[ROOT] Updating and saving a canvas

From: Alberto Garcia Raboso (Alberto.Garcia.Raboso@cern.ch)
Date: Wed Sep 18 2002 - 13:05:35 MEST 

Hi ROOTers,

The following piece of code tries to:
   * Create one canvas, and a pad inside.
   * Draw a graph, update the canvas and save it.
   * Clear the pad.
   * Draw another graph, update the canvas and save it.
   * etc.
   * clear the screen and free memory
The problem is that when I call pCanv->Update() for the first time, ROOT
begins to do it while the script goes on running, so calling several
times pCanv->SaveAs(...) before finishing the first update of the
Canvas. Thus some of the files contain an empty canvas, while others
have a semi-drawn one.

It seems like updating the canvas uses a thread independent from the one
that runs the script... is it right? Does anybody know how to make ROOT
update completely the Canvas before executing the next line of code?

Thanks in advance,

Alberto

THE CODE:

//
// Create Canvas and Pad
//
TCanvas *pCanv = new TCanvas("pCanv", "" ,200, 100, 1100, 800);
TPad *pPad = new TPad("pPad", "", 0.03, 0.03, 0.97, 0.97);
pCanv->SetFillColor(10);
pCanv->SetGrid();

//
// Draw fpScatter
//
TH1F *GraphFrame = pPad->DrawFrame(fpCentral->GetPlotLimXMin(),
	fpCentral->GetPlotLimYMin(), fpCentral->GetPlotLimXMax(),
	fpCentral->GetPlotLimYMax(), fHistTitle.Data());
GraphFrame->GetXaxis()->SetTitle("#phi_{b} (rad/512)");
GraphFrame->GetXaxis()->CenterTitle();
GraphFrame->GetYaxis()->SetTitle("#Delta#phi (rad/4096)");
GraphFrame->GetYaxis()->CenterTitle();
fpScatter->SetMarkerStyle(1);
fpScatter->SetMarkerSize(0.35);
fpScatter->SetMarkerColor(4);
fpScatter->Draw("P");
pCanv->Update();
pCanv->SaveAs( (const Char_t*) ( TString("Sc") + fFileName +
	TString(".ps") ) );
pPad->Clear();

//
// Draw fpHist
//
fpHistPt->SetStats(kFALSE);
fpHistPt->GetXaxis()->SetTitle("p_{t} (GeV/c)");
fpHistPt->GetXaxis()->CenterTitle();
fpHistPt->GetYaxis()->SetTitle("Number of hits");
fpHistPt->GetYaxis()->CenterTitle();
fpHistPt->Draw();
pCanv->Update();
pCanv->SaveAs( (const Char_t*) ( TString("hPt") + fFileName +
	TString(".ps") ) );
pPad->Clear();

... more like this ...
		
//
// Clear screen
//
delete pPad;
delete pCanv;

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alberto Garcia Raboso
CERN / EP
CH-1211 Geneva 23, Switzerland
Office 40-2B-19 (+41 22 76 71626)
E-Mail: Alberto.Garcia.Raboso@cern.ch
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Well, farewell, my hobbits! You should come safe to your own
homes now, and I shall not be kept awake for fear of your
peril. We will send word when we may, and some of us may yet
meet at times; but I fear that we shall not all be gathered
together ever again.

                      The return of the King. J.R.R. Tolkien
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This archive was generated by hypermail 2b29 : Sat Jan 04 2003 - 23:51:10 MET