void HighlightGraph(TVirtualPad *pad, TObject *obj, Int_t i, Int_t dummy);


void hlGraph1()
{
   auto Canvas = new TCanvas("Canvas", "Canvas", 0, 0, 700, 500);

   auto g = new TGraph();
   double x,y;

   for (Int_t i=0;i<10;i++) {
      x = i*0.1;
      y = 10*sin(x+0.2);
      g->SetPoint(i,x,y);
   }

   g->Draw("A*");

   g->SetHighlight();
   Canvas->HighlightConnect("HighlightGraph(TVirtualPad*,TObject*,Int_t,Int_t)");
}


void HighlightGraph(TVirtualPad *pad, TObject *obj, Int_t i, Int_t dummy)
{
   auto g = (TGraph*) obj;
   double *x = g->GetX();
   double *y = g->GetY();
   printf("x(%d) = %g y(%d) = %g\n",i,x[i],i,y[i]);
}