Qt: Use Window/AutoFillBackground for game list background

Fixes scrolling glitching out, as well as the background not showing in
the Qt Windows 11 theme.

src/core/system.cpp

@@ -496,6 +496,12 @@ bool System::ProcessStartup(Error* error)
   // Initialize rapidyaml before anything can use it.
   SetRymlCallbacks();
 
+#ifdef __linux__
+  // Running DuckStation out of /usr/lib is not supported and makes no sense.
+  if (std::memcmp(EmuFolders::AppRoot.data(), "/usr/""lib", 8) == 0)
+    return false;
+#endif
+
   return true;
 }
 

src/duckstation-qt/gamelistwidget.cpp

@@ -1428,6 +1428,7 @@ void GameListWidget::reloadThemeSpecificImages()
 
 void GameListWidget::updateBackground(bool reload_image)
 {
+  const bool had_image = !m_background_image.isNull();
   if (reload_image)
   {
     m_background_image = QImage();
@@ -1444,8 +1445,13 @@ void GameListWidget::updateBackground(bool reload_image)
 
   if (m_background_image.isNull())
   {
-    m_ui.stack->setPalette(palette());
-    m_list_view->setAlternatingRowColors(true);
+    if (had_image)
+    {
+      m_ui.stack->setPalette(qApp->palette(m_ui.stack));
+      m_ui.stack->setAutoFillBackground(false);
+      m_list_view->setAlternatingRowColors(true);
+    }
+
     return;
   }
 
@@ -1458,8 +1464,10 @@ void GameListWidget::updateBackground(bool reload_image)
         return;
 
       QPalette new_palette(m_ui.stack->palette());
-      new_palette.setBrush(QPalette::Base, QPixmap::fromImage(image));
+      new_palette.setBrush(QPalette::Window, QPixmap::fromImage(image));
+      new_palette.setBrush(QPalette::Base, Qt::transparent);
       m_ui.stack->setPalette(new_palette);
+      m_ui.stack->setAutoFillBackground(true);
       m_list_view->setAlternatingRowColors(false);
     };
   });

src/duckstation-qt/qthost.cpp

@@ -531,12 +531,7 @@ bool QtHost::SetCriticalFolders()
   // the resources directory should exist, bail out if not
   const std::string rcc_path = Path::Combine(EmuFolders::Resources, "duckstation-qt.rcc");
   if (!FileSystem::FileExists(rcc_path.c_str()) || !QResource::registerResource(QString::fromStdString(rcc_path)) ||
-      !FileSystem::DirectoryExists(EmuFolders::Resources.c_str())
-#ifdef __linux__
-      // Broken packages that won't stop distributing my application.
-      || StringUtil::StartsWithNoCase(EmuFolders::AppRoot, "/usr""/lib")
-#endif
-  )
+      !FileSystem::DirectoryExists(EmuFolders::Resources.c_str()))
   {
     QMessageBox::critical(nullptr, QStringLiteral("Error"),
                           QStringLiteral("Resources are missing, your installation is incomplete."));