6 files changed, 55 insertions, 43 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