#include "TCanvas.h"
#include "TLine.h"
#include "TMath.h"
#include "TH2.h"

void DrawLine(Int_t event, Int_t px, Int_t py, TObject *selected)
{
  TCanvas *c = (TCanvas *) gTQSender;
  TPad *pad = (TPad *) c->GetSelectedPad();
  if (! pad) return;

  static Double_t x0, y0, x1, y1;
  
  static Int_t pxold, pyold;
  static Int_t px0, py0;
  static Int_t linedrawn;
  static TLine *line = 0;
  
  switch (event) {
     
  case kButton1Down:
    gVirtualX->SetLineColor(-1);
    x0 = pad->AbsPixeltoX(px);
    y0 = pad->AbsPixeltoY(py);
    px0   = px; py0   = py;
    pxold = px; pyold = py;
    linedrawn = 0;
    break;

  case kButton1Motion:
    if (linedrawn) gVirtualX->DrawLine(px0, py0, pxold, pyold);
    pxold = px;
    pyold = py;
    linedrawn = 1;
    gVirtualX->DrawLine(px0, py0, pxold, pyold);
    break;

  case kButton1Up:
    if (px == px0 && py == py0) break;
    x1 = pad->AbsPixeltoX(px);
    y1 = pad->AbsPixeltoY(py);
    pad->Modified(kTRUE);
    if (pad->GetLogx()) {
      x0 = TMath::Power(10,x0);
      x1 = TMath::Power(10,x1);
    }
    if (pad->GetLogy()) {
      y0 = TMath::Power(10,y0);
      y1 = TMath::Power(10,y1);
    }
    
    if (! line) {
      line = new TLine(x0,y0,x1,y1);
      line->Draw();
    } else {
      line->SetX1(x0);
      line->SetY1(y0);
      line->SetX2(x1);
      line->SetY2(y1);
//       line->Draw();
    }
//     pad->Modified();
    pad->Update();

    break;
  }
  
}

void test(Option_t *option = "")
{
  TCanvas *c1 = new TCanvas("c1");
  TH2F *h0 = new TH2F("h0", "test", 1000, -4, 4, 1000, -4, 4);
  h0->FillRandom("gaus", 10000);
  h0->Draw(option);
  c1->Connect("ProcessedEvent(Int_t,Int_t,Int_t,TObject*)",
	      0, 0, "DrawLine(Int_t,Int_t,Int_t,TObject*)");
}