/// \file
/// \ingroup tutorial_hist
/// \notebook -js
/// Demo of Timers.
///
/// Simple example illustrating how to use the C++ interpreter
/// to fill histograms in a loop and show the graphics results
/// This program is a variant of the tutorial "hsum".
/// It illustrates the use of Timers.
///
/// \macro_image
/// \macro_code
///
/// \author Rene Brun

Float_t progressRatio = 0.;
TSlider *slider = nullptr;
TCanvas *c1 = nullptr;

void hsumUpdate()
{
// called when Timer times out
   if (slider) slider->SetRange(0., progressRatio);
   c1->Modified();
   c1->Update();
}

void hsumTimer(Int_t nfill=100000)
{
   c1 = new TCanvas("c1","The HSUM example",200,10,600,400);
   c1->SetGrid();

   // Create some histograms.
   auto total  = new TH1F("total","This is the total distribution",100,-4,4);
   auto main   = new TH1F("main","Main contributor",100,-4,4);
   auto s1     = new TH1F("s1","This is the first signal",100,-4,4);
   auto s2     = new TH1F("s2","This is the second signal",100,-4,4);
   total->Sumw2();   // store the sum of squares of weights
   total->SetMarkerStyle(21);
   total->SetMarkerSize(0.7);
   main->SetFillColor(16);
   s1->SetFillColor(42);
   s2->SetFillColor(46);
   total->SetMaximum(nfill/20.);
   total->Draw("e1p");
   main->Draw("same");
   s1->Draw("same");
   s2->Draw("same");
   c1->Update();

   slider = new TSlider("slider","test",4.2,0,4.6,0.8*total->GetMaximum(),38);
   slider->SetFillColor(46);

   // Create a TTimer (hsumUpdate called every 300 msec)
   TTimer timer("hsumUpdate()",300);
   timer.TurnOn();

   // Fill histograms randomly
   Float_t xs1, xs2, xmain;
   gRandom->SetSeed();
   for (Int_t i=0; i<nfill; i++) {
      progressRatio = i * 1. / nfill;
      if (gSystem->ProcessEvents()) break;
      xmain = gRandom->Gaus(-1,1.5);
      xs1   = gRandom->Gaus(-0.5,0.5);
      xs2   = gRandom->Landau(1,0.15);
      main->Fill(xmain);
      s1->Fill(xs1,0.3);
      s2->Fill(xs2,0.2);
      total->Fill(xmain);
      total->Fill(xs1,0.3);
      total->Fill(xs2,0.2);
   }
   timer.TurnOff();
   hsumUpdate();
}