Qt: Show dialog on startup for settings version mismatch

For the QMessageBox to appear, error reporting is performed again after
main window creation.

src/duckstation-qt/main.cpp

@@ -55,6 +55,8 @@ int main(int argc, char* argv[])
     window->startupUpdateCheck();
   }
 
+  window->reportSettingsVersionMismatchString();
+
   int result = app.exec();
 
   window.reset();

src/duckstation-qt/mainwindow.cpp

@@ -1088,6 +1088,13 @@ void MainWindow::startupUpdateCheck()
   checkForUpdates(false);
 }
 
+void MainWindow::reportSettingsVersionMismatchString()
+{
+  const QString mismatch_str = QString::fromStdString(m_host_interface->GetSettingsVersionMismatchString());
+  if (!mismatch_str.isEmpty())
+    reportError(mismatch_str);
+}
+
 void MainWindow::updateDebugMenuVisibility()
 {
   const bool visible = m_host_interface->GetBoolSettingValue("Main", "ShowDebugMenu", false);

src/duckstation-qt/mainwindow.h

@@ -30,6 +30,10 @@ public:
   /// Performs update check if enabled in settings.
   void startupUpdateCheck();
 
+  /// Reports m_host_interface's settings version mismatch string. Does nothing if string is empty (no settings version
+  /// mismatch detected).
+  void reportSettingsVersionMismatchString();
+
 public Q_SLOTS:
   /// Updates debug menu visibility (hides if disabled).
   void updateDebugMenuVisibility();

src/frontend-common/common_host_interface.cpp

@@ -1995,8 +1995,10 @@ void CommonHostInterface::CheckSettings(SettingsInterface& si)
   if (settings_version == SETTINGS_VERSION)
     return;
 
-  ReportFormattedError("Settings version %d does not match expected version %d, resetting", settings_version,
-                       SETTINGS_VERSION);
+  m_settings_version_mismatch_str = StringUtil::StdStringFromFormat(
+    "Settings version %d does not match expected version %d, resetting", settings_version, SETTINGS_VERSION);
+  ReportError(m_settings_version_mismatch_str.c_str());
+
   si.Clear();
   si.SetIntValue("Main", "SettingsVersion", SETTINGS_VERSION);
   SetDefaultSettings(si);
@@ -2101,6 +2103,11 @@ void CommonHostInterface::CheckForSettingsChanges(const Settings& old_settings)
   UpdateInputMap();
 }
 
+const std::string& CommonHostInterface::GetSettingsVersionMismatchString() const
+{
+  return m_settings_version_mismatch_str;
+}
+
 void CommonHostInterface::SetTimerResolutionIncreased(bool enabled)
 {
   if (m_timer_resolution_increased == enabled)

src/frontend-common/common_host_interface.h

@@ -174,6 +174,10 @@ public:
   /// Reloads post processing shaders with the current configuration.
   void ReloadPostProcessingShaders();
 
+  /// Returns an empty string if no settings version mismatch was detected, non-empty otherwise. Should not be called
+  /// before CheckSettings(SettingsInterface& si).
+  const std::string& GetSettingsVersionMismatchString() const;
+
 protected:
   enum : u32
   {
@@ -371,6 +375,8 @@ private:
   // running in batch mode? i.e. exit after stopping emulation
   bool m_batch_mode = false;
 
+  std::string m_settings_version_mismatch_str;
+
 #ifdef WITH_DISCORD_PRESENCE
   // discord rich presence
   bool m_discord_presence_enabled = false;