...

46 files changed, 336 insertions, 179 deletions

diff --git a/demos/CMakeLists.txt b/demos/CMakeLists.txt
index f3b4afde..17a8fbed 100644
--- a/demos/CMakeLists.txt
+++ b/demos/CMakeLists.txt
@@ -1,8 +1,6 @@
 add_library(cru_demo_base INTERFACE)
 
-if(WIN32)
-	target_link_libraries(cru_demo_base INTERFACE cru_win_gui)
-endif()
+target_link_libraries(cru_demo_base INTERFACE cru_platform_boostrap)
 
 if(WIN32) # Currently only enable tests on Windows.
 	add_subdirectory(main)
diff --git a/demos/input_method/main.cpp b/demos/input_method/main.cpp
index 5a6dc942..b509cd97 100644
--- a/demos/input_method/main.cpp
+++ b/demos/input_method/main.cpp
@@ -1,3 +1,4 @@
+#include "cru/platform/bootstrap/Bootstrap.hpp"
 #include "cru/platform/graphics/Factory.hpp"
 #include "cru/platform/graphics/Font.hpp"
 #include "cru/platform/graphics/Painter.hpp"
@@ -10,7 +11,7 @@ int main() {
   using namespace cru::platform::graphics;
   using namespace cru::platform::gui;
 
-  auto application = CreateUiApplication();
+  IUiApplication* application = boostrap::CreateUiApplication();
 
   auto graph_factory = application->GetGraphFactory();
 
diff --git a/demos/main/main.cpp b/demos/main/main.cpp
index 541a2320..af2625a9 100644
--- a/demos/main/main.cpp
+++ b/demos/main/main.cpp
@@ -1,4 +1,5 @@
 #include "cru/platform/HeapDebug.hpp"
+#include "cru/platform/bootstrap/Bootstrap.hpp"
 #include "cru/platform/gui/UiApplication.hpp"
 #include "cru/platform/gui/Window.hpp"
 #include "cru/ui/Base.hpp"
@@ -9,7 +10,7 @@
 #include "cru/ui/controls/Window.hpp"
 #include "cru/ui/host/WindowHost.hpp"
 
-using cru::platform::gui::CreateUiApplication;
+using cru::platform::gui::IUiApplication;
 using cru::ui::controls::Button;
 using cru::ui::controls::FlexLayout;
 using cru::ui::controls::TextBlock;
@@ -21,7 +22,7 @@ int main() {
   cru::platform::SetupHeapDebug();
 #endif
 
-  auto application = CreateUiApplication();
+  IUiApplication* application = cru::platform::boostrap::CreateUiApplication();
 
   const auto window = Window::Create();
 
diff --git a/demos/scroll_view/main.cpp b/demos/scroll_view/main.cpp
index f6b29934..2d65f68f 100644
--- a/demos/scroll_view/main.cpp
+++ b/demos/scroll_view/main.cpp
@@ -1,14 +1,16 @@
+#include "cru/platform/bootstrap/Bootstrap.hpp"
 #include "cru/platform/gui/UiApplication.hpp"
 #include "cru/ui/controls/ScrollView.hpp"
 #include "cru/ui/controls/TextBlock.hpp"
 #include "cru/ui/controls/Window.hpp"
 
+using cru::platform::gui::IUiApplication;
 using cru::ui::controls::ScrollView;
 using cru::ui::controls::TextBlock;
 using cru::ui::controls::Window;
 
 int main() {
-  auto application = cru::platform::gui::CreateUiApplication();
+  IUiApplication* application = cru::platform::boostrap::CreateUiApplication();
 
   auto window = Window::Create();
 
diff --git a/include/cru/common/Base.hpp b/include/cru/common/Base.hpp
index 93b0008c..5ed1e763 100644
--- a/include/cru/common/Base.hpp
+++ b/include/cru/common/Base.hpp
@@ -36,6 +36,12 @@
   classname(classname&&) = delete; \
   classname& operator=(classname&&) = delete;
 
+#define CRU_DEFAULT_DESTRUCTOR(classname) ~classname() override = default;
+
+#define CRU_DEFAULT_CONSTRUCTOR_DESTRUCTOR(classname) \
+  classname() = default;                              \
+  ~classname() override = default;
+
 namespace cru {
 class CRU_BASE_API Object {
  public:
@@ -66,21 +72,4 @@ inline void hash_combine(std::size_t& s, const T& v) {
 #define CRU_DEFINE_CLASS_LOG_TAG(tag) \
  private:                             \
   constexpr static std::u16string_view log_tag = tag;
-
-class CRU_BASE_API Exception {
- public:
-  Exception() = default;
-  Exception(std::u16string message) : message_(std::move(message)) {}
-
-  CRU_DEFAULT_COPY(Exception)
-  CRU_DEFAULT_MOVE(Exception)
-
-  virtual ~Exception() = default;
-
- public:
-  std::u16string GetMessage() const { return message_; }
-
- private:
-  std::u16string message_;
-};
 }  // namespace cru
diff --git a/include/cru/common/Exception.hpp b/include/cru/common/Exception.hpp
new file mode 100644
index 00000000..861bf5e9
--- /dev/null
+++ b/include/cru/common/Exception.hpp
@@ -0,0 +1,21 @@
+#pragma once
+#include "String.hpp"
+
+namespace cru {
+class CRU_BASE_API Exception {
+ public:
+  Exception() = default;
+  Exception(String message) : message_(std::move(message)) {}
+
+  CRU_DEFAULT_COPY(Exception)
+  CRU_DEFAULT_MOVE(Exception)
+
+  virtual ~Exception() = default;
+
+ public:
+  String GetMessage() const { return message_; }
+
+ private:
+  String message_;
+};
+}  // namespace cru
diff --git a/include/cru/common/String.hpp b/include/cru/common/String.hpp
index ea9480f0..e779e3a6 100644
--- a/include/cru/common/String.hpp
+++ b/include/cru/common/String.hpp
@@ -9,21 +9,24 @@
 namespace cru {
 class CRU_BASE_API String {
  public:
-  static String fromUtf8(const char* str, Index size);
+  static String FromUtf8(std::string_view str) {
+    return FromUtf8(str.data(), str.size());
+  }
+  static String FromUtf8(const char* str, Index size);
 
-  static String fromUtf16(const std::uint16_t* str) { return String(str); }
-  static String fromUtf16(const std::uint16_t* str, Index size) {
+  static String FromUtf16(const std::uint16_t* str) { return String(str); }
+  static String FromUtf16(const std::uint16_t* str, Index size) {
     return String(str, size);
   }
 
-  static String fromUtf16(const char16_t* str) { return String(str); }
-  static String fromUtf16(const char16_t* str, Index size) {
+  static String FromUtf16(const char16_t* str) { return String(str); }
+  static String FromUtf16(const char16_t* str, Index size) {
     return String(str, size);
   }
 
 #ifdef CRU_PLATFORM_WINDOWS
-  static String fromUtf16(wchar_t* str) { return String(str); }
-  static String fromUtf16(wchar_t* str, Index size) {
+  static String FromUtf16(wchar_t* str) { return String(str); }
+  static String FromUtf16(wchar_t* str, Index size) {
     return String(str, size);
   }
 #endif
@@ -49,10 +52,12 @@ class CRU_BASE_API String {
 
   String(const char16_t* str);
   String(const char16_t* str, Index size);
+  String(const std::u16string& str) : String(str.data(), str.size()) {}
 
 #ifdef CRU_PLATFORM_WINDOWS
   String(const wchar_t* str);
   String(const wchar_t* str, Index size);
+  String(const std::wstring& str) : String(str.data(), str.size()) {}
 #endif
 
   String(const String& other);
@@ -121,6 +126,19 @@ class CRU_BASE_API String {
     this->insert(cend(), str, size);
   }
 
+ public:
+  const char16_t* Char16CStr() const {
+    return reinterpret_cast<const char16_t*>(c_str());
+  }
+
+#ifdef CRU_PLATFORM_WINDOWS
+  const wchar_t* WinCStr() const {
+    return reinterpret_cast<const wchar_t*>(c_str());
+  }
+#endif
+
+  std::string ToUtf8() const;
+
  private:
   static std::uint16_t kEmptyBuffer[1];
 
diff --git a/include/cru/common/StringUtil.hpp b/include/cru/common/StringUtil.hpp
index 481566a6..985f0032 100644
--- a/include/cru/common/StringUtil.hpp
+++ b/include/cru/common/StringUtil.hpp
@@ -1,5 +1,6 @@
 #pragma once
 #include "Base.hpp"
+#include "Exception.hpp"
 
 #include <functional>
 #include <string>
diff --git a/include/cru/platform/Base.hpp b/include/cru/platform/Base.hpp
new file mode 100644
index 00000000..8589e6cb
--- /dev/null
+++ b/include/cru/platform/Base.hpp
@@ -0,0 +1,11 @@
+#pragma once
+
+#ifdef CRU_PLATFORM_WINDOWS
+#ifdef CRU_PLATFORM_EXPORT_API
+#define CRU_PLATFORM_API __declspec(dllexport)
+#else
+#define CRU_PLATFORM_API __declspec(dllimport)
+#endif
+#else
+#define CRU_PLATFORM_API
+#endif
diff --git a/include/cru/platform/Check.hpp b/include/cru/platform/Check.hpp
index d3180582..9ecd2d1d 100644
--- a/include/cru/platform/Check.hpp
+++ b/include/cru/platform/Check.hpp
@@ -10,32 +10,31 @@
 
 namespace cru::platform {
 template <typename TTarget>
-TTarget* CheckPlatform(INativeResource* resource,
-                       const std::u16string_view& target_platform) {
+TTarget* CheckPlatform(IPlatformResource* resource,
+                       const String& target_platform) {
   Expects(resource);
   const auto result = dynamic_cast<TTarget*>(resource);
   if (result == nullptr) {
-    throw UnsupportPlatformException(fmt::format(
+    throw UnsupportPlatformException(String::FromUtf8(fmt::format(
         "Try to convert resource to target platform failed. Platform id of "
         "resource to convert: {} . Target platform id: {} .",
-        ToUtf8(resource->GetPlatformId()), ToUtf8(target_platform)));
+        resource->GetPlatformId().ToUtf8(), target_platform.ToUtf8())));
   }
   return result;
 }
 
 template <typename TTarget, typename TSource>
-std::shared_ptr<TTarget> CheckPlatform(
-    const std::shared_ptr<TSource>& resource,
-    const std::u16string_view& target_platform) {
-  static_assert(std::is_base_of_v<INativeResource, TSource>,
+std::shared_ptr<TTarget> CheckPlatform(const std::shared_ptr<TSource>& resource,
+                                       const String& target_platform) {
+  static_assert(std::is_base_of_v<IPlatformResource, TSource>,
                 "TSource must be a subclass of INativeResource.");
   Expects(resource);
   const auto result = std::dynamic_pointer_cast<TTarget>(resource);
   if (result == nullptr) {
-    throw UnsupportPlatformException(fmt::format(
+    throw UnsupportPlatformException(String::FromUtf8(fmt::format(
         "Try to convert resource to target platform failed. Platform id of "
         "resource to convert: {} . Target platform id: {} .",
-        ToUtf8(resource->GetPlatformId()), ToUtf8(target_platform)));
+        resource->GetPlatformId().ToUtf8(), target_platform.ToUtf8())));
   }
   return result;
 }
diff --git a/include/cru/platform/Color.hpp b/include/cru/platform/Color.hpp
index 530695b2..a6793269 100644
--- a/include/cru/platform/Color.hpp
+++ b/include/cru/platform/Color.hpp
@@ -1,5 +1,7 @@
 #pragma once
-#include "boost/functional/hash.hpp"
+#include "cru/platform/Base.hpp"
+
+#include <boost/functional/hash.hpp>
 
 #include <cstdint>
 #include <optional>
@@ -7,7 +9,7 @@
 #include <unordered_map>
 
 namespace cru::platform {
-struct Color {
+struct CRU_PLATFORM_API Color {
   constexpr Color() : Color(0, 0, 0, 255) {}
   constexpr Color(std::uint8_t red, std::uint8_t green, std::uint8_t blue,
                   std::uint8_t alpha = 255)
diff --git a/include/cru/platform/Exception.hpp b/include/cru/platform/Exception.hpp
index 8b958a1d..379753d4 100644
--- a/include/cru/platform/Exception.hpp
+++ b/include/cru/platform/Exception.hpp
@@ -1,28 +1,43 @@
 #pragma once
+#include "Base.hpp"
 #include "cru/common/Base.hpp"
-
-#include <stdexcept>
+#include "cru/common/Exception.hpp"
 
 namespace cru::platform {
-class PlatformException : public std::runtime_error {
+class CRU_PLATFORM_API PlatformException : public Exception {
  public:
-  using runtime_error::runtime_error;  // inherit constructors
+  using Exception::Exception;  // inherit constructors
+
+  CRU_DEFAULT_COPY(PlatformException)
+  CRU_DEFAULT_MOVE(PlatformException)
+
+  CRU_DEFAULT_DESTRUCTOR(PlatformException)
 };
 
 // This exception is thrown when a resource is used on another platform.
 // Of course, you can't mix resources of two different platform.
 // For example, Win32 Brush (may add in the future) with Direct Painter.
-class UnsupportPlatformException : public std::runtime_error {
+class CRU_PLATFORM_API UnsupportPlatformException : public Exception {
  public:
-  using runtime_error::runtime_error;  // inherit constructors
+  using Exception::Exception;  // inherit constructors
+
+  CRU_DEFAULT_COPY(UnsupportPlatformException)
+  CRU_DEFAULT_MOVE(UnsupportPlatformException)
+
+  CRU_DEFAULT_DESTRUCTOR(UnsupportPlatformException)
 };
 
 // This exception is thrown when a resource has been disposed and not usable
 // again.
 // For example, calling Build twice on a GeometryBuilder::Build will lead to
 // this exception.
-class ReuseException : public std::runtime_error {
+class CRU_PLATFORM_API ReuseException : public Exception {
  public:
-  using runtime_error::runtime_error;  // inherit constructors
+  using Exception::Exception;  // inherit constructors
+
+  CRU_DEFAULT_COPY(ReuseException)
+  CRU_DEFAULT_MOVE(ReuseException)
+
+  CRU_DEFAULT_DESTRUCTOR(ReuseException)
 };
 }  // namespace cru::platform
diff --git a/include/cru/platform/Resource.hpp b/include/cru/platform/Resource.hpp
index 7a85d9c1..b55da43a 100644
--- a/include/cru/platform/Resource.hpp
+++ b/include/cru/platform/Resource.hpp
@@ -1,10 +1,15 @@
 #pragma once
+#include "Base.hpp"
+
 #include "cru/common/Base.hpp"
+#include "cru/common/String.hpp"
 
 #include <string_view>
 
 namespace cru::platform {
-struct INativeResource : virtual Interface {
-  virtual std::u16string_view GetPlatformId() const = 0;
+struct CRU_PLATFORM_API IPlatformResource : virtual Interface {
+  CRU_DEFAULT_CONSTRUCTOR_DESTRUCTOR(IPlatformResource)
+
+  virtual String GetPlatformId() const = 0;
 };
 }  // namespace cru::platform
diff --git a/include/cru/platform/bootstrap/Bootstrap.hpp b/include/cru/platform/bootstrap/Bootstrap.hpp
new file mode 100644
index 00000000..730df28c
--- /dev/null
+++ b/include/cru/platform/bootstrap/Bootstrap.hpp
@@ -0,0 +1,17 @@
+#pragma once
+#include "cru/platform/gui/UiApplication.hpp"
+
+#ifdef CRU_PLATFORM_WINDOWS
+#ifdef CRU_PLATFORM_BOOTSTRAP_EXPORT_API
+#define CRU_PLATFORM_BOOTSTRAP_API __declspec(dllexport)
+#else
+#define CRU_PLATFORM_BOOTSTRAP_API __declspec(dllimport)
+#endif
+#else
+#define CRU_PLATFORM_BOOTSTRAP_API
+#endif
+
+namespace cru::platform::boostrap {
+CRU_PLATFORM_BOOTSTRAP_API cru::platform::gui::IUiApplication*
+CreateUiApplication();
+}
diff --git a/include/cru/platform/graphics/Base.hpp b/include/cru/platform/graphics/Base.hpp
index e751ebdb..25881772 100644
--- a/include/cru/platform/graphics/Base.hpp
+++ b/include/cru/platform/graphics/Base.hpp
@@ -21,4 +21,4 @@ struct TextHitTestResult {
   bool trailing;
   bool insideText;
 };
-}  // namespace cru::platform::graph
+}  // namespace cru::platform::graphics
diff --git a/include/cru/platform/graphics/Brush.hpp b/include/cru/platform/graphics/Brush.hpp
index 10c666b5..18d9705e 100644
--- a/include/cru/platform/graphics/Brush.hpp
+++ b/include/cru/platform/graphics/Brush.hpp
@@ -8,4 +8,4 @@ struct ISolidColorBrush : virtual IBrush {
   virtual Color GetColor() = 0;
   virtual void SetColor(const Color& color) = 0;
 };
-}  // namespace cru::platform::graph
+}  // namespace cru::platform::graphics
diff --git a/include/cru/platform/graphics/Factory.hpp b/include/cru/platform/graphics/Factory.hpp
index f9018e13..4ee10204 100644
--- a/include/cru/platform/graphics/Factory.hpp
+++ b/include/cru/platform/graphics/Factory.hpp
@@ -11,7 +11,7 @@
 
 namespace cru::platform::graphics {
 // Entry point of the graph module.
-struct IGraphFactory : virtual INativeResource {
+struct IGraphFactory : virtual IPlatformResource {
   virtual std::unique_ptr<ISolidColorBrush> CreateSolidColorBrush() = 0;
 
   virtual std::unique_ptr<IGeometryBuilder> CreateGeometryBuilder() = 0;
diff --git a/include/cru/platform/graphics/Font.hpp b/include/cru/platform/graphics/Font.hpp
index 70392a69..c8a155fc 100644
--- a/include/cru/platform/graphics/Font.hpp
+++ b/include/cru/platform/graphics/Font.hpp
@@ -5,4 +5,4 @@ namespace cru::platform::graphics {
 struct IFont : virtual IGraphResource {
   virtual float GetFontSize() = 0;
 };
-}  // namespace cru::platform::graph
+}  // namespace cru::platform::graphics
diff --git a/include/cru/platform/graphics/Geometry.hpp b/include/cru/platform/graphics/Geometry.hpp
index b0ce6ad9..cc8f8761 100644
--- a/include/cru/platform/graphics/Geometry.hpp
+++ b/include/cru/platform/graphics/Geometry.hpp
@@ -17,4 +17,4 @@ struct IGeometryBuilder : virtual IGraphResource {
 
   virtual std::unique_ptr<IGeometry> Build() = 0;
 };
-}  // namespace cru::platform::graph
+}  // namespace cru::platform::graphics
diff --git a/include/cru/platform/graphics/Painter.hpp b/include/cru/platform/graphics/Painter.hpp
index f75ea52b..24592f95 100644
--- a/include/cru/platform/graphics/Painter.hpp
+++ b/include/cru/platform/graphics/Painter.hpp
@@ -3,7 +3,7 @@
 
 namespace cru::platform::graphics {
 
-struct IPainter : virtual INativeResource {
+struct IPainter : virtual IPlatformResource {
   virtual Matrix GetTransform() = 0;
   virtual void SetTransform(const Matrix& matrix) = 0;
 
diff --git a/include/cru/platform/graphics/Resource.hpp b/include/cru/platform/graphics/Resource.hpp
index a1625ce4..212e5b18 100644
--- a/include/cru/platform/graphics/Resource.hpp
+++ b/include/cru/platform/graphics/Resource.hpp
@@ -4,7 +4,7 @@
 namespace cru::platform::graphics {
 struct IGraphFactory;
 
-struct IGraphResource : virtual INativeResource {
+struct IGraphResource : virtual IPlatformResource {
   virtual IGraphFactory* GetGraphFactory() = 0;
 };
-}  // namespace cru::platform::graph
+}  // namespace cru::platform::graphics
diff --git a/include/cru/platform/gui/Base.hpp b/include/cru/platform/gui/Base.hpp
index fd9d265c..4c2a8034 100644
--- a/include/cru/platform/gui/Base.hpp
+++ b/include/cru/platform/gui/Base.hpp
@@ -1,11 +1,20 @@
 #pragma once
-#include "Keyboard.hpp"
 #include "cru/common/Base.hpp"
 #include "cru/common/Bitmask.hpp"
 #include "cru/platform/graphics/Base.hpp"
 
 #include "../Resource.hpp"
 
+#ifdef CRU_PLATFORM_WINDOWS
+#ifdef CRU_PLATFORM_GUI_EXPORT_API
+#define CRU_PLATFORM_GUI_API __declspec(dllexport)
+#else
+#define CRU_PLATFORM_GUI_API __declspec(dllimport)
+#endif
+#else
+#define CRU_PLATFORM_GUI_API
+#endif
+
 namespace cru::platform::gui {
 struct ICursor;
 struct ICursorManager;
@@ -24,26 +33,4 @@ constexpr MouseButton left{0b1};
 constexpr MouseButton middle{0b10};
 constexpr MouseButton right{0b100};
 }  // namespace mouse_buttons
-
-struct NativeMouseButtonEventArgs {
-  MouseButton button;
-  Point point;
-  KeyModifier modifier;
-};
-
-struct NativeMouseWheelEventArgs {
-  // Positive means down. Negative means up. 
-  float delta;
-  Point point;
-  KeyModifier modifier;
-};
-
-struct NativeKeyEventArgs {
-  KeyCode key;
-  KeyModifier modifier;
-};
-
-enum class FocusChangeType { Gain, Lost };
-
-enum class MouseEnterLeaveType { Enter, Leave };
 }  // namespace cru::platform::gui
diff --git a/include/cru/platform/gui/Cursor.hpp b/include/cru/platform/gui/Cursor.hpp
index 316496a0..abc8b064 100644
--- a/include/cru/platform/gui/Cursor.hpp
+++ b/include/cru/platform/gui/Cursor.hpp
@@ -6,9 +6,9 @@
 namespace cru::platform::gui {
 enum class SystemCursorType { Arrow, Hand, IBeam };
 
-struct ICursor : virtual INativeResource {};
+struct ICursor : virtual IPlatformResource {};
 
-struct ICursorManager : virtual INativeResource {
+struct ICursorManager : virtual IPlatformResource {
   virtual std::shared_ptr<ICursor> GetSystemCursor(SystemCursorType type) = 0;
 
   // TODO: Add method to create cursor.
diff --git a/include/cru/platform/gui/InputMethod.hpp b/include/cru/platform/gui/InputMethod.hpp
index 9d090eab..9b07959c 100644
--- a/include/cru/platform/gui/InputMethod.hpp
+++ b/include/cru/platform/gui/InputMethod.hpp
@@ -22,7 +22,7 @@ struct CompositionText {
   TextRange selection;
 };
 
-struct IInputMethodContext : virtual INativeResource {
+struct IInputMethodContext : virtual IPlatformResource {
   // Return true if you should draw composition text manually. Return false if
   // system will take care of that for you.
   virtual bool ShouldManuallyDrawCompositionText() = 0;
diff --git a/include/cru/platform/gui/Keyboard.hpp b/include/cru/platform/gui/Keyboard.hpp
index 6c29239b..b93b44fa 100644
--- a/include/cru/platform/gui/Keyboard.hpp
+++ b/include/cru/platform/gui/Keyboard.hpp
@@ -1,5 +1,6 @@
 #pragma once
 #include "cru/common/Bitmask.hpp"
+#include "cru/platform/gui/Base.hpp"
 
 #include <string>
 #include <string_view>
@@ -122,7 +123,7 @@ struct KeyModifiers {
   static constexpr KeyModifier alt{0b100};
 };
 
-std::u16string_view ToString(KeyCode key_code);
-std::u16string ToString(KeyModifier key_modifier,
-                        std::u16string_view separator = u"+");
+CRU_PLATFORM_GUI_API std::u16string_view ToString(KeyCode key_code);
+CRU_PLATFORM_GUI_API std::u16string ToString(
+    KeyModifier key_modifier, std::u16string_view separator = u"+");
 }  // namespace cru::platform::gui
diff --git a/include/cru/platform/gui/TimerHelper.hpp b/include/cru/platform/gui/TimerHelper.hpp
new file mode 100644
index 00000000..a61d2f04
--- /dev/null
+++ b/include/cru/platform/gui/TimerHelper.hpp
@@ -0,0 +1,69 @@
+#pragma once
+#include "UiApplication.hpp"
+
+namespace cru::platform::gui {
+
+class TimerAutoCanceler {
+ public:
+  TimerAutoCanceler() : id_(0) {}
+  explicit TimerAutoCanceler(long long id) : id_(id) {}
+
+  CRU_DELETE_COPY(TimerAutoCanceler)
+
+  TimerAutoCanceler(TimerAutoCanceler&& other) : id_(other.id_) {
+    other.id_ = 0;
+  }
+
+  TimerAutoCanceler& operator=(TimerAutoCanceler&& other) {
+    if (&other == this) {
+      return *this;
+    }
+    Reset(other.id_);
+    other.id_ = 0;
+    return *this;
+  }
+
+  TimerAutoCanceler& operator=(long long other) {
+    return this->operator=(TimerAutoCanceler(other));
+  }
+
+  ~TimerAutoCanceler() { Reset(); }
+
+  long long Release() {
+    auto temp = id_;
+    id_ = 0;
+    return temp;
+  }
+
+  void Reset(long long id = 0) {
+    if (id_ > 0) IUiApplication::GetInstance()->CancelTimer(id_);
+    id_ = id;
+  }
+
+  explicit operator bool() const { return id_; }
+
+ private:
+  long long id_;
+};
+
+class TimerListAutoCanceler {
+ public:
+  TimerListAutoCanceler() = default;
+  CRU_DELETE_COPY(TimerListAutoCanceler)
+  CRU_DEFAULT_MOVE(TimerListAutoCanceler)
+  ~TimerListAutoCanceler() = default;
+
+  TimerListAutoCanceler& operator+=(long long id) {
+    list_.push_back(TimerAutoCanceler(id));
+    return *this;
+  }
+
+  void Clear() { list_.clear(); }
+
+  bool IsEmpty() const { return list_.empty(); }
+
+ private:
+  std::vector<TimerAutoCanceler> list_;
+};
+
+}  // namespace cru::platform::gui
diff --git a/include/cru/platform/gui/UiApplication.hpp b/include/cru/platform/gui/UiApplication.hpp
index 5a5b0b13..407e4fa1 100644
--- a/include/cru/platform/gui/UiApplication.hpp
+++ b/include/cru/platform/gui/UiApplication.hpp
@@ -20,7 +20,7 @@ struct CreateWindowFlags {
 };
 
 // The entry point of a ui application.
-struct IUiApplication : public virtual INativeResource {
+struct CRU_PLATFORM_GUI_API IUiApplication : public virtual IPlatformResource {
  public:
   static IUiApplication* GetInstance() { return instance; }
 
@@ -66,70 +66,4 @@ struct IUiApplication : public virtual INativeResource {
 
   virtual ICursorManager* GetCursorManager() = 0;
 };
-
-class TimerAutoCanceler {
- public:
-  TimerAutoCanceler() : id_(0) {}
-  explicit TimerAutoCanceler(long long id) : id_(id) {}
-
-  CRU_DELETE_COPY(TimerAutoCanceler)
-
-  TimerAutoCanceler(TimerAutoCanceler&& other) : id_(other.id_) {
-    other.id_ = 0;
-  }
-
-  TimerAutoCanceler& operator=(TimerAutoCanceler&& other) {
-    if (&other == this) {
-      return *this;
-    }
-    Reset(other.id_);
-    other.id_ = 0;
-    return *this;
-  }
-
-  TimerAutoCanceler& operator=(long long other) {
-    return this->operator=(TimerAutoCanceler(other));
-  }
-
-  ~TimerAutoCanceler() { Reset(); }
-
-  long long Release() {
-    auto temp = id_;
-    id_ = 0;
-    return temp;
-  }
-
-  void Reset(long long id = 0) {
-    if (id_ > 0) IUiApplication::GetInstance()->CancelTimer(id_);
-    id_ = id;
-  }
-
-  explicit operator bool() const { return id_; }
-
- private:
-  long long id_;
-};
-
-class TimerListAutoCanceler {
- public:
-  TimerListAutoCanceler() = default;
-  CRU_DELETE_COPY(TimerListAutoCanceler)
-  CRU_DEFAULT_MOVE(TimerListAutoCanceler)
-  ~TimerListAutoCanceler() = default;
-
-  TimerListAutoCanceler& operator+=(long long id) {
-    list_.push_back(TimerAutoCanceler(id));
-    return *this;
-  }
-
-  void Clear() { list_.clear(); }
-
-  bool IsEmpty() const { return list_.empty(); }
-
- private:
-  std::vector<TimerAutoCanceler> list_;
-};
-
-// Bootstrap from this.
-std::unique_ptr<IUiApplication> CreateUiApplication();
 }  // namespace cru::platform::gui
diff --git a/include/cru/platform/gui/Window.hpp b/include/cru/platform/gui/Window.hpp
index b2129322..3502868a 100644
--- a/include/cru/platform/gui/Window.hpp
+++ b/include/cru/platform/gui/Window.hpp
@@ -1,14 +1,38 @@
 #pragma once
 #include "Base.hpp"
 
+#include "Keyboard.hpp"
+
 #include "cru/common/Event.hpp"
 
 #include <string_view>
 
 namespace cru::platform::gui {
+enum class FocusChangeType { Gain, Lost };
+
+enum class MouseEnterLeaveType { Enter, Leave };
+
+struct NativeMouseButtonEventArgs {
+  MouseButton button;
+  Point point;
+  KeyModifier modifier;
+};
+
+struct NativeMouseWheelEventArgs {
+  // Positive means down. Negative means up.
+  float delta;
+  Point point;
+  KeyModifier modifier;
+};
+
+struct NativeKeyEventArgs {
+  KeyCode key;
+  KeyModifier modifier;
+};
+
 // Represents a native window, which exposes some low-level events and
 // operations.
-struct INativeWindow : virtual INativeResource {
+struct INativeWindow : virtual IPlatformResource {
   virtual void Close() = 0;
 
   virtual INativeWindow* GetParent() = 0;
diff --git a/include/cru/ui/controls/TextHostControlService.hpp b/include/cru/ui/controls/TextHostControlService.hpp
index 340228fe..f39d9456 100644
--- a/include/cru/ui/controls/TextHostControlService.hpp
+++ b/include/cru/ui/controls/TextHostControlService.hpp
@@ -2,10 +2,12 @@
 #include "Base.hpp"
 
 #include "cru/platform/gui/InputMethod.hpp"
+#include "cru/platform/gui/TimerHelper.hpp"
 #include "cru/platform/gui/UiApplication.hpp"
 #include "cru/ui/controls/Control.hpp"
 #include "cru/ui/helper/ShortcutHub.hpp"
 
+
 #include <functional>
 #include <string>
 
diff --git a/include/cru/ui/host/LayoutPaintCycler.hpp b/include/cru/ui/host/LayoutPaintCycler.hpp
index ed543afa..861fff41 100644
--- a/include/cru/ui/host/LayoutPaintCycler.hpp
+++ b/include/cru/ui/host/LayoutPaintCycler.hpp
@@ -1,6 +1,7 @@
 #pragma once
 #include "../Base.hpp"
 
+#include "cru/platform/gui/TimerHelper.hpp"
 #include "cru/platform/gui/UiApplication.hpp"
 
 #include <chrono>
diff --git a/include/cru/ui/render/ScrollBar.hpp b/include/cru/ui/render/ScrollBar.hpp
index 005cf3bb..ce6f1b98 100644
--- a/include/cru/ui/render/ScrollBar.hpp
+++ b/include/cru/ui/render/ScrollBar.hpp
@@ -7,11 +7,13 @@
 #include "cru/platform/graphics/Geometry.hpp"
 #include "cru/platform/graphics/Painter.hpp"
 #include "cru/platform/gui/Cursor.hpp"
+#include "cru/platform/gui/TimerHelper.hpp"
 #include "cru/platform/gui/UiApplication.hpp"
 #include "cru/ui/Base.hpp"
 #include "cru/ui/controls/Control.hpp"
 #include "cru/ui/helper/ClickDetector.hpp"
 
+
 #include <gsl/pointers>
 #include <memory>
 #include <optional>
diff --git a/include/cru/win/graphics/direct/Resource.hpp b/include/cru/win/graphics/direct/Resource.hpp
index f60f373e..e6ffb203 100644
--- a/include/cru/win/graphics/direct/Resource.hpp
+++ b/include/cru/win/graphics/direct/Resource.hpp
@@ -8,9 +8,9 @@
 namespace cru::platform::graphics::win::direct {
 class DirectGraphFactory;
 
-class DirectResource : public Object, public virtual INativeResource {
+class DirectResource : public Object, public virtual IPlatformResource {
  public:
-  static constexpr std::u16string_view k_platform_id = u"Windows Direct";
+  static String kPlatformId;
 
  protected:
   DirectResource() = default;
@@ -22,7 +22,7 @@ class DirectResource : public Object, public virtual INativeResource {
   ~DirectResource() override = default;
 
  public:
-  std::u16string_view GetPlatformId() const final { return k_platform_id; }
+  String GetPlatformId() const final { return kPlatformId; }
 };
 
 class DirectGraphResource : public DirectResource,
diff --git a/include/cru/win/gui/Resource.hpp b/include/cru/win/gui/Resource.hpp
index 1f6f0a4a..4215de69 100644
--- a/include/cru/win/gui/Resource.hpp
+++ b/include/cru/win/gui/Resource.hpp
@@ -4,9 +4,9 @@
 #include "cru/platform/Resource.hpp"
 
 namespace cru::platform::gui::win {
-class WinNativeResource : public Object, public virtual INativeResource {
+class WinNativeResource : public Object, public virtual IPlatformResource {
  public:
-  static constexpr std::u16string_view k_platform_id = u"Windows";
+  static String kPlatformId;
 
  protected:
   WinNativeResource() = default;
@@ -18,6 +18,6 @@ class WinNativeResource : public Object, public virtual INativeResource {
   ~WinNativeResource() override = default;
 
  public:
-  std::u16string_view GetPlatformId() const final { return k_platform_id; }
+  String GetPlatformId() const final { return kPlatformId; }
 };
 }  // namespace cru::platform::gui::win
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index d5d544ee..94961746 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -8,6 +8,7 @@ target_sources(cru_base PUBLIC
 	${CRU_BASE_INCLUDE_DIR}/Base.hpp
 	${CRU_BASE_INCLUDE_DIR}/Bitmask.hpp
 	${CRU_BASE_INCLUDE_DIR}/Event.hpp
+	${CRU_BASE_INCLUDE_DIR}/Exception.hpp
 	${CRU_BASE_INCLUDE_DIR}/Format.hpp
 	${CRU_BASE_INCLUDE_DIR}/Logger.hpp
 	${CRU_BASE_INCLUDE_DIR}/PreConfig.hpp
diff --git a/src/common/String.cpp b/src/common/String.cpp
index ce124575..91422d48 100644
--- a/src/common/String.cpp
+++ b/src/common/String.cpp
@@ -1,8 +1,14 @@
 #include "cru/common/String.hpp"
+#include "cru/common/StringUtil.hpp"
 
 #include <cstring>
+#include <string_view>
 
 namespace cru {
+String String::FromUtf8(const char* str, Index size) {
+  return String{cru::ToUtf16(std::string_view(str, size))};
+}
+
 std::uint16_t String::kEmptyBuffer[1] = {0};
 
 template <typename C>
@@ -138,4 +144,8 @@ String::iterator String::erase(const_iterator start, const_iterator end) {
   return s;
 }
 
+std::string String::ToUtf8() const {
+  return cru::ToUtf8(std::u16string_view(Char16CStr(), size()));
+}
+
 }  // namespace cru
diff --git a/src/platform/CMakeLists.txt b/src/platform/CMakeLists.txt
index 23f4a0f6..f5f48795 100644
--- a/src/platform/CMakeLists.txt
+++ b/src/platform/CMakeLists.txt
@@ -1,8 +1,10 @@
 set(CRU_PLATFORM_BASE_INCLUDE_DIR ${CRU_INCLUDE_DIR}/cru/platform)
-add_library(cru_platform_base STATIC
+add_library(cru_platform_base SHARED
+	ForDllExport.cpp
 	Color.cpp
 )
 target_sources(cru_platform_base PUBLIC
+	${CRU_PLATFORM_BASE_INCLUDE_DIR}/Base.hpp
 	${CRU_PLATFORM_BASE_INCLUDE_DIR}/Check.hpp
 	${CRU_PLATFORM_BASE_INCLUDE_DIR}/Color.hpp
 	${CRU_PLATFORM_BASE_INCLUDE_DIR}/Exception.hpp
@@ -12,6 +14,8 @@ target_sources(cru_platform_base PUBLIC
 	${CRU_PLATFORM_BASE_INCLUDE_DIR}/Resource.hpp
 )
 target_link_libraries(cru_platform_base PUBLIC cru_base)
+target_compile_definitions(cru_platform_base PRIVATE CRU_PLATFORM_EXPORT_API)
 
 add_subdirectory(graphics)
 add_subdirectory(gui)
+add_subdirectory(bootstrap)
diff --git a/src/platform/ForDllExport.cpp b/src/platform/ForDllExport.cpp
new file mode 100644
index 00000000..743a9efa
--- /dev/null
+++ b/src/platform/ForDllExport.cpp
@@ -0,0 +1,2 @@
+#include "cru/platform/Exception.hpp"
+#include "cru/platform/Resource.hpp"
diff --git a/src/platform/bootstrap/Bootstrap.cpp b/src/platform/bootstrap/Bootstrap.cpp
new file mode 100644
index 00000000..99b5badb
--- /dev/null
+++ b/src/platform/bootstrap/Bootstrap.cpp
@@ -0,0 +1,15 @@
+#include "cru/platform/bootstrap/Bootstrap.hpp"
+
+#ifdef CRU_PLATFORM_WINDOWS
+#include "cru/win/gui/UiApplication.hpp"
+#else
+#endif
+
+namespace cru::platform::boostrap {
+cru::platform::gui::IUiApplication* CreateUiApplication() {
+#ifdef CRU_PLATFORM_WINDOWS
+  return new cru::platform::gui::win::WinUiApplication();
+#else
+#endif
+}
+}  // namespace cru::platform::boostrap
diff --git a/src/platform/bootstrap/CMakeLists.txt b/src/platform/bootstrap/CMakeLists.txt
new file mode 100644
index 00000000..7759415f
--- /dev/null
+++ b/src/platform/bootstrap/CMakeLists.txt
@@ -0,0 +1,13 @@
+set(CRU_PLATFORM_BOOTSTRAP_INCLUDE_DIR ${CRU_INCLUDE_DIR}/cru/platform/bootstrap)
+add_library(cru_platform_boostrap SHARED
+	Bootstrap.cpp
+)
+target_sources(cru_platform_boostrap PUBLIC
+	${CRU_PLATFORM_BOOTSTRAP_INCLUDE_DIR}/Bootstrap.hpp
+)
+
+if(WIN32)
+	target_link_libraries(cru_platform_boostrap PUBLIC cru_win_gui)
+endif()
+
+target_compile_definitions(cru_platform_boostrap PRIVATE CRU_PLATFORM_BOOTSTRAP_EXPORT_API)
diff --git a/src/platform/gui/CMakeLists.txt b/src/platform/gui/CMakeLists.txt
index aca7620c..7f16a0e0 100644
--- a/src/platform/gui/CMakeLists.txt
+++ b/src/platform/gui/CMakeLists.txt
@@ -1,5 +1,5 @@
 set(CRU_PLATFORM_GUI_INCLUDE_DIR ${CRU_INCLUDE_DIR}/cru/platform/gui)
-add_library(cru_platform_gui STATIC
+add_library(cru_platform_gui SHARED
 	Keyboard.cpp
 	UiApplication.cpp
 )
@@ -12,3 +12,4 @@ target_sources(cru_platform_gui PUBLIC
 	${CRU_PLATFORM_GUI_INCLUDE_DIR}/UiApplication.hpp
 )
 target_link_libraries(cru_platform_gui PUBLIC cru_platform_graphics)
+target_compile_definitions(cru_platform_gui PRIVATE CRU_PLATFORM_GUI_EXPORT_API)
diff --git a/src/win/Exception.cpp b/src/win/Exception.cpp
index 8d2eee23..df2103fd 100644
--- a/src/win/Exception.cpp
+++ b/src/win/Exception.cpp
@@ -5,13 +5,13 @@
 
 namespace cru::platform::win {
 
-inline std::string HResultMakeMessage(
-    HRESULT h_result, std::optional<std::string_view> message) {
+inline String HResultMakeMessage(HRESULT h_result,
+                                 std::optional<String> message) {
   if (message.has_value())
-    return fmt::format(FMT_STRING("HRESULT: {:#08x}. Message: {}"), h_result,
-                       *message);
+    return fmt::format(FMT_STRING(L"HRESULT: {:#08x}. Message: {}"), h_result,
+                       message->WinCStr());
   else
-    return fmt::format(FMT_STRING("HRESULT: {:#08x}."), h_result);
+    return fmt::format(FMT_STRING(L"HRESULT: {:#08x}."), h_result);
 }
 
 HResultError::HResultError(HRESULT h_result)
@@ -20,19 +20,21 @@ HResultError::HResultError(HRESULT h_result)
 
 HResultError::HResultError(HRESULT h_result,
                            std::string_view additional_message)
-    : PlatformException(HResultMakeMessage(h_result, additional_message)),
+    : PlatformException(HResultMakeMessage(
+          h_result, String::FromUtf8(additional_message.data(),
+                                     additional_message.size()))),
       h_result_(h_result) {}
 
-inline std::string Win32MakeMessage(DWORD error_code,
-                                       std::string_view message) {
-  return fmt::format("Last error code: {:#04x}.\nMessage: {}\n", error_code,
-                     message);
+inline String Win32MakeMessage(DWORD error_code, String message) {
+  return fmt::format(L"Last error code: {:#04x}.\nMessage: {}\n", error_code,
+                     message.WinCStr());
 }
 
 Win32Error::Win32Error(std::string_view message)
     : Win32Error(::GetLastError(), message) {}
 
 Win32Error::Win32Error(DWORD error_code, std::string_view message)
-    : PlatformException(Win32MakeMessage(error_code, message)),
+    : PlatformException(Win32MakeMessage(
+          error_code, String::FromUtf8(message.data(), message.size()))),
       error_code_(error_code) {}
 }  // namespace cru::platform::win
diff --git a/src/win/graphics/direct/Geometry.cpp b/src/win/graphics/direct/Geometry.cpp
index 8aa961b2..d07a819f 100644
--- a/src/win/graphics/direct/Geometry.cpp
+++ b/src/win/graphics/direct/Geometry.cpp
@@ -13,7 +13,7 @@ D2DGeometryBuilder::D2DGeometryBuilder(DirectGraphFactory* factory)
 
 void D2DGeometryBuilder::CheckValidation() {
   if (!IsValid())
-    throw ReuseException("The geometry builder is already disposed.");
+    throw ReuseException(L"The geometry builder is already disposed.");
 }
 
 void D2DGeometryBuilder::BeginFigure(const Point& point) {
diff --git a/src/win/graphics/direct/Painter.cpp b/src/win/graphics/direct/Painter.cpp
index d6999cfa..26ef92ec 100644
--- a/src/win/graphics/direct/Painter.cpp
+++ b/src/win/graphics/direct/Painter.cpp
@@ -106,7 +106,7 @@ void D2DPainter::EndDraw() {
 void D2DPainter::CheckValidation() {
   if (!is_drawing_) {
     throw cru::platform::ReuseException(
-        "Can't do that on painter after end drawing.");
+        L"Can't do that on painter after end drawing.");
   }
 }
 }  // namespace cru::platform::graphics::win::direct
diff --git a/src/win/graphics/direct/Resource.cpp b/src/win/graphics/direct/Resource.cpp
index 2b4a0772..6ae74e64 100644
--- a/src/win/graphics/direct/Resource.cpp
+++ b/src/win/graphics/direct/Resource.cpp
@@ -3,6 +3,8 @@
 #include "cru/win/graphics/direct/Factory.hpp"
 
 namespace cru::platform::graphics::win::direct {
+String DirectResource::kPlatformId = u"Windows Direct";
+
 DirectGraphResource::DirectGraphResource(DirectGraphFactory* factory)
     : factory_(factory) {
   Expects(factory);
diff --git a/src/win/gui/CMakeLists.txt b/src/win/gui/CMakeLists.txt
index 48bed00d..53dfe69b 100644
--- a/src/win/gui/CMakeLists.txt
+++ b/src/win/gui/CMakeLists.txt
@@ -8,6 +8,7 @@ add_library(cru_win_gui STATIC
 	GodWindow.cpp
 	InputMethod.cpp
 	Keyboard.cpp
+	Resource.cpp
 	TimerManager.cpp
 	UiApplication.cpp
 	Window.cpp
diff --git a/src/win/gui/Resource.cpp b/src/win/gui/Resource.cpp
new file mode 100644
index 00000000..dc4de173
--- /dev/null
+++ b/src/win/gui/Resource.cpp
@@ -0,0 +1,6 @@
+#include "cru/win/gui/Resource.hpp"
+#include "cru/win/gui/Window.hpp"
+
+namespace cru::platform::gui::win {
+String WinNativeResource::kPlatformId = u"Windows";
+}