Qt: Check screen bounds when restoring window positions

Ensure that the geometry is not off-screen.

It won't work on Wankland, and apparently doesn't support multiple monitors on X11.

So I'm just going to disable the whole thing on Linux, not just because my care
levels are practically non-existant, but also because I don't want to deal with
people moaning that their window manager's behavior is causing positions to
revert to the primary monitor. Just yolo it and hope for the best....

src/duckstation-qt/qtutils.cpp

@@ -12,7 +12,6 @@
 #include "common/error.h"
 #include "common/log.h"
 
-#include <QtCore/QCoreApplication>
 #include <QtCore/QMetaObject>
 #include <QtGui/QDesktopServices>
 #include <QtGui/QGuiApplication>
@@ -479,6 +478,41 @@ bool QtUtils::RestoreWindowGeometry(std::string_view window_name, QWidget* widge
     return TryMigrateWindowGeometry(si, window_name, widget);
   }
 
+  // Ensure that the geometry is not off-screen. This is quite painful to do, but better than spawning the
+  // window off-screen. It also won't work on Wankland, and apparently doesn't support multiple monitors
+  // on X11, but who cares. I'm just going to disable the whole thing on Linux, because I don't want to
+  // deal with people moaning that their window manager's behavior is causing positions to revert to the
+  // primary monitor, so just yolo it and hope for the best....
+#ifndef __linux__
+  bool window_is_offscreen = true;
+  for (const QScreen* screen : qApp->screens())
+  {
+    const QRect screen_geometry = screen->geometry();
+    if (screen_geometry.contains(x, y))
+    {
+      window_is_offscreen = false;
+      break;
+    }
+  }
+  if (window_is_offscreen)
+  {
+    // If the window is off-screen, we will just center it on the primary screen.
+    const QScreen* primary_screen = QGuiApplication::primaryScreen();
+    if (primary_screen)
+    {
+      // Might be a different monitor, clamp to size.
+      const QRect screen_geometry = primary_screen->availableGeometry();
+      w = std::min(w, screen_geometry.width());
+      h = std::min(h, screen_geometry.height());
+      x = screen_geometry.x() + (screen_geometry.width() - w) / 2;
+      y = screen_geometry.y() + (screen_geometry.height() - h) / 2;
+    }
+
+    WARNING_LOG("Saved window position for {} is off-screen, centering to primary screen ({},{} w={},h={})",
+                window_name, x, y, w, h);
+  }
+#endif // __linux__
+
   widget->setGeometry(x, y, w, h);
   if (maximized)
     widget->setWindowState(widget->windowState() | Qt::WindowMaximized);