Respect system colour scheme for title bar colour (#109)

UnleashedRecomp/os/linux/user_linux.cpp

@@ -0,0 +1,6 @@
+#include <os/user_detail.h>
+
+bool os::user::detail::IsDarkTheme()
+{
+    return false;
+}

UnleashedRecomp/os/user.cpp

@@ -0,0 +1,7 @@
+#include <os/user.h>
+#include <os/user_detail.h>
+
+bool os::user::IsDarkTheme()
+{
+    return detail::IsDarkTheme();
+}

UnleashedRecomp/os/user.h

@@ -0,0 +1,6 @@
+#pragma once
+
+namespace os::user
+{
+    bool IsDarkTheme();
+}

UnleashedRecomp/os/user_detail.h

@@ -0,0 +1,6 @@
+#pragma once
+
+namespace os::user::detail
+{
+    bool IsDarkTheme();
+}

UnleashedRecomp/os/win32/user_win32.cpp

@@ -0,0 +1,23 @@
+#include <os/user_detail.h>
+
+bool os::user::detail::IsDarkTheme()
+{
+    HKEY hKey;
+
+    if (RegOpenKeyExA(HKEY_CURRENT_USER, "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize", 0, KEY_READ, &hKey) == ERROR_SUCCESS)
+    {
+        DWORD value = 0;
+        DWORD valueSize = sizeof(value);
+
+        if (RegQueryValueExA(hKey, "AppsUseLightTheme", nullptr, nullptr, (LPBYTE)&value, &valueSize) == ERROR_SUCCESS)
+        {
+            RegCloseKey(hKey);
+
+            return value == 0;
+        }
+
+        RegCloseKey(hKey);
+    }
+
+    return false;
+}