Merge bitcoin-core/gui#547: Override BitcoinApplication::event() to handle QEvent::Quit

e7fc50681e qt: Override BitcoinApplication::event() to handle QEvent::Quit (Hennadii Stepanov)

Pull request description:

  bitcoin-core/gui#336 introduced a regression when termination requests from a platform are not handled properly.

  This PR fixes this regression. On macOS shutdown after clicking "Quit" in Dock icon menu, and during logout works again.

  Fixes bitcoin-core/gui#545.

ACKs for top commit:
  RandyMcMillan:
    tACK e7fc50681e
  Sjors:
    tACK e7fc50681e (rebased on master) indeed fixes the crash described in #545
  promag:
    Tested ACK e7fc50681e on macOS 10.15 with Qt 5.15.2.

Tree-SHA512: 236a483dc0828f22999469e133b8ac9f0b6267ec2a27004c3ebaa967689ddb972ea1fa90c1dd41f3bff3d17bf571a707babcef53bd79fd711fda98cfbf120131

src/qt/bitcoin.cpp

@@ -454,6 +454,16 @@ WId BitcoinApplication::getMainWinId() const
     return window->winId();
 }
 
+bool BitcoinApplication::event(QEvent* e)
+{
+    if (e->type() == QEvent::Quit) {
+        requestShutdown();
+        return true;
+    }
+
+    return QApplication::event(e);
+}
+
 static void SetupUIArgs(ArgsManager& argsman)
 {
     argsman.AddArg("-choosedatadir", strprintf("Choose data directory on startup (default: %u)", DEFAULT_CHOOSE_DATADIR), ArgsManager::ALLOW_ANY, OptionsCategory::GUI);

src/qt/bitcoin.h

@@ -92,6 +92,9 @@ Q_SIGNALS:
     void splashFinished();
     void windowShown(BitcoinGUI* window);
 
+protected:
+    bool event(QEvent* e) override;
+
 private:
     std::optional<InitExecutor> m_executor;
     OptionsModel *optionsModel;