Loop over TLegend entries

[tcarli]

Hello,

I have a constructed a TLegend object with sereral entries.

It is possible to loop over the entries, get a pointer to TLegendEntry
and then modify it ?

Does somebody has an example ?

Looking at the code, I see method that should in principle allow to do that,
but it looks rather design towards interactive use.

Regards,

      Tancredi

[hegner]

Hi Tancredi,

what you would need to do is using TLegend::GetListOfPrimitives. This gives you a TList with all the entries.

Benedikt

[ferhue]

This is a duplicate of:

Moving through Collections of type Legend

I am a novice programmer, and after a few hours of trying to understand the examples and documentation, I am stuck. What I want to do is access a particular entry of my legend so I can adjust its text size. I can do using leg as my legend name: TLegendEntry ent = (TLegendEntry)leg->GetListOfPrimitives()->First(); and get the first entry fine although I don’t fully understand the above line. However, say I have a legend of 10 entries and want to access the third. I don’t understand the class TI…

Example:

// TLegend* l was already defined and drawn
if(l==NULL) return;
TIter next(l->GetListOfPrimitives());
TLegendEntry* le;
UInt_t n = 1;
while((le=(TLegendEntry*)next()))
{
	le->SetOption("l");
	n++;
}

Alternatively:

TLegendEntry *tle = (TLegendEntry *)listA->At(2);

[Danilo]

Just to add something to the absolutely correct answer of ferhue and Benedikt, if you are using a version of ROOT6 you can do

auto primitives = l->GetListOfPrimitives();
for (auto primitiveObj :  *primitives){
    auto primitive = (TLegendEntry*)primitiveObj;
    primitive->SetOption("l");
}

D