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void LinesEditor::printWhiteSpaces( QPainter &p ){			const int contentsY = verticalScrollBar()->value();	const qreal pageBottom = contentsY + viewport()->height();	const QFontMetrics fm = QFontMetrics( currentFont() );		for ( QTextBlock block = document()->begin(); block.isValid(); block = block.next() )	{		QTextLayout* layout = block.layout();		const QRectF boundingRect = layout->boundingRect();		QPointF position = layout->position();				if ( position.y() +boundingRect.height() < contentsY )			continue;		if ( position.y() > pageBottom )			break;				const QString txt = block.text();		const int len = txt.length();				for ( int i=0; i<len; i++)		{			QPixmap *p1 = 0;						if (txt[i] == ' ' )				p1 = &spacePixmap;			else if (txt[i] == '\t' )				p1 = &tabPixmap;			else 				continue;						// pixmaps are of size 8x8 pixels			QTextCursor cursor = textCursor();			cursor.setPosition( block.position() + i, QTextCursor::MoveAnchor);						QRect r = cursorRect( cursor );			int x = r.x() + 4;			int y = r.y() + fm.height() / 2 - 5;			p.drawPixmap( x, y, *p1 );		}	}}