/*
  Just a test for a "precision" cursor to be used to modify some histogram data
 */

TH1F *histogram; //!< histogram to work on.
//--------------------------------------------------
// some key cosntants.
const int KEY_ARROW_UP    []={0, 4115};
const int KEY_ARROW_DOWN  []={0, 4117};
const int KEY_ARROW_LEFT  []={0, 4114};
const int KEY_ARROW_RIGHT []={0, 4116};
const int KEY_PLUS        []={43, 43};
const int KEY_MINUS       []={45, 45};
//--------------------------------------------------

// the real work is here:
void myfunc()
{
  // graphical stuff
  static TMarker *marker=NULL;;
  static TMarker *marker1=NULL;;
  static TLatex *infos=NULL;
  // data
  static int bin=0;

  int px = gPad->GetEventX();
  int py = gPad->GetEventY();
  //  printf("myfunc called with %d %d\n",px,py);

  if(marker==NULL)
    {// first call: init what is needed
      bin=histogram->GetNbinsX()/2;
      double firstx=histogram->GetXaxis()->GetBinCenter(bin);
      infos=new TLatex(0.12,0.8,"");
      infos->SetNDC();
      infos->Draw();
      marker=new TMarker(firstx,0,4);
      marker1=new TMarker(firstx,0,3);
      marker->SetMarkerColor(2);;
      marker1->SetMarkerColor(2);;

      marker->SetMarkerSize(2);;
      marker1->SetMarkerSize(3);;
      marker->Draw();
      marker1->Draw();
      
      px= KEY_ARROW_UP[0];
    }
  if(px== KEY_ARROW_UP[0] || px==KEY_PLUS[0] || px==KEY_MINUS[0])
    {
      // modify marker pos or histo data
      if(py == KEY_PLUS[1] || py == KEY_ARROW_UP[1])	
	histogram->AddBinContent(bin,1);      
      if(py == KEY_MINUS[1] || py == KEY_ARROW_DOWN[1])
	histogram->AddBinContent(bin,-1);	
      if(py == KEY_ARROW_LEFT[1])  bin --;
      if(py == KEY_ARROW_RIGHT[1]) bin ++;

      // check bin coordinates
      if(bin<1) bin=1;
      if(bin>histogram->GetNbinsX()) bin=histogram->GetNbinsX();

      // update markers and info
      marker->SetX(histogram->GetBinCenter(bin));
      marker->SetY( histogram->GetBinContent(bin));
      marker1->SetX(marker->GetX());
      marker1->SetY(marker->GetY());
      infos->SetTitle(Form("Bin %3d, value %3.0f\n",bin, marker->GetY()));

      // update canvas.
      gPad->Modified();
      gPad->Update();
    }
  // done.
}

//=====================================================================================

void test_precisioncursor()
{
  TCanvas *c= new TCanvas("c","Test of a precision cursor");

  // build some histo
  histogram=new TH1F("h1","Test histogram",100,-3,3);
  histogram->FillRandom("gaus");
  histogram->SetStats(kFALSE);
  histogram->Draw();

  // add some "instructions"
  TLatex *l1= new TLatex(0.3,0.95,"Left/Right arrow keys to move cursor");
  l1->SetNDC(); l1->Draw();
  TLatex *l2= new TLatex(0.3,0.9,"Up/Down or +- keys to change histo value");
  l2->SetNDC(); l2->Draw();

  // GO!
  c->AddExec("func","myfunc()");
  myfunc(); // for first draw of cursor
}