# how apply edge collapsing within selected surface

I'm using CGAL edge collapsing to remove edges on mesh and it's working successfully .

But I want to run the edge collapsing process within selected surface on mesh viewer .

I preview the Geomview (.off ) using the following code:

QWidget* centralWidget = new QWidget(viewer);
centralWidget->setSizePolicy(QSizePolicy::Maximum,QSizePolicy::Maximum);
setCentralWidget( new CGAL::SimpleLCCViewerQt<LCC, CGAL::DefaultColorFunctorLCC>(&qWin ,
lcc,
"Basic LCC Viewer",
false,
fcolor ) );
show();


So, How Can I select specific surface region on mesh viewer and apply the edge collapsing on the selected surface only ?

I appreciate any help .