if no pixmap was given and parent-widget is valid, use a snapshot of the widget as drag-icon

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@1476 0778d3d1-df1d-0410-868b-ea421aaaa00d

src/gui/string_pair_drag.cpp

@@ -41,7 +41,17 @@ stringPairDrag::stringPairDrag( const QString & _key, const QString & _value,
 					const QPixmap & _icon, QWidget * _w ) :
 	QDrag( _w )
 {
-	setPixmap( _icon );
+	if( _icon.isNull() && _w )
+	{
+		setPixmap( QPixmap::grabWidget( _w ).scaled(
+						64, 64,
+						Qt::KeepAspectRatio,
+						Qt::SmoothTransformation ) );
+	}
+	else
+	{
+		setPixmap( _icon );
+	}
 	QString txt = _key + ":" + _value;
 	QMimeData * m = new QMimeData();
 	m->setData( mimeType(), txt.toAscii() );