...

13 files changed, 202 insertions, 144 deletions

diff --git a/include/cru/common/StringUtil.hpp b/include/cru/common/StringUtil.hpp
new file mode 100644
index 00000000..a44ae6b4
--- /dev/null
+++ b/include/cru/common/StringUtil.hpp
@@ -0,0 +1,39 @@
+#pragma once
+#include "Base.hpp"
+
+namespace cru {
+using CodePoint = std::int32_t;
+constexpr CodePoint k_code_point_end = -1;
+
+class TextEncodeException : public std::runtime_error {
+ public:
+  using runtime_error::runtime_error;
+};
+
+class Utf8Iterator : public Object {
+ public:
+  explicit Utf8Iterator(const std::string_view& string) : string_(string) {}
+  Utf8Iterator(const std::string_view& string, Index position)
+      : string_(string), position_(position) {}
+
+  CRU_DEFAULT_COPY(Utf8Iterator)
+  CRU_DEFAULT_MOVE(Utf8Iterator)
+
+  ~Utf8Iterator() = default;
+
+ public:
+  void SetToHead() { position_ = 0; }
+  void SetPosition(Index position) { position_ = position; }
+
+  // Advance current position and get next code point. Return k_code_point_end
+  // if there is no next code unit(point). Throw TextEncodeException if decoding
+  // fails.
+  CodePoint Next();
+
+  Index CurrentPosition() const { return this->position_; }
+
+ private:
+  std::string_view string_;
+  Index position_ = 0;
+};
+}  // namespace cru
diff --git a/include/cru/platform/GraphBase.hpp b/include/cru/platform/GraphBase.hpp
index 0d4effd4..28dab1e6 100644
--- a/include/cru/platform/GraphBase.hpp
+++ b/include/cru/platform/GraphBase.hpp
@@ -249,6 +249,7 @@ struct TextRange final {
   constexpr TextRange(const gsl::index position, const gsl::index count = 0)
       : position(position), count(count) {}
 
+  gsl::index GetStart() const { return position; }
   gsl::index GetEnd() const { return position + count; }
 
   TextRange Normalize() const {
diff --git a/include/cru/ui/Base.hpp b/include/cru/ui/Base.hpp
index c59d1b60..9036a47b 100644
--- a/include/cru/ui/Base.hpp
+++ b/include/cru/ui/Base.hpp
@@ -185,6 +185,10 @@ class Control;
 class ClickDetector;
 class UiHost;
 
+namespace render {
+class RenderObject;
+}
+
 //-------------------- region: basic types --------------------
 namespace internal {
 constexpr int align_start = 0;
diff --git a/include/cru/ui/UiEvent.hpp b/include/cru/ui/UiEvent.hpp
index 79d0f7e3..39f26aee 100644
--- a/include/cru/ui/UiEvent.hpp
+++ b/include/cru/ui/UiEvent.hpp
@@ -13,10 +13,6 @@ namespace cru::platform::graph {
 struct IPainter;
 }
 
-namespace cru::ui {
-class Control;
-}
-
 namespace cru::ui::event {
 class UiEventArgs : public Object {
  public:
@@ -88,6 +84,7 @@ class MouseEventArgs : public UiEventArgs {
 
   // This point is relative to window client lefttop.
   Point GetPoint() const { return point_.value_or(Point{}); }
+  Point GetPointToContent(render::RenderObject* render_target) const;
 
  private:
   std::optional<Point> point_;
diff --git a/include/cru/ui/render/ScrollRenderObject.hpp b/include/cru/ui/render/ScrollRenderObject.hpp
index 0c1fb16b..20b7278c 100644
--- a/include/cru/ui/render/ScrollRenderObject.hpp
+++ b/include/cru/ui/render/ScrollRenderObject.hpp
@@ -28,6 +28,9 @@ class ScrollRenderObject : public RenderObject {
   void SetScrollOffset(const Point& offset);
   Point GetRawScrollOffset() const { return scroll_offset_; }
 
+  // Rect lefttop relative to content rect.
+  void ScrollToContain(const Rect& rect);
+
  protected:
   void OnDrawCore(platform::graph::IPainter* painter) override;
 
diff --git a/include/cru/win/String.hpp b/include/cru/win/String.hpp
index 3d68cff7..ac07f57b 100644
--- a/include/cru/win/String.hpp
+++ b/include/cru/win/String.hpp
@@ -16,7 +16,7 @@ way.)
 #pragma once
 #include "WinPreConfig.hpp"
 
-#include "cru/common/Base.hpp"
+#include "cru/common/StringUtil.hpp"
 
 #include <cstdint>
 #include <stdexcept>
@@ -37,38 +37,6 @@ inline bool IsSurrogatePairTrailing(wchar_t c) {
   return c >= 0xDC00 && c <= 0xDFFF;
 }
 
-using CodePoint = std::int32_t;
-constexpr CodePoint k_code_point_end = -1;
-
-class TextEncodeException : public std::runtime_error {
- public:
-  using runtime_error::runtime_error;
-};
-
-class Utf8Iterator : public Object {
- public:
-  Utf8Iterator(const std::string_view& string) : string_(string) {}
-
-  CRU_DEFAULT_COPY(Utf8Iterator)
-  CRU_DEFAULT_MOVE(Utf8Iterator)
-
-  ~Utf8Iterator() = default;
-
- public:
-  void SetToHead() { position_ = 0; }
-
-  // Advance current position and get next code point. Return k_code_point_end
-  // if there is no next code unit(point). Throw TextEncodeException if decoding
-  // fails.
-  CodePoint Next();
-
-  int CurrentPosition() const { return this->position_; }
-
- private:
-  std::string_view string_;
-  int position_ = 0;
-};
-
 class Utf16Iterator : public Object {
   static_assert(
       sizeof(wchar_t) == 2,
@@ -91,17 +59,17 @@ class Utf16Iterator : public Object {
   // fails.
   CodePoint Next();
 
-  int CurrentPosition() const { return this->position_; }
+  Index CurrentPosition() const { return this->position_; }
 
  private:
   std::wstring_view string_;
-  int position_ = 0;
+  Index position_ = 0;
 };
 
-int IndexUtf8ToUtf16(const std::string_view& utf8_string, int utf8_index,
-                     const std::wstring_view& utf16_string);
+Index IndexUtf8ToUtf16(const std::string_view& utf8_string, Index utf8_index,
+                       const std::wstring_view& utf16_string);
 
-int IndexUtf16ToUtf8(const std::wstring_view& utf16_string, int utf16_index,
-                     const std::string_view& utf8_string);
+Index IndexUtf16ToUtf8(const std::wstring_view& utf16_string, Index utf16_index,
+                       const std::string_view& utf8_string);
 
 }  // namespace cru::platform::win
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index d53b9740..6a18ef2b 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(CRU_BASE_INCLUDE_DIR ${CRU_INCLUDE_DIR}/cru/common)
 add_library(cru_base STATIC 
 	Logger.cpp
+	StringUtil.cpp
 )
 target_sources(cru_base PUBLIC
 	${CRU_BASE_INCLUDE_DIR}/Base.hpp
@@ -9,6 +10,7 @@ target_sources(cru_base PUBLIC
 	${CRU_BASE_INCLUDE_DIR}/Logger.hpp
 	${CRU_BASE_INCLUDE_DIR}/PreConfig.hpp
 	${CRU_BASE_INCLUDE_DIR}/SelfResolvable.hpp
+	${CRU_BASE_INCLUDE_DIR}/StringUtil.hpp
 )
 target_include_directories(cru_base PUBLIC ${CRU_INCLUDE_DIR})
 target_compile_definitions(cru_base PUBLIC $<$<CONFIG:Debug>:CRU_DEBUG>)
diff --git a/src/common/StringUtil.cpp b/src/common/StringUtil.cpp
new file mode 100644
index 00000000..31a5effd
--- /dev/null
+++ b/src/common/StringUtil.cpp
@@ -0,0 +1,69 @@
+#include "cru/common/StringUtil.hpp"
+
+namespace cru {
+template <typename UInt, int number_of_bit>
+inline std::enable_if_t<std::is_unsigned_v<UInt>, CodePoint> ExtractBits(
+    UInt n) {
+  return static_cast<CodePoint>(n & ((1u << number_of_bit) - 1));
+}
+
+CodePoint Utf8Iterator::Next() {
+  if (position_ == static_cast<Index>(string_.length()))
+    return k_code_point_end;
+
+  const auto cu0 = static_cast<std::uint8_t>(string_[position_++]);
+
+  auto read_next_folowing_code = [this]() -> CodePoint {
+    if (this->position_ == static_cast<Index>(string_.length()))
+      throw TextEncodeException(
+          "Unexpected end when read continuing byte of multi-byte code point.");
+
+#ifdef CRU_DEBUG
+    const auto u = static_cast<std::uint8_t>(string_[position_]);
+    if (!(u & (1u << 7)) || (u & (1u << 6))) {
+      throw TextEncodeException(
+          "Unexpected bad-format (not 0b10xxxxxx) continuing byte of "
+          "multi-byte code point.");
+    }
+#endif
+
+    return ExtractBits<std::uint8_t, 6>(string_[position_++]);
+  };
+
+  if ((1u << 7) & cu0) {
+    if ((1u << 6) & cu0) {      // 2~4-length code point
+      if ((1u << 5) & cu0) {    // 3~4-length code point
+        if ((1u << 4) & cu0) {  // 4-length code point
+#ifdef CRU_DEBUG
+          if (cu0 & (1u << 3)) {
+            throw TextEncodeException(
+                "Unexpected bad-format begin byte (not 0b10xxxxxx) of 4-byte "
+                "code point.");
+          }
+#endif
+
+          const CodePoint s0 = ExtractBits<std::uint8_t, 3>(cu0) << (6 * 3);
+          const CodePoint s1 = read_next_folowing_code() << (6 * 2);
+          const CodePoint s2 = read_next_folowing_code() << 6;
+          const CodePoint s3 = read_next_folowing_code();
+          return s0 + s1 + s2 + s3;
+        } else {  // 3-length code point
+          const CodePoint s0 = ExtractBits<std::uint8_t, 4>(cu0) << (6 * 2);
+          const CodePoint s1 = read_next_folowing_code() << 6;
+          const CodePoint s2 = read_next_folowing_code();
+          return s0 + s1 + s2;
+        }
+      } else {  // 2-length code point
+        const CodePoint s0 = ExtractBits<std::uint8_t, 5>(cu0) << 6;
+        const CodePoint s1 = read_next_folowing_code();
+        return s0 + s1;
+      }
+    } else {
+      throw TextEncodeException(
+          "Unexpected bad-format (0b10xxxxxx) begin byte of a code point.");
+    }
+  } else {
+    return static_cast<CodePoint>(cu0);
+  }
+}
+}  // namespace cru
diff --git a/src/ui/CMakeLists.txt b/src/ui/CMakeLists.txt
index 954dacb0..6c50ec57 100644
--- a/src/ui/CMakeLists.txt
+++ b/src/ui/CMakeLists.txt
@@ -10,6 +10,7 @@ add_library(cru_ui STATIC
 	Helper.cpp
 	LayoutControl.cpp
 	NoChildControl.cpp
+	UiEvent.cpp
 	UiHost.cpp
 	UiManager.cpp
 	Window.cpp
diff --git a/src/ui/UiEvent.cpp b/src/ui/UiEvent.cpp
new file mode 100644
index 00000000..74dd54dc
--- /dev/null
+++ b/src/ui/UiEvent.cpp
@@ -0,0 +1,10 @@
+#include "cru/ui/UiEvent.hpp"
+
+#include "cru/ui/render/RenderObject.hpp"
+
+namespace cru::ui::event {
+Point MouseEventArgs::GetPointToContent(
+    render::RenderObject* render_object) const {
+  return render_object->FromRootToContent(GetPoint());
+}
+}  // namespace cru::ui::event
diff --git a/src/ui/controls/TextControlService.hpp b/src/ui/controls/TextControlService.hpp
index 5fc8d987..94d9ebf8 100644
--- a/src/ui/controls/TextControlService.hpp
+++ b/src/ui/controls/TextControlService.hpp
@@ -78,11 +78,12 @@ class TextControlService : public Object {
     }
   }
 
-  std::optional<TextRange> GetSelection() {
-    return this->control_->GetTextRenderObject()->GetSelectionRange();
+  gsl::not_null<render::TextRenderObject*> GetTextRenderObject() {
+    return this->control_->GetTextRenderObject();
   }
-  void SetSelection(std::optional<TextRange> selection) {
-    this->control_->GetTextRenderObject()->SetSelectionRange(selection);
+
+  render::ScrollRenderObject* GetScrollRenderObject() {
+    return this->control_->GetScrollRenderObject();
   }
 
  private:
@@ -91,7 +92,7 @@ class TextControlService : public Object {
       this->control_->ReleaseMouse();
       this->select_down_button_ = std::nullopt;
     }
-    this->control_->GetTextRenderObject()->SetSelectionRange(std::nullopt);
+    this->GetTextRenderObject()->SetSelectionRange(std::nullopt);
   }
 
   void SetupCaret() {
@@ -100,16 +101,16 @@ class TextControlService : public Object {
     // Cancel first anyhow for safety.
     application->CancelTimer(this->caret_timer_id_);
 
-    this->control_->GetTextRenderObject()->SetDrawCaret(true);
+    this->GetTextRenderObject()->SetDrawCaret(true);
     this->caret_timer_id_ = application->SetInterval(
         std::chrono::milliseconds(this->caret_blink_duration_),
-        [this] { this->control_->GetTextRenderObject()->ToggleDrawCaret(); });
+        [this] { this->GetTextRenderObject()->ToggleDrawCaret(); });
   }
 
   void TearDownCaret() {
     const auto application = GetUiApplication();
     application->CancelTimer(this->caret_timer_id_);
-    this->control_->GetTextRenderObject()->SetDrawCaret(false);
+    this->GetTextRenderObject()->SetDrawCaret(false);
   }
 
   template <typename TArgs>
@@ -121,6 +122,29 @@ class TextControlService : public Object {
             std::bind(handler, this, std::placeholders::_1))});
   }
 
+  void StartSelection(Index start) {
+    const auto text_render_object = this->GetTextRenderObject();
+    text_render_object->SetSelectionRange(TextRange{start, 0});
+    text_render_object->SetCaretPosition(start);
+    log::TagDebug(log_tag, "Text selection started, position: {}.", position);
+  }
+
+  void UpdateSelection(Index new_end) {
+    if (!old_selection.has_value()) return;
+
+    const auto text_render_object = this->GetTextRenderObject();
+    const auto old_selection = text_render_object->GetSelectionRange();
+    const auto old_start = old_selection->GetStart();
+    this->GetTextRenderObject()->SetSelectionRange(
+        TextRange::FromTwoSides(old_start, new_end));
+    text_render_object->SetCaretPosition(new_end);
+    log::TagDebug(log_tag, "Text selection updated, range: {}, {}.", old_start,
+                  new_end);
+    if (const auto scroll_render_object = this->GetScrollRenderObject()) {
+      //TODO: Implement this.      
+    }
+  }
+
   void SetupHandlers() {
     Expects(event_revoker_guards_.empty());
 
@@ -130,22 +154,20 @@ class TextControlService : public Object {
                     &TextControlService::MouseDownHandler);
     SetupOneHandler(&Control::MouseUpEvent,
                     &TextControlService::MouseUpHandler);
+    SetupOneHandler(&Control::KeyDownEvent,
+                    &TextControlService::KeyDownHandler);
+    SetupOneHandler(&Control::KeyUpEvent, &TextControlService::KeyUpHandler);
     SetupOneHandler(&Control::LoseFocusEvent,
                     &TextControlService::LoseFocusHandler);
   }
 
   void MouseMoveHandler(event::MouseEventArgs& args) {
     if (this->select_down_button_.has_value()) {
-      const auto text_render_object = this->control_->GetTextRenderObject();
+      const auto text_render_object = this->GetTextRenderObject();
       const auto result = text_render_object->TextHitTest(
-          text_render_object->FromRootToContent(args.GetPoint()));
+          args.GetPointToContent(text_render_object));
       const auto position = result.position + (result.trailing ? 1 : 0);
-      log::TagDebug(log_tag,
-                    "Text selection changed on mouse move, range: {}, {}.",
-                    position, this->select_start_position_);
-      this->control_->GetTextRenderObject()->SetSelectionRange(
-          TextRange::FromTwoSides(position, this->select_start_position_));
-      text_render_object->SetCaretPosition(position);
+      UpdateSelection(position);
     }
   }
 
@@ -155,16 +177,12 @@ class TextControlService : public Object {
     } else {
       if (!this->control_->CaptureMouse()) return;
       if (!this->control_->RequestFocus()) return;
-      const auto text_render_object = this->control_->GetTextRenderObject();
+      const auto text_render_object = this->GetTextRenderObject();
       this->select_down_button_ = args.GetButton();
       const auto result = text_render_object->TextHitTest(
-          text_render_object->FromRootToContent(args.GetPoint()));
+          args.GetPointToContent(text_render_object));
       const auto position = result.position + (result.trailing ? 1 : 0);
-      text_render_object->SetSelectionRange(std::nullopt);
-      text_render_object->SetCaretPosition(position);
-      this->select_start_position_ = position;
-      log::TagDebug(log_tag, "Begin to select text, start position: {}.",
-                    position);
+      StartSelection(position);
     }
   }
 
@@ -173,10 +191,13 @@ class TextControlService : public Object {
         this->select_down_button_.value() == args.GetButton()) {
       this->control_->ReleaseMouse();
       this->select_down_button_ = std::nullopt;
-      log::TagDebug(log_tag, "End selecting text.");
     }
   }
 
+  void KeyDownHandler(event::KeyEventArgs& args) {}
+
+  void KeyUpHandler(event::KeyEventArgs& args) {}
+
   void LoseFocusHandler(event::FocusChangeEventArgs& args) {
     if (!args.IsWindow()) this->AbortSelection();
   }
@@ -193,8 +214,5 @@ class TextControlService : public Object {
 
   // nullopt means not selecting
   std::optional<MouseButton> select_down_button_;
-
-  // before the char
-  int select_start_position_;
 };
 }  // namespace cru::ui::controls
diff --git a/src/ui/render/ScrollRenderObject.cpp b/src/ui/render/ScrollRenderObject.cpp
index a367afd9..77367970 100644
--- a/src/ui/render/ScrollRenderObject.cpp
+++ b/src/ui/render/ScrollRenderObject.cpp
@@ -67,6 +67,11 @@ void ScrollRenderObject::SetScrollOffset(const Point& offset) {
   InvalidateLayout();
 }
 
+void ScrollToContain(const Rect& rect) {
+  // TODO: Implement this.
+  throw std::runtime_error("Not implemented.");
+}
+
 Size ScrollRenderObject::OnMeasureContent(const MeasureRequirement& requirement,
                                           const MeasureSize& preferred_size) {
   if (const auto child = GetSingleChild()) {
diff --git a/src/win/String.cpp b/src/win/String.cpp
index 65a280f2..eb585523 100644
--- a/src/win/String.cpp
+++ b/src/win/String.cpp
@@ -54,74 +54,16 @@ inline std::enable_if_t<std::is_unsigned_v<UInt>, CodePoint> ExtractBits(
   return static_cast<CodePoint>(n & ((1u << number_of_bit) - 1));
 }
 
-CodePoint Utf8Iterator::Next() {
-  if (position_ == static_cast<int>(string_.length())) return k_code_point_end;
-
-  const auto cu0 = static_cast<std::uint8_t>(string_[position_++]);
-
-  auto read_next_folowing_code = [this]() -> CodePoint {
-    if (this->position_ == static_cast<int>(string_.length()))
-      throw TextEncodeException(
-          "Unexpected end when read continuing byte of multi-byte code point.");
-
-#ifdef CRU_DEBUG
-    const auto u = static_cast<std::uint8_t>(string_[position_]);
-    if (!(u & (1u << 7)) || (u & (1u << 6))) {
-      throw TextEncodeException(
-          "Unexpected bad-format (not 0b10xxxxxx) continuing byte of "
-          "multi-byte code point.");
-    }
-#endif
-
-    return ExtractBits<std::uint8_t, 6>(string_[position_++]);
-  };
-
-  if ((1u << 7) & cu0) {
-    if ((1u << 6) & cu0) {      // 2~4-length code point
-      if ((1u << 5) & cu0) {    // 3~4-length code point
-        if ((1u << 4) & cu0) {  // 4-length code point
-#ifdef CRU_DEBUG
-          if (cu0 & (1u << 3)) {
-            throw TextEncodeException(
-                "Unexpected bad-format begin byte (not 0b10xxxxxx) of 4-byte "
-                "code point.");
-          }
-#endif
-
-          const CodePoint s0 = ExtractBits<std::uint8_t, 3>(cu0) << (6 * 3);
-          const CodePoint s1 = read_next_folowing_code() << (6 * 2);
-          const CodePoint s2 = read_next_folowing_code() << 6;
-          const CodePoint s3 = read_next_folowing_code();
-          return s0 + s1 + s2 + s3;
-        } else {  // 3-length code point
-          const CodePoint s0 = ExtractBits<std::uint8_t, 4>(cu0) << (6 * 2);
-          const CodePoint s1 = read_next_folowing_code() << 6;
-          const CodePoint s2 = read_next_folowing_code();
-          return s0 + s1 + s2;
-        }
-      } else {  // 2-length code point
-        const CodePoint s0 = ExtractBits<std::uint8_t, 5>(cu0) << 6;
-        const CodePoint s1 = read_next_folowing_code();
-        return s0 + s1;
-      }
-    } else {
-      throw TextEncodeException(
-          "Unexpected bad-format (0b10xxxxxx) begin byte of a code point.");
-    }
-  } else {
-    return static_cast<CodePoint>(cu0);
-  }
-}
-
 CodePoint Utf16Iterator::Next() {
-  if (position_ == static_cast<int>(string_.length())) return k_code_point_end;
+  if (position_ == static_cast<Index>(string_.length()))
+    return k_code_point_end;
 
   const auto cu0 = static_cast<std::uint16_t>(string_[position_++]);
 
   if (cu0 < 0xd800u || cu0 >= 0xe000u) {  // 1-length code point
     return static_cast<CodePoint>(cu0);
   } else if (cu0 <= 0xdbffu) {  // 2-length code point
-    if (position_ == static_cast<int>(string_.length())) {
+    if (position_ == static_cast<Index>(string_.length())) {
       throw TextEncodeException(
           "Unexpected end when reading second code unit of surrogate pair.");
     }
@@ -145,12 +87,12 @@ CodePoint Utf16Iterator::Next() {
   }
 }
 
-int IndexUtf8ToUtf16(const std::string_view& utf8_string, int utf8_index,
-                     const std::wstring_view& utf16_string) {
-  if (utf8_index >= static_cast<int>(utf8_string.length()))
-    return static_cast<int>(utf16_string.length());
+Index IndexUtf8ToUtf16(const std::string_view& utf8_string, Index utf8_index,
+                       const std::wstring_view& utf16_string) {
+  if (utf8_index >= static_cast<Index>(utf8_string.length()))
+    return utf16_string.length();
 
-  int cp_index = 0;
+  Index cp_index = 0;
   Utf8Iterator iter{utf8_string};
   while (iter.CurrentPosition() <= utf8_index) {
     iter.Next();
@@ -158,19 +100,19 @@ int IndexUtf8ToUtf16(const std::string_view& utf8_string, int utf8_index,
   }
 
   Utf16Iterator result_iter{utf16_string};
-  for (int i = 0; i < cp_index - 1; i++) {
+  for (Index i = 0; i < cp_index - 1; i++) {
     if (result_iter.Next() == k_code_point_end) break;
   }
 
   return result_iter.CurrentPosition();
 }
 
-int IndexUtf16ToUtf8(const std::wstring_view& utf16_string, int utf16_index,
-                     const std::string_view& utf8_string) {
-  if (utf16_index >= static_cast<int>(utf16_string.length()))
-    return static_cast<int>(utf8_string.length());
+Index IndexUtf16ToUtf8(const std::wstring_view& utf16_string, Index utf16_index,
+                       const std::string_view& utf8_string) {
+  if (utf16_index >= static_cast<Index>(utf16_string.length()))
+    return utf8_string.length();
 
-  int cp_index = 0;
+  Index cp_index = 0;
   Utf16Iterator iter{utf16_string};
   while (iter.CurrentPosition() <= utf16_index) {
     iter.Next();
@@ -178,11 +120,10 @@ int IndexUtf16ToUtf8(const std::wstring_view& utf16_string, int utf16_index,
   }
 
   Utf8Iterator result_iter{utf8_string};
-  for (int i = 0; i < cp_index - 1; i++) {
+  for (Index i = 0; i < cp_index - 1; i++) {
     if (result_iter.Next() == k_code_point_end) break;
   }
 
   return result_iter.CurrentPosition();
 }
-
 }  // namespace cru::platform::win