5 files changed, 500 insertions, 144 deletions

diff --git a/src/ui/controls/Control.cpp b/src/ui/controls/Control.cpp
index 93213ecf..e903b5b3 100644
--- a/src/ui/controls/Control.cpp
+++ b/src/ui/controls/Control.cpp
@@ -1,10 +1,12 @@
 #include "cru/ui/controls/Control.h"
+#include "cru/ui/controls/Window.h"
 
 #include "cru/platform/gui/Cursor.h"
 #include "cru/platform/gui/UiApplication.h"
-#include "cru/ui/host/WindowHost.h"
 #include "cru/ui/style/StyleRuleSet.h"
 
+#include <format>
+
 namespace cru::ui::controls {
 using platform::gui::ICursor;
 using platform::gui::IUiApplication;
@@ -15,32 +17,45 @@ Control::Control() {
   style_rule_set_bind_ =
       std::make_unique<style::StyleRuleSetBind>(this, style_rule_set_);
 
-  MouseEnterEvent()->Direct()->AddHandler([this](events::MouseEventArgs&) {
-    this->is_mouse_over_ = true;
-    this->OnMouseHoverChange(true);
-  });
+  MouseEnterEvent()->Direct()->AddHandler(
+      [this](events::MouseEventArgs&) { this->is_mouse_over_ = true; });
 
-  MouseLeaveEvent()->Direct()->AddHandler([this](events::MouseEventArgs&) {
-    this->is_mouse_over_ = false;
-    this->OnMouseHoverChange(true);
-  });
+  MouseLeaveEvent()->Direct()->AddHandler(
+      [this](events::MouseEventArgs&) { this->is_mouse_over_ = false; });
 }
 
 Control::~Control() {
-  if (host::WindowHost::IsInEventHandling()) {
-    // Don't delete control during event handling. Use DeleteLater.
-    std::terminate();
+  if (auto window = GetWindow()) {
+    if (window->IsInEventHandling()) {
+      // Don't delete control during event handling. Use DeleteLater.
+      std::terminate();
+    }
   }
 
-  in_destruction_ = true;
   RemoveFromParent();
 }
 
+std::string Control::GetDebugId() const {
+  return std::format("{}({})", GetControlType(),
+                     static_cast<const void*>(this));
+}
+
+Window* Control::GetWindow() {
+  auto parent = this;
+  while (parent) {
+    if (auto window = dynamic_cast<Window*>(parent)) {
+      return window;
+    }
+    parent = parent->GetParent();
+  }
+  return nullptr;
+}
+
 void Control::SetParent(Control* parent) {
   if (parent_ == parent) return;
   auto old_parent = parent_;
   parent_ = parent;
-  OnParentChangedCore(old_parent, parent);
+  OnParentChanged(old_parent, parent);
 }
 
 void Control::RemoveFromParent() {
@@ -49,39 +64,49 @@ void Control::RemoveFromParent() {
   }
 }
 
+controls::Control* Control::HitTest(const Point& point) {
+  const auto render_object = GetRenderObject()->HitTest(point);
+  if (render_object) {
+    const auto control = render_object->GetAttachedControl();
+    assert(control);
+    return control;
+  }
+  return nullptr;
+}
+
 bool Control::HasFocus() {
-  auto host = GetWindowHost();
-  if (host == nullptr) return false;
+  auto window = GetWindow();
+  if (window == nullptr) return false;
 
-  return host->GetFocusControl() == this;
+  return window->GetFocusControl() == this;
 }
 
 bool Control::CaptureMouse() {
-  auto host = GetWindowHost();
-  if (host == nullptr) return false;
+  auto window = GetWindow();
+  if (window == nullptr) return false;
 
-  return host->CaptureMouseFor(this);
+  return window->SetMouseCaptureControl(this);
 }
 
 void Control::SetFocus() {
-  auto host = GetWindowHost();
-  if (host == nullptr) return;
+  auto window = GetWindow();
+  if (window == nullptr) return;
 
-  host->SetFocusControl(this);
+  window->SetFocusControl(this);
 }
 
 bool Control::ReleaseMouse() {
-  auto host = GetWindowHost();
-  if (host == nullptr) return false;
-
-  return host->CaptureMouseFor(nullptr);
+  auto window = GetWindow();
+  if (window == nullptr) return false;
+  if (window->GetMouseCaptureControl() != this) return false;
+  return window->SetMouseCaptureControl(nullptr);
 }
 
 bool Control::IsMouseCaptured() {
-  auto host = GetWindowHost();
-  if (host == nullptr) return false;
+  auto window = GetWindow();
+  if (window == nullptr) return false;
 
-  return host->GetMouseCaptureControl() == this;
+  return window->GetMouseCaptureControl() == this;
 }
 
 std::shared_ptr<ICursor> Control::GetCursor() { return cursor_; }
@@ -99,42 +124,13 @@ std::shared_ptr<ICursor> Control::GetInheritedCursor() {
 
 void Control::SetCursor(std::shared_ptr<ICursor> cursor) {
   cursor_ = std::move(cursor);
-  const auto host = GetWindowHost();
-  if (host != nullptr) {
-    host->UpdateCursor();
+  const auto window = GetWindow();
+  if (window != nullptr) {
+    window->UpdateCursor();
   }
 }
 
 std::shared_ptr<style::StyleRuleSet> Control::GetStyleRuleSet() {
   return style_rule_set_;
 }
-
-void Control::OnParentChangedCore(Control* old_parent, Control* new_parent) {
-  auto new_window_host =
-      new_parent == nullptr ? nullptr : new_parent->GetWindowHost();
-  if (window_host_ != new_window_host) {
-    auto old_host = window_host_;
-    window_host_ = new_window_host;
-    OnWindowHostChangedCore(old_host, new_window_host);
-  }
-
-  if (!in_destruction_) OnParentChanged(old_parent, new_parent);
-}
-
-void Control::OnWindowHostChangedCore(host::WindowHost* old_host,
-                                      host::WindowHost* new_host) {
-  if (old_host != nullptr) {
-    old_host->OnControlDetach(this);
-  }
-
-  if (!in_destruction_) {
-    ForEachChild([old_host, new_host](Control* child) {
-      child->window_host_ = new_host;
-      child->OnWindowHostChangedCore(old_host, new_host);
-    });
-    OnWindowHostChanged(old_host, new_host);
-  }
-}
-
-void Control::OnPrepareDelete() { RemoveFromParent(); }
 }  // namespace cru::ui::controls
diff --git a/src/ui/controls/Popup.cpp b/src/ui/controls/Popup.cpp
deleted file mode 100644
index 238ddbd4..00000000
--- a/src/ui/controls/Popup.cpp
+++ /dev/null
@@ -1,18 +0,0 @@
-#include "cru/ui/controls/Popup.h"
-
-#include "cru/platform/gui/UiApplication.h"
-#include "cru/ui/controls/RootControl.h"
-#include "cru/ui/host/WindowHost.h"
-#include "cru/ui/render/StackLayoutRenderObject.h"
-
-#include <memory>
-
-namespace cru::ui::controls {
-Popup::Popup(Control* attached_control) : RootControl(attached_control) {
-  GetWindowHost()->GetNativeWindow()->SetStyleFlag(
-      cru::platform::gui::WindowStyleFlags::NoCaptionAndBorder);
-  SetGainFocusOnCreateAndDestroyWhenLoseFocus(true);
-}
-
-Popup::~Popup() = default;
-}  // namespace cru::ui::controls
diff --git a/src/ui/controls/RootControl.cpp b/src/ui/controls/RootControl.cpp
deleted file mode 100644
index 7be1c630..00000000
--- a/src/ui/controls/RootControl.cpp
+++ /dev/null
@@ -1,49 +0,0 @@
-#include "cru/ui/controls/RootControl.h"
-
-#include "cru/platform/gui/Window.h"
-#include "cru/ui/Base.h"
-#include "cru/ui/host/WindowHost.h"
-
-#include <memory>
-
-namespace cru::ui::controls {
-RootControl::RootControl(Control* attached_control)
-    : attached_control_(attached_control) {
-  GetContainerRenderObject()->SetDefaultHorizontalAlignment(Alignment::Stretch);
-  GetContainerRenderObject()->SetDefaultVertialAlignment(Alignment::Stretch);
-  window_host_ = std::make_unique<host::WindowHost>(this);
-
-  Control::window_host_ = this->window_host_.get();
-
-  window_host_->SetLayoutPreferToFillWindow(true);
-}
-
-RootControl::~RootControl() {}
-
-platform::gui::INativeWindow* RootControl::GetNativeWindow() {
-  return window_host_->GetNativeWindow();
-}
-
-void RootControl::SetGainFocusOnCreateAndDestroyWhenLoseFocus(bool value) {
-  gain_focus_on_create_and_destroy_when_lose_focus_event_guard_.Clear();
-  if (value) {
-    auto native_window = window_host_->GetNativeWindow();
-
-    gain_focus_on_create_and_destroy_when_lose_focus_event_guard_ +=
-        native_window->VisibilityChangeEvent()->AddHandler(
-            [native_window](platform::gui::WindowVisibilityType type) {
-              if (type == platform::gui::WindowVisibilityType::Show) {
-                native_window->RequestFocus();
-              }
-            });
-
-    gain_focus_on_create_and_destroy_when_lose_focus_event_guard_ +=
-        native_window->FocusEvent()->AddHandler(
-            [native_window](platform::gui::FocusChangeType type) {
-              if (type == platform::gui::FocusChangeType::Lose) {
-                native_window->Close();
-              }
-            });
-  }
-}
-}  // namespace cru::ui::controls
diff --git a/src/ui/controls/TextHostControlService.cpp b/src/ui/controls/TextHostControlService.cpp
index 99090951..f51199c9 100644
--- a/src/ui/controls/TextHostControlService.cpp
+++ b/src/ui/controls/TextHostControlService.cpp
@@ -13,8 +13,8 @@
 #include "cru/ui/Base.h"
 #include "cru/ui/DebugFlags.h"
 #include "cru/ui/components/Menu.h"
+#include "cru/ui/controls/Window.h"
 #include "cru/ui/helper/ShortcutHub.h"
-#include "cru/ui/host/WindowHost.h"
 #include "cru/ui/render/ScrollRenderObject.h"
 #include "cru/ui/render/TextRenderObject.h"
 
@@ -293,9 +293,9 @@ void TextHostControlService::DeleteText(TextRange range,
 
 platform::gui::IInputMethodContext*
 TextHostControlService ::GetInputMethodContext() {
-  host::WindowHost* host = this->control_->GetWindowHost();
-  if (!host) return nullptr;
-  platform::gui::INativeWindow* native_window = host->GetNativeWindow();
+  Window* window = this->control_->GetWindow();
+  if (!window) return nullptr;
+  platform::gui::INativeWindow* native_window = window->GetNativeWindow();
   if (!native_window) return nullptr;
   return native_window->GetInputMethodContext();
 }
@@ -340,12 +340,13 @@ void TextHostControlService::SetCaretBlinkDuration(int milliseconds) {
 
 void TextHostControlService::ScrollToCaret() {
   if (const auto scroll_render_object = this->GetScrollRenderObject()) {
-    auto window_host = this->control_->GetWindowHost();
-    if (window_host)
-      window_host->RunAfterLayoutStable([this, scroll_render_object]() {
-        const auto caret_rect = this->GetTextRenderObject()->GetCaretRect();
-        scroll_render_object->ScrollToContain(caret_rect, Thickness{5.f});
-      });
+    scroll_to_caret_timer_canceler_.Reset(
+        platform::gui::IUiApplication::GetInstance()->SetImmediate(
+            [this, scroll_render_object] {
+              const auto caret_rect =
+                  this->GetTextRenderObject()->GetCaretRect();
+              scroll_render_object->ScrollToContain(caret_rect, Thickness{5.f});
+            }));
   }
 }
 
@@ -587,10 +588,10 @@ void TextHostControlService::GainFocusHandler(
               this->ReplaceSelectedText(text);
             });
 
-    host::WindowHost* window_host = control_->GetWindowHost();
-    if (window_host)
+    auto window = control_->GetWindow();
+    if (window)
       input_method_context_event_guard_ +=
-          window_host->AfterLayoutEvent()->AddHandler(
+          window->AfterLayoutEvent()->AddHandler(
               [this](auto) { this->UpdateInputMethodPosition(); });
     SetCaretVisible(true);
   }
@@ -700,7 +701,9 @@ void TextHostControlService::SetUpShortcuts() {
 void TextHostControlService::OpenContextMenu(const Point& position,
                                              ContextMenuItem items) {
   CRU_LOG_TAG_DEBUG("Open context menu.");
-  context_menu_.reset(new components::PopupMenu());
+  if (!context_menu_) {
+    context_menu_.reset(new components::PopupMenu());
+  }
   auto menu = context_menu_->GetMenu();
   menu->ClearItems();
   if (items & ContextMenuItem::kSelectAll) {
diff --git a/src/ui/controls/Window.cpp b/src/ui/controls/Window.cpp
index b1881136..e6abc48d 100644
--- a/src/ui/controls/Window.cpp
+++ b/src/ui/controls/Window.cpp
@@ -1,7 +1,431 @@
 #include "cru/ui/controls/Window.h"
 
+#include "cru/platform/gui/UiApplication.h"
+#include "cru/platform/gui/Window.h"
+#include "cru/ui/Base.h"
+
+#include <cassert>
+
 namespace cru::ui::controls {
-Window::Window(Control* attached_control) : RootControl(attached_control) {}
+Window::Window()
+    : event_handling_count_(0),
+      native_window_(CreateNativeWindow()),
+      focus_control_(this),
+      mouse_hover_control_(nullptr),
+      mouse_captured_control_(nullptr),
+      layout_prefer_to_fill_window_(true),
+      attached_control_(nullptr) {
+  GetContainerRenderObject()->SetDefaultHorizontalAlignment(Alignment::Stretch);
+  GetContainerRenderObject()->SetDefaultVertialAlignment(Alignment::Stretch);
+}
 
 Window::~Window() {}
+
+Window* Window::CreatePopup() {
+  auto window = new Window();
+  window->GetNativeWindow()->SetStyleFlag(
+      platform::gui::WindowStyleFlags::NoCaptionAndBorder);
+  window->SetGainFocusOnCreateAndDestroyWhenLoseFocus(true);
+  return window;
+}
+
+std::string Window::GetControlType() const { return std::string(kControlType); }
+
+void Window::SetAttachedControl(Control* control) {
+  attached_control_ = control;
+}
+
+platform::gui::INativeWindow* Window::GetNativeWindow() {
+  return native_window_.get();
+}
+
+void Window::SetGainFocusOnCreateAndDestroyWhenLoseFocus(bool value) {
+  gain_focus_on_create_and_destroy_when_lose_focus_event_guard_.Clear();
+  if (value) {
+    gain_focus_on_create_and_destroy_when_lose_focus_event_guard_ +=
+        native_window_->VisibilityChangeEvent()->AddHandler(
+            [this](platform::gui::WindowVisibilityType type) {
+              if (type == platform::gui::WindowVisibilityType::Show) {
+                native_window_->RequestFocus();
+              }
+            });
+
+    gain_focus_on_create_and_destroy_when_lose_focus_event_guard_ +=
+        native_window_->FocusEvent()->AddHandler(
+            [this](platform::gui::FocusChangeType type) {
+              if (type == platform::gui::FocusChangeType::Lose) {
+                native_window_->Close();
+              }
+            });
+  }
+}
+
+namespace {
+template <typename T>
+inline void BindNativeEvent(
+    Window* window, platform::gui::INativeWindow* native_window,
+    IEvent<T>* event,
+    void (Window::*handler)(platform::gui::INativeWindow*,
+                            typename IEvent<T>::Args)) {
+  event->AddHandler(
+      std::bind(handler, window, native_window, std::placeholders::_1));
+}
+}  // namespace
+
+namespace {
+bool IsAncestor(Control* control, Control* ancestor) {
+  while (control != nullptr) {
+    if (control == ancestor) return true;
+    control = control->GetParent();
+  }
+  return false;
+}
+
+// Ancestor at last.
+std::vector<Control*> GetAncestorList(Control* control) {
+  if (control == nullptr) return {};
+
+  std::vector<Control*> l;
+  while (control != nullptr) {
+    l.push_back(control);
+    control = control->GetParent();
+  }
+  return l;
+}
+
+Control* FindLowestCommonAncestor(Control* left, Control* right) {
+  if (left == nullptr || right == nullptr) return nullptr;
+
+  auto&& left_list = GetAncestorList(left);
+  auto&& right_list = GetAncestorList(right);
+
+  // the root is different
+  if (left_list.back() != right_list.back()) return nullptr;
+
+  // find the last same control or the last control (one is ancestor of the
+  // other)
+  auto left_iter = left_list.crbegin();
+  auto right_iter = right_list.crbegin();
+
+  while (true) {
+    if (left_iter == left_list.crend()) {
+      return left_list.front();
+    }
+    if (right_iter == right_list.crend()) {
+      return right_list.front();
+    }
+    if (*left_iter != *right_iter) {
+      return *(--left_iter);
+    }
+    ++left_iter;
+    ++right_iter;
+  }
+}
+}  // namespace
+
+std::unique_ptr<platform::gui::INativeWindow> Window::CreateNativeWindow() {
+  const auto ui_application = platform::gui::IUiApplication::GetInstance();
+
+  auto native_window = ui_application->CreateWindow();
+  assert(native_window);
+
+  BindNativeEvent(this, native_window, native_window->DestroyEvent(),
+                  &Window::OnNativeDestroy);
+  BindNativeEvent(this, native_window, native_window->PaintEvent(),
+                  &Window::OnNativePaint);
+  BindNativeEvent(this, native_window, native_window->ResizeEvent(),
+                  &Window::OnNativeResize);
+  BindNativeEvent(this, native_window, native_window->FocusEvent(),
+                  &Window::OnNativeFocus);
+  BindNativeEvent(this, native_window, native_window->MouseEnterLeaveEvent(),
+                  &Window::OnNativeMouseEnterLeave);
+  BindNativeEvent(this, native_window, native_window->MouseMoveEvent(),
+                  &Window::OnNativeMouseMove);
+  BindNativeEvent(this, native_window, native_window->MouseDownEvent(),
+                  &Window::OnNativeMouseDown);
+  BindNativeEvent(this, native_window, native_window->MouseUpEvent(),
+                  &Window::OnNativeMouseUp);
+  BindNativeEvent(this, native_window, native_window->MouseWheelEvent(),
+                  &Window::OnNativeMouseWheel);
+  BindNativeEvent(this, native_window, native_window->KeyDownEvent(),
+                  &Window::OnNativeKeyDown);
+  BindNativeEvent(this, native_window, native_window->KeyUpEvent(),
+                  &Window::OnNativeKeyUp);
+
+  return std::unique_ptr<platform::gui::INativeWindow>(native_window);
+}
+
+void Window::InvalidatePaint() {
+  repaint_schedule_canceler_.Reset(
+      platform::gui::IUiApplication::GetInstance()->SetImmediate(
+          [this] { Repaint(); }));
+}
+
+void Window::InvalidateLayout() {
+  relayout_schedule_canceler_.Reset(
+      platform::gui::IUiApplication::GetInstance()->SetImmediate(
+          [this] { Relayout(); }));
+}
+
+bool Window::IsLayoutPreferToFillWindow() const {
+  return layout_prefer_to_fill_window_;
+}
+
+void Window::SetLayoutPreferToFillWindow(bool value) {
+  if (value == layout_prefer_to_fill_window_) return;
+  layout_prefer_to_fill_window_ = value;
+  InvalidateLayout();
+}
+
+void Window::Repaint() {
+  auto painter = native_window_->BeginPaint();
+  painter->Clear(colors::white);
+  GetRenderObject()->Draw(painter.get());
+  painter->EndDraw();
+}
+
+void Window::Relayout() { RelayoutWithSize(native_window_->GetClientSize()); }
+
+void Window::RelayoutWithSize(const Size& available_size,
+                              bool set_window_size_to_fit_content) {
+  auto render_object = GetRenderObject();
+  render_object->Measure(
+      render::MeasureRequirement{
+          available_size,
+          !set_window_size_to_fit_content && IsLayoutPreferToFillWindow()
+              ? render::MeasureSize(available_size)
+              : render::MeasureSize::NotSpecified()},
+      render::MeasureSize::NotSpecified());
+
+  if (set_window_size_to_fit_content) {
+    native_window_->SetClientSize(render_object->GetDesiredSize());
+  }
+
+  render_object->Layout(Point{});
+  CRU_LOG_TAG_DEBUG("A relayout is finished.");
+
+  AfterLayoutEvent_.Raise(nullptr);
+
+  InvalidatePaint();
+}
+
+Control* Window::GetFocusControl() { return focus_control_; }
+
+void Window::SetFocusControl(Control* control) {
+  if (control == nullptr) control = this;
+  if (focus_control_ == control) return;
+
+  const auto old_focus_control = focus_control_;
+
+  focus_control_ = control;
+
+  DispatchFocusControlChangeEvent(old_focus_control, focus_control_, false);
+}
+
+Control* Window::GetMouseCaptureControl() { return mouse_captured_control_; }
+
+bool Window::SetMouseCaptureControl(Control* control) {
+  if (!native_window_->CaptureMouse()) return false;
+
+  if (control == mouse_captured_control_) return true;
+
+  if (control == nullptr) {
+    native_window_->ReleaseMouse();
+    const auto old_capture_control = mouse_captured_control_;
+    mouse_captured_control_ =
+        nullptr;  // update this in case this is used in event handlers
+    if (old_capture_control != mouse_hover_control_) {
+      DispatchMouseHoverControlChangeEvent(
+          old_capture_control, mouse_hover_control_,
+          native_window_->GetMousePosition(), true, false);
+    }
+    UpdateCursor();
+    return true;
+  }
+
+  if (mouse_captured_control_) return false;
+
+  mouse_captured_control_ = control;
+  DispatchMouseHoverControlChangeEvent(
+      mouse_hover_control_, mouse_captured_control_,
+      native_window_->GetMousePosition(), false, true);
+  UpdateCursor();
+  return true;
+}
+
+std::shared_ptr<platform::gui::ICursor> Window::GetOverrideCursor() {
+  return override_cursor_;
+}
+
+void Window::SetOverrideCursor(std::shared_ptr<platform::gui::ICursor> cursor) {
+  if (cursor == override_cursor_) return;
+  override_cursor_ = cursor;
+  UpdateCursor();
+}
+
+bool Window::IsInEventHandling() { return event_handling_count_; }
+
+void Window::UpdateCursor() {
+  if (override_cursor_) {
+    native_window_->SetCursor(override_cursor_);
+  } else {
+    const auto capture = GetMouseCaptureControl();
+    native_window_->SetCursor(
+        (capture ? capture : GetMouseHoverControl())->GetInheritedCursor());
+  }
+}
+
+void Window::OnNativeDestroy(platform::gui::INativeWindow* window,
+                             std::nullptr_t) {
+  CRU_UNUSED(window)
+}
+
+void Window::OnNativePaint(platform::gui::INativeWindow* window,
+                           std::nullptr_t) {
+  CRU_UNUSED(window)
+  InvalidatePaint();
+}
+
+void Window::OnNativeResize(platform::gui::INativeWindow* window,
+                            const Size& size) {
+  CRU_UNUSED(window)
+  CRU_UNUSED(size)
+
+  InvalidateLayout();
+}
+
+void Window::OnNativeFocus(platform::gui::INativeWindow* window,
+                           platform::gui::FocusChangeType focus) {
+  CRU_UNUSED(window)
+
+  focus == platform::gui::FocusChangeType::Gain
+      ? DispatchEvent(focus_control_, &Control::GainFocusEvent, nullptr, true)
+      : DispatchEvent(focus_control_, &Control::LoseFocusEvent, nullptr, true);
+}
+
+void Window::OnNativeMouseEnterLeave(platform::gui::INativeWindow* window,
+                                     platform::gui::MouseEnterLeaveType type) {
+  CRU_UNUSED(window)
+
+  if (type == platform::gui::MouseEnterLeaveType::Leave) {
+    DispatchEvent(mouse_hover_control_, &Control::MouseLeaveEvent, nullptr);
+    mouse_hover_control_ = nullptr;
+  }
+}
+
+void Window::OnNativeMouseMove(platform::gui::INativeWindow* window,
+                               const Point& point) {
+  CRU_UNUSED(window)
+
+  // Find the first control that hit test succeed.
+  const auto new_mouse_hover_control = HitTest(point);
+  const auto old_mouse_hover_control = mouse_hover_control_;
+  mouse_hover_control_ = new_mouse_hover_control;
+
+  if (mouse_captured_control_) {
+    const auto n = FindLowestCommonAncestor(new_mouse_hover_control,
+                                            mouse_captured_control_);
+    const auto o = FindLowestCommonAncestor(old_mouse_hover_control,
+                                            mouse_captured_control_);
+    bool a = IsAncestor(o, n);
+    if (a) {
+      DispatchEvent(o, &Control::MouseLeaveEvent, n);
+    } else {
+      DispatchEvent(n, &Control::MouseEnterEvent, o, point);
+    }
+    DispatchEvent(mouse_captured_control_, &Control::MouseMoveEvent, nullptr,
+                  point);
+    UpdateCursor();
+    return;
+  }
+
+  DispatchMouseHoverControlChangeEvent(
+      old_mouse_hover_control, new_mouse_hover_control, point, false, false);
+  DispatchEvent(new_mouse_hover_control, &Control::MouseMoveEvent, nullptr,
+                point);
+  UpdateCursor();
+}
+
+void Window::OnNativeMouseDown(
+    platform::gui::INativeWindow* window,
+    const platform::gui::NativeMouseButtonEventArgs& args) {
+  CRU_UNUSED(window)
+
+  Control* control =
+      mouse_captured_control_ ? mouse_captured_control_ : HitTest(args.point);
+  DispatchEvent(control, &Control::MouseDownEvent, nullptr, args.point,
+                args.button, args.modifier);
+}
+
+void Window::OnNativeMouseUp(
+    platform::gui::INativeWindow* window,
+    const platform::gui::NativeMouseButtonEventArgs& args) {
+  CRU_UNUSED(window)
+
+  Control* control =
+      mouse_captured_control_ ? mouse_captured_control_ : HitTest(args.point);
+  DispatchEvent(control, &Control::MouseUpEvent, nullptr, args.point,
+                args.button, args.modifier);
+}
+
+void Window::OnNativeMouseWheel(
+    platform::gui::INativeWindow* window,
+    const platform::gui::NativeMouseWheelEventArgs& args) {
+  CRU_UNUSED(window)
+
+  Control* control =
+      mouse_captured_control_ ? mouse_captured_control_ : HitTest(args.point);
+  DispatchEvent(control, &Control::MouseWheelEvent, nullptr, args.point,
+                args.delta, args.modifier);
+}
+
+void Window::OnNativeKeyDown(platform::gui::INativeWindow* window,
+                             const platform::gui::NativeKeyEventArgs& args) {
+  CRU_UNUSED(window)
+
+  DispatchEvent(focus_control_, &Control::KeyDownEvent, nullptr, args.key,
+                args.modifier);
+}
+
+void Window::OnNativeKeyUp(platform::gui::INativeWindow* window,
+                           const platform::gui::NativeKeyEventArgs& args) {
+  CRU_UNUSED(window)
+
+  DispatchEvent(focus_control_, &Control::KeyUpEvent, nullptr, args.key,
+                args.modifier);
+}
+
+void Window::DispatchFocusControlChangeEvent(Control* old_control,
+                                             Control* new_control,
+                                             bool is_window) {
+  if (new_control != old_control) {
+    const auto lowest_common_ancestor =
+        FindLowestCommonAncestor(old_control, new_control);
+    DispatchEvent(old_control, &Control::LoseFocusEvent, lowest_common_ancestor,
+                  is_window);
+    DispatchEvent(new_control, &Control::GainFocusEvent, lowest_common_ancestor,
+                  is_window);
+  }
+}
+
+void Window::DispatchMouseHoverControlChangeEvent(Control* old_control,
+                                                  Control* new_control,
+                                                  const Point& point,
+                                                  bool no_leave,
+                                                  bool no_enter) {
+  if (new_control != old_control)  // if the mouse-hover-on control changed
+  {
+    const auto lowest_common_ancestor =
+        FindLowestCommonAncestor(old_control, new_control);
+    if (!no_leave && old_control != nullptr)
+      DispatchEvent(old_control, &Control::MouseLeaveEvent,
+                    lowest_common_ancestor);  // dispatch mouse leave event.
+    if (!no_enter && new_control != nullptr) {
+      DispatchEvent(new_control, &Control::MouseEnterEvent,
+                    lowest_common_ancestor,
+                    point);  // dispatch mouse enter event.
+    }
+  }
+}
+
 }  // namespace cru::ui::controls