Problem with gPad

ROOT
1

Hello,
I have a problem I don’t understand. I would like to put two markers on a TH1F (when I press a button) and so I’ve written the following code:

TMarker *mark[3]; //global variable

void MyMainFrame::DoModify()
{
TCanvas *fCanvas=fEcanvas->GetCanvas();
fCanvas->cd();
ica=0;
nmarker=0;

gPad->SetFillColor(0); //why the code needs this line to works good?

fCanvas->Connect(“ProcessedEvent(Int_t,Int_t,Int_t,TObject*)”, 0, 0,“mettimarker(Int_t,Int_t,Int_t,TObject*)”);
while(ica!=1)
{
usleep(100);
gClient->HandleInput();
}
fCanvas->Disconnect(“ProcessedEvent(Int_t,Int_t,Int_t,TObject*)”);
}

void mettimarker(Int_t event,Int_t x,Int_t y,TObject* selected)
{
TCanvas *fCanvas = (TCanvas *) gTQSender;
fCanvas->cd();
if(event==61 && ica!=1 &&nmarker<2>SetX(gPad->AbsPixeltoX(x));
mark[nmarker]->SetY(gPad->AbsPixeltoY(y));

mark[nmarker]->SetMarkerStyle(23);
mark[nmarker]->SetMarkerColor(2);

mark[nmarker]->Draw();
gPad->Modified();
gPad->Update();

nmarker++;
}
}

where fCanvas is defined as:
private:
TRootEmbeddedCanvas *fEcanvas;

MyMainFrame::MyMainFrame(const TGWindow *p, UInt_t w, UInt_t h)
{
fMain=new TGMainFrame(p,w,h);
fEcanvas= new TRootEmbeddedCanvas(“Ecanvas”,fMain,200,200);
fMain->AddFrame(fEcanvas,new TGLayoutHints(kLHintsExpandX|kLHintsExpandY,10,10,10,1));
}

The code works well only if I write the command line (that I don’t need)
gPad->SetFillColor(0);
while, if I don’t do this, I get the error messagg:

Error: non class,struct,union object $gPad used with . or ->
when I move on the pad?

Thanks for your help!
Regards

paola

2

In CINT the gPad pointer is only visible if it is non null.

Cheers,
Philippe.

3

Ok, I understand, but, then, what is the right way to set the gPad pointer to a not null value?
Isn’t it not null when I write:
fCanvas->cd(); ?

Thank you very much for your help
Regards

Paola

4

Hi,

I think the problem is during the parsing (so nothing is executing).
I recommend that instead of using gPad you use the following code
(which any is clearer):

TVirtualPad *current = fCanvas->cd(); current->SetFillColor(0); //why the code needs this line to works good? Alternatively you could just compile your macro via ACLiC.
Cheers,
Philippe.

5

Thank you very much for your help!

Regards
Paola