qt: Make splash and shutdown window ignore close events

It's strange to be able to close these windows while there is work
in progress.

Also set Qt::WA_DeleteOnClose on both windows to make sure that they
are deleted eventually, no matter what happens.

src/qt/bitcoin.cpp

@@ -339,6 +339,9 @@ void BitcoinApplication::createWindow(bool isaTestNet)
 void BitcoinApplication::createSplashScreen(bool isaTestNet)
 {
     SplashScreen *splash = new SplashScreen(0, isaTestNet);
+    // We don't hold a direct pointer to the splash screen after creation, so use
+    // Qt::WA_DeleteOnClose to make sure that the window will be deleted eventually.
+    splash->setAttribute(Qt::WA_DeleteOnClose);
     splash->show();
     connect(this, SIGNAL(splashFinished(QWidget*)), splash, SLOT(slotFinish(QWidget*)));
 }

src/qt/splashscreen.cpp

@@ -14,8 +14,9 @@
 #endif
 
 #include <QApplication>
-#include <QPainter>
+#include <QCloseEvent>
 #include <QDesktopWidget>
+#include <QPainter>
 
 SplashScreen::SplashScreen(Qt::WindowFlags f, bool isTestNet) :
     QWidget(0, f), curAlignment(0)
@@ -113,7 +114,6 @@ SplashScreen::~SplashScreen()
 void SplashScreen::slotFinish(QWidget *mainWin)
 {
     hide();
-    deleteLater();
 }
 
 static void InitMessage(SplashScreen *splash, const std::string &message)
@@ -175,3 +175,8 @@ void SplashScreen::paintEvent(QPaintEvent *event)
     painter.drawText(r, curAlignment, curMessage);
 }
 
+void SplashScreen::closeEvent(QCloseEvent *event)
+{
+    event->ignore();
+}
+

src/qt/splashscreen.h

@@ -7,7 +7,11 @@
 
 #include <QSplashScreen>
 
-/** class for the splashscreen with information of the running client
+/** Class for the splashscreen with information of the running client.
+ *
+ * @note this is intentionally not a QSplashScreen. Bitcoin Core initialization
+ * can take a long time, and in that case a progress window that cannot be
+ * moved around and minimized has turned out to be frustrating to the user.
  */
 class SplashScreen : public QWidget
 {
@@ -19,6 +23,7 @@ public:
 
 protected:
     void paintEvent(QPaintEvent *event);
+    void closeEvent(QCloseEvent *event);
 
 public slots:
     /** Slot to call finish() method as it's not defined as slot */

src/qt/utilitydialog.cpp

@@ -15,6 +15,7 @@
 
 #include <stdio.h>
 
+#include <QCloseEvent>
 #include <QLabel>
 #include <QRegExp>
 #include <QVBoxLayout>
@@ -106,18 +107,26 @@ void HelpMessageDialog::on_okButton_accepted()
 
 
 /** "Shutdown" window */
+ShutdownWindow::ShutdownWindow(QWidget *parent, Qt::WindowFlags f):
+    QWidget(parent, f)
+{
+    QVBoxLayout *layout = new QVBoxLayout();
+    layout->addWidget(new QLabel(
+        tr("Bitcoin Core is shutting down...") + "<br /><br />" +
+        tr("Do not shut down the computer until this window disappears.")));
+    setLayout(layout);
+}
+
 void ShutdownWindow::showShutdownWindow(BitcoinGUI *window)
 {
     if (!window)
         return;
 
     // Show a simple window indicating shutdown status
-    QWidget *shutdownWindow = new QWidget();
-    QVBoxLayout *layout = new QVBoxLayout();
-    layout->addWidget(new QLabel(
-        tr("Bitcoin Core is shutting down...") + "<br /><br />" +
-        tr("Do not shut down the computer until this window disappears.")));
-    shutdownWindow->setLayout(layout);
+    QWidget *shutdownWindow = new ShutdownWindow();
+    // We don't hold a direct pointer to the shutdown window after creation, so use
+    // Qt::WA_DeleteOnClose to make sure that the window will be deleted eventually.
+    shutdownWindow->setAttribute(Qt::WA_DeleteOnClose);
     shutdownWindow->setWindowTitle(window->windowTitle());
 
     // Center shutdown window at where main window was
@@ -125,3 +134,8 @@ void ShutdownWindow::showShutdownWindow(BitcoinGUI *window)
     shutdownWindow->move(global.x() - shutdownWindow->width() / 2, global.y() - shutdownWindow->height() / 2);
     shutdownWindow->show();
 }
+
+void ShutdownWindow::closeEvent(QCloseEvent *event)
+{
+    event->ignore();
+}

src/qt/utilitydialog.h

@@ -37,12 +37,16 @@ private slots:
 
 
 /** "Shutdown" window */
-class ShutdownWindow : public QObject
+class ShutdownWindow : public QWidget
 {
     Q_OBJECT
 
 public:
+    ShutdownWindow(QWidget *parent=0, Qt::WindowFlags f=0);
     static void showShutdownWindow(BitcoinGUI *window);
+
+protected:
+    void closeEvent(QCloseEvent *event);
 };
 
 #endif // UTILITYDIALOG_H