qt: Do not exit and re-enter main event loop during shutdown

src/qt/bitcoin.cpp

@@ -54,6 +54,7 @@
 #include <QThread>
 #include <QTimer>
 #include <QTranslator>
+#include <QWindow>
 
 #if defined(QT_STATICPLUGIN)
 #include <QtPlugin>
@@ -258,6 +259,7 @@ void BitcoinApplication::createOptionsModel(bool resetSettings)
 void BitcoinApplication::createWindow(const NetworkStyle *networkStyle)
 {
     window = new BitcoinGUI(node(), platformStyle, networkStyle, nullptr);
+    connect(window, &BitcoinGUI::quitRequested, this, &BitcoinApplication::requestShutdown);
 
     pollShutdownTimer = new QTimer(window);
     connect(pollShutdownTimer, &QTimer::timeout, window, &BitcoinGUI::detectShutdown);
@@ -325,13 +327,17 @@ void BitcoinApplication::requestInitialize()
 
 void BitcoinApplication::requestShutdown()
 {
+    for (const auto w : QGuiApplication::topLevelWindows()) {
+        w->hide();
+    }
+
     // Show a simple window indicating shutdown status
     // Do this first as some of the steps may take some time below,
     // for example the RPC console may still be executing a command.
     shutdownWindow.reset(ShutdownWindow::showShutdownWindow(window));
 
     qDebug() << __func__ << ": Requesting shutdown";
-    window->hide();
+
     // Must disconnect node signals otherwise current thread can deadlock since
     // no event loop is running.
     window->unsubscribeFromCoreSignals();
@@ -408,13 +414,13 @@ void BitcoinApplication::initializeResult(bool success, interfaces::BlockAndHead
         pollShutdownTimer->start(200);
     } else {
         Q_EMIT splashFinished(); // Make sure splash screen doesn't stick around during shutdown
-        quit(); // Exit first main loop invocation
+        requestShutdown();
     }
 }
 
 void BitcoinApplication::shutdownResult()
 {
-    quit(); // Exit second main loop invocation after shutdown finished
+    quit();
 }
 
 void BitcoinApplication::handleRunawayException(const QString &message)
@@ -637,8 +643,6 @@ int GuiMain(int argc, char* argv[])
 #if defined(Q_OS_WIN)
             WinShutdownMonitor::registerShutdownBlockReason(QObject::tr("%1 didn't yet exit safely…").arg(PACKAGE_NAME), (HWND)app.getMainWinId());
 #endif
-            app.exec();
-            app.requestShutdown();
             app.exec();
             rv = app.getReturnValue();
         } else {

src/qt/bitcoin.h

@@ -56,8 +56,6 @@ public:
 
     /// Request core initialization
     void requestInitialize();
-    /// Request core shutdown
-    void requestShutdown();
 
     /// Get process return value
     int getReturnValue() const { return returnValue; }
@@ -73,6 +71,8 @@ public:
 
 public Q_SLOTS:
     void initializeResult(bool success, interfaces::BlockAndHeaderTipInfo tip_info);
+    /// Request core shutdown
+    void requestShutdown();
     void shutdownResult();
     /// Handle runaway exceptions. Shows a message box with the problem and quits the program.
     void handleRunawayException(const QString &message);

src/qt/bitcoingui.cpp

@@ -371,7 +371,7 @@ void BitcoinGUI::createActions()
     m_mask_values_action->setStatusTip(tr("Mask the values in the Overview tab"));
     m_mask_values_action->setCheckable(true);
 
-    connect(quitAction, &QAction::triggered, qApp, QApplication::quit);
+    connect(quitAction, &QAction::triggered, this, &BitcoinGUI::quitRequested);
     connect(aboutAction, &QAction::triggered, this, &BitcoinGUI::aboutClicked);
     connect(aboutQtAction, &QAction::triggered, qApp, QApplication::aboutQt);
     connect(optionsAction, &QAction::triggered, this, &BitcoinGUI::optionsClicked);
@@ -991,6 +991,7 @@ void BitcoinGUI::openOptionsDialogWithTab(OptionsDialog::Tab tab)
         return;
 
     auto dlg = new OptionsDialog(this, enableWallet);
+    connect(dlg, &OptionsDialog::quitOnReset, this, &BitcoinGUI::quitRequested);
     dlg->setCurrentTab(tab);
     dlg->setModel(clientModel->getOptionsModel());
     GUIUtil::ShowModalDialogAndDeleteOnClose(dlg);
@@ -1216,7 +1217,7 @@ void BitcoinGUI::closeEvent(QCloseEvent *event)
             // close rpcConsole in case it was open to make some space for the shutdown window
             rpcConsole->close();
 
-            QApplication::quit();
+            Q_EMIT quitRequested();
         }
         else
         {
@@ -1410,7 +1411,7 @@ void BitcoinGUI::detectShutdown()
     {
         if(rpcConsole)
             rpcConsole->hide();
-        qApp->quit();
+        Q_EMIT quitRequested();
     }
 }
 

src/qt/bitcoingui.h

@@ -214,6 +214,7 @@ private:
     void openOptionsDialogWithTab(OptionsDialog::Tab tab);
 
 Q_SIGNALS:
+    void quitRequested();
     /** Signal raised when a URI was entered or dragged to the GUI */
     void receivedURI(const QString &uri);
     /** Signal raised when RPC console shown */

src/qt/optionsdialog.cpp

@@ -290,7 +290,8 @@ void OptionsDialog::on_resetButton_clicked()
 
         /* reset all options and close GUI */
         model->Reset();
-        QApplication::quit();
+        close();
+        Q_EMIT quitOnReset();
     }
 }
 

src/qt/optionsdialog.h

@@ -68,6 +68,7 @@ private Q_SLOTS:
 
 Q_SIGNALS:
     void proxyIpChecks(QValidatedLineEdit *pUiProxyIp, uint16_t nProxyPort);
+    void quitOnReset();
 
 private:
     Ui::OptionsDialog *ui;