C++ QwtPlotCanvas::backingStore方法代码示例

//! Event filter
bool QwtPlotDirectPainter::eventFilter( QObject *, QEvent *event )
{
    if ( event->type() == QEvent::Paint )
    {
        reset();

        if ( d_data->seriesItem )
        {
            const QPaintEvent *pe = static_cast< QPaintEvent *>( event );

            QwtPlotCanvas *canvas = d_data->seriesItem->plot()->canvas();

            QPainter painter( canvas );
            painter.setClipRegion( pe->region() );

            bool copyCache = testAttribute( CopyBackingStore )
                && canvas->testPaintAttribute( QwtPlotCanvas::BackingStore );

            if ( copyCache )
            {
                // is something valid in the cache ?
                copyCache = ( canvas->backingStore() != NULL )
                    && !canvas->backingStore()->isNull();
            }

            if ( copyCache )
            {
                painter.drawPixmap( 
                    canvas->contentsRect().topLeft(), 
                    *canvas->backingStore() );
            }
            else
            {
                renderItem( &painter, canvas->contentsRect(),
                    d_data->seriesItem, d_data->from, d_data->to );
            }

            return true; // don't call QwtPlotCanvas::paintEvent()
        }
    }

    return false;
}

//! Event filter
bool QwtPlotDirectPainter::eventFilter( QObject *, QEvent *event )
{
    if ( event->type() == QEvent::Paint )
    {
        reset();

        if ( d_data->seriesItem )
        {
            const QPaintEvent *pe = static_cast< QPaintEvent *>( event );

            QWidget *canvas = d_data->seriesItem->plot()->canvas();

            QPainter painter( canvas );
            painter.setClipRegion( pe->region() );

            bool doCopyCache = testAttribute( CopyBackingStore );

            if ( doCopyCache )
            {
                QwtPlotCanvas *plotCanvas = 
                    qobject_cast<QwtPlotCanvas *>( canvas );
                if ( plotCanvas )
                {
                    doCopyCache = qwtHasBackingStore( plotCanvas );
                    if ( doCopyCache )
                    {
                        painter.drawPixmap( plotCanvas->contentsRect().topLeft(), 
                            *plotCanvas->backingStore() );
                    }
                }
            }

            if ( !doCopyCache )
            {
                qwtRenderItem( &painter, canvas->contentsRect(),
                    d_data->seriesItem, d_data->from, d_data->to );
            }

            return true; // don't call QwtPlotCanvas::paintEvent()
        }
    }

    return false;
}

/*!
  \brief Draw a set of points of a seriesItem.

  When observing an measurement while it is running, new points have to be
  added to an existing seriesItem. drawSeries can be used to display them avoiding
  a complete redraw of the canvas.

  Setting plot()->canvas()->setAttribute(Qt::WA_PaintOutsidePaintEvent, true);
  will result in faster painting, if the paint engine of the canvas widget
  supports this feature.

  \param seriesItem Item to be painted
  \param from Index of the first point to be painted
  \param to Index of the last point to be painted. If to < 0 the
         series will be painted to its last point.
*/
void QwtPlotDirectPainter::drawSeries(
    QwtPlotAbstractSeriesItem *seriesItem, int from, int to )
{
    if ( seriesItem == NULL || seriesItem->plot() == NULL )
        return;

    QwtPlotCanvas *canvas = seriesItem->plot()->canvas();
    const QRect canvasRect = canvas->contentsRect();

    const bool hasBackingStore = 
        canvas->testPaintAttribute( QwtPlotCanvas::BackingStore ) 
        && canvas->backingStore() && !canvas->backingStore()->isNull();

    if ( hasBackingStore )
    {
        QPainter painter( const_cast<QPixmap *>( canvas->backingStore() ) );

        if ( d_data->hasClipping )
            painter.setClipRegion( d_data->clipRegion );

        renderItem( &painter, canvasRect, seriesItem, from, to );

        if ( testAttribute( QwtPlotDirectPainter::FullRepaint ) )
        {
            canvas->repaint();
            return;
        }
    }

    bool immediatePaint = true;
    if ( !canvas->testAttribute( Qt::WA_WState_InPaintEvent ) )
    {
        immediatePaint = false;
    }

    if ( immediatePaint )
    {
        if ( !d_data->painter.isActive() )
        {
            reset();

            d_data->painter.begin( canvas );
            canvas->installEventFilter( this );
        }

        if ( d_data->hasClipping )
        {
            d_data->painter.setClipRegion( 
                QRegion( canvasRect ) & d_data->clipRegion );
        }
        else
        {
            if ( !d_data->painter.hasClipping() )
                d_data->painter.setClipRect( canvasRect );
        }

        renderItem( &d_data->painter, canvasRect, seriesItem, from, to );

        if ( d_data->attributes & QwtPlotDirectPainter::AtomicPainter )
        {
            reset();
        }
        else
        {
            if ( d_data->hasClipping )
                d_data->painter.setClipping( false );
        }
    }
    else
    {
        reset();

        d_data->seriesItem = seriesItem;
        d_data->from = from;
        d_data->to = to;

        QRegion clipRegion = canvasRect;
        if ( d_data->hasClipping )
            clipRegion &= d_data->clipRegion;

        canvas->installEventFilter( this );
        canvas->repaint(clipRegion);
        canvas->removeEventFilter( this );

//.........这里部分代码省略.........

/*!
  \brief Draw a set of points of a seriesItem.

  When observing an measurement while it is running, new points have to be
  added to an existing seriesItem. drawSeries() can be used to display them avoiding
  a complete redraw of the canvas.

  Setting plot()->canvas()->setAttribute(Qt::WA_PaintOutsidePaintEvent, true);
  will result in faster painting, if the paint engine of the canvas widget
  supports this feature.

  \param seriesItem Item to be painted
  \param from Index of the first point to be painted
  \param to Index of the last point to be painted. If to < 0 the
         series will be painted to its last point.
*/
void QwtPlotDirectPainter::drawSeries(
    QwtPlotSeriesItem *seriesItem, int from, int to )
{
    if ( seriesItem == NULL || seriesItem->plot() == NULL )
        return;

    QWidget *canvas = seriesItem->plot()->canvas();
    const QRect canvasRect = canvas->contentsRect();

    QwtPlotCanvas *plotCanvas = qobject_cast<QwtPlotCanvas *>( canvas );

    if ( plotCanvas && qwtHasBackingStore( plotCanvas ) )
    {
        QPainter painter( const_cast<QPixmap *>( plotCanvas->backingStore() ) );

        if ( d_data->hasClipping )
            painter.setClipRegion( d_data->clipRegion );

        qwtRenderItem( &painter, canvasRect, seriesItem, from, to );

        painter.end();

        if ( testAttribute( QwtPlotDirectPainter::FullRepaint ) )
        {
            plotCanvas->repaint();
            return;
        }
    }

    bool immediatePaint = true;
    if ( !canvas->testAttribute( Qt::WA_WState_InPaintEvent ) ) 
    {
#if QT_VERSION < 0x050000
        if ( !canvas->testAttribute( Qt::WA_PaintOutsidePaintEvent ) )
#endif
            immediatePaint = false;
    }

    if ( immediatePaint )
    {
        if ( !d_data->painter.isActive() )
        {
            reset();

            d_data->painter.begin( canvas );
            canvas->installEventFilter( this );
        }

        if ( d_data->hasClipping )
        {
            d_data->painter.setClipRegion( 
                QRegion( canvasRect ) & d_data->clipRegion );
        }
        else
        {
            if ( !d_data->painter.hasClipping() )
                d_data->painter.setClipRect( canvasRect );
        }

        qwtRenderItem( &d_data->painter, canvasRect, seriesItem, from, to );

        if ( d_data->attributes & QwtPlotDirectPainter::AtomicPainter )
        {
            reset();
        }
        else
        {
            if ( d_data->hasClipping )
                d_data->painter.setClipping( false );
        }
    }
    else
    {
        reset();

        d_data->seriesItem = seriesItem;
        d_data->from = from;
        d_data->to = to;

        QRegion clipRegion = canvasRect;
        if ( d_data->hasClipping )
            clipRegion &= d_data->clipRegion;

        canvas->installEventFilter( this );
//.........这里部分代码省略.........