QSplashScreen Weirdness

I have a problem using QSplashScreen. My application generates a log (text) file and has a menu item to let the user view a parsed display of this file in a table in a dialog. Since the file can be up to 500k, it takes a while to parse so I use a QSplashScreen to distract the user ;) during the parsing (sometimes more than 5000 lines). The QSplashScreen is semi-transparent and displays a message indicating how many lines of the log file have been parsed.

I know this is not normal usage of a QSplashScreen but it works fine except for the following.

My problem is that if a user repeatedly clicks outside the QSplashScreen, in the main window title bar for example, after reading between 700 and 1200 lines of the > 5000 line file:

• the message in the QSplashScreen freezes at a line number (but the file continues to be parsed)
• the main window MAY be drawn over the QSplashScreen
• the client area of the main window goes away (repainted in white)
• when the file is finished being read, the dialog displays the log file contents correctly but the QSplashScreen is drawn on top and never goes away until the application closes

While all of the results above are irritating, the worst is that the splash screen never goes away (even after the dialog is gone).

I have tried trapping (and ignoring) the mousePressEvents in both the main window and the dialog but the mousePressEvent() function never gets the mouse events while the QSplashScreen is active. This is not surprising since it appears that the QSplashScreen has focus.

I noticed that a mouse press should cause the splash screen to become hidden, but in this case it doesn't happen.

BTW, I'm using 4.2.2 with VS2005.

Any suggestions for fixing this weird mouse click problem?

Code:

---

// From the class definition...
    QTableWidget*    m_logTable;
    MainWin*         m_pMainWin;
    QSplashScreen*   m_pSplash;
    QFile            m_logFile;
 
// Show Log file dialog ctor
ShowLog::ShowLog( QWidget *pParent ) : QDialog( pParent )
{
    m_pMainWin = static_cast<MainWin*>( pParent );
    QDir::setCurrent( QDir::currentPath() );
 
    m_logFile.setFileName( LOG_FILENAME );
 
    QIODevice::OpenMode nOpenMode = QIODevice::ReadOnly | QIODevice::Text;
 
    if ( !m_logFile.exists() )
        reject();
 
    if ( !m_logFile.open( nOpenMode ) )
        reject();
 
    QPixmap pMap( SHOWLOG_SPLASH_IMG );
 
    // Make the corners fully transparent (rounded-corner bitmap)
    if ( !pMap.mask().isNull() )
    {
        QImage img( SHOWLOG_SPLASH_IMG );
        if ( img.hasAlphaChannel() )
            pMap.setMask( QBitmap::fromImage( img.createAlphaMask() ) );
        else
            pMap.setMask( QBitmap::fromImage( img.createHeuristicMask() ) );
    }
 
    ui.setupUi( this );
 
    QPalette palette = ui.centralWidget->palette();
    palette.setColor( ui.centralWidget->backgroundRole(), COLOR_ManageBkg );
    ui.centralWidget->setPalette( palette );
 
    m_logTable = new QTableWidget( 0, 4, this );
 
    // Layout the Show Logfile dialog
    .
    .
    .
    // Initialize the text stream
    QTextStream logStream( &m_logFile );
    QString sLine, sSrc, sType, sTime, sMsg;
    QString sMsgText( "   Reading %1: line %2" );
    Qt::ItemFlags flags;
    int start, end, nRow = 0;
 
    // Skip the header
    while ( (sLine = logStream.readLine())[0] == '*' );
 
    // Set up the splash screen
    m_pSplash = new QSplashScreen( pParent, pMap );
    m_pSplash->setWindowOpacity( 0.8 ); // make the image semi-transparent
    palette = m_pSplash->palette();
    palette.setBrush( QPalette::Window, QBrush( pMap ) );
    m_pSplash->setPalette( palette );
    m_pSplash->setFixedSize( pMap.size() );
    m_pSplash->setMask( pMap.mask() );
    QFont font = m_pSplash->font();
    font.setBold( true );
    m_pSplash->setFont( font );  // Set the m_pSplash font to bold
 
    // Center the splash screen in the main application window
    m_pSplash->move( m_pMainWin->pos().x() +
                        (m_pMainWin->frameGeometry().width() / 2) -
                        (m_pSplash->frameGeometry().width() / 2),
                     m_pMainWin->pos().y() +
                        (m_pMainWin->frameGeometry().height() / 2) -
                        (m_pSplash->frameGeometry().height() / 2) );
    m_pSplash->show();
 
    // Load the text
    while ( !logStream.atEnd() || !sLine.isEmpty() )
    {
        if ( sLine.isEmpty() ) // skip any empty lines
        {
            sLine = logStream.readLine();
            continue;
        }
 
        // Parse the Source
        .
        .
        .
        // Fill a table row
        m_logTable->insertRow( nRow );
        .
        .
        .
        nRow++;
        sLine = logStream.readLine();
 
        // Incremental splash message
        m_pSplash->showMessage( sMsgText.arg( LOG_FILENAME ).arg( nRow ),
                                nMsgAlignment, textColor );
    }
 
    // Close the QFile
    if ( m_logFile.isOpen() )
        m_logFile.close();
 
    // Set sort indicator in column headers
    m_logTable->horizontalHeader()->setSortIndicatorShown( true );
    m_logTable->setSortingEnabled( true );
 
    m_pSplash->finish( this );
 
}

---

hi,
Maybe disabling main window while splash is active would fix your error?

Why not use QProgressDialog or another modal dialog instead?

Quote:

---

Originally Posted by mchara

disabling main window while splash is active

---

Disabling the main window would seem like the way to go, unfortunately it doesn't seem to take effect until after the splash screen goes away and after the dialog is shown.

Code:

---

void MainWin::showLog( void )
{
	setEnabled( false );
 
	ShowLog showDlg( this ); 
	showDlg.exec();
 
	setEnabled( true );
 
} // showLog(

---

This call is a slot for the menu selection triggered() signal and it appears that the setEnabled() is preempted by the splash screen action in the dialog ctor.

Quote:

---

Originally Posted by wysota

Why not use QProgressDialog or another modal dialog instead?

---

I wanted to use a splash screen because I don't know in advance what the maximum number of parsable (is this a word?) lines I have to deal with. Although, I may be able to get similar functionality with some other type of modal dialog. I just liked the idea of having a semi-transparent, rounded corner bitmap and the QSplashScreen allowed me to do that with just a few lines of code.

Do you have another modal dialog type in mind?

Quote:

---

Originally Posted by mclark

Do you have another modal dialog type in mind?

---

Subclass QDialog, make it frameless and display a label on it that contains the bitmap of your choice. You can also use QWidget::setMask to make it round or something...

Quote:

---

Originally Posted by wysota

Subclass QDialog, make it frameless and display a label on it that contains the bitmap of your choice. You can also use QWidget::setMask to make it round or something...

---

Thanks for the suggestion wysota.

The code below 'kind of' works. A semi-transparent, rounded-corner dialog appears with the pixmap in it. If I only add the label with the pixmap, the pixmap appears as if it is inside the dialog. What I mean by that is there is a band of semi-transparent area around all 4 sides of the pixmap. Shrinking the dialog size only clips the pixmap.

For parsing progress display, I thought I could add a second label to display the message text (similar to what QSplashScreen offers.) This never shows.

Is there a way to have the pixmap in the label to completely fill the dialog area without clipping, and, for a line of text to be superimposed on the pixmap?

Code:

---

QPixmap pMap( SHOWLOG_SPLASH_IMG );
 
// Make the corners fully transparent (rounded-corner bitmap)
if ( !pMap.mask().isNull() )
{
    QImage img( SHOWLOG_SPLASH_IMG );
    if ( img.hasAlphaChannel() )
        pMap.setMask( QBitmap::fromImage( img.createAlphaMask() ) );
    else
        pMap.setMask( QBitmap::fromImage( img.createHeuristicMask() ) );
}
 
QDialog splashDlg( this, Qt::FramelessWindowHint );
 
splashDlg.setWindowOpacity( 0.8 ); // make the dialog semi-transparent
palette = splashDlg.palette();
palette.setBrush( QPalette::Window, QBrush( pMap ) );
splashDlg.setPalette( palette );
splashDlg.setFixedSize( pMap.size().width(), pMap.size().height() + 40 );
splashDlg.setMask( pMap.mask() );
 
QFont font = splashDlg.font();
font.setBold( true );
splashDlg.setFont( font );  // Set the splashDlg font to bold
 
QLabel* pTxtLabel = new QLabel();
QLabel* pImgLabel = new QLabel();
pImgLabel->resize( pMap.size() );
pImgLabel->setPixmap( pMap );
 
QVBoxLayout *vSplashBox = new QVBoxLayout( &splashDlg );
vSplashBox->addWidget( pTxtLabel, Qt::AlignTop | Qt::AlignLeft );
vSplashBox->addWidget( pImgLabel, Qt::AlignCenter );
 
splashDlg.show();
    .
    .
    .
while ( !logStream.atEnd() || !sLine.isEmpty() )
{
    .
    .
    .
    // Increment splash message every 50 iterations
    if ( !(nRow % 50) )
        pTxtLabel->setText( sMsgText.arg( LOG_FILENAME ).arg( nRow ) );
}
 
splashDlg.close();

---

If you override paint event of the dialog and draw the image there yourself, it should work. You can also use a label for that - just make sure it's not part of the layout and that it is lowered behind other widgets of the dialog. I'd suggest reimplementing the paint event though.

I went with you're earlier suggestion of using a progress dialog. I get the file size and use that as my max value. In my line reading loop I increment the progress value with the length of the current line.

But, if clicking around the main window during the progress dialog progression, when the progress dialog goes away and the log display dialog shows, I get some unexpected data in the table in the dialog, and when closing it, a crash. This only happens in the release version of the app, I assume that the MS IDE is handling these problems in the debug version although I get no indications of problems.

I'm doing the file parsing in a loop in the log display dialog constructor, could this be a problem? If so, I'm not sure how else to do this using QDialog.

I'd have to see the exact code. What you describe shouldn't happen, provided your progress dialog is modal.

UPDATE: The crashing is due to bad data (log file stored in the debug directory is good while the file in the release directory was bad). So, I'll skip the QSplashScreen for now - still has the white-out problem I mentioned in the beginning of this thread - and go with the QProgressDialog. Thanks for your time, you do a great service!

Here is the whole bloody mess... I'm going to remove all progress dialog modifications (FramelessWindowHint, opacity, font type and color...) and see what happens. Thanks for taking the time to review this with me. I very much appreciate it.

Doing only the following has no effect. Still get a crash if multi-clicking on the main window header.

Code:

---

QProgressDialog progDlg( QString( "Reading %1 . . ." ).arg( LOG_FILENAME ),
                                  "Cancel", 0, nProgDlgMax, this );
progDlg.setModal( true );

---

Code:

---

class ShowLog : public QDialog
{
    Q_OBJECT
 
public:
    ShowLog( QWidget* pParent = 0 );
	virtual ~ShowLog() {}
 
private:
    Ui::ShowLogClass ui;
 
	QTableWidget*	m_logTable;
	MainWin*		m_pMainWin;
 
private slots:
	void on_okBtn_clicked( void )	{ accept(); }
	void on_clearBtn_clicked( void );
 
};
 
ShowLog::ShowLog( QWidget *pParent ) : QDialog( pParent )
{
    m_pMainWin = static_cast<MainWin*>( pParent );
    QDir::setCurrent( QDir::currentPath() );
 
    QFile logFile( LOG_FILENAME );
 
    QIODevice::OpenMode nOpenMode = QIODevice::ReadOnly | QIODevice::Text;
 
    if ( !logFile.exists() || !logFile.open( nOpenMode ) )
        reject();
 
    ui.setupUi( this );
 
    QPalette palette = ui.centralWidget->palette();
    palette.setColor( ui.centralWidget->backgroundRole(), COLOR_ManageBkg );
    ui.centralWidget->setPalette( palette );
 
    m_logTable = new QTableWidget( 0, 4, this );
 
    // Layout the Show Logfile dialog
    QStringList sLabels;
    sLabels << "Source" << "Type" << "Time" << "Message";
 
    m_logTable->setHorizontalHeaderLabels( sLabels );
    m_logTable->verticalHeader()->hide();
    m_logTable->setColumnWidth( COL0_Src, 78 );
    m_logTable->setColumnWidth( COL1_Type, 70 );
    m_logTable->setColumnWidth( COL2_Time, 130 );
    m_logTable->setColumnWidth( COL3_Msg, 510 );
    m_logTable->setMinimumWidth( 775 );
    // Enable sorting after the table is populated, otherwise sorting
    // may interfere with the insertion order
    m_logTable->setSortingEnabled( false );
 
    QSize bs = ui.okBtn->sizeHint().expandedTo( ui.clearBtn->sizeHint() );
    ui.okBtn->setFixedSize( bs );
    ui.clearBtn->setFixedSize( bs );
    ui.okBtn->setDefault( true );
 
    // Set the "What's This?" text for controls
    m_logTable->setWhatsThis( WT_LOG_TABLE );
    ui.okBtn->setWhatsThis( WT_OK_BTN );
    ui.clearBtn->setWhatsThis( WT_CLEARLOG_BTN );
 
    QVBoxLayout *vbox = new QVBoxLayout( this );
    vbox->addSpacing( 10 );
    vbox->addWidget( m_logTable, Qt::AlignHCenter );
    vbox->addStretch( 0 );
    vbox->addSpacing( 15 );
 
    // Add a stretch to either side of the box to keep the
    // button centered whenever stretching horizontally
    QHBoxLayout* hbox = new QHBoxLayout();
    hbox->addStretch();
    hbox->addSpacing( 100 );
    hbox->addWidget( ui.clearBtn );
    hbox->addSpacing( 60 );
    hbox->addWidget( ui.okBtn );
    hbox->addSpacing( 100 );
    hbox->addStretch();
 
    vbox->addLayout( hbox );
    vbox->addSpacing( 7 );
 
    resize( sizeHint() );
 
    // Create a splash-like dialog
    qint64 nProgDlgMax = logFile.size();
    QProgressDialog progDlg( QString( "Reading %1 . . ." ).arg( LOG_FILENAME ),
                             "Cancel", 0, nProgDlgMax, this, Qt::FramelessWindowHint );
    progDlg.setModal( true );
    progDlg.setWindowOpacity( 0.92 ); // make the dialog semi-transparent
    palette = progDlg.palette();
    palette.setColor( QPalette::WindowText, QColor( 64, 64, 64 ) );
    progDlg.setPalette( palette );
    progDlg.setFixedSize( 350, 110 );
    QFont font = progDlg.font();
    font.setBold( true );
    progDlg.setFont( font );  // Set the splash font to bold
    progDlg.setForegroundRole( QPalette::WindowText );
 
    // Center the splash screen in the main application window
    progDlg.move( m_pMainWin->pos().x() +
                    (m_pMainWin->frameGeometry().width() / 2) -
                    (progDlg.frameGeometry().width() / 2),
                  m_pMainWin->pos().y() +
                    (m_pMainWin->frameGeometry().height() / 2) -
                    (progDlg.frameGeometry().height() / 2) );
 
    // Initialize the text stream
    QTextStream logStream( &logFile );
    QString sLine, sSrc, sType, sTime, sMsg;
    Qt::ItemFlags flags;
    int start, end, nRow = 0;
    int    nProgDlgValue = 0;
 
    const int nTextAlignment = Qt::AlignCenter;
    const int nMsgTextAlign = Qt::AlignLeft | Qt::AlignVCenter;
    const Qt::ItemFlags itemFlags = Qt::ItemIsEditable | Qt::ItemIsSelectable;
 
    // Skip the header
    while ( (sLine = logStream.readLine())[0] == '*' )
        nProgDlgValue += sLine.length();
 
    // Load the text
    while ( !logStream.atEnd() || !sLine.isEmpty() )
    {
        if ( sLine.isEmpty() ) // skip any empty lines
        {
            sLine = logStream.readLine();
            continue;
        }
 
        sSrc.clear();
        sType.clear();
        sTime.clear();
        sMsg.clear();
        start = 0;
 
        // Parse the Source
        end = sLine.indexOf( ' ', start, Qt::CaseSensitive ); 
        for ( int i = 0; i < 3; i++ )
            sSrc[i] = sLine[start + i];
 
        if ( sSrc == "LIB" )
            sSrc = "Library";
        else if ( sSrc == "APP" )
            sSrc = "GCE";
        else if ( sSrc == "DBG" )
            sSrc = "Debug";
        else if ( sSrc == "SYS" )
            sSrc = "System";
        else if ( sSrc == "SEC" )
            sSrc = "Security";
        else
            sSrc = "Unknown";
 
        start = end + 1;
 
        // Parse the Type
        end = sLine.indexOf( ' ', start, Qt::CaseSensitive ); 
        for ( int i = 0; i < 3; i++ )
            sType[i] = sLine[start + i];
 
        if ( sType == "INF" )
            sType = "Information";
        else if ( sType == "ERR" )
            sType = "Error";
        else if ( sType == "WRN" )
            sType = "Warning";
        else
            sType = "Unknown";
 
        start = end + 1;
 
        // Parse the Time
        end = sLine.indexOf( CDL_COOKIE, start, Qt::CaseSensitive ); 
        for ( int i = 0; i < 19; i++ )
            sTime[i] = sLine[start + i];
 
        sTime[sTime.indexOf( ' ', 0 )] = '/';  // for year/month
        sTime[sTime.indexOf( ' ', 0 )] = '/';  // for month/day
        start = end + 4;
 
        // Get the message
        sMsg = sLine.right( sLine.count() - start ); 
 
        // Fill a table row
        m_logTable->insertRow( nRow );
 
        // Add message source
        m_logTable->setItem( nRow, COL0_Src, new QTableWidgetItem( sSrc ) );
        m_logTable->item( nRow, COL0_Src )->setTextAlignment( nTextAlignment );
        // Set as read-only
        flags = m_logTable->item( nRow, COL0_Src )->flags();
        flags ^= itemFlags;
        m_logTable->item( nRow, COL0_Src )->setFlags( flags );
 
        // Add message type
        m_logTable->setItem( nRow, COL1_Type, new QTableWidgetItem( sType ) );
        m_logTable->item( nRow, COL1_Type )->setTextAlignment( nTextAlignment );
        // Set as read-only
        flags = m_logTable->item( nRow, COL1_Type )->flags();
        flags ^= itemFlags;
        m_logTable->item( nRow, COL1_Type )->setFlags( flags );
 
        // Add message time
        m_logTable->setItem( nRow, COL2_Time, new QTableWidgetItem( sTime ) );
        m_logTable->item( nRow, COL2_Time )->setTextAlignment( nTextAlignment );
        // Set as read-only
        flags = m_logTable->item( nRow, COL2_Time )->flags();
        flags ^= itemFlags;
        m_logTable->item( nRow, COL2_Time )->setFlags( flags );
 
        // Add message
        m_logTable->setItem( nRow, COL3_Msg, new QTableWidgetItem( sMsg ) );
        m_logTable->item( nRow, COL3_Msg )->setTextAlignment( nMsgTextAlign );
        // Set as read-only
        flags = m_logTable->item( nRow, COL3_Msg )->flags();
        flags ^= itemFlags;
        m_logTable->item( nRow, COL3_Msg )->setFlags( flags );
 
        nRow++;
        sLine = logStream.readLine();
 
        // Increment progress bar
        progDlg.setValue( nProgDlgValue += sLine.length() );
        m_pMainWin->m_pApp->processEvents();
 
        if ( progDlg.wasCanceled() )
            break;
    }
 
    // Close the QFile
    if ( logFile.isOpen() )
        logFile.close();
 
    // Enable sorting
    m_logTable->setSortingEnabled( true );
 
}

---

I'd suggest doing it a bit another way. You need to implement your functionality in a slot that can be called multiple times - once for every iteration. Then create the progress dialog, make a connection between a single shot timer and your slot and call exec() on the dialog.

Set a 0 timeout for the timer and at the end of your slot start a 0-timeout single shot timer again. Something like:

Code:

---

QProgressDialog dlg(this);
iteration = 0;
startSlot();
dlg.exec();
//...
void X:startSlot(){
  iteration++;
  if(iteration<1000)
    QTimer::singleShot(0, this, SLOT(startSlot()));
}

---

The main idea is to make sure you call exec on the progress dialog. See if your app crashes then.

Hi,
disabling main window may fail because you are not processing event loop while reading log and setEnabled is queued there so it's done after log reading.
Even if you want to use progress dialog, you shall call QCoreApplication::processEvents from time to time according to qt manual.

And one another approach - maybe read your log file in separate thread.