How to detect a mouse click on an object

ROOT
1

Dear all,
I am trying to do something when cliking a TMarker drawn on a canvas.
I wrote the following code based on
http://root.cern.ch/phpBB2/viewtopic.php?t=3527&highlight=mouse+click.

void MyClass::Draw()
{
  if (! cm) cm = new TCanvas("cm", "MyClass", 600, 600);
  cm->DrawFrame(-150, -150, 150, 150);
  cm->SetGrid();
  g->Draw("contzsame"); // g is a pointer to a TGraph2D object

  for (int i = 0; i < g->GetN(); ++i) {
    TMarker *m = new TMarker(g->GetX()[i], g->GetY()[i], 20);
    m->SetUniqueID(i);
    m->SetMarkerSize(0.8);
    m->Draw();
  }

  cm->Update();
  cm->Connect("ProcessedEvent(Int_t,Int_t,Int_t,TObject*)", "MyClass", this,
	      "DrawProfile(Int_t,Int_t,Int_t,TObject*)");
  cm->SetEditable(kFALSE);
}

void MyClass::DrawProfile(Int_t event, Int_t x, Int_t y, TObject *selected)
{
  TCanvas *c = (TCanvas *) gTQSender;
  if (event == kButton1Down) {
    TString objName = selected->IsA()->GetName();
    if (objName == "TMarker") {
      TMarker *m = (TMarker *) selected;
      int iDet = m->GetUniqueID(); // iDet
      std::cout << "Marker #: " << iDet << std::endl;
      // do something
      ...
    }
  }
}

But when another object such as a TLine is also drawn on the canvas overlapping with the markers,
the ProcessedEvent() always recognize a cllicked object as a line and not as a marker.
TMarker::Pop() did not fix this problem.
Is there any way to detect a click on a specific kind of object overlapping with other objects?

Thank you.

2

Can you send a small macro (I can run) reproducing the problem ? It is true that if the TLine is on top of the TMarker it will be seen first. But “popping” the marker should work (or send the TLine to the back).

3

Hi,
thank you for your reply.

I figured out the solution.
I was trying to pop only overlapping markers with a line.
I don’t know why, but this was not enough.
Somehow, only after executing Pop() for all markers on the canvas, they are actually poped and respond to a click.
Thank you for your advice.