A usefull method to automatically add a TLegend to a TPad?

ROOT
1

Hello Root Developpers,
I have added a simple method to a TPad in order to build automatically a TLegend from the primitives in the TPad. Only those deriving from TAttLine, TAttMarker and TAttFill are added, excluding TPave and TFrame derived classes. I have also added a new entry in the context menu of the TPad to build the TLegend from the GUI. I feel this could be useful to everybody and that this method could be added as a “standard” method of the TPad class. Here is the code:

in gpad/inc/TPad.h

......... 
   virtual TVirtualViewer3D *GetViewer3D(Option_t * type = ""); // *MENU*
   virtual void              ReleaseViewer3D(Option_t * type = "");
   // void SetViewer3D(TVirtualViewer3D *v) {fViewer3D = v;}

  virtual TLegend *BuildLegend(void); // *MENU*

   ClassDef(TPad,8)  //A Graphics pad
};

in gpad/src/TPad.cxx

//______________________________________________________________________________
TLegend *TPad::BuildLegend(void)
{
   //
   // Build a legend from the graphical objects in the pad
   //
TList *lop=GetListOfPrimitives();
TLegend *leg=0;
TIter next(lop);
TObject *o=0;
while( (o=next()) )
 {
 if((o->InheritsFrom("TAttLine") || 
    o->InheritsFrom("TAttMarker") || 
    o->InheritsFrom("TAttFill")) && 
    ( !(o->InheritsFrom("TFrame")) &&
      !(o->InheritsFrom("TPave")) ))
  {
  if(!leg)
   {
   leg=new TLegend(0.5,0.67,0.88,0.88,Form("Legend of pad %s",gPad->GetName()));
   }
  TString mes;
  if(o->InheritsFrom("TNamed") && strlen(((TNamed *)o)->GetTitle()))
   mes=((TNamed *)o)->GetTitle();
  else if(strlen(o->GetName()))
   mes=o->GetName();
  else
   mes=o->ClassName();
  TString opt("");
  if(o->InheritsFrom("TAttLine")) opt+="l";
  if(o->InheritsFrom("TAttMarker")) opt+="p";
  if(o->InheritsFrom("TAttFill")) opt+="f";
  leg->AddEntry(o,mes.Data(),opt.Data());
  } 
 }
if(leg)
 {
 leg->Draw();
 }
else
 {
 Info("BuildLegend(void)","No object to build a TLegend...");
 } 
return leg;
}

Friendly

Daniel CUSSOL

2

Daniel,

This is a good idea. we will add this method.

Rene

3

Hi Daniel,

Your new code is now in TPad. Thanks.

Olivier

4

Hello René and Olivier,
Glad to feel useful to the ROOT community! Thanks for adding this method.
Friendly

Daniel