Qt/Windows: Match system color scheme.

Use windowsvista style for light, dark fusion scheme for dark.

qt/src/main.cpp

@@ -6,6 +6,7 @@
 #include <clocale>
 #include <qnamespace.h>
 #include <QStyle>
+#include <QStyleHints>
 
 #ifndef _WIN32
 #include <csignal>
@@ -27,6 +28,8 @@ int main(int argc, char *argv[])
     QGuiApplication::setDesktopFileName("snes9x-gtk");
 
     if (emu.qtapp->platformName() == "windows")
+    {
+        if (emu.qtapp->styleHints()->colorScheme() == Qt::ColorScheme::Dark)
         {
             emu.qtapp->setStyle("fusion");
 
@@ -58,6 +61,11 @@ int main(int argc, char *argv[])
             darkPalette.setColor(QPalette::Disabled, QPalette::Light, darkGray);
             emu.qtapp->setPalette(darkPalette);
         }
+        else
+        {
+            emu.qtapp->setStyle("windowsvista");
+        }
+    }
 
 #ifndef _WIN32
     auto quit_handler = [](int) { QApplication::quit(); };