DolphinQt: On Windows, detect whether the system is using a dark theme.

Co-authored-by: FearlessTobi <thm.frey@gmail.com>

Source/Core/DolphinQt/Main.cpp

@@ -2,11 +2,13 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #ifdef _WIN32
+#include <cstdio>
 #include <string>
 #include <vector>
 
 #include <Windows.h>
-#include <cstdio>
+
+#include <winrt/Windows.UI.ViewManagement.h>
 #endif
 
 #ifdef __linux__
@@ -244,6 +246,20 @@ int main(int argc, char* argv[])
     DolphinAnalytics::Instance().ReportDolphinStart("qt");
 
     MainWindow win{std::move(boot), static_cast<const char*>(options.get("movie"))};
+
+#ifdef _WIN32
+    // Check if the system is set to dark mode so we can set the default theme and window
+    // decorations accordingly.
+    {
+      using namespace winrt::Windows::UI::ViewManagement;
+      const UISettings settings;
+      const auto& color = settings.GetColorValue(UIColorType::Foreground);
+
+      const bool is_system_dark = 5 * color.G + 2 * color.R + color.B > 8 * 128;
+      Settings::Instance().SetSystemDark(is_system_dark);
+    }
+#endif
+
     Settings::Instance().SetCurrentUserStyle(Settings::Instance().GetCurrentUserStyle());
     win.Show();
 

Source/Core/DolphinQt/Settings.cpp

@@ -47,6 +47,8 @@
 #include "VideoCommon/NetPlayChatUI.h"
 #include "VideoCommon/NetPlayGolfUI.h"
 
+static bool s_system_dark = false;
+
 Settings::Settings()
 {
   qRegisterMetaType<Core::State>();
@@ -125,6 +127,16 @@ QString Settings::GetCurrentUserStyle() const
   return QFileInfo(GetQSettings().value(QStringLiteral("userstyle/path")).toString()).fileName();
 }
 
+void Settings::SetSystemDark(bool dark)
+{
+  s_system_dark = dark;
+}
+
+bool Settings::IsSystemDark()
+{
+  return s_system_dark;
+}
+
 // Calling this before the main window has been created breaks the style of some widgets.
 void Settings::SetCurrentUserStyle(const QString& stylesheet_name)
 {

Source/Core/DolphinQt/Settings.h

@@ -52,6 +52,8 @@ public:
 
   // UI
   void SetThemeName(const QString& theme_name);
+  void SetSystemDark(bool dark);
+  bool IsSystemDark();
   void SetCurrentUserStyle(const QString& stylesheet_name);
   QString GetCurrentUserStyle() const;