Fix macOS build.

36 files changed, 242 insertions, 121 deletions

diff --git a/include/cru/base/Osx.h b/include/cru/base/Osx.h
index fbdffc54..e42a4fe5 100644
--- a/include/cru/base/Osx.h
+++ b/include/cru/base/Osx.h
@@ -7,9 +7,10 @@
 #endif
 
 #include "Range.h"
-#include "String.h"
 
 #include <CoreFoundation/CoreFoundation.h>
+#include <string>
+#include <string_view>
 
 namespace cru {
 template <typename CFClassRef>
@@ -29,8 +30,8 @@ class CFWrapper {
   }
 };
 
-CFWrapper<CFStringRef> ToCFString(StringView string);
-String FromCFStringRef(CFStringRef string);
+CFWrapper<CFStringRef> ToCFString(std::string_view string);
+std::string FromCFStringRef(CFStringRef string);
 
 CFRange ToCFRange(const Range& range);
 Range FromCFRange(const CFRange& range);
diff --git a/include/cru/base/StringUtil.h b/include/cru/base/StringUtil.h
index 54e7b6e6..8c7841d7 100644
--- a/include/cru/base/StringUtil.h
+++ b/include/cru/base/StringUtil.h
@@ -375,4 +375,9 @@ class CodePointIterator {
 using Utf8CodePointIterator = CodePointIterator<char, &Utf8NextCodePoint>;
 using Utf16CodePointIterator =
     CodePointIterator<Utf16CodeUnit, &Utf16NextCodePoint>;
+
+Index Utf8IndexCodeUnitToCodePoint(const Utf8CodeUnit* ptr, Index size, Index position);
+Index Utf8IndexCodePointToCodeUnit(const Utf8CodeUnit* ptr, Index size, Index position);
+Index Utf16IndexCodeUnitToCodePoint(const Utf16CodeUnit* ptr, Index size, Index position);
+Index Utf16IndexCodePointToCodeUnit(const Utf16CodeUnit* ptr, Index size, Index position);
 }  // namespace cru::string
diff --git a/include/cru/platform/Color.h b/include/cru/platform/Color.h
index 53252cc4..f7c82dec 100644
--- a/include/cru/platform/Color.h
+++ b/include/cru/platform/Color.h
@@ -2,8 +2,10 @@
 #include "Base.h"
 
 #include <cru/base/Base.h>
+#include <cru/base/StringUtil.h>
 
 #include <cstdint>
+#include <format>
 #include <optional>
 #include <string_view>
 
@@ -248,6 +250,10 @@ struct std::hash<cru::platform::Color> {
   }
 };
 
+template <>
+struct std::formatter<cru::platform::Color, char>
+    : cru::string::ImplementFormatterByToString<cru::platform::Color> {};
+
 namespace cru::platform {
 std::optional<Color> GetPredefinedColorByName(std::string_view name);
 
diff --git a/include/cru/platform/graphics/quartz/Brush.h b/include/cru/platform/graphics/quartz/Brush.h
index 9b29ef59..73aa2f6d 100644
--- a/include/cru/platform/graphics/quartz/Brush.h
+++ b/include/cru/platform/graphics/quartz/Brush.h
@@ -36,7 +36,7 @@ class QuartzSolidColorBrush : public QuartzBrush,
 
   void Select(CGContextRef context) override;
 
-  String GetDebugString() override;
+  std::string GetDebugString() override;
 
  private:
   Color color_;
diff --git a/include/cru/platform/graphics/quartz/Convert.h b/include/cru/platform/graphics/quartz/Convert.h
index c5a1a6cc..fd6159a6 100644
--- a/include/cru/platform/graphics/quartz/Convert.h
+++ b/include/cru/platform/graphics/quartz/Convert.h
@@ -1,6 +1,4 @@
 #pragma once
-#include "cru/base/Range.h"
-#include "cru/base/String.h"
 #include "cru/base/io/Stream.h"
 #include "cru/platform/Matrix.h"
 
diff --git a/include/cru/platform/graphics/quartz/Factory.h b/include/cru/platform/graphics/quartz/Factory.h
index 042e35ca..61d8dbdb 100644
--- a/include/cru/platform/graphics/quartz/Factory.h
+++ b/include/cru/platform/graphics/quartz/Factory.h
@@ -21,11 +21,11 @@ class QuartzGraphicsFactory : public OsxQuartzResource,
 
   std::unique_ptr<IGeometryBuilder> CreateGeometryBuilder() override;
 
-  std::unique_ptr<IFont> CreateFont(String font_family,
+  std::unique_ptr<IFont> CreateFont(std::string font_family,
                                     float font_size) override;
 
   std::unique_ptr<ITextLayout> CreateTextLayout(std::shared_ptr<IFont> font,
-                                                String text) override;
+                                                std::string text) override;
 
   IImageFactory* GetImageFactory() override;
 
diff --git a/include/cru/platform/graphics/quartz/Font.h b/include/cru/platform/graphics/quartz/Font.h
index 975607b9..d110b59b 100644
--- a/include/cru/platform/graphics/quartz/Font.h
+++ b/include/cru/platform/graphics/quartz/Font.h
@@ -8,7 +8,7 @@
 namespace cru::platform::graphics::quartz {
 class OsxCTFont : public OsxQuartzResource, public virtual IFont {
  public:
-  OsxCTFont(IGraphicsFactory* graphics_factory, const String& name, float size);
+  OsxCTFont(IGraphicsFactory* graphics_factory, const std::string& name, float size);
 
   CRU_DELETE_COPY(OsxCTFont)
   CRU_DELETE_MOVE(OsxCTFont)
@@ -17,11 +17,11 @@ class OsxCTFont : public OsxQuartzResource, public virtual IFont {
 
   CTFontRef GetCTFont() const { return ct_font_; }
 
-  String GetFontName() override;
+  std::string GetFontName() override;
   float GetFontSize() override;
 
  private:
-  String name_;
+  std::string name_;
   CTFontRef ct_font_;
 };
 }  // namespace cru::platform::graphics::quartz
diff --git a/include/cru/platform/graphics/quartz/Resource.h b/include/cru/platform/graphics/quartz/Resource.h
index d28e4055..23fe6fa9 100644
--- a/include/cru/platform/graphics/quartz/Resource.h
+++ b/include/cru/platform/graphics/quartz/Resource.h
@@ -1,7 +1,7 @@
 #pragma once
-#include "cru/platform/osx/Resource.h"
 #include "cru/platform/graphics/Base.h"
 #include "cru/platform/graphics/Resource.h"
+#include "cru/platform/osx/Resource.h"
 
 namespace cru::platform::graphics::quartz {
 class OsxQuartzResource : public platform::osx::OsxResource,
@@ -15,7 +15,7 @@ class OsxQuartzResource : public platform::osx::OsxResource,
   ~OsxQuartzResource() override = default;
 
  public:
-  String GetPlatformId() const override { return u"OSX Quartz"; }
+  std::string GetPlatformId() const override { return "OSX Quartz"; }
 
   IGraphicsFactory* GetGraphicsFactory() override { return graphics_factory_; }
 
diff --git a/include/cru/platform/graphics/quartz/TextLayout.h b/include/cru/platform/graphics/quartz/TextLayout.h
index bbb417f6..e53ee464 100644
--- a/include/cru/platform/graphics/quartz/TextLayout.h
+++ b/include/cru/platform/graphics/quartz/TextLayout.h
@@ -11,7 +11,7 @@ namespace cru::platform::graphics::quartz {
 class OsxCTTextLayout : public OsxQuartzResource, public virtual ITextLayout {
  public:
   OsxCTTextLayout(IGraphicsFactory* graphics_factory,
-                  std::shared_ptr<OsxCTFont> font, const String& str);
+                  std::shared_ptr<OsxCTFont> font, const std::string& str);
 
   CRU_DELETE_COPY(OsxCTTextLayout)
   CRU_DELETE_MOVE(OsxCTTextLayout)
@@ -19,8 +19,8 @@ class OsxCTTextLayout : public OsxQuartzResource, public virtual ITextLayout {
   ~OsxCTTextLayout() override;
 
  public:
-  String GetText() override { return text_; }
-  void SetText(String new_text) override;
+  std::string GetText() override { return text_; }
+  void SetText(std::string new_text) override;
 
   std::shared_ptr<IFont> GetFont() override { return font_; }
   void SetFont(std::shared_ptr<IFont> font) override;
@@ -46,10 +46,10 @@ class OsxCTTextLayout : public OsxQuartzResource, public virtual ITextLayout {
 
   Matrix GetTransform() { return transform_; }
 
-  String GetDebugString() override;
+  std::string GetDebugString() override;
 
  private:
-  void DoSetText(String text);
+  void DoSetText(std::string text);
 
   void ReleaseResource();
   void RecreateFrame();
@@ -68,8 +68,8 @@ class OsxCTTextLayout : public OsxQuartzResource, public virtual ITextLayout {
 
   std::shared_ptr<OsxCTFont> font_;
 
-  String text_;
-  String actual_text_;
+  std::string text_;
+  std::string actual_text_;
   CFMutableAttributedStringRef cf_attributed_text_;
 
   CTFramesetterRef ct_framesetter_ = nullptr;
diff --git a/include/cru/platform/gui/osx/Clipboard.h b/include/cru/platform/gui/osx/Clipboard.h
index b4dcce4c..6672f84d 100644
--- a/include/cru/platform/gui/osx/Clipboard.h
+++ b/include/cru/platform/gui/osx/Clipboard.h
@@ -22,8 +22,8 @@ class OsxClipboard : public OsxGuiResource, public virtual IClipboard {
   ~OsxClipboard() override;
 
  public:
-  String GetText() override;
-  void SetText(String text) override;
+  std::string GetText() override;
+  void SetText(std::string text) override;
 
  private:
   std::unique_ptr<details::OsxClipboardPrivate> p_;
diff --git a/include/cru/platform/gui/osx/InputMethod.h b/include/cru/platform/gui/osx/InputMethod.h
index cbfdae6c..067d86ea 100644
--- a/include/cru/platform/gui/osx/InputMethod.h
+++ b/include/cru/platform/gui/osx/InputMethod.h
@@ -46,7 +46,7 @@ class OsxInputMethodContext : public OsxGuiResource,
 
   IEvent<std::nullptr_t>* CompositionEvent() override;
 
-  IEvent<StringView>* TextEvent() override;
+  IEvent<std::string>* TextEvent() override;
 
   bool IsEnabled();
 
diff --git a/include/cru/platform/gui/osx/Menu.h b/include/cru/platform/gui/osx/Menu.h
index c5cc756a..05f21e1c 100644
--- a/include/cru/platform/gui/osx/Menu.h
+++ b/include/cru/platform/gui/osx/Menu.h
@@ -25,8 +25,8 @@ class OsxMenuItem : public OsxGuiResource, public virtual IMenuItem {
   ~OsxMenuItem() override;
 
  public:
-  String GetTitle() override;
-  void SetTitle(String title) override;
+  std::string GetTitle() override;
+  void SetTitle(std::string title) override;
   bool IsEnabled() override;
   void SetEnabled(bool enabled) override;
   IMenu* GetParentMenu() override;
diff --git a/include/cru/platform/gui/osx/Resource.h b/include/cru/platform/gui/osx/Resource.h
index 1eec7d09..1253544c 100644
--- a/include/cru/platform/gui/osx/Resource.h
+++ b/include/cru/platform/gui/osx/Resource.h
@@ -1,7 +1,7 @@
 #pragma once
 #include "cru/platform/osx/Resource.h"
 
-#include "cru/platform/gui/Base.h"
+#include <cru/platform/gui/UiApplication.h>
 
 namespace cru::platform::gui::osx {
 class OsxGuiResource : public platform::osx::OsxResource {
@@ -14,7 +14,7 @@ class OsxGuiResource : public platform::osx::OsxResource {
   ~OsxGuiResource() override = default;
 
  public:
-  String GetPlatformId() const override { return u"OSX GUI"; }
+  std::string GetPlatformId() const override { return "OSX GUI"; }
 
   IUiApplication* GetUiApplication() const { return ui_application_; }
 
diff --git a/include/cru/platform/gui/osx/UiApplication.h b/include/cru/platform/gui/osx/UiApplication.h
index 2d2c119c..f0e311dc 100644
--- a/include/cru/platform/gui/osx/UiApplication.h
+++ b/include/cru/platform/gui/osx/UiApplication.h
@@ -51,9 +51,9 @@ class OsxUiApplication : public OsxGuiResource, public virtual IUiApplication {
 
   IMenu* GetApplicationMenu() override;
 
-  std::optional<String> ShowSaveDialog(SaveDialogOptions options) override;
+  std::optional<std::string> ShowSaveDialog(SaveDialogOptions options) override;
 
-  std::optional<std::vector<String>> ShowOpenDialog(
+  std::optional<std::vector<std::string>> ShowOpenDialog(
       OpenDialogOptions options) override;
 
  private:
diff --git a/include/cru/platform/gui/osx/Window.h b/include/cru/platform/gui/osx/Window.h
index 6cefbe8e..d00136b0 100644
--- a/include/cru/platform/gui/osx/Window.h
+++ b/include/cru/platform/gui/osx/Window.h
@@ -36,8 +36,8 @@ class OsxWindow : public OsxGuiResource, public INativeWindow {
   WindowStyleFlag GetStyleFlag() override;
   void SetStyleFlag(WindowStyleFlag flag) override;
 
-  String GetTitle() override;
-  void SetTitle(String title) override;
+  std::string GetTitle() override;
+  void SetTitle(std::string title) override;
 
   WindowVisibilityType GetVisibility() override;
   void SetVisibility(WindowVisibilityType visibility) override;
diff --git a/include/cru/platform/osx/Resource.h b/include/cru/platform/osx/Resource.h
index d30ee31b..4a3b6b7d 100644
--- a/include/cru/platform/osx/Resource.h
+++ b/include/cru/platform/osx/Resource.h
@@ -4,10 +4,6 @@
 namespace cru::platform::osx {
 class OsxResource : public Object, public virtual IPlatformResource {
  public:
-  CRU_DEFAULT_CONSTRUCTOR_DESTRUCTOR(OsxResource)
-  CRU_DELETE_COPY(OsxResource)
-  CRU_DELETE_MOVE(OsxResource)
-
-  String GetPlatformId() const override { return u"OSX"; }
+  std::string GetPlatformId() const override { return "OSX"; }
 };
 }  // namespace cru::platform::osx
diff --git a/src/base/Osx.cpp b/src/base/Osx.cpp
index 46b923fe..d979f542 100644
--- a/src/base/Osx.cpp
+++ b/src/base/Osx.cpp
@@ -1,19 +1,22 @@
 #include "cru/base/Osx.h"
+#include "cru/base/StringUtil.h"
 
 namespace cru {
-CFWrapper<CFStringRef> ToCFString(StringView string) {
+CFWrapper<CFStringRef> ToCFString(std::string_view string) {
   return CFWrapper<CFStringRef>(CFStringCreateWithBytes(
       nullptr, reinterpret_cast<const UInt8*>(string.data()),
-      string.size() * sizeof(std::uint16_t), kCFStringEncodingUTF16, false));
+      string.size() * sizeof(char), kCFStringEncodingUTF8, false));
 }
 
-String FromCFStringRef(CFStringRef string) {
+std::string FromCFStringRef(CFStringRef string) {
   auto length = CFStringGetLength(string);
 
-  String result;
+  std::string result;
 
   for (int i = 0; i < length; i++) {
-    result.AppendCodePoint(CFStringGetCharacterAtIndex(string, i));
+    cru::string::Utf8EncodeCodePointAppend(
+        CFStringGetCharacterAtIndex(string, i),
+        [&result](char c) { result += c; });
   }
 
   return result;
diff --git a/src/base/StringUtil.cpp b/src/base/StringUtil.cpp
index 581ebcab..4cd662d1 100644
--- a/src/base/StringUtil.cpp
+++ b/src/base/StringUtil.cpp
@@ -357,4 +357,51 @@ Index Utf16NextWord(const Utf16CodeUnit* ptr, Index size, Index position,
       ptr, size, position, is_space);
 }
 
+template <typename CharType,
+          NextCodePointFunctionType<CharType> NextCodePointFunction>
+static Index IndexCodeUnitToCodePoint(const CharType* ptr, Index size,
+                                      Index position) {
+  CodePointIterator<CharType, NextCodePointFunction> iter(ptr, size);
+  Index result = 0;
+  while (!iter.IsPastEnd() && iter.GetPosition() < position) {
+    ++iter;
+    ++result;
+  }
+  return result;
+}
+
+template <typename CharType,
+          NextCodePointFunctionType<CharType> NextCodePointFunction>
+static Index IndexCodePointToCodeUnit(const CharType* ptr, Index size,
+                                      Index position) {
+  CodePointIterator<CharType, NextCodePointFunction> iter(ptr, size);
+  for (Index i = 0; i < position; i++) {
+    ++iter;
+  }
+  return iter.GetPosition();
+}
+
+Index Utf8IndexCodeUnitToCodePoint(const Utf8CodeUnit* ptr, Index size,
+                                   Index position) {
+  return IndexCodeUnitToCodePoint<Utf8CodeUnit, Utf8NextCodePoint>(ptr, size,
+                                                                   position);
+}
+
+Index Utf8IndexCodePointToCodeUnit(const Utf8CodeUnit* ptr, Index size,
+                                   Index position) {
+  return IndexCodePointToCodeUnit<Utf8CodeUnit, Utf8NextCodePoint>(ptr, size,
+                                                                   position);
+}
+
+Index Utf16IndexCodeUnitToCodePoint(const Utf16CodeUnit* ptr, Index size,
+                                    Index position) {
+  return IndexCodeUnitToCodePoint<Utf16CodeUnit, Utf16NextCodePoint>(ptr, size,
+                                                                     position);
+}
+Index Utf16IndexCodePointToCodeUnit(const Utf16CodeUnit* ptr, Index size,
+                                    Index position) {
+  return IndexCodePointToCodeUnit<Utf16CodeUnit, Utf16NextCodePoint>(ptr, size,
+                                                                     position);
+}
+
 }  // namespace cru::string
diff --git a/src/base/io/Stream.cpp b/src/base/io/Stream.cpp
index 1aafc839..e07f2899 100644
--- a/src/base/io/Stream.cpp
+++ b/src/base/io/Stream.cpp
@@ -1,7 +1,9 @@
 #include "cru/base/io/Stream.h"
 #include "cru/base/Exception.h"
 
+#include <algorithm>
 #include <format>
+#include <iterator>
 #include <utility>
 
 namespace cru::io {
@@ -193,6 +195,10 @@ Buffer Stream::ReadToEnd(Index grow_size) {
 
 std::string Stream::ReadToEndAsUtf8String() {
   auto buffer = ReadToEnd();
-  return std::string(buffer.GetUsedBeginPtr(), buffer.GetUsedEndPtr());
+  std::string result;
+  std::transform(buffer.GetUsedBeginPtr(), buffer.GetUsedEndPtr(),
+                 std::back_inserter(result),
+                 [](std::byte c) { return static_cast<char>(c); });
+  return result;
 }
 }  // namespace cru::io
diff --git a/src/platform/graphics/quartz/Brush.cpp b/src/platform/graphics/quartz/Brush.cpp
index ea740eb3..c5784e51 100644
--- a/src/platform/graphics/quartz/Brush.cpp
+++ b/src/platform/graphics/quartz/Brush.cpp
@@ -1,6 +1,5 @@
 #include "cru/platform/graphics/quartz/Brush.h"
-#include "cru/base/String.h"
-#include "cru/base/Format.h"
+#include <format>
 
 namespace cru::platform::graphics::quartz {
 QuartzSolidColorBrush::QuartzSolidColorBrush(IGraphicsFactory* graphics_factory,
@@ -30,7 +29,7 @@ void QuartzSolidColorBrush::Select(CGContextRef context) {
   CGContextSetFillColorWithColor(context, cg_color_);
 }
 
-String QuartzSolidColorBrush::GetDebugString() {
-  return Format(u"QuartzSolidColorBrush(Color: {})", color_);
+std::string QuartzSolidColorBrush::GetDebugString() {
+  return std::format("QuartzSolidColorBrush(Color: {})", color_);
 }
 }  // namespace cru::platform::graphics::quartz
diff --git a/src/platform/graphics/quartz/Convert.cpp b/src/platform/graphics/quartz/Convert.cpp
index 06720982..06699b0c 100644
--- a/src/platform/graphics/quartz/Convert.cpp
+++ b/src/platform/graphics/quartz/Convert.cpp
@@ -1,5 +1,4 @@
 #include "cru/platform/graphics/quartz/Convert.h"
-#include <cstdint>
 
 namespace cru::platform::graphics::quartz {
 
diff --git a/src/platform/graphics/quartz/Factory.cpp b/src/platform/graphics/quartz/Factory.cpp
index 862c0966..69e9c607 100644
--- a/src/platform/graphics/quartz/Factory.cpp
+++ b/src/platform/graphics/quartz/Factory.cpp
@@ -1,12 +1,12 @@
 #include "cru/platform/graphics/quartz/Factory.h"
 
+#include "cru/platform/Check.h"
+#include "cru/platform/graphics/ImageFactory.h"
 #include "cru/platform/graphics/quartz/Brush.h"
 #include "cru/platform/graphics/quartz/Font.h"
 #include "cru/platform/graphics/quartz/Geometry.h"
 #include "cru/platform/graphics/quartz/ImageFactory.h"
 #include "cru/platform/graphics/quartz/TextLayout.h"
-#include "cru/platform/Check.h"
-#include "cru/platform/graphics/ImageFactory.h"
 
 #include <memory>
 
@@ -26,13 +26,13 @@ QuartzGraphicsFactory::CreateGeometryBuilder() {
   return std::make_unique<QuartzGeometryBuilder>(this);
 }
 
-std::unique_ptr<IFont> QuartzGraphicsFactory::CreateFont(String font_family,
-                                                         float font_size) {
+std::unique_ptr<IFont> QuartzGraphicsFactory::CreateFont(
+    std::string font_family, float font_size) {
   return std::make_unique<OsxCTFont>(this, font_family, font_size);
 }
 
 std::unique_ptr<ITextLayout> QuartzGraphicsFactory::CreateTextLayout(
-    std::shared_ptr<IFont> font, String text) {
+    std::shared_ptr<IFont> font, std::string text) {
   auto f = CheckPlatform<OsxCTFont>(font, GetPlatformId());
   return std::make_unique<OsxCTTextLayout>(this, f, text);
 }
diff --git a/src/platform/graphics/quartz/Font.cpp b/src/platform/graphics/quartz/Font.cpp
index 0c03e5e0..12a8aa7f 100644
--- a/src/platform/graphics/quartz/Font.cpp
+++ b/src/platform/graphics/quartz/Font.cpp
@@ -4,8 +4,8 @@
 #include "cru/platform/graphics/quartz/Resource.h"
 
 namespace cru::platform::graphics::quartz {
-OsxCTFont::OsxCTFont(IGraphicsFactory* graphics_factory, const String& name,
-                     float size)
+OsxCTFont::OsxCTFont(IGraphicsFactory* graphics_factory,
+                     const std::string& name, float size)
     : OsxQuartzResource(graphics_factory), name_(name) {
   auto n = ToCFString(name);
 
@@ -20,6 +20,6 @@ OsxCTFont::OsxCTFont(IGraphicsFactory* graphics_factory, const String& name,
 
 OsxCTFont::~OsxCTFont() { CFRelease(ct_font_); }
 
-String OsxCTFont::GetFontName() { return name_; }
+std::string OsxCTFont::GetFontName() { return name_; }
 float OsxCTFont::GetFontSize() { return CTFontGetSize(ct_font_); }
 }  // namespace cru::platform::graphics::quartz
diff --git a/src/platform/graphics/quartz/Image.cpp b/src/platform/graphics/quartz/Image.cpp
index d4ccd416..a6c7c65b 100644
--- a/src/platform/graphics/quartz/Image.cpp
+++ b/src/platform/graphics/quartz/Image.cpp
@@ -36,7 +36,7 @@ std::unique_ptr<IPainter> QuartzImage::CreatePainter() {
   if (!buffer_)
     throw Exception(
         "Failed to create painter for image because failed to get its "
-        u"buffer.");
+        "buffer.");
 
   auto width = CGImageGetWidth(image_);
   auto height = CGImageGetHeight(image_);
diff --git a/src/platform/graphics/quartz/ImageFactory.cpp b/src/platform/graphics/quartz/ImageFactory.cpp
index 2090828c..69fa502d 100644
--- a/src/platform/graphics/quartz/ImageFactory.cpp
+++ b/src/platform/graphics/quartz/ImageFactory.cpp
@@ -30,14 +30,14 @@ std::unique_ptr<IImage> QuartzImageFactory::DecodeFromStream(
       new QuartzImage(GetGraphicsFactory(), this, cg_image, true));
 }
 
-static String GetImageFormatUniformTypeIdentifier(ImageFormat format) {
+static std::string GetImageFormatUniformTypeIdentifier(ImageFormat format) {
   switch (format) {
     case ImageFormat::Png:
-      return u"public.png";
+      return "public.png";
     case ImageFormat::Jpeg:
-      return u"public.jpeg";
+      return "public.jpeg";
     case ImageFormat::Gif:
-      return u"com.compuserve.gif";
+      return "com.compuserve.gif";
     default:
       throw Exception("Unknown image format.");
   }
diff --git a/src/platform/graphics/quartz/TextLayout.cpp b/src/platform/graphics/quartz/TextLayout.cpp
index 8c573c7a..87f85b77 100644
--- a/src/platform/graphics/quartz/TextLayout.cpp
+++ b/src/platform/graphics/quartz/TextLayout.cpp
@@ -1,18 +1,19 @@
 #include "cru/platform/graphics/quartz/TextLayout.h"
 #include "cru/base/Base.h"
 #include "cru/base/Osx.h"
-#include "cru/base/Format.h"
-#include "cru/platform/graphics/quartz/Convert.h"
-#include "cru/platform/graphics/quartz/Resource.h"
+#include "cru/base/StringUtil.h"
 #include "cru/platform/Check.h"
 #include "cru/platform/graphics/Base.h"
+#include "cru/platform/graphics/quartz/Convert.h"
+#include "cru/platform/graphics/quartz/Resource.h"
 
+#include <format>
 #include <limits>
 
 namespace cru::platform::graphics::quartz {
 OsxCTTextLayout::OsxCTTextLayout(IGraphicsFactory* graphics_factory,
                                  std::shared_ptr<OsxCTFont> font,
-                                 const String& str)
+                                 const std::string& str)
     : OsxQuartzResource(graphics_factory),
       max_width_(std::numeric_limits<float>::max()),
       max_height_(std::numeric_limits<float>::max()),
@@ -35,7 +36,7 @@ void OsxCTTextLayout::SetFont(std::shared_ptr<IFont> font) {
   RecreateFrame();
 }
 
-void OsxCTTextLayout::DoSetText(String text) {
+void OsxCTTextLayout::DoSetText(std::string text) {
   text_ = std::move(text);
 
   if (text_.empty()) {
@@ -67,14 +68,15 @@ void OsxCTTextLayout::DoSetText(String text) {
       head_empty_line_count_ = 1;
       actual_text_ = {};
     } else {
-      actual_text_ = String(text_.cbegin() + head_empty_line_count_,
-                            text_.cend() - tail_empty_line_count_);
+      actual_text_ = std::string(text_.cbegin() + head_empty_line_count_,
+                                 text_.cend() - tail_empty_line_count_);
     }
   }
 
   auto s = ToCFString(actual_text_);
   cf_attributed_text_ = CFAttributedStringCreateMutable(nullptr, 0);
-  CFAttributedStringReplaceString(cf_attributed_text_, CFRangeMake(0, 0), s.ref);
+  CFAttributedStringReplaceString(cf_attributed_text_, CFRangeMake(0, 0),
+                                  s.ref);
   Ensures(cf_attributed_text_);
   CFAttributedStringSetAttribute(
       cf_attributed_text_,
@@ -82,7 +84,7 @@ void OsxCTTextLayout::DoSetText(String text) {
       kCTFontAttributeName, font_->GetCTFont());
 }
 
-void OsxCTTextLayout::SetText(String new_text) {
+void OsxCTTextLayout::SetText(std::string new_text) {
   if (new_text == text_) return;
 
   CFRelease(cf_attributed_text_);
@@ -199,10 +201,11 @@ TextHitTestResult OsxCTTextLayout::HitTest(const Point& point) {
   if (point.y >= th) {
     for (int i = 1; i <= tail_empty_line_count_; ++i) {
       if (point.y < th + i * font_->GetFontSize()) {
-        return {text_.size() - (tail_empty_line_count_ - i), false, false};
+        return {static_cast<Index>(text_.size() - (tail_empty_line_count_ - i)),
+                false, false};
       }
     }
-    return {text_.size(), false, false};
+    return {static_cast<Index>(text_.size()), false, false};
   }
 
   auto p = point;
@@ -236,24 +239,28 @@ TextHitTestResult OsxCTTextLayout::HitTest(const Point& point) {
       bool inside_text;
 
       if (pp.x < bounds.origin.x) {
-        po = actual_text_.IndexFromCodePointToCodeUnit(range.location);
+        po = cru::string::Utf8IndexCodePointToCodeUnit(
+            actual_text_.data(), actual_text_.size(), range.location);
         inside_text = false;
       } else if (pp.x > bounds.origin.x + bounds.size.width) {
-        po = actual_text_.IndexFromCodePointToCodeUnit(range.location +
-                                                       range.length);
+        po = cru::string::Utf8IndexCodePointToCodeUnit(
+            actual_text_.data(), actual_text_.size(),
+            range.location + range.length);
         inside_text = false;
       } else {
         int position = CTLineGetStringIndexForPosition(
             line,
             CGPointMake(pp.x - line_origins_[i].x, pp.y - line_origins_[i].y));
 
-        po = actual_text_.IndexFromCodePointToCodeUnit(position);
+        po = cru::string::Utf8IndexCodePointToCodeUnit(
+            actual_text_.data(), actual_text_.size(), position);
         inside_text = true;
       }
 
       if (po != 0 &&
-          po == actual_text_.IndexFromCodePointToCodeUnit(range.location +
-                                                          range.length) &&
+          po == cru::string::Utf8IndexCodePointToCodeUnit(
+                    actual_text_.data(), actual_text_.size(),
+                    range.location + range.length) &&
           actual_text_[po - 1] == u'\n') {
         --po;
       }
@@ -357,15 +364,16 @@ CTFrameRef OsxCTTextLayout::CreateFrameWithColor(const Color& color) {
   return frame;
 }
 
-String OsxCTTextLayout::GetDebugString() {
-  return Format(u"OsxCTTextLayout(text: {}, size: ({}, {}))", text_, max_width_,
-                max_height_);
+std::string OsxCTTextLayout::GetDebugString() {
+  return std::format("OsxCTTextLayout(text: {}, size: ({}, {}))", text_,
+                     max_width_, max_height_);
 }
 
 CGRect OsxCTTextLayout::DoGetTextBounds(bool includingTrailingSpace) {
   if (actual_text_.empty()) return CGRect{};
 
-  auto rects = DoTextRangeRect(TextRange{0, actual_text_.size()});
+  auto rects =
+      DoTextRangeRect(TextRange{0, static_cast<Index>(actual_text_.size())});
 
   float left = std::numeric_limits<float>::max();
   float bottom = std::numeric_limits<float>::max();
@@ -398,7 +406,12 @@ CGRect OsxCTTextLayout::DoGetTextBoundsIncludingEmptyLines(
 std::vector<CGRect> OsxCTTextLayout::DoTextRangeRect(
     const TextRange& text_range) {
   const auto r =
-      actual_text_.RangeFromCodeUnitToCodePoint(text_range).Normalize();
+      Range::FromTwoSides(
+          cru::string::Utf8IndexCodeUnitToCodePoint(
+              actual_text_.data(), actual_text_.size(), text_range.position),
+          cru::string::Utf8IndexCodeUnitToCodePoint(
+              actual_text_.data(), actual_text_.size(), text_range.GetEnd()))
+          .Normalize();
 
   std::vector<CGRect> results;
 
@@ -430,7 +443,8 @@ CGRect OsxCTTextLayout::DoTextSinglePoint(Index position, bool trailing) {
 
   if (actual_text_.empty()) return CGRectMake(0, 0, 0, font_->GetFontSize());
 
-  position = actual_text_.IndexFromCodeUnitToCodePoint(position);
+  position = cru::string::Utf8IndexCodeUnitToCodePoint(
+      actual_text_.data(), actual_text_.size(), position);
 
   for (int i = 0; i < line_count_; i++) {
     auto line = lines_[i];
diff --git a/src/platform/gui/osx/Clipboard.mm b/src/platform/gui/osx/Clipboard.mm
index d87ab7e3..a09bca1c 100644
--- a/src/platform/gui/osx/Clipboard.mm
+++ b/src/platform/gui/osx/Clipboard.mm
@@ -13,30 +13,30 @@ OsxClipboard::OsxClipboard(cru::platform::gui::IUiApplication* ui_application,
 
 OsxClipboard::~OsxClipboard() {}
 
-String OsxClipboard::GetText() { return p_->GetText(); }
+std::string OsxClipboard::GetText() { return p_->GetText(); }
 
-void OsxClipboard::SetText(String text) { p_->SetText(text); }
+void OsxClipboard::SetText(std::string text) { p_->SetText(text); }
 
 namespace details {
 OsxClipboardPrivate::OsxClipboardPrivate(NSPasteboard* pasteboard) : pasteboard_(pasteboard) {}
 
 OsxClipboardPrivate::~OsxClipboardPrivate() {}
 
-String OsxClipboardPrivate::GetText() {
+std::string OsxClipboardPrivate::GetText() {
   auto result = [pasteboard_ readObjectsForClasses:@[ NSString.class ] options:nil];
   if (result == nil) {
     CRU_LOG_TAG_WARN("Failed to get text from clipboard");
-    return u"";
+    return "";
   } else {
     if (result.count == 0) {
-      return u"";
+      return "";
     } else {
       return FromCFStringRef((CFStringRef)result[0]);
     }
   }
 }
 
-void OsxClipboardPrivate::SetText(String text) {
+void OsxClipboardPrivate::SetText(std::string text) {
   auto cf_string = ToCFString(text);
   [pasteboard_ clearContents];
   [pasteboard_ writeObjects:@[ (NSString*)cf_string.ref ]];
diff --git a/src/platform/gui/osx/ClipboardPrivate.h b/src/platform/gui/osx/ClipboardPrivate.h
index 41554297..5019ba17 100644
--- a/src/platform/gui/osx/ClipboardPrivate.h
+++ b/src/platform/gui/osx/ClipboardPrivate.h
@@ -17,8 +17,8 @@ class OsxClipboardPrivate : public Object {
   ~OsxClipboardPrivate();
 
  public:
-  String GetText();
-  void SetText(String text);
+  std::string GetText();
+  void SetText(std::string text);
 
  private:
   NSPasteboard* pasteboard_;
diff --git a/src/platform/gui/osx/InputMethod.mm b/src/platform/gui/osx/InputMethod.mm
index c3532ab6..c17dab3d 100644
--- a/src/platform/gui/osx/InputMethod.mm
+++ b/src/platform/gui/osx/InputMethod.mm
@@ -24,7 +24,7 @@ void OsxInputMethodContextPrivate::RaiseCompositionEndEvent() {
 }
 void OsxInputMethodContextPrivate::RaiseCompositionEvent() { composition_event_.Raise(nullptr); }
 
-void OsxInputMethodContextPrivate::RaiseTextEvent(StringView text) { text_event_.Raise(text); }
+void OsxInputMethodContextPrivate::RaiseTextEvent(std::string text) { text_event_.Raise(text); }
 
 void OsxInputMethodContextPrivate::PerformSel(SEL sel) {
   // [window_->p_->GetNSWindow() performSelector:sel];
@@ -77,7 +77,7 @@ IEvent<std::nullptr_t>* OsxInputMethodContext::CompositionEvent() {
   return &p_->composition_event_;
 }
 
-IEvent<StringView>* OsxInputMethodContext::TextEvent() { return &p_->text_event_; }
+IEvent<std::string>* OsxInputMethodContext::TextEvent() { return &p_->text_event_; }
 
 bool OsxInputMethodContext::IsEnabled() { return p_->is_enabled_; }
 }
diff --git a/src/platform/gui/osx/InputMethodPrivate.h b/src/platform/gui/osx/InputMethodPrivate.h
index ac2d1bf4..39f3be02 100644
--- a/src/platform/gui/osx/InputMethodPrivate.h
+++ b/src/platform/gui/osx/InputMethodPrivate.h
@@ -24,7 +24,7 @@ class OsxInputMethodContextPrivate {
   void RaiseCompositionStartEvent();
   void RaiseCompositionEndEvent();
   void RaiseCompositionEvent();
-  void RaiseTextEvent(StringView text);
+  void RaiseTextEvent(std::string text);
 
   Point GetCandidateWindowPosition() const { return candidate_window_point_; }
   void SetCandidateWindowPosition(const Point& p) {
@@ -56,7 +56,7 @@ class OsxInputMethodContextPrivate {
   Event<std::nullptr_t> composition_start_event_;
   Event<std::nullptr_t> composition_event_;
   Event<std::nullptr_t> composition_end_event_;
-  Event<StringView> text_event_;
+  Event<std::string> text_event_;
 
   bool is_enabled_ = false;
 };
diff --git a/src/platform/gui/osx/Keyboard.mm b/src/platform/gui/osx/Keyboard.mm
index da4c85f0..ea1d2d4e 100644
--- a/src/platform/gui/osx/Keyboard.mm
+++ b/src/platform/gui/osx/Keyboard.mm
@@ -267,16 +267,16 @@ NSString* ConvertKeyCodeToKeyEquivalent(KeyCode key_code) {
 
 NSEventModifierFlags ConvertKeyModifier(KeyModifier k) {
   NSEventModifierFlags flags = 0;
-  if (k & KeyModifiers::shift) {
+  if (k & KeyModifiers::Shift) {
     flags |= NSEventModifierFlagShift;
   }
-  if (k & KeyModifiers::ctrl) {
+  if (k & KeyModifiers::Ctrl) {
     flags |= NSEventModifierFlagControl;
   }
-  if (k & KeyModifiers::alt) {
+  if (k & KeyModifiers::Alt) {
     flags |= NSEventModifierFlagOption;
   }
-  if (k & KeyModifiers::command) {
+  if (k & KeyModifiers::Command) {
     flags |= NSEventModifierFlagCommand;
   }
   return flags;
diff --git a/src/platform/gui/osx/Menu.mm b/src/platform/gui/osx/Menu.mm
index 45beddee..0eea19ec 100644
--- a/src/platform/gui/osx/Menu.mm
+++ b/src/platform/gui/osx/Menu.mm
@@ -60,9 +60,9 @@ OsxMenuItem::OsxMenuItem(IUiApplication* ui_application) : OsxGuiResource(ui_app
 
 OsxMenuItem::~OsxMenuItem() { delete p_; }
 
-String OsxMenuItem::GetTitle() { return FromCFStringRef((CFStringRef)[p_->menu_item_ title]); }
+std::string OsxMenuItem::GetTitle() { return FromCFStringRef((CFStringRef)[p_->menu_item_ title]); }
 
-void OsxMenuItem::SetTitle(String title) {
+void OsxMenuItem::SetTitle(std::string title) {
   auto cf_title = ToCFString(title);
   [p_->menu_item_ setTitle:(NSString*)(cf_title.ref)];
 }
diff --git a/src/platform/gui/osx/UiApplication.mm b/src/platform/gui/osx/UiApplication.mm
index 7e744928..fca21075 100644
--- a/src/platform/gui/osx/UiApplication.mm
+++ b/src/platform/gui/osx/UiApplication.mm
@@ -177,7 +177,7 @@ graphics::IGraphicsFactory* OsxUiApplication::GetGraphicsFactory() {
   return p_->quartz_graphics_factory_.get();
 }
 
-std::optional<String> OsxUiApplication::ShowSaveDialog(SaveDialogOptions options) {
+std::optional<std::string> OsxUiApplication::ShowSaveDialog(SaveDialogOptions options) {
   NSSavePanel* panel = [NSSavePanel savePanel];
   [panel setTitle:(NSString*)ToCFString(options.title).ref];
   [panel setPrompt:(NSString*)ToCFString(options.prompt).ref];
@@ -201,7 +201,7 @@ std::optional<String> OsxUiApplication::ShowSaveDialog(SaveDialogOptions options
   }
 }
 
-std::optional<std::vector<String>> OsxUiApplication::ShowOpenDialog(OpenDialogOptions options) {
+std::optional<std::vector<std::string>> OsxUiApplication::ShowOpenDialog(OpenDialogOptions options) {
   NSOpenPanel* panel = [NSOpenPanel openPanel];
   [panel setTitle:(NSString*)ToCFString(options.title).ref];
   [panel setPrompt:(NSString*)ToCFString(options.prompt).ref];
@@ -223,7 +223,7 @@ std::optional<std::vector<String>> OsxUiApplication::ShowOpenDialog(OpenDialogOp
 
   auto model_result = [panel runModal];
   if (model_result == NSModalResponseOK) {
-    std::vector<String> result;
+    std::vector<std::string> result;
     for (NSURL* url in [panel URLs]) {
       result.push_back(FromCFStringRef((CFStringRef)[url path]));
     }
diff --git a/src/platform/gui/osx/Window.mm b/src/platform/gui/osx/Window.mm
index 6559cf70..65d31ab8 100644
--- a/src/platform/gui/osx/Window.mm
+++ b/src/platform/gui/osx/Window.mm
@@ -10,6 +10,7 @@
 #include "cru/platform/graphics/NullPainter.h"
 #include "cru/platform/graphics/quartz/Convert.h"
 #include "cru/platform/graphics/quartz/Painter.h"
+#include "cru/platform/gui/Input.h"
 #include "cru/platform/gui/TimerHelper.h"
 #include "cru/platform/gui/osx/Cursor.h"
 #include "cru/platform/gui/osx/InputMethod.h"
@@ -29,7 +30,6 @@ constexpr int key_down_debug = 0;
 }
 
 using ::cru::FromCFStringRef;
-using ::cru::ToCFString;
 using cru::platform::graphics::quartz::Convert;
 namespace cru::platform::gui::osx {
 namespace {
@@ -250,9 +250,9 @@ void OsxWindow::SetStyleFlag(WindowStyleFlag flag) {
   }
 }
 
-String OsxWindow::GetTitle() { return p_->title_; }
+std::string OsxWindow::GetTitle() { return p_->title_; }
 
-void OsxWindow::SetTitle(String title) {
+void OsxWindow::SetTitle(std::string title) {
   p_->title_ = title;
 
   if (p_->window_) {
@@ -401,13 +401,13 @@ namespace {
 cru::platform::gui::KeyModifier GetKeyModifier(NSEvent* event) {
   cru::platform::gui::KeyModifier key_modifier;
   if (event.modifierFlags & NSEventModifierFlagControl)
-    key_modifier |= cru::platform::gui::KeyModifiers::ctrl;
+    key_modifier |= cru::platform::gui::KeyModifiers::Ctrl;
   if (event.modifierFlags & NSEventModifierFlagOption)
-    key_modifier |= cru::platform::gui::KeyModifiers::alt;
+    key_modifier |= cru::platform::gui::KeyModifiers::Alt;
   if (event.modifierFlags & NSEventModifierFlagShift)
-    key_modifier |= cru::platform::gui::KeyModifiers::shift;
+    key_modifier |= cru::platform::gui::KeyModifiers::Shift;
   if (event.modifierFlags & NSEventModifierFlagCommand)
-    key_modifier |= cru::platform::gui::KeyModifiers::command;
+    key_modifier |= cru::platform::gui::KeyModifiers::Command;
   return key_modifier;
 }
 }  // namespace
@@ -504,28 +504,28 @@ cru::platform::gui::KeyModifier GetKeyModifier(NSEvent* event) {
   auto key_modifier = GetKeyModifier(event);
   cru::platform::Point p(event.locationInWindow.x, event.locationInWindow.y);
 
-  _p->OnMouseDown(cru::platform::gui::mouse_buttons::left, p, key_modifier);
+  _p->OnMouseDown(cru::platform::gui::MouseButtons::Left, p, key_modifier);
 }
 
 - (void)mouseUp:(NSEvent*)event {
   auto key_modifier = GetKeyModifier(event);
   cru::platform::Point p(event.locationInWindow.x, event.locationInWindow.y);
 
-  _p->OnMouseUp(cru::platform::gui::mouse_buttons::left, p, key_modifier);
+  _p->OnMouseUp(cru::platform::gui::MouseButtons::Left, p, key_modifier);
 }
 
 - (void)rightMouseDown:(NSEvent*)event {
   auto key_modifier = GetKeyModifier(event);
   cru::platform::Point p(event.locationInWindow.x, event.locationInWindow.y);
 
-  _p->OnMouseDown(cru::platform::gui::mouse_buttons::right, p, key_modifier);
+  _p->OnMouseDown(cru::platform::gui::MouseButtons::Right, p, key_modifier);
 }
 
 - (void)rightMouseUp:(NSEvent*)event {
   auto key_modifier = GetKeyModifier(event);
   cru::platform::Point p(event.locationInWindow.x, event.locationInWindow.y);
 
-  _p->OnMouseUp(cru::platform::gui::mouse_buttons::right, p, key_modifier);
+  _p->OnMouseUp(cru::platform::gui::MouseButtons::Right, p, key_modifier);
 }
 
 - (void)scrollWheel:(NSEvent*)event {
@@ -611,17 +611,17 @@ const std::unordered_set<KeyCode> input_context_handle_codes_when_has_text{
 
   if (input_context->IsEnabled()) {
     if (input_context_handle_codes.count(c) &&
-        !(key_modifier & ~cru::platform::gui::KeyModifiers::shift)) {
+        !(key_modifier & ~cru::platform::gui::KeyModifiers::Shift)) {
       handled = [[self inputContext] handleEvent:event];
     } else if (input_context_handle_codes_when_has_text.count(c) && !key_modifier) {
       if (!input_context->GetCompositionText().text.empty()) {
         handled = [[self inputContext] handleEvent:event];
       } else {
         if (c == KeyCode::Return) {
-          _input_context_p->RaiseTextEvent(u"\n");
+          _input_context_p->RaiseTextEvent("\n");
           handled = true;
         } else if (c == KeyCode::Space) {
-          _input_context_p->RaiseTextEvent(u" ");
+          _input_context_p->RaiseTextEvent(" ");
           handled = true;
         }
       }
@@ -688,9 +688,11 @@ const std::unordered_set<KeyCode> input_context_handle_codes_when_has_text{
 
   cru::platform::gui::CompositionText composition_text;
   composition_text.text = FromCFStringRef((CFStringRef)[_input_context_text string]);
-  composition_text.selection.position = ss.IndexFromCodePointToCodeUnit(selectedRange.location);
+  composition_text.selection.position =
+      cru::string::Utf8IndexCodePointToCodeUnit(ss.data(), ss.size(), selectedRange.location);
   composition_text.selection.count =
-      ss.IndexFromCodePointToCodeUnit(selectedRange.location + selectedRange.length) -
+      cru::string::Utf8IndexCodePointToCodeUnit(ss.data(), ss.size(),
+                                                selectedRange.location + selectedRange.length) -
       composition_text.selection.position;
   _input_context_p->SetCompositionText(composition_text);
   _input_context_p->RaiseCompositionEvent();
diff --git a/src/platform/gui/osx/WindowPrivate.h b/src/platform/gui/osx/WindowPrivate.h
index 478ce4e5..9e1b2a6c 100644
--- a/src/platform/gui/osx/WindowPrivate.h
+++ b/src/platform/gui/osx/WindowPrivate.h
@@ -83,7 +83,7 @@ class OsxWindowPrivate {
   INativeWindow* parent_ = nullptr;
   WindowStyleFlag style_flag_ = WindowStyleFlag{};
 
-  String title_;
+  std::string title_;
 
   Rect content_rect_;
 
diff --git a/test/base/StringUtilTest.cpp b/test/base/StringUtilTest.cpp
index 32fd0d88..fda30627 100644
--- a/test/base/StringUtilTest.cpp
+++ b/test/base/StringUtilTest.cpp
@@ -1,6 +1,7 @@
 #include "cru/base/StringUtil.h"
 
 #include <catch2/catch_test_macros.hpp>
+#include <string_view>
 
 using cru::Index;
 using namespace cru::string;
@@ -127,6 +128,50 @@ TEST_CASE("StringUtil Utf16CodePointIterator", "[string]") {
   REQUIRE(code_points == expected_code_points);
 }
 
+TEST_CASE("StringUtil Utf8IndexCodeUnitToCodePoint", "[string]") {
+  std::string_view text = "aπ你🤣!";
+  Index current = text.size();
+  REQUIRE(Utf8IndexCodeUnitToCodePoint(text.data(), text.size(), 0) == 0);
+  REQUIRE(Utf8IndexCodeUnitToCodePoint(text.data(), text.size(), 1) == 1);
+  REQUIRE(Utf8IndexCodeUnitToCodePoint(text.data(), text.size(), 3) == 2);
+  REQUIRE(Utf8IndexCodeUnitToCodePoint(text.data(), text.size(), 6) == 3);
+  REQUIRE(Utf8IndexCodeUnitToCodePoint(text.data(), text.size(), 10) == 4);
+  REQUIRE(Utf8IndexCodeUnitToCodePoint(text.data(), text.size(), 11) == 5);
+}
+
+TEST_CASE("StringUtil Utf8IndexCodePointToCodeUnit", "[string]") {
+  std::string_view text = "aπ你🤣!";
+  Index current = text.size();
+  REQUIRE(Utf8IndexCodePointToCodeUnit(text.data(), text.size(), 0) == 0);
+  REQUIRE(Utf8IndexCodePointToCodeUnit(text.data(), text.size(), 1) == 1);
+  REQUIRE(Utf8IndexCodePointToCodeUnit(text.data(), text.size(), 2) == 3);
+  REQUIRE(Utf8IndexCodePointToCodeUnit(text.data(), text.size(), 3) == 6);
+  REQUIRE(Utf8IndexCodePointToCodeUnit(text.data(), text.size(), 4) == 10);
+  REQUIRE(Utf8IndexCodePointToCodeUnit(text.data(), text.size(), 5) == 11);
+}
+
+TEST_CASE("StringUtil Utf16IndexCodeUnitToCodePoint", "[string]") {
+  std::u16string_view text = u"aπ你🤣!";
+  Index current = text.size();
+  REQUIRE(Utf16IndexCodeUnitToCodePoint(text.data(), text.size(), 0) == 0);
+  REQUIRE(Utf16IndexCodeUnitToCodePoint(text.data(), text.size(), 1) == 1);
+  REQUIRE(Utf16IndexCodeUnitToCodePoint(text.data(), text.size(), 2) == 2);
+  REQUIRE(Utf16IndexCodeUnitToCodePoint(text.data(), text.size(), 3) == 3);
+  REQUIRE(Utf16IndexCodeUnitToCodePoint(text.data(), text.size(), 5) == 4);
+  REQUIRE(Utf16IndexCodeUnitToCodePoint(text.data(), text.size(), 6) == 5);
+}
+
+TEST_CASE("StringUtil Utf16IndexCodePointToCodeUnit", "[string]") {
+  std::u16string_view text = u"aπ你🤣!";
+  Index current = text.size();
+  REQUIRE(Utf16IndexCodePointToCodeUnit(text.data(), text.size(), 0) == 0);
+  REQUIRE(Utf16IndexCodePointToCodeUnit(text.data(), text.size(), 1) == 1);
+  REQUIRE(Utf16IndexCodePointToCodeUnit(text.data(), text.size(), 2) == 2);
+  REQUIRE(Utf16IndexCodePointToCodeUnit(text.data(), text.size(), 3) == 3);
+  REQUIRE(Utf16IndexCodePointToCodeUnit(text.data(), text.size(), 4) == 5);
+  REQUIRE(Utf16IndexCodePointToCodeUnit(text.data(), text.size(), 5) == 6);
+}
+
 TEST_CASE("ParseToNumber Work", "[string]") {
   auto r1 = ParseToNumber<int>("123");
   REQUIRE(r1.valid);