void THStack_varwidth()
{
  Double_t bins[13] = {0, 0.5, 1, 4, 5, 6, 7, 8, 8.5, 8.6, 8.7, 9, 10};

  TH1D* h1 = new TH1D("h1", "", 12, bins);
  h1->FillRandom("pol2",100000);

  TH1D* h2 = new TH1D("h2", "", 12, bins);
  h2->FillRandom("pol0",100000);

  h1->SetFillColor(kRed);
  h2->SetFillColor(kBlue);

  TCanvas* c = new TCanvas();

  THStack* stack = new THStack();
  stack->Add(h1);
  stack->Add(h2);
  stack->Draw();

  stack->GetXaxis()->SetRangeUser(4, 9);
  stack->Draw();

}