...

29 files changed, 171 insertions, 105 deletions

diff --git a/include/cru/common/Base.hpp b/include/cru/common/Base.hpp
index ff7ab31e..409c2b0e 100644
--- a/include/cru/common/Base.hpp
+++ b/include/cru/common/Base.hpp
@@ -44,4 +44,8 @@ struct Interface {
 }
 
 using Index = gsl::index;
+
+#define CRU_DEFINE_CLASS_LOG_TAG(tag) \
+ private:                             \
+  constexpr static std::string_view log_tag = tag;
 }  // namespace cru
diff --git a/include/cru/common/Logger.hpp b/include/cru/common/Logger.hpp
index bd16678b..f76e4626 100644
--- a/include/cru/common/Logger.hpp
+++ b/include/cru/common/Logger.hpp
@@ -15,7 +15,7 @@ enum class LogLevel { Debug, Info, Warn, Error };
 struct ILogSource : virtual Interface {
   // Write the string s. LogLevel is just a helper. It has no effect on the
   // content to write.
-  virtual void Write(LogLevel level, const std::string_view& s) = 0;
+  virtual void Write(LogLevel level, std::string_view s) = 0;
 };
 
 class StdioLogSource : public virtual ILogSource {
@@ -27,7 +27,7 @@ class StdioLogSource : public virtual ILogSource {
 
   ~StdioLogSource() override = default;
 
-  void Write(LogLevel level, const std::string_view& s) override {
+  void Write(LogLevel level, std::string_view s) override {
     // TODO: Emmm... Since it is buggy to use narrow char in UTF-8 on Windows. I
     // think this implementation might be broken. (However, I didn't test it.)
     // Maybe, I should detect Windows and use wide char (And I didn't test this
@@ -58,7 +58,8 @@ class Logger : public Object {
   void RemoveSource(ILogSource* source);
 
  public:
-  void Log(LogLevel level, const std::string_view& s);
+  void Log(LogLevel level, std::string_view s);
+  void Log(LogLevel level, std::string_view tag, std::string_view s);
 
  public:
   std::list<std::unique_ptr<ILogSource>> sources_;
@@ -89,4 +90,31 @@ void Error(TArgs&&... args) {
   Logger::GetInstance()->Log(LogLevel::Error,
                              fmt::format(std::forward<TArgs>(args)...));
 }
+
+template <typename... TArgs>
+void TagDebug([[maybe_unused]] std::string_view tag,
+              [[maybe_unused]] TArgs&&... args) {
+#ifdef CRU_DEBUG
+  Logger::GetInstance()->Log(LogLevel::Debug, tag,
+                             fmt::format(std::forward<TArgs>(args)...));
+#endif
+}
+
+template <typename... TArgs>
+void TagInfo(std::string_view tag, TArgs&&... args) {
+  Logger::GetInstance()->Log(LogLevel::Info, tag,
+                             fmt::format(std::forward<TArgs>(args)...));
+}
+
+template <typename... TArgs>
+void TagWarn(std::string_view tag, TArgs&&... args) {
+  Logger::GetInstance()->Log(LogLevel::Warn, tag,
+                             fmt::format(std::forward<TArgs>(args)...));
+}
+
+template <typename... TArgs>
+void TagError(std::string_view tag, TArgs&&... args) {
+  Logger::GetInstance()->Log(LogLevel::Error, tag,
+                             fmt::format(std::forward<TArgs>(args)...));
+}
 }  // namespace cru::log
diff --git a/include/cru/ui/ClickDetector.hpp b/include/cru/ui/ClickDetector.hpp
index f5fd3d8f..3977fb8e 100644
--- a/include/cru/ui/ClickDetector.hpp
+++ b/include/cru/ui/ClickDetector.hpp
@@ -1,7 +1,6 @@
 #pragma once
 #include "Control.hpp"
 
-
 namespace cru::ui {
 class ClickEventArgs : Object {
  public:
@@ -37,6 +36,8 @@ enum class ClickState {
 };
 
 class ClickDetector : public Object {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::ClickDetector")
+
  public:
   explicit ClickDetector(Control* control);
 
diff --git a/include/cru/ui/UiHost.hpp b/include/cru/ui/UiHost.hpp
index 651dab81..1a5c6302 100644
--- a/include/cru/ui/UiHost.hpp
+++ b/include/cru/ui/UiHost.hpp
@@ -32,6 +32,8 @@ struct AfterLayoutEventArgs {};
 // 4. Delete Window when deleting_ is false and IsRetainAfterDestroy is false in
 // OnNativeDestroy.
 class UiHost : public Object, public SelfResolvable<UiHost> {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::UiHost")
+
  public:
   // This will create root window render object and attach it to window.
   // It will also create and manage a native window.
diff --git a/include/cru/ui/render/BorderRenderObject.hpp b/include/cru/ui/render/BorderRenderObject.hpp
index db989453..94e888d4 100644
--- a/include/cru/ui/render/BorderRenderObject.hpp
+++ b/include/cru/ui/render/BorderRenderObject.hpp
@@ -3,6 +3,8 @@
 
 namespace cru::ui::render {
 class BorderRenderObject : public RenderObject {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::render::BorderRenderObject")
+
  public:
   BorderRenderObject();
   BorderRenderObject(const BorderRenderObject& other) = delete;
diff --git a/include/cru/ui/render/FlexLayoutRenderObject.hpp b/include/cru/ui/render/FlexLayoutRenderObject.hpp
index 4b1e079d..87a41c7e 100644
--- a/include/cru/ui/render/FlexLayoutRenderObject.hpp
+++ b/include/cru/ui/render/FlexLayoutRenderObject.hpp
@@ -74,6 +74,8 @@ namespace cru::ui::render {
 // and just fill the rest space with blank.
 //
 class FlexLayoutRenderObject : public LayoutRenderObject<FlexChildLayoutData> {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::render::FlexLayoutRenderObject")
+
  public:
   FlexLayoutRenderObject() = default;
   FlexLayoutRenderObject(const FlexLayoutRenderObject& other) = delete;
diff --git a/include/cru/ui/render/LayoutHelper.hpp b/include/cru/ui/render/LayoutHelper.hpp
index 8536c451..3469ccf0 100644
--- a/include/cru/ui/render/LayoutHelper.hpp
+++ b/include/cru/ui/render/LayoutHelper.hpp
@@ -9,5 +9,6 @@ float CalculateAnchorByAlignment(Alignment alignment, float start_point,
 
 MeasureLength StackLayoutCalculateChildMaxLength(
     MeasureLength parent_preferred_size, MeasureLength parent_max_size,
-    MeasureLength child_min_size, std::string_view exceeds_message);
+    MeasureLength child_min_size, std::string_view log_tag,
+    std::string_view exceeds_message);
 }  // namespace cru::ui::render
diff --git a/include/cru/ui/render/RenderObject.hpp b/include/cru/ui/render/RenderObject.hpp
index 2d9cd817..2e784afc 100644
--- a/include/cru/ui/render/RenderObject.hpp
+++ b/include/cru/ui/render/RenderObject.hpp
@@ -37,6 +37,8 @@ namespace cru::ui::render {
 class RenderObject : public Object {
   friend WindowRenderObject;
 
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::render::RenderObject")
+
  protected:
   enum class ChildMode {
     None,
diff --git a/include/cru/ui/render/StackLayoutRenderObject.hpp b/include/cru/ui/render/StackLayoutRenderObject.hpp
index f6b4ffb7..534d7f22 100644
--- a/include/cru/ui/render/StackLayoutRenderObject.hpp
+++ b/include/cru/ui/render/StackLayoutRenderObject.hpp
@@ -23,6 +23,8 @@ namespace cru::ui::render {
 // to min size.
 class StackLayoutRenderObject
     : public LayoutRenderObject<StackChildLayoutData> {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::render:StackLayoutRenderObject")
+
  public:
   StackLayoutRenderObject() = default;
   CRU_DELETE_COPY(StackLayoutRenderObject)
diff --git a/include/cru/ui/render/TextRenderObject.hpp b/include/cru/ui/render/TextRenderObject.hpp
index 26c8db40..77a92b4f 100644
--- a/include/cru/ui/render/TextRenderObject.hpp
+++ b/include/cru/ui/render/TextRenderObject.hpp
@@ -18,6 +18,8 @@ namespace cru::ui::render {
 // If the result layout box is bigger than actual text box, then text is center
 // aligned.
 class TextRenderObject : public RenderObject {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::render::TextRenderObject")
+
  public:
   constexpr static float default_caret_width = 2;
 
diff --git a/include/cru/win/native/Cursor.hpp b/include/cru/win/native/Cursor.hpp
index 152374d8..44a6a362 100644
--- a/include/cru/win/native/Cursor.hpp
+++ b/include/cru/win/native/Cursor.hpp
@@ -7,6 +7,8 @@
 
 namespace cru::platform::native::win {
 class WinCursor : public WinNativeResource, public virtual ICursor {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::platform::native::win::WinCursor")
+
  public:
   WinCursor(HCURSOR handle, bool auto_destroy);
 
diff --git a/include/cru/win/native/GodWindow.hpp b/include/cru/win/native/GodWindow.hpp
index 1dd99661..0820bdb3 100644
--- a/include/cru/win/native/GodWindow.hpp
+++ b/include/cru/win/native/GodWindow.hpp
@@ -5,6 +5,8 @@
 
 namespace cru::platform::native::win {
 class GodWindow : public Object {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::platform::native::win::GodWindow")
+
  public:
   explicit GodWindow(WinUiApplication* application);
 
diff --git a/include/cru/win/native/InputMethod.hpp b/include/cru/win/native/InputMethod.hpp
index 0e9634aa..45422ace 100644
--- a/include/cru/win/native/InputMethod.hpp
+++ b/include/cru/win/native/InputMethod.hpp
@@ -5,13 +5,15 @@
 #pragma once
 #include "Resource.hpp"
 
-#include "cru/platform/native/InputMethod.hpp"
 #include "WindowNativeMessageEventArgs.hpp"
+#include "cru/platform/native/InputMethod.hpp"
 
 #include <imm.h>
 
 namespace cru::platform::native::win {
 class AutoHIMC : public Object {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::platform::native::win::AutoHIMC")
+
  public:
   explicit AutoHIMC(HWND hwnd);
 
@@ -33,6 +35,8 @@ class AutoHIMC : public Object {
 
 class WinInputMethodContext : public WinNativeResource,
                               public virtual IInputMethodContext {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::platform::native::win::WinInputMethodContext")
+
  public:
   WinInputMethodContext(gsl::not_null<WinNativeWindow*> window);
 
diff --git a/include/cru/win/native/Window.hpp b/include/cru/win/native/Window.hpp
index 80bee39e..521a0a06 100644
--- a/include/cru/win/native/Window.hpp
+++ b/include/cru/win/native/Window.hpp
@@ -1,13 +1,15 @@
 #pragma once
 #include "Resource.hpp"
 
-#include "cru/platform/native/Window.hpp"
 #include "WindowNativeMessageEventArgs.hpp"
+#include "cru/platform/native/Window.hpp"
 
 #include <memory>
 
 namespace cru::platform::native::win {
 class WinNativeWindow : public WinNativeResource, public virtual INativeWindow {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::platform::native::win::WinNativeWindow")
+
  public:
   WinNativeWindow(WinUiApplication* application, WindowClass* window_class,
                   DWORD window_style, WinNativeWindow* parent);
diff --git a/src/common/Logger.cpp b/src/common/Logger.cpp
index ed9f9e64..da55047a 100644
--- a/src/common/Logger.cpp
+++ b/src/common/Logger.cpp
@@ -42,12 +42,12 @@ std::string_view LogLevelToString(LogLevel level) {
     case LogLevel::Error:
       return "ERROR";
     default:
-      std::abort();
+      std::terminate();
   }
 }
 }  // namespace
 
-void Logger::Log(LogLevel level, const std::string_view &s) {
+void Logger::Log(LogLevel level, std::string_view s) {
 #ifndef CRU_DEBUG
   if (level == LogLevel::Debug) {
     return;
@@ -62,4 +62,20 @@ void Logger::Log(LogLevel level, const std::string_view &s) {
                                      LogLevelToString(level), s));
   }
 }
+
+void Logger::Log(LogLevel level, std::string_view tag, std::string_view s) {
+#ifndef CRU_DEBUG
+  if (level == LogLevel::Debug) {
+    return;
+  }
+#endif
+  for (const auto &source : sources_) {
+    auto now = std::time(nullptr);
+    std::array<char, 50> buffer;
+    std::strftime(buffer.data(), 50, "%c", std::localtime(&now));
+
+    source->Write(level, fmt::format("[{}] {} {}: {}\n", buffer.data(),
+                                     LogLevelToString(level), tag, s));
+  }
+}
 }  // namespace cru::log
diff --git a/src/ui/ClickDetector.cpp b/src/ui/ClickDetector.cpp
index e873efd4..93e6f303 100644
--- a/src/ui/ClickDetector.cpp
+++ b/src/ui/ClickDetector.cpp
@@ -44,7 +44,8 @@ ClickDetector::ClickDetector(Control* control) {
             if (this->enable_ && (button & this->trigger_button_) &&
                 this->state_ == ClickState::Hover) {
               if (!this->control_->CaptureMouse()) {
-                log::Debug("Failed to capture mouse when begin click.");
+                log::TagDebug(log_tag,
+                              "Failed to capture mouse when begin click.");
                 return;
               }
               this->down_point_ = args.GetPoint();
@@ -120,7 +121,8 @@ void ClickDetector::SetState(ClickState state) {
         UnreachableCode();
     }
   };
-  log::Debug("Click state changed, new state: {}.", to_string(state));
+  log::TagDebug(log_tag, "Click state changed, new state: {}.",
+                to_string(state));
 #endif
 
   state_ = state;
diff --git a/src/ui/UiHost.cpp b/src/ui/UiHost.cpp
index 9bde06ad..975d0ffe 100644
--- a/src/ui/UiHost.cpp
+++ b/src/ui/UiHost.cpp
@@ -146,14 +146,13 @@ void UiHost::InvalidatePaint() {
 }
 
 void UiHost::InvalidateLayout() {
+  log::TagDebug(log_tag, "A relayout is requested.");
   if (!need_layout_) {
     platform::native::IUiApplication::GetInstance()->InvokeLater(
         [resolver = this->CreateResolver()] {
           if (const auto host = resolver.Resolve()) {
             host->Relayout();
             host->need_layout_ = false;
-            host->after_layout_event_.Raise(AfterLayoutEventArgs{});
-            log::Debug("A relayout finished.");
             host->InvalidatePaint();
           }
         });
@@ -171,6 +170,8 @@ void UiHost::Relayout() {
                                  render::MeasureSize::NotSpecified()},
       render::MeasureSize::NotSpecified());
   root_render_object_->Layout(Point{});
+  after_layout_event_.Raise(AfterLayoutEventArgs{});
+  log::TagDebug(log_tag, "A relayout is finished.");
 }
 
 bool UiHost::RequestFocusFor(Control* control) {
diff --git a/src/ui/controls/TextControlService.hpp b/src/ui/controls/TextControlService.hpp
index ad0db343..c320b0c5 100644
--- a/src/ui/controls/TextControlService.hpp
+++ b/src/ui/controls/TextControlService.hpp
@@ -5,9 +5,9 @@
 #include "cru/platform/graph/Painter.hpp"
 #include "cru/platform/native/UiApplication.hpp"
 #include "cru/ui/Control.hpp"
+#include "cru/ui/UiEvent.hpp"
 #include "cru/ui/render/CanvasRenderObject.hpp"
 #include "cru/ui/render/TextRenderObject.hpp"
-#include "cru/ui/UiEvent.hpp"
 
 namespace cru::ui::controls {
 constexpr int k_default_caret_blink_duration = 500;
@@ -18,6 +18,8 @@ constexpr int k_default_caret_blink_duration = 500;
 // ```
 template <typename TControl>
 class TextControlService : public Object {
+  CRU_DEFINE_CLASS_LOG_TAG("cru::ui::controls::TextControlService")
+
  public:
   TextControlService(TControl* control);
 
@@ -175,10 +177,9 @@ void TextControlService<TControl>::MouseMoveHandler(
     const auto result = text_render_object->TextHitTest(
         text_render_object->FromRootToContent(args.GetPoint()));
     const auto position = result.position + (result.trailing ? 1 : 0);
-    log::Debug(
-        "TextControlService: Text selection changed on mouse move, range: {}, "
-        "{}.",
-        position, this->select_start_position_);
+    log::TagDebug(log_tag,
+                  "Text selection changed on mouse move, range: {}, {}.",
+                  position, this->select_start_position_);
     this->control_->GetTextRenderObject()->SetSelectionRange(
         TextRange::FromTwoSides(
             static_cast<unsigned>(position),
@@ -203,8 +204,8 @@ void TextControlService<TControl>::MouseDownHandler(
     text_render_object->SetSelectionRange(std::nullopt);
     text_render_object->SetCaretPosition(position);
     this->select_start_position_ = position;
-    log::Debug("TextControlService: Begin to select text, start position: {}.",
-               position);
+    log::TagDebug(log_tag, "Begin to select text, start position: {}.",
+                  position);
   }
 }
 
@@ -215,7 +216,7 @@ void TextControlService<TControl>::MouseUpHandler(
       this->select_down_button_.value() == args.GetButton()) {
     this->control_->ReleaseMouse();
     this->select_down_button_ = std::nullopt;
-    log::Debug("TextControlService: End selecting text.");
+    log::TagDebug(log_tag, "End selecting text.");
   }
 }
 
diff --git a/src/ui/render/BorderRenderObject.cpp b/src/ui/render/BorderRenderObject.cpp
index 6513c4c4..f2e3eb9b 100644
--- a/src/ui/render/BorderRenderObject.cpp
+++ b/src/ui/render/BorderRenderObject.cpp
@@ -57,7 +57,7 @@ void BorderRenderObject::OnDrawCore(platform::graph::IPainter* painter) {
                           background_brush_.get());
   if (is_border_enabled_) {
     if (border_brush_ == nullptr) {
-      log::Warn("Border is enabled but brush is null");
+      log::TagWarn(log_tag, "Border is enabled but border brush is null.");
     } else {
       painter->FillGeometry(geometry_.get(), border_brush_.get());
     }
@@ -93,9 +93,9 @@ Size BorderRenderObject::OnMeasureCore(const MeasureRequirement& requirement,
   if (!requirement.max.width.IsNotSpecified()) {
     const auto max_width = requirement.max.width.GetLengthOrMax();
     if (coerced_space_size.width > max_width) {
-      log::Warn(
-          "BorderRenderObject: During measure, horizontal length of padding, "
-          "border and margin is bigger than required max length.");
+      log::TagWarn(log_tag,
+                   "(Measure) Horizontal length of padding, border and margin "
+                   "is bigger than required max length.");
       coerced_space_size.width = max_width;
     }
     content_requirement.max.width = max_width - coerced_space_size.width;
@@ -109,9 +109,9 @@ Size BorderRenderObject::OnMeasureCore(const MeasureRequirement& requirement,
   if (!requirement.max.height.IsNotSpecified()) {
     const auto max_height = requirement.max.height.GetLengthOrMax();
     if (coerced_space_size.height > max_height) {
-      log::Warn(
-          "BorderRenderObject: During measure, vertical length of padding, "
-          "border and margin is bigger than required max length.");
+      log::TagWarn(log_tag,
+                   "(Measure) Vertical length of padding, border and margin is "
+                   "bigger than required max length.");
       coerced_space_size.height = max_height;
     }
     content_requirement.max.height = max_height - coerced_space_size.height;
@@ -149,15 +149,9 @@ void BorderRenderObject::OnLayoutCore() {
   auto content_size = size - space_size;
 
   if (content_size.width < 0) {
-    log::Warn(
-        "BorderRenderObject: During layout, horizontal length of padding, "
-        "border and margin is bigger than available length.");
     content_size.width = 0;
   }
   if (content_size.height < 0) {
-    log::Warn(
-        "BorderRenderObject: During layout, vertical length of padding, "
-        "border and margin is bigger than available length.");
     content_size.height = 0;
   }
 
diff --git a/src/ui/render/FlexLayoutRenderObject.cpp b/src/ui/render/FlexLayoutRenderObject.cpp
index 9e5139ff..8e6b41fe 100644
--- a/src/ui/render/FlexLayoutRenderObject.cpp
+++ b/src/ui/render/FlexLayoutRenderObject.cpp
@@ -87,7 +87,8 @@ template <typename direction_tag_t,
 Size FlexLayoutMeasureContentImpl(
     const MeasureRequirement& requirement, const MeasureSize& preferred_size,
     const std::vector<RenderObject*>& children,
-    const std::vector<FlexChildLayoutData>& layout_data) {
+    const std::vector<FlexChildLayoutData>& layout_data,
+    std::string_view log_tag) {
   Expects(children.size() == layout_data.size());
 
   direction_tag_t direction_tag;
@@ -109,9 +110,9 @@ Size FlexLayoutMeasureContentImpl(
     child_cross_measure_requirement.push_back(
         StackLayoutCalculateChildMaxLength(
             preferred_cross_length, max_cross_length,
-            GetCross(child->GetMinSize(), direction_tag),
-            "StackLayoutRenderObject: Child's min cross size is bigger than "
-            "parent's max cross size."));
+            GetCross(child->GetMinSize(), direction_tag), log_tag,
+            "(Measure) Child's min cross size is bigger than parent's max "
+            "cross size."));
   }
 
   // step 1.
@@ -312,9 +313,9 @@ Size FlexLayoutMeasureContentImpl(
 
   if (max_main_length.IsSpecified() &&
       total_length > max_main_length.GetLengthOrUndefined()) {
-    log::Warn(
-        "FlexLayoutRenderObject: Children's main axis length exceeds required "
-        "max length.");
+    log::TagWarn(
+        log_tag,
+        "(Measure) Children's main axis length exceeds required max length.");
     total_length = max_main_length.GetLengthOrUndefined();
   } else if (min_main_length.IsSpecified() &&
              total_length < min_main_length.GetLengthOrUndefined()) {
@@ -336,10 +337,12 @@ Size FlexLayoutRenderObject::OnMeasureContent(
                            direction_ == FlexDirection::HorizontalReverse);
   if (horizontal) {
     return FlexLayoutMeasureContentImpl<tag_horizontal_t>(
-        requirement, preferred_size, GetChildren(), GetChildLayoutDataList());
+        requirement, preferred_size, GetChildren(), GetChildLayoutDataList(),
+        log_tag);
   } else {
     return FlexLayoutMeasureContentImpl<tag_vertical_t>(
-        requirement, preferred_size, GetChildren(), GetChildLayoutDataList());
+        requirement, preferred_size, GetChildren(), GetChildLayoutDataList(),
+        log_tag);
   }
 }
 
diff --git a/src/ui/render/LayoutHelper.cpp b/src/ui/render/LayoutHelper.cpp
index 31cf5c08..9f94b84d 100644
--- a/src/ui/render/LayoutHelper.cpp
+++ b/src/ui/render/LayoutHelper.cpp
@@ -19,9 +19,10 @@ float CalculateAnchorByAlignment(Alignment alignment, float start_point,
 
 MeasureLength StackLayoutCalculateChildMaxLength(
     MeasureLength parent_preferred_size, MeasureLength parent_max_size,
-    MeasureLength child_min_size, std::string_view exceeds_message) {
+    MeasureLength child_min_size, std::string_view log_tag,
+    std::string_view exceeds_message) {
   if (parent_max_size.GetLengthOrMax() < child_min_size.GetLengthOr0()) {
-    log::Warn(exceeds_message);
+    log::TagWarn(log_tag, exceeds_message);
     return parent_max_size;
   }
 
diff --git a/src/ui/render/RenderObject.cpp b/src/ui/render/RenderObject.cpp
index d9977f2a..66b62e6e 100644
--- a/src/ui/render/RenderObject.cpp
+++ b/src/ui/render/RenderObject.cpp
@@ -151,9 +151,9 @@ Size RenderObject::OnMeasureCore(const MeasureRequirement& requirement,
   if (!requirement.max.width.IsNotSpecified()) {
     const auto max_width = requirement.max.width.GetLengthOrMax();
     if (coerced_space_size.width > max_width) {
-      log::Warn(
-          "RenderObject: During measure, horizontal length of padding and "
-          "margin is bigger than required max length.");
+      log::TagWarn(log_tag,
+                   "(Measure) Horizontal length of padding and margin is "
+                   "bigger than required max length.");
       coerced_space_size.width = max_width;
     }
     content_requirement.max.width = max_width - coerced_space_size.width;
@@ -167,9 +167,9 @@ Size RenderObject::OnMeasureCore(const MeasureRequirement& requirement,
   if (!requirement.max.height.IsNotSpecified()) {
     const auto max_height = requirement.max.height.GetLengthOrMax();
     if (coerced_space_size.height > max_height) {
-      log::Warn(
-          "RenderObject: During measure, vertical length of padding and "
-          "margin is bigger than required max length.");
+      log::TagWarn(log_tag,
+                   "(Measure) Vertical length of padding and margin is bigger "
+                   "than required max length.");
       coerced_space_size.height = max_height;
     }
     content_requirement.max.height = max_height - coerced_space_size.height;
@@ -198,15 +198,9 @@ void RenderObject::OnLayoutCore() {
   auto content_size = total_size - space_size;
 
   if (content_size.width < 0) {
-    log::Warn(
-        "RenderObject: During layout, horizontal length of padding and margin "
-        "is bigger than available length.");
     content_size.width = 0;
   }
   if (content_size.height < 0) {
-    log::Warn(
-        "RenderObject: During layout, vertical length of padding and margin "
-        "is bigger than available length.");
     content_size.height = 0;
   }
 
diff --git a/src/ui/render/StackLayoutRenderObject.cpp b/src/ui/render/StackLayoutRenderObject.cpp
index a6ed7708..168ff379 100644
--- a/src/ui/render/StackLayoutRenderObject.cpp
+++ b/src/ui/render/StackLayoutRenderObject.cpp
@@ -14,14 +14,14 @@ Size StackLayoutRenderObject::OnMeasureContent(
         MeasureRequirement{
             MeasureSize{StackLayoutCalculateChildMaxLength(
                             preferred_size.width, requirement.max.width,
-                            child->GetMinSize().width,
-                            "StackLayoutRenderObject: Child's min width is "
-                            "bigger than parent's max width."),
+                            child->GetMinSize().width, log_tag,
+                            "(Measure) Child's min width is bigger than "
+                            "parent's max width."),
                         StackLayoutCalculateChildMaxLength(
                             preferred_size.height, requirement.max.height,
-                            child->GetMinSize().height,
-                            "StackLayoutRenderObject: Child's min height is "
-                            "bigger than parent's max height.")},
+                            child->GetMinSize().height, log_tag,
+                            "(Measure) Child's min height is bigger than "
+                            "parent's max height.")},
             MeasureSize::NotSpecified()},
         MeasureSize::NotSpecified());
     const auto size = child->GetSize();
diff --git a/src/ui/render/TextRenderObject.cpp b/src/ui/render/TextRenderObject.cpp
index ce1c3fa3..87a3c352 100644
--- a/src/ui/render/TextRenderObject.cpp
+++ b/src/ui/render/TextRenderObject.cpp
@@ -170,8 +170,8 @@ Size TextRenderObject::OnMeasureContent(const MeasureRequirement& requirement,
 
   if (requirement.max.width.IsSpecified() &&
       text_size.width > requirement.max.width.GetLengthOrUndefined()) {
-    log::Warn(
-        "TextRenderObject: Text actual width exceeds the required max width.");
+    log::TagWarn(log_tag,
+                 "(Measure) Text actual width exceeds the required max width.");
     result.width = requirement.max.width.GetLengthOrUndefined();
   } else {
     result.width = std::max(result.width, preferred_size.width.GetLengthOr0());
@@ -180,9 +180,9 @@ Size TextRenderObject::OnMeasureContent(const MeasureRequirement& requirement,
 
   if (requirement.max.height.IsSpecified() &&
       text_size.height > requirement.max.height.GetLengthOrUndefined()) {
-    log::Warn(
-        "TextRenderObject: Text actual height exceeds the required max "
-        "height.");
+    log::TagWarn(
+        log_tag,
+        "(Measure) Text actual height exceeds the required max height.");
     result.height = requirement.max.height.GetLengthOrUndefined();
   } else {
     result.height =
diff --git a/src/win/DebugLogger.hpp b/src/win/DebugLogger.hpp
index 381803bc..4ca1567b 100644
--- a/src/win/DebugLogger.hpp
+++ b/src/win/DebugLogger.hpp
@@ -14,7 +14,7 @@ class WinDebugLoggerSource : public ::cru::log::ILogSource {
 
   ~WinDebugLoggerSource() = default;
 
-  void Write(::cru::log::LogLevel level, const std::string_view& s) override {
+  void Write(::cru::log::LogLevel level, std::string_view s) override {
     CRU_UNUSED(level)
 
     const std::wstring&& ws = ToUtf16String(s);
diff --git a/src/win/native/Cursor.cpp b/src/win/native/Cursor.cpp
index ca8bb1cd..a6ab5bfc 100644
--- a/src/win/native/Cursor.cpp
+++ b/src/win/native/Cursor.cpp
@@ -16,8 +16,8 @@ WinCursor::~WinCursor() {
     if (!::DestroyCursor(handle_)) {
       // This is not a fetal error but might still need notice because it may
       // cause leak.
-      log::Warn("Failed to destroy a cursor. Last error code: {}",
-                ::GetLastError());
+      log::TagWarn(log_tag, "Failed to destroy a cursor. Last error code: {}",
+                   ::GetLastError());
     }
   }
 }
diff --git a/src/win/native/GodWindow.cpp b/src/win/native/GodWindow.cpp
index 076954d4..8ef2788e 100644
--- a/src/win/native/GodWindow.cpp
+++ b/src/win/native/GodWindow.cpp
@@ -1,11 +1,11 @@
 #include "cru/win/native/GodWindow.hpp"
 
+#include "GodWindowMessage.hpp"
+#include "Timer.hpp"
 #include "cru/common/Logger.hpp"
 #include "cru/win/native/Exception.hpp"
 #include "cru/win/native/UiApplication.hpp"
 #include "cru/win/native/WindowClass.hpp"
-#include "GodWindowMessage.hpp"
-#include "Timer.hpp"
 
 namespace cru::platform::native::win {
 constexpr auto god_window_class_name = L"GodWindowClass";
@@ -45,7 +45,7 @@ GodWindow::GodWindow(WinUiApplication* application) {
 GodWindow::~GodWindow() {
   if (!::DestroyWindow(hwnd_)) {
     // Although this could be "safely" ignore.
-    log::Warn("Failed to destroy god window.");
+    log::TagWarn(log_tag, "Failed to destroy god window.");
   }
 }
 
diff --git a/src/win/native/InputMethod.cpp b/src/win/native/InputMethod.cpp
index 2e31108e..d3d989f3 100644
--- a/src/win/native/InputMethod.cpp
+++ b/src/win/native/InputMethod.cpp
@@ -1,11 +1,11 @@
 #include "cru/win/native/InputMethod.hpp"
 
+#include "DpiUtil.hpp"
 #include "cru/common/Logger.hpp"
 #include "cru/platform/Check.hpp"
 #include "cru/win/Exception.hpp"
-#include "cru/win/native/Window.hpp"
 #include "cru/win/String.hpp"
-#include "DpiUtil.hpp"
+#include "cru/win/native/Window.hpp"
 
 #include <vector>
 
@@ -35,7 +35,7 @@ AutoHIMC& AutoHIMC::operator=(AutoHIMC&& other) {
 AutoHIMC::~AutoHIMC() {
   if (handle_) {
     if (!::ImmReleaseContext(hwnd_, handle_))
-      log::Warn("AutoHIMC: Failed to release HIMC.");
+      log::TagWarn(log_tag, "Failed to release HIMC.");
   }
 }
 
@@ -169,7 +169,7 @@ void WinInputMethodContext::EnableIME() {
   const auto hwnd = native_window->GetWindowHandle();
 
   if (::ImmAssociateContextEx(hwnd, nullptr, IACE_DEFAULT) == FALSE) {
-    log::Warn("WinInputMethodContext: Failed to enable ime.");
+    log::TagWarn(log_tag, "Failed to enable ime.");
   }
 }
 
@@ -181,13 +181,11 @@ void WinInputMethodContext::DisableIME() {
   AutoHIMC himc{hwnd};
 
   if (!::ImmNotifyIME(himc.Get(), NI_COMPOSITIONSTR, CPS_COMPLETE, 0)) {
-    log::Warn(
-        "WinInputMethodContext: Failed to complete composition before disable "
-        "ime.");
+    log::TagWarn(log_tag, "Failed to complete composition before disable ime.");
   }
 
   if (::ImmAssociateContextEx(hwnd, nullptr, 0) == FALSE) {
-    log::Warn("WinInputMethodContext: Failed to disable ime.");
+    log::TagWarn(log_tag, "Failed to disable ime.");
   }
 }
 
@@ -197,7 +195,7 @@ void WinInputMethodContext::CompleteComposition() {
   auto himc = *std::move(optional_himc);
 
   if (!::ImmNotifyIME(himc.Get(), NI_COMPOSITIONSTR, CPS_COMPLETE, 0)) {
-    log::Warn("WinInputMethodContext: Failed to complete composition.");
+    log::TagWarn(log_tag, "Failed to complete composition.");
   }
 }
 
@@ -207,7 +205,7 @@ void WinInputMethodContext::CancelComposition() {
   auto himc = *std::move(optional_himc);
 
   if (!::ImmNotifyIME(himc.Get(), NI_COMPOSITIONSTR, CPS_CANCEL, 0)) {
-    log::Warn("WinInputMethodContext: Failed to complete composition.");
+    log::TagWarn(log_tag, "Failed to complete composition.");
   }
 }
 
@@ -230,9 +228,8 @@ void WinInputMethodContext::SetCandidateWindowPosition(const Point& point) {
   form.ptCurrentPos = DipToPi(point);
 
   if (!::ImmSetCandidateWindow(himc.Get(), &form))
-    log::Debug(
-        "WinInputMethodContext: Failed to set input method candidate window "
-        "position.");
+    log::TagDebug(log_tag,
+                  "Failed to set input method candidate window position.");
 }
 
 IEvent<std::nullptr_t>* WinInputMethodContext::CompositionStartEvent() {
@@ -261,9 +258,9 @@ void WinInputMethodContext::OnWindowNativeMessage(
         // I don't think this will happen because normal key strike without ime
         // should only trigger ascci character. If it is a charater from
         // supplementary planes, it should be handled with ime messages.
-        log::Warn(
-            "WinInputMethodContext: A WM_CHAR message for character from "
-            "supplementary planes is ignored.");
+        log::TagWarn(log_tag,
+                     "A WM_CHAR message for character from supplementary "
+                     "planes is ignored.");
       } else {
         wchar_t s[1] = {c};
         auto str = platform::win::ToUtf8String({s, 1});
@@ -275,9 +272,8 @@ void WinInputMethodContext::OnWindowNativeMessage(
     case WM_IME_COMPOSITION: {
       composition_event_.Raise(nullptr);
       auto composition_text = GetCompositionText();
-      log::Debug(
-          "WinInputMethodContext: WM_IME_COMPOSITION composition text:\n{}",
-          composition_text);
+      log::TagDebug(log_tag, "WM_IME_COMPOSITION composition text:\n{}",
+                    composition_text);
       if (message.l_param & GCS_RESULTSTR) {
         auto result_string = GetResultString();
         text_event_.Raise(result_string);
diff --git a/src/win/native/Window.cpp b/src/win/native/Window.cpp
index 9dde1af3..22505bd6 100644
--- a/src/win/native/Window.cpp
+++ b/src/win/native/Window.cpp
@@ -1,17 +1,17 @@
 #include "cru/win/native/Window.hpp"
 
+#include "DpiUtil.hpp"
+#include "WindowD2DPainter.hpp"
+#include "WindowManager.hpp"
 #include "cru/common/Logger.hpp"
 #include "cru/platform/Check.hpp"
+#include "cru/win/String.hpp"
 #include "cru/win/native/Cursor.hpp"
 #include "cru/win/native/Exception.hpp"
 #include "cru/win/native/Keyboard.hpp"
 #include "cru/win/native/UiApplication.hpp"
 #include "cru/win/native/WindowClass.hpp"
 #include "cru/win/native/WindowRenderTarget.hpp"
-#include "cru/win/String.hpp"
-#include "DpiUtil.hpp"
-#include "WindowD2DPainter.hpp"
-#include "WindowManager.hpp"
 
 #include <imm.h>
 #include <windowsx.h>
@@ -124,7 +124,7 @@ bool WinNativeWindow::ReleaseMouse() {
 }
 
 void WinNativeWindow::RequestRepaint() {
-  log::Debug("A repaint is requested.");
+  log::TagDebug(log_tag, "A repaint is requested.");
   if (!::InvalidateRect(hwnd_, nullptr, FALSE))
     throw Win32Error(::GetLastError(), "Failed to invalidate window.");
   if (!::UpdateWindow(hwnd_))
@@ -144,19 +144,20 @@ void WinNativeWindow::SetCursor(std::shared_ptr<ICursor> cursor) {
 
   if (!::SetClassLongPtrW(hwnd_, GCLP_HCURSOR,
                           reinterpret_cast<LONG_PTR>(cursor_->GetHandle()))) {
-    log::Warn(
-        "Failed to set cursor because failed to set class long. Last error "
-        "code: {}.",
-        ::GetLastError());
+    log::TagWarn(log_tag,
+                 "Failed to set cursor because failed to set class long. Last "
+                 "error code: {}.",
+                 ::GetLastError());
     return;
   }
 
   if (!IsVisible()) return;
 
   auto lg = [](const std::string_view& reason) {
-    log::Warn(
-        "Failed to set cursor because {} when window is visible. (We need "
-        "to update cursor if it is inside the window.) Last error code: {}.",
+    log::TagWarn(
+        log_tag,
+        "Failed to set cursor because {} when window is visible. (We need to "
+        "update cursor if it is inside the window.) Last error code: {}.",
         reason, ::GetLastError());
   };
 
@@ -353,6 +354,7 @@ void WinNativeWindow::OnDestroyInternal() {
 void WinNativeWindow::OnPaintInternal() {
   paint_event_.Raise(nullptr);
   ValidateRect(hwnd_, nullptr);
+  log::TagDebug(log_tag, "A repaint is finished.");
 }
 
 void WinNativeWindow::OnResizeInternal(const int new_width,