set OpaquePaintEvent attribute for all widgets where suitable - makes whole GUI less sluggish :)

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@1835 0778d3d1-df1d-0410-868b-ea421aaaa00d

src/gui/widgets/visualization_widget.cpp

@@ -45,7 +45,7 @@ visualizationWidget::visualizationWidget( const QPixmap & _bg, QWidget * _p,
 	m_active( FALSE )
 {
 	setFixedSize( s_background.width(), s_background.height() );
-
+	setAttribute( Qt::WA_OpaquePaintEvent, true );
 
 	const fpp_t frames = engine::getMixer()->framesPerPeriod();
 	m_buffer = new sampleFrame[frames];