        const auto selection = GetSelection();
-        if (selection.count == 0) {
-          SetSelection(DeleteCharPrevious(GetCaretPosition()));
-        } else {
-          this->DeleteSelectedText();
-        }
-      } break;
-      case KeyCode::Delete: {
-        if (!IsEditable()) return;
-        const auto selection = GetSelection();
-        if (selection.count == 0) {
-          DeleteChar(GetCaretPosition());
-        } else {
-          this->DeleteSelectedText();
-        }
-      } break;
-      case KeyCode::Left: {
-        const auto key_modifier = args.GetKeyModifier();
-        const bool shift = key_modifier & KeyModifiers::shift;
-        auto text = this->GetTextView();
-        if (shift) {
-          auto selection = this->GetSelection();
-          gsl::index new_position;
-          Utf16PreviousCodePoint(text, selection.GetEnd(), &new_position);
-          selection.AdjustEnd(new_position);
-          this->SetSelection(selection);
-        } else {
-          const auto caret = this->GetCaretPosition();
-          gsl::index new_position;
-          Utf16PreviousCodePoint(text, caret, &new_position);
-          this->SetSelection(new_position);
-        }
-      } break;
-      case KeyCode::Right: {
-        const auto key_modifier = args.GetKeyModifier();
-        const bool shift = key_modifier & KeyModifiers::shift;
-        auto text = this->GetTextView();
-        if (shift) {
-          auto selection = this->GetSelection();
-          gsl::index new_position;
-          Utf16NextCodePoint(text, selection.GetEnd(), &new_position);
-          selection.AdjustEnd(new_position);
-          this->SetSelection(selection);
-        } else {
-          const auto caret = this->GetCaretPosition();
-          gsl::index new_position;
-          Utf16NextCodePoint(text, caret, &new_position);
-          this->SetSelection(new_position);
-        }
-      } break;
-      default:
-        break;
-    }
-  }
-
-  void GainFocusHandler(event::FocusChangeEventArgs& args) {
-    CRU_UNUSED(args);
-    if (editable_) {
-      auto input_method_context = GetInputMethodContext();
-      if (input_method_context == nullptr) return;
-      input_method_context->EnableIME();
-      auto sync = [this](std::nullptr_t) {
-        this->SyncTextRenderObject();
-        ScrollToCaret();
-      };
-      input_method_context_event_guard_ +=
-          input_method_context->CompositionStartEvent()->AddHandler(
-              [this](std::nullptr_t) { this->DeleteSelectedText(); });
-      input_method_context_event_guard_ +=
-          input_method_context->CompositionEvent()->AddHandler(sync);
-      input_method_context_event_guard_ +=
-          input_method_context->CompositionEndEvent()->AddHandler(sync);
-      input_method_context_event_guard_ +=
-          input_method_context->TextEvent()->AddHandler(
-              [this](const std::u16string_view& text) {
-                if (text == u"\b") return;
-                this->ReplaceSelectedText(text);
-              });
-
-      host::WindowHost* window_host = control_->GetWindowHost();
-      if (window_host)
-        input_method_context_event_guard_ +=
-            window_host->AfterLayoutEvent()->AddHandler(
-                [this](auto) { this->UpdateInputMethodPosition(); });
-      SetCaretVisible(true);
-    }
-  }
-
-  void LoseFocusHandler(event::FocusChangeEventArgs& args) {
-    if (!args.IsWindow()) this->AbortSelection();
-    input_method_context_event_guard_.Clear();
-    auto input_method_context = GetInputMethodContext();
-    if (input_method_context) {
-      input_method_context->DisableIME();
-    }
-    SetCaretVisible(false);
-    SyncTextRenderObject();
-  }
-
- private:
-  gsl::not_null<TControl*> control_;
-  EventRevokerListGuard event_guard_;
-  EventRevokerListGuard input_method_context_event_guard_;
-
-  std::u16string text_;
-  TextRange selection_;
-
-  bool enable_ = false;
-  bool editable_ = false;
-
-  bool caret_visible_ = false;
-  platform::gui::TimerAutoCanceler caret_timer_canceler_;
-  int caret_blink_duration_ = k_default_caret_blink_duration;
-
-  helper::ShortcutHub shortcut_hub_;
-
-  // nullopt means not selecting
-  std::optional<MouseButton> select_down_button_;
-};
-}  // namespace cru::ui::controls
diff --git a/src/ui/controls/TextHostControlService.cpp b/src/ui/controls/TextHostControlService.cpp
new file mode 100644
index 00000000..1ce3f642
--- /dev/null
+++ b/src/ui/controls/TextHostControlService.cpp
@@ -0,0 +1,458 @@
+#include "cru/ui/controls/TextHostControlService.hpp"
+
+#include "../Helper.hpp"
+#include "cru/common/Logger.hpp"
+#include "cru/common/StringUtil.hpp"
+#include "cru/platform/graphics/Font.hpp"
+#include "cru/platform/graphics/Painter.hpp"
+#include "cru/platform/gui/Cursor.hpp"
+#include "cru/platform/gui/InputMethod.hpp"
+#include "cru/platform/gui/UiApplication.hpp"
+#include "cru/platform/gui/Window.hpp"
+#include "cru/ui/Base.hpp"
+#include "cru/ui/DebugFlags.hpp"
+#include "cru/ui/controls/Control.hpp"
+#include "cru/ui/events/UiEvent.hpp"
+#include "cru/ui/helper/ShortcutHub.hpp"
+#include "cru/ui/host/WindowHost.hpp"
+#include "cru/ui/render/CanvasRenderObject.hpp"
+#include "cru/ui/render/ScrollRenderObject.hpp"
+#include "cru/ui/render/TextRenderObject.hpp"
+#include "gsl/gsl_assert"
+#include "gsl/pointers"
+
+namespace cru::ui::controls {
+TextHostControlService::TextHostControlService(gsl::not_null<Control*> control)
+    : control_(control),
+      text_host_control_(dynamic_cast<ITextHostControl*>(control.get())) {}
+
+void TextHostControlService::SetEnabled(bool enable) {
+  if (enable == this->enable_) return;
+  this->enable_ = enable;
+  if (enable) {
+    this->SetUpHandlers();
+    if (this->caret_visible_) {
+      this->SetupCaret();
+    }
+    this->control_->SetCursor(
+        GetUiApplication()->GetCursorManager()->GetSystemCursor(
+            platform::gui::SystemCursorType::IBeam));
+  } else {
+    this->AbortSelection();
+    this->TearDownHandlers();
+    this->TearDownCaret();
+    this->control_->SetCursor(nullptr);
+  }
+}
+
+void TextHostControlService::SetEditable(bool editable) {
+  this->editable_ = editable;
+  if (!editable) CancelComposition();
+}
+
+void TextHostControlService::SetText(std::u16string text,
+                                     bool stop_composition) {
+  this->text_ = std::move(text);
+  CoerceSelection();
+  if (stop_composition) {
+    CancelComposition();
+  }
+  SyncTextRenderObject();
+}
+
+void TextHostControlService::InsertText(gsl::index position,
+                                        std::u16string_view text,
+                                        bool stop_composition) {
+  if (!Utf16IsValidInsertPosition(this->text_, position)) {
+    log::TagError(log_tag, u"Invalid text insert position.");
+    return;
+  }
+  this->text_.insert(this->text_.cbegin() + position, text.begin(), text.end());
+  if (stop_composition) {
+    CancelComposition();
+  }
+  SyncTextRenderObject();
+}
+
+void TextHostControlService::DeleteChar(gsl::index position,
+                                        bool stop_composition) {
+  if (!Utf16IsValidInsertPosition(this->text_, position)) {
+    log::TagError(log_tag, u"Invalid text delete position.");
+    return;
+  }
+  if (position == static_cast<gsl::index>(this->text_.size())) return;
+  Index next;
+  Utf16NextCodePoint(this->text_, position, &next);
+  this->DeleteText(TextRange::FromTwoSides(position, next), stop_composition);
+}
+
+// Return the position of deleted character.
+gsl::index TextHostControlService::DeleteCharPrevious(gsl::index position,
+                                                      bool stop_composition) {
+  if (!Utf16IsValidInsertPosition(this->text_, position)) {
+    log::TagError(log_tag, u"Invalid text delete position.");
+    return 0;
+  }
+  if (position == 0) return 0;
+  Index previous;
+  Utf16PreviousCodePoint(this->text_, position, &previous);
+  this->DeleteText(TextRange::FromTwoSides(previous, position),
+                   stop_composition);
+  return previous;
+}
+
+void TextHostControlService::DeleteText(TextRange range,
+                                        bool stop_composition) {
+  if (range.count == 0) return;
+  range = range.Normalize();
+  if (!Utf16IsValidInsertPosition(this->text_, range.GetStart())) {
+    log::TagError(log_tag, u"Invalid text delete start position.");
+    return;
+  }
+  if (!Utf16IsValidInsertPosition(this->text_, range.GetStart())) {
+    log::TagError(log_tag, u"Invalid text delete end position.");
+    return;
+  }
+  this->text_.erase(this->text_.cbegin() + range.GetStart(),
+                    this->text_.cbegin() + range.GetEnd());
+  this->CoerceSelection();
+  if (stop_composition) {
+    CancelComposition();
+  }
+  this->SyncTextRenderObject();
+}
+
+platform::gui::IInputMethodContext*
+TextHostControlService ::GetInputMethodContext() {
+  host::WindowHost* host = this->control_->GetWindowHost();
+  if (!host) return nullptr;
+  platform::gui::INativeWindow* native_window = host->GetNativeWindow();
+  if (!native_window) return nullptr;
+  return native_window->GetInputMethodContext();
+}
+
+void TextHostControlService::CancelComposition() {
+  auto input_method_context = GetInputMethodContext();
+  if (input_method_context == nullptr) return;
+  input_method_context->CancelComposition();
+}
+
+std::optional<platform::gui::CompositionText>
+TextHostControlService::GetCompositionInfo() {
+  auto input_method_context = GetInputMethodContext();
+  if (input_method_context == nullptr) return std::nullopt;
+  auto composition_info = input_method_context->GetCompositionText();
+  if (composition_info.text.empty()) return std::nullopt;
+  return composition_info;
+}
+
+void TextHostControlService::SetCaretVisible(bool visible) {
+  if (visible == this->caret_visible_) return;
+
+  this->caret_visible_ = visible;
+
+  if (this->enable_) {
+    if (visible) {
+      this->SetupCaret();
+    } else {
+      this->TearDownCaret();
+    }
+  }
+}
+
+void TextHostControlService::SetCaretBlinkDuration(int milliseconds) {
+  if (this->caret_blink_duration_ == milliseconds) return;
+
+  if (this->enable_ && this->caret_visible_) {
+    this->TearDownCaret();
+    this->SetupCaret();
+  }
+}
+
+void TextHostControlService::ScrollToCaret() {
+  if (const auto scroll_render_object = this->GetScrollRenderObject()) {
+    this->control_->GetWindowHost()->RunAfterLayoutStable(
+        [this, scroll_render_object]() {
+          const auto caret_rect = this->GetTextRenderObject()->GetCaretRect();
+          scroll_render_object->ScrollToContain(caret_rect, Thickness{5.f});
+        });
+  }
+}
+
+gsl::not_null<render::TextRenderObject*>
+TextHostControlService::GetTextRenderObject() {
+  return this->text_host_control_->GetTextRenderObject();
+}
+
+render::ScrollRenderObject* TextHostControlService::GetScrollRenderObject() {
+  return this->text_host_control_->GetScrollRenderObject();
+}
+
+void TextHostControlService::SetSelection(gsl::index caret_position) {
+  this->SetSelection(TextRange{caret_position, 0});
+}
+
+void TextHostControlService::SetSelection(TextRange selection,
+                                          bool scroll_to_caret) {
+  this->selection_ = selection;
+  CoerceSelection();
+  SyncTextRenderObject();
+  if (scroll_to_caret) {
+    this->ScrollToCaret();
+  }
+}
+
+void TextHostControlService::ReplaceSelectedText(std::u16string_view text) {
+  DeleteSelectedText();
+  InsertText(GetSelection().GetStart(), text);
+  SetSelection(GetSelection().GetStart() + text.size());
+}
+
+void TextHostControlService::DeleteSelectedText() {
+  this->DeleteText(GetSelection());
+  SetSelection(GetSelection().Normalize().GetStart());
+}
+
+void TextHostControlService::SetupCaret() {
+  const auto application = GetUiApplication();
+  this->GetTextRenderObject()->SetDrawCaret(true);
+  this->caret_timer_canceler_.Reset(application->SetInterval(
+      std::chrono::milliseconds(this->caret_blink_duration_),
+      [this] { this->GetTextRenderObject()->ToggleDrawCaret(); }));
+}
+
+void TextHostControlService::TearDownCaret() {
+  this->caret_timer_canceler_.Reset();
+  this->GetTextRenderObject()->SetDrawCaret(false);
+}
+
+void TextHostControlService::CoerceSelection() {
+  this->selection_ = this->selection_.CoerceInto(0, text_.size());
+}
+
+void TextHostControlService::StartSelection(Index start) {
+  SetSelection(start);
+  if constexpr (debug_flags::text_service)
+    log::TagDebug(log_tag, u"Text selection started, position: {}.", start);
+}
+
+void TextHostControlService::UpdateSelection(Index new_end) {
+  auto selection = GetSelection();
+  selection.ChangeEnd(new_end);
+  this->SetSelection(selection);
+  if constexpr (debug_flags::text_service)
+    log::TagDebug(log_tag, u"Text selection updated, range: {}, {}.",
+                  selection.GetStart(), selection.GetEnd());
+}
+
+void TextHostControlService::SyncTextRenderObject() {
+  const auto text_render_object = this->GetTextRenderObject();
+  const auto composition_info = this->GetCompositionInfo();
+  if (composition_info) {
+    const auto caret_position = GetCaretPosition();
+    auto text = this->text_;
+    text.insert(caret_position, composition_info->text);
+    text_render_object->SetText(text);
+    text_render_object->SetCaretPosition(caret_position +
+                                         composition_info->selection.GetEnd());
+    auto selection = composition_info->selection;
+    selection.position += caret_position;
+    text_render_object->SetSelectionRange(selection);
+  } else {
+    text_render_object->SetText(this->text_);
+    text_render_object->SetCaretPosition(this->GetCaretPosition());
+    text_render_object->SetSelectionRange(this->GetSelection());
+  }
+}
+
+void TextHostControlService::AbortSelection() {
+  if (this->mouse_move_selecting_) {
+    this->control_->ReleaseMouse();
+    this->mouse_move_selecting_ = false;
+  }
+  this->GetTextRenderObject()->SetSelectionRange(std::nullopt);
+}
+
+void TextHostControlService::UpdateInputMethodPosition() {
+  if (auto input_method_context = this->GetInputMethodContext()) {
+    Point right_bottom =
+        this->GetTextRenderObject()->GetTotalOffset() +
+        this->GetTextRenderObject()->GetCaretRect().GetRightBottom();
+    right_bottom.x += 5;
+    right_bottom.y += 5;
+
+    if constexpr (debug_flags::text_service) {
+      log::TagDebug(log_tag,
+                    u"Calculate input method candidate window position: {}.",
+                    right_bottom.ToDebugString());
+    }
+
+    input_method_context->SetCandidateWindowPosition(right_bottom);
+  }
+}
+
+void TextHostControlService::TearDownHandlers() {
+  event_guard_.Clear();
+  shortcut_hub_.Uninstall();
+}
+void TextHostControlService::SetUpHandlers() {
+  Expects(event_guard_.IsEmpty());
+
+  SetupOneHandler(&Control::MouseMoveEvent,
+                  &TextHostControlService::MouseMoveHandler);
+  SetupOneHandler(&Control::MouseDownEvent,
+                  &TextHostControlService::MouseDownHandler);
+  SetupOneHandler(&Control::MouseUpEvent,
+                  &TextHostControlService::MouseUpHandler);
+  SetupOneHandler(&Control::KeyDownEvent,
+                  &TextHostControlService::KeyDownHandler);
+  SetupOneHandler(&Control::GainFocusEvent,
+                  &TextHostControlService::GainFocusHandler);
+  SetupOneHandler(&Control::LoseFocusEvent,
+                  &TextHostControlService::LoseFocusHandler);
+
+  shortcut_hub_.Install(control_);
+}
+
+void TextHostControlService::MouseDownHandler(
+    event::MouseButtonEventArgs& args) {
+  if (this->mouse_move_selecting_) {
+    return;
+  } else {
+    this->control_->SetFocus();
+    if (!this->control_->CaptureMouse()) return;
+    this->mouse_move_selecting_ = true;
+    const auto text_render_object = this->GetTextRenderObject();
+    const auto result = text_render_object->TextHitTest(
+        args.GetPointToContent(text_render_object));
+    const auto position = result.position + (result.trailing ? 1 : 0);
+    StartSelection(position);
+  }
+}
+
+void TextHostControlService::MouseUpHandler(event::MouseButtonEventArgs&) {
+  if (mouse_move_selecting_) {
+    this->control_->ReleaseMouse();
+    this->mouse_move_selecting_ = false;
+  }
+}
+
+void TextHostControlService::MouseMoveHandler(event::MouseEventArgs& args) {
+  if (this->mouse_move_selecting_) {
+    const auto text_render_object = this->GetTextRenderObject();
+    const auto result = text_render_object->TextHitTest(
+        args.GetPointToContent(text_render_object));
+    const auto position = result.position + (result.trailing ? 1 : 0);
+    UpdateSelection(position);
+  }
+}
+
+void TextHostControlService::KeyDownHandler(event::KeyEventArgs& args) {
+  const auto key_code = args.GetKeyCode();
+  using cru::platform::gui::KeyCode;
+  using cru::platform::gui::KeyModifiers;
+
+  switch (key_code) {
+    case KeyCode::Backspace: {
+      if (!IsEditable()) return;
+      const auto selection = GetSelection();
+      if (selection.count == 0) {
+        SetSelection(DeleteCharPrevious(GetCaretPosition()));
+      } else {
+        this->DeleteSelectedText();
+      }
+    } break;
+    case KeyCode::Delete: {
+      if (!IsEditable()) return;
+      const auto selection = GetSelection();
+      if (selection.count == 0) {
+        DeleteChar(GetCaretPosition());
+      } else {
+        this->DeleteSelectedText();
+      }
+    } break;
+    case KeyCode::Left: {
+      const auto key_modifier = args.GetKeyModifier();
+      const bool shift = key_modifier & KeyModifiers::shift;
+      auto text = this->GetTextView();
+      if (shift) {
+        auto selection = this->GetSelection();
+        gsl::index new_position;
+        Utf16PreviousCodePoint(text, selection.GetEnd(), &new_position);
+        selection.ChangeEnd(new_position);
+        this->SetSelection(selection);
+      } else {
+        const auto caret = this->GetCaretPosition();
+        gsl::index new_position;
+        Utf16PreviousCodePoint(text, caret, &new_position);
+        this->SetSelection(new_position);
+      }
+    } break;
+    case KeyCode::Right: {
+      const auto key_modifier = args.GetKeyModifier();
+      const bool shift = key_modifier & KeyModifiers::shift;
+      auto text = this->GetTextView();
+      if (shift) {
+        auto selection = this->GetSelection();
+        gsl::index new_position;
+        Utf16NextCodePoint(text, selection.GetEnd(), &new_position);
+        selection.ChangeEnd(new_position);
+        this->SetSelection(selection);
+      } else {
+        const auto caret = this->GetCaretPosition();
+        gsl::index new_position;
+        Utf16NextCodePoint(text, caret, &new_position);
+        this->SetSelection(new_position);
+      }
+    } break;
+    default:
+      break;
+  }
+}
+
+void TextHostControlService::GainFocusHandler(
+    event::FocusChangeEventArgs& args) {
+  CRU_UNUSED(args);
+  if (editable_) {
+    auto input_method_context = GetInputMethodContext();
+    if (input_method_context == nullptr) return;
+    input_method_context->EnableIME();
+    auto sync = [this](std::nullptr_t) {
+      this->SyncTextRenderObject();
+      ScrollToCaret();
+    };
+    input_method_context_event_guard_ +=
+        input_method_context->CompositionStartEvent()->AddHandler(
+            [this](std::nullptr_t) { this->DeleteSelectedText(); });
+    input_method_context_event_guard_ +=
+        input_method_context->CompositionEvent()->AddHandler(sync);
+    input_method_context_event_guard_ +=
+        input_method_context->CompositionEndEvent()->AddHandler(sync);
+    input_method_context_event_guard_ +=
+        input_method_context->TextEvent()->AddHandler(
+            [this](const std::u16string_view& text) {
+              if (text == u"\b") return;
+              this->ReplaceSelectedText(text);
+            });
+
+    host::WindowHost* window_host = control_->GetWindowHost();
+    if (window_host)
+      input_method_context_event_guard_ +=
+          window_host->AfterLayoutEvent()->AddHandler(
+              [this](auto) { this->UpdateInputMethodPosition(); });
+    SetCaretVisible(true);
+  }
+}
+
+void TextHostControlService::LoseFocusHandler(
+    event::FocusChangeEventArgs& args) {
+  if (!args.IsWindow()) this->AbortSelection();
+  input_method_context_event_guard_.Clear();
+  auto input_method_context = GetInputMethodContext();
+  if (input_method_context) {
+    input_method_context->DisableIME();
+  }
+  SetCaretVisible(false);
+  SyncTextRenderObject();
+}
+}  // namespace cru::ui::controls