TLegend.cxx

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// @(#)root/graf:$Id$
// Author: Matthew.Adam.Dobbs   06/09/99

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#include <stdio.h>

#include "TStyle.h"
#include "TLatex.h"
#include "TLine.h"
#include "TBox.h"
#include "TMarker.h"
#include "TLegend.h"
#include "TList.h"
#include "TVirtualPad.h"
#include "TMath.h"
#include "TROOT.h"
#include "TLegendEntry.h"
#include "Riostream.h"
#include "TMultiGraph.h"
#include "THStack.h"

ClassImp(TLegend)

/** \class TLegend
\ingroup BasicGraphics

This class displays a legend box (TPaveText) containing several legend entries.

Each legend entry is made of a reference to a ROOT object, a text label and an
option specifying which graphical attributes (marker/line/fill) should be
displayed.

The following example shows how to create a legend. In this example the legend
contains a histogram, a function and a graph. The histogram is put in the legend
using its reference pointer whereas the graph and the function are added
using their names. Note that, because `TGraph` constructors do not have the
`TGraph` name as parameter, the graph name should be specified using the
`SetName` method.

When an object is added by name, a scan is performed on the list of objects
contained in the current pad (`gPad`) and also in the possible
`TMultiGraph` and `THStack` present in the pad. If a matching
name is found, the corresponding object is added in the legend using its pointer.

Begin_Macro(source)
{
   TCanvas *c1 = new TCanvas("c1","c1",600,500);
   gStyle->SetOptStat(0);

   TH1F *h1 = new TH1F("h1","TLegend Example",200,-10,10);
   h1->FillRandom("gaus",30000);
   h1->SetFillColor(kGreen);
   h1->SetFillStyle(3003);
   h1->Draw();

   TF1 *f1=new TF1("f1","1000*TMath::Abs(sin(x)/x)",-10,10);
   f1->SetLineColor(kBlue);
   f1->SetLineWidth(4);
   f1->Draw("same");

   const Int_t n = 20;
   Double_t x[n], y[n], ex[n], ey[n];
   for (Int_t i=0;i<n;i++) {
      x[i]  = i*0.1;
      y[i]  = 1000*sin(x[i]+0.2);
      x[i]  = 17.8*x[i]-8.9;
      ex[i] = 1.0;
      ey[i] = 10.*i;
   }
   TGraphErrors *gr = new TGraphErrors(n,x,y,ex,ey);
   gr->SetName("gr");
   gr->SetLineColor(kRed);
   gr->SetLineWidth(2);
   gr->SetMarkerStyle(21);
   gr->SetMarkerSize(1.3);
   gr->SetMarkerColor(7);
   gr->Draw("P");

   leg = new TLegend(0.1,0.7,0.48,0.9);
   leg->SetHeader("The Legend Title","C"); // option "C" allows to center the header
   leg->AddEntry(h1,"Histogram filled with random numbers","f");
   leg->AddEntry("f1","Function abs(#frac{sin(x)}{x})","l");
   leg->AddEntry("gr","Graph with error bars","lep");
   leg->Draw();

   return c1;
}
End_Macro


`TLegend` inherits from `TAttText` therefore changing any
text attributes (text alignment, font, color...) on a legend will changed the
text attributes on each line.

In particular it can be interesting to change the text alignement that way. In
order to have a base-line vertical alignment instead of a centered one simply do:
~~~ {.cpp}
   leg->SetTextAlign(13);
~~~
or
~~~ {.cpp}
   leg->SetTextAlign(11);
~~~
The default value of some `TLegend` attributes can be changed using
`gStyle`. The default settings are:
~~~ {.cpp}
   SetLegendBorderSize(1);
   SetLegendFillColor(0);
   SetLegendFont(42);
   SetLegendTextSize(0.);
~~~
The global attributes change the default values for the next created legends.

Text attributes can be also changed individually on each legend entry:
~~~ {.cpp}
   TLegendEntry *le = leg->AddEntry(h1,"Histogram filled with random numbers","f");
   le->SetTextColor(kBlue);;
~~~

Note that the `TPad` class has a method to build automatically a legend
for all objects in the pad. It is called `TPad::BuildLegend()`.

Each item in the legend is added using the `AddEntry` method. This
method defines the object to be added (by reference or name), the label
associated to this object and an option which a combination of:

  - L: draw line associated with TAttLine if obj inherits from TAttLine
  - P: draw polymarker associated with TAttMarker if obj inherits from TAttMarker
  - F: draw a box with fill associated wit TAttFill if obj inherits TAttFill
  - E: draw vertical error bar

As shown in the following example, passing a NULL pointer as first parameter in
`AddEntry` is also valid. This allows to add text or blank lines in a
legend.

Begin_Macro(source)
{
   TCanvas *c2 = new TCanvas("c2","c2",500,300);

   TLegend* leg = new TLegend(0.2, 0.2, .8, .8);
   TH1* h = new TH1F("", "", 1, 0, 1);

   leg->AddEntry(h, "Histogram \"h\"", "l");
   leg->AddEntry((TObject*)0, "", "");
   leg->AddEntry((TObject*)0, "Some text", "");
   leg->AddEntry((TObject*)0, "", "");
   leg->AddEntry(h, "Histogram \"h\" again", "l");

   leg->Draw();
   return c2;
}
End_Macro

It is possible to draw the legend entries over several columns using
the method `SetNColumns()` like in the following example.

Begin_Macro(source)
{
   TCanvas *c3 = new TCanvas("c2","c2",500,300);

   TLegend* leg = new TLegend(0.2, 0.2, .8, .8);
   TH1* h = new TH1F("", "", 1, 0, 1);

   leg-> SetNColumns(2);

   leg->AddEntry(h, "Column 1 line 1", "l");
   leg->AddEntry(h, "Column 2 line 1", "l");
   leg->AddEntry(h, "Column 1 line 2", "l");
   leg->AddEntry(h, "Column 2 line 2", "l");

   leg->Draw();
   return c3;
}
End_Macro
*/

////////////////////////////////////////////////////////////////////////////////
/// Default constructor.

TLegend::TLegend(): TPave(), TAttText(12,0,1,gStyle->GetLegendFont(),0)
{
   fPrimitives = 0;
   SetDefaults();
   SetBorderSize(gStyle->GetLegendBorderSize());
   SetFillColor(gStyle->GetLegendFillColor());
}

////////////////////////////////////////////////////////////////////////////////
/// Normal constructor.
///
/// A TLegend is a Pave with several TLegendEntry(s).
/// x1,y1,x2,y2 are the coordinates of the Legend in the current pad
/// (in normalised coordinates by default)
/// "header" is the title that will be displayed at the top of the legend
/// it is treated like a regular entry and supports TLatex. The default
/// is no header (header = 0).
/// The options are the same as for TPave Default = "brNDC"

TLegend::TLegend( Double_t x1, Double_t y1,Double_t x2, Double_t y2,
                  const char *header, Option_t *option)
        :TPave(x1,y1,x2,y2,4,option), TAttText(12,0,1,gStyle->GetLegendFont(),0)
{
   fPrimitives = new TList;
   if ( header && strlen(header) > 0) {
      TLegendEntry *headerEntry = new TLegendEntry( 0, header, "h" );
      headerEntry->SetTextAlign(0);
      headerEntry->SetTextAngle(0);
      headerEntry->SetTextColor(0);
      headerEntry->SetTextFont(gStyle->GetLegendFont());
      headerEntry->SetTextSize(0);
      fPrimitives->AddFirst(headerEntry);
   }
   SetDefaults();
   SetBorderSize(gStyle->GetLegendBorderSize());
   SetFillColor(gStyle->GetLegendFillColor());
}

////////////////////////////////////////////////////////////////////////////////
/// Copy constructor.

TLegend::TLegend( const TLegend &legend ) : TPave(legend), TAttText(legend),
                                            fPrimitives(0)
{
  if (legend.fPrimitives) {
      fPrimitives = new TList();
      TListIter it(legend.fPrimitives);
      while (TLegendEntry *e = (TLegendEntry *)it.Next()) {
         TLegendEntry *newentry = new TLegendEntry(*e);
         fPrimitives->Add(newentry);
      }
   }
   ((TLegend&)legend).Copy(*this);
}

////////////////////////////////////////////////////////////////////////////////
/// Assignment operator.

TLegend& TLegend::operator=(const TLegend &lg)
{
   if(this!=&lg) {
      TPave::operator=(lg);
      TAttText::operator=(lg);
      fPrimitives=lg.fPrimitives;
      fEntrySeparation=lg.fEntrySeparation;
      fMargin=lg.fMargin;
      fNColumns=lg.fNColumns;
   }
   return *this;
}

////////////////////////////////////////////////////////////////////////////////
/// Default destructor.

TLegend::~TLegend()
{
   if (fPrimitives) fPrimitives->Delete();
   delete fPrimitives;
   fPrimitives = 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Add a new entry to this legend. "obj" is the object to be represented.
/// "label" is the text you wish to associate with obj in the legend.
/// If "label" is null or empty, the title of the object will be used.
///
/// Options are:
///
///  - L: draw line associated with TAttLine if obj inherits from TAttLine
///  - P: draw polymarker associated with TAttMarker if obj inherits from TAttMarker
///  - F: draw a box with fill associated wit TAttFill if obj inherits TAttFill
///  - E: draw vertical error bar if option "L" is also specified

TLegendEntry *TLegend::AddEntry(const TObject *obj, const char *label, Option_t *option)
{
   const char *lab = label;

   if (obj && (!label || strlen(label)==0)) lab = obj->GetTitle();
   TLegendEntry *newentry = new TLegendEntry( obj, lab, option );
   if ( !fPrimitives ) fPrimitives = new TList;
   fPrimitives->Add(newentry);
   return newentry;
}

////////////////////////////////////////////////////////////////////////////////
/// Add a new entry to this legend. "name" is the name of an object in the pad to
/// be represented label is the text you wish to associate with obj in the legend
/// if label is null or empty, the title of the object will be used.
///
/// Options are:
///
///  - L: draw line associated with TAttLine if obj inherits from TAttLine
///  - P: draw polymarker associated with TAttMarker if obj inherits from TAttMarker
///  - F: draw a box with fill associated wit TAttFill if obj inherits TAttFill
///  - E: draw vertical error bar if option "L" is also specified

TLegendEntry *TLegend::AddEntry(const char *name, const char *label, Option_t *option)
{
   if (!gPad) {
      Error("AddEntry", "need to create a canvas first");
      return 0;
   }

   TObject *obj = gPad->FindObject(name);

   // If the object "name" has not been found, the following code tries to
   // find it in TMultiGraph or THStack possibly present in the current pad.
   if (!obj) {
      TList *lop = gPad->GetListOfPrimitives();
      if (lop) {
         TObject *o=0;
         TIter next(lop);
         while( (o=next()) ) {
            if ( o->InheritsFrom(TMultiGraph::Class() ) ) {
               TList * grlist = ((TMultiGraph *)o)->GetListOfGraphs();
               obj = grlist->FindObject(name);
               if (obj) break;
            }
            if ( o->InheritsFrom(THStack::Class() ) ) {
               TList * hlist = ((THStack *)o)->GetHists();
               obj = hlist->FindObject(name);
               if (obj) break;
            }
         }
      }
   }

   return AddEntry( obj, label, option );
}

////////////////////////////////////////////////////////////////////////////////
/// Clear all entries in this legend, including the header.

void TLegend::Clear( Option_t *)
{
   if (!fPrimitives) return;
   fPrimitives->Delete();
}

////////////////////////////////////////////////////////////////////////////////
/// Copy this legend into "obj".

void TLegend::Copy( TObject &obj ) const
{
   TPave::Copy(obj);
   TAttText::Copy((TLegend&)obj);
   ((TLegend&)obj).fEntrySeparation = fEntrySeparation;
   ((TLegend&)obj).fMargin = fMargin;
   ((TLegend&)obj).fNColumns = fNColumns;
}

////////////////////////////////////////////////////////////////////////////////
/// Delete entry at the mouse position.

void TLegend::DeleteEntry()
{
   if ( !fPrimitives ) return;
   TLegendEntry* entry = GetEntry();   // get entry pointed by the mouse
   if ( !entry ) return;
   fPrimitives->Remove(entry);
   delete entry;
}

////////////////////////////////////////////////////////////////////////////////
/// Draw this legend with its current attributes.

void TLegend::Draw( Option_t *option )
{
   AppendPad(option);
}

////////////////////////////////////////////////////////////////////////////////
/// Edit the fill attributes for the entry pointed by the mouse.

void TLegend::EditEntryAttFill()
{
   TLegendEntry* entry = GetEntry();   // get entry pointed by the mouse
   if ( !entry ) return;
   gROOT->SetSelectedPrimitive( entry );
   entry->SetFillAttributes();
}

////////////////////////////////////////////////////////////////////////////////
/// Edit the line attributes for the entry pointed by the mouse.

void TLegend::EditEntryAttLine()
{
   TLegendEntry* entry = GetEntry();   // get entry pointed by the mouse
   if ( !entry ) return;
   gROOT->SetSelectedPrimitive( entry );
   entry->SetLineAttributes();
}

////////////////////////////////////////////////////////////////////////////////
/// Edit the marker attributes for the entry pointed by the mouse.

void TLegend::EditEntryAttMarker()
{
   TLegendEntry* entry = GetEntry();   // get entry pointed by the mouse
   if ( !entry ) return;
   gROOT->SetSelectedPrimitive( entry );
   entry->SetMarkerAttributes();
}

////////////////////////////////////////////////////////////////////////////////
/// Edit the text attributes for the entry pointed by the mouse.

void TLegend::EditEntryAttText()
{
   TLegendEntry* entry = GetEntry();   // get entry pointed by the mouse
   if ( !entry ) return;
   gROOT->SetSelectedPrimitive( entry );
   entry->SetTextAttributes();
}

////////////////////////////////////////////////////////////////////////////////
/// Get entry pointed to by the mouse.
/// This method is mostly a tool for other methods inside this class.

TLegendEntry *TLegend::GetEntry() const
{
   if (!gPad) {
      Error("GetEntry", "need to create a canvas first");
      return 0;
   }

   Int_t nRows = GetNRows();
   if ( nRows == 0 ) return 0;

   Double_t ymouse = gPad->AbsPixeltoY(gPad->GetEventY())-fY1;
   Double_t yspace = (fY2 - fY1)/nRows;

   Int_t nColumns = GetNColumns();
   Double_t xmouse = gPad->AbsPixeltoX(gPad->GetEventX())-fX1;
   Double_t xspace = 0.;
   if (nColumns > 0) xspace = (fX2 - fX1)/nColumns;

   Int_t ix = 1;
   if (xspace > 0.) ix = (Int_t)(xmouse/xspace)+1;
   if (ix > nColumns) ix = nColumns;
   if (ix < 1)        ix = 1;

   Int_t iy = nRows-(Int_t)(ymouse/yspace);
   if (iy > nRows) iy = nRows;
   if (iy < 1)     iy = 1;

   Int_t nloops = TMath::Min(ix+(nColumns*(iy-1)), fPrimitives->GetSize());

   TIter next(fPrimitives);
   TLegendEntry *entry = 0;

   for (Int_t i=1; i<= nloops; i++) entry = (TLegendEntry *)next();

   return entry;
}

////////////////////////////////////////////////////////////////////////////////
/// Returns the header, which is the title that appears at the top
/// of the legend.

const char *TLegend::GetHeader() const
{
   if ( !fPrimitives ) return 0;
      TIter next(fPrimitives);
   TLegendEntry *first;   // header is always the first entry
   if ((  first = (TLegendEntry*)next()  )) {
      TString opt = first->GetOption();
      opt.ToLower();
      if ( opt.Contains("h") ) return first->GetLabel();
   }
   return 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Add a new entry before the entry at the mouse position.

void TLegend::InsertEntry( const char* objectName, const char* label, Option_t* option)
{
   if (!gPad) {
      Error("InsertEntry", "need to create a canvas first");
      return;
   }

   TLegendEntry* beforeEntry = GetEntry();   // get entry pointed by the mouse
   TObject *obj = gPad->FindObject( objectName );

   // note either obj OR beforeEntry may be zero at this point

   TLegendEntry *newentry = new TLegendEntry( obj, label, option );

   if ( !fPrimitives ) fPrimitives = new TList;
   if ( beforeEntry ) {
      fPrimitives->AddBefore( (TObject*)beforeEntry, (TObject*)newentry );
   } else {
      fPrimitives->Add((TObject*)newentry);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Paint this legend with its current attributes.

void TLegend::Paint( Option_t* option )
{
   TPave::ConvertNDCtoPad();
   TPave::PaintPave(fX1,fY1,fX2,fY2,GetBorderSize(),option);
   PaintPrimitives();
}

////////////////////////////////////////////////////////////////////////////////
/// Get the number of rows.

Int_t TLegend::GetNRows() const
{
   Int_t nEntries = 0;
   if ( fPrimitives ) nEntries = fPrimitives->GetSize();
   if ( nEntries == 0 ) return 0;

   Int_t nRows;
   if(GetHeader() != NULL) nRows = 1 + (Int_t) TMath::Ceil((Double_t) (nEntries-1)/fNColumns);
   else  nRows = (Int_t) TMath::Ceil((Double_t) nEntries/fNColumns);

   return nRows;
}

////////////////////////////////////////////////////////////////////////////////
/// Set the number of columns for the legend. The header, if set, is given
/// its own row. After that, every nColumns entries are inserted into the
/// same row. For example, if one calls legend.SetNColumns(2), and there
/// is no header, then the first two TObjects added to the legend will be
/// in the first row, the next two will appear in the second row, and so on.

void TLegend::SetNColumns(Int_t nColumns)
{
   if(nColumns < 1) {
      Warning("TLegend::SetNColumns", "illegal value nColumns = %d; keeping fNColumns = %d", nColumns, fNColumns);
      return;
   }
   fNColumns = nColumns;
}

////////////////////////////////////////////////////////////////////////////////
/// Paint the entries (list of primitives) for this legend.

void TLegend::PaintPrimitives()
{
   Int_t nRows = GetNRows();
   if ( nRows == 0 ) return;

   // Evaluate text size as a function of the number of entries
   //  taking into account their real size after drawing latex
   // Note: in pixel coords y1 > y2=0, but x2 > x1=0
   //       in NDC          y2 > y1,   and x2 > x1

   Double_t x1 = fX1NDC;
   Double_t y1 = fY1NDC;
   Double_t x2 = fX2NDC;
   Double_t y2 = fY2NDC;
   Double_t margin = fMargin*( x2-x1 )/fNColumns;
   Double_t boxwidth = margin;
   Double_t boxw = boxwidth*0.35;
   Double_t yspace = (y2-y1)/nRows;
   Double_t yspace2 = yspace/2.;
   Double_t textsize = GetTextSize();
   Double_t save_textsize = textsize;
   if (textsize==0.) {
      SetTextSize(gStyle->GetLegendTextSize());
      textsize = GetTextSize();
   }
   Bool_t autosize = kFALSE;
   Double_t* columnWidths = new Double_t[fNColumns];
   memset(columnWidths, 0, fNColumns*sizeof(Double_t));

   if ( textsize == 0 ) {
      autosize = kTRUE;
      textsize = ( 1. - fEntrySeparation ) * yspace;

      // find the max width and height (in pad coords) of one latex entry label
      Double_t maxentrywidth = 0, maxentryheight = 0;
      TIter nextsize(fPrimitives);
      TLegendEntry *entrysize;
      Int_t iColumn = 0;
      while (( entrysize = (TLegendEntry *)nextsize() )) {
         TLatex entrytex( 0, 0, entrysize->GetLabel() );
         entrytex.SetNDC();
         Style_t tfont = entrysize->GetTextFont();
         if (tfont == 0) tfont = GetTextFont();
         if (tfont%10 == 3) --tfont;
         entrytex.SetTextFont(tfont);
         entrytex.SetTextSize(textsize);
         if ( entrytex.GetYsize() > maxentryheight ) {
            maxentryheight = entrytex.GetYsize();
         }
         TString opt = entrysize->GetOption();
         opt.ToLower();
         if ( opt.Contains("h") ) {
            if ( entrytex.GetXsize() > maxentrywidth ) {
               maxentrywidth = entrytex.GetXsize();
            }
         } else {
            if ( entrytex.GetXsize() > columnWidths[iColumn] ) {
               columnWidths[iColumn] = entrytex.GetXsize();
            }
            iColumn++;
            iColumn %= fNColumns;
         }
         Double_t tmpMaxWidth = 0.0;
         for(int i=0; i<fNColumns; i++) tmpMaxWidth += columnWidths[i];
         if ( tmpMaxWidth > maxentrywidth) maxentrywidth = tmpMaxWidth;
      }
      // make sure all labels fit in the allotted space
      Double_t tmpsize_h = maxentryheight /(gPad->GetY2() - gPad->GetY1());
      textsize = TMath::Min( textsize, tmpsize_h );
      Double_t tmpsize_w = textsize*(fX2-fX1)*(1.0-fMargin)/maxentrywidth;
      if(fNColumns > 1) tmpsize_w = textsize*(fX2-fX1)*(1.0-fMargin-fColumnSeparation)/maxentrywidth;
      textsize = TMath::Min( textsize, tmpsize_w );
      SetTextSize( textsize );
   }

   // Update column widths, put into NDC units
   // block off this section of code to make sure all variables are local:
   // don't want to ruin initialisation of these variables later on
   {
      TIter next(fPrimitives);
      TLegendEntry *entry;
      Int_t iColumn = 0;
      memset(columnWidths, 0, fNColumns*sizeof(Double_t));
      while (( entry = (TLegendEntry *)next() )) {
         TLatex entrytex( 0, 0, entry->GetLabel() );
         entrytex.SetNDC();
         Style_t tfont = entry->GetTextFont();
         if (tfont == 0) tfont = GetTextFont();
         if (autosize && tfont%10 == 3) --tfont;
         entrytex.SetTextFont(tfont);
         if(entry->GetTextSize() == 0) entrytex.SetTextSize(textsize);
         TString opt = entry->GetOption();
         opt.ToLower();
         if (!opt.Contains("h")) {
            if ( entrytex.GetXsize() > columnWidths[iColumn] ) {
               columnWidths[iColumn] = entrytex.GetXsize();
            }
            iColumn++;
            iColumn %= fNColumns;
         }
      }
      double totalWidth = 0.0;
      for(int i=0; i<fNColumns; i++) totalWidth += columnWidths[i];
      if(fNColumns > 1) totalWidth /= (1.0-fMargin-fColumnSeparation);
      else totalWidth /= (1.0 - fMargin);
      for(int i=0; i<fNColumns; i++) {
         columnWidths[i] = columnWidths[i]/totalWidth*(x2-x1) + margin;
      }
   }

   Double_t ytext = y2 + 0.5*yspace;  // y-location of 0th entry

   // iterate over and paint all the TLegendEntries
   TIter next(fPrimitives);
   TLegendEntry *entry;
   Int_t iColumn = 0;
   while (( entry = (TLegendEntry *)next() )) {
      if(iColumn == 0) ytext -= yspace;

      // Draw Label in Latexmargin

      Short_t talign = entry->GetTextAlign();
      Float_t tangle = entry->GetTextAngle();
      Color_t tcolor = entry->GetTextColor();
      Style_t tfont  = entry->GetTextFont();
      Size_t  tsize  = entry->GetTextSize();
      // if the user hasn't set a parameter, then set it to the TLegend value
      if (talign == 0) entry->SetTextAlign(GetTextAlign());
      if (tangle == 0) entry->SetTextAngle(GetTextAngle());
      if (tcolor == 0) entry->SetTextColor(GetTextColor());
      if (tfont  == 0) {
         tfont = GetTextFont();
         if (autosize && tfont%10 == 3) --tfont;
         entry->SetTextFont(tfont);
      }
      if (tsize  == 0) entry->SetTextSize(GetTextSize());
      // set x,y according to the requested alignment
      Double_t x=0,y=0;
      Int_t halign = entry->GetTextAlign()/10;
      Double_t entrymargin = margin;
      // for the header the margin is near zero
      TString opt = entry->GetOption();
      opt.ToLower();
      x1 = fX1NDC;
      x2 = fX2NDC;
      if ( opt.Contains("h") ) entrymargin = margin/10.;
      else if (fNColumns > 1) {
         for(int i=0; i<iColumn; i++) x1 += columnWidths[i] + fColumnSeparation*(fX2NDC-fX1NDC)/(fNColumns-1);
         x2 = x1 + columnWidths[iColumn];
         iColumn++;
         iColumn %= fNColumns;
      }
      if (halign == 1) x = x1 + entrymargin;
      if (halign == 2) x = 0.5*( (x1+entrymargin) + x2 );
      if (halign == 3) x = x2 - entrymargin/10.;
      Int_t valign = entry->GetTextAlign()%10;

      if (valign == 1) y = ytext - (1. - fEntrySeparation)* yspace2;
      if (valign == 3) y = ytext + (1. - fEntrySeparation)* yspace2;

      // The vertical alignment "centered" is treated in a special way
      // to ensure a better spacing between lines.
      if (valign == 2) {
         Float_t tsizepad = textsize;
         if (tfont%10 == 3) tsizepad = (gPad->AbsPixeltoY(0) - gPad->AbsPixeltoY(textsize))/(gPad->GetY2() - gPad->GetY1());
         if (yspace2 < tsizepad) {
            entry->SetTextAlign(10*halign+1);
            y = ytext - (1. - fEntrySeparation)* yspace2/2.;
         } else {
            y = ytext;
         }
      }

      TLatex entrytex( x, y, entry->GetLabel() );
      entrytex.SetNDC();
      entry->TAttText::Copy(entrytex);
      entrytex.Paint();

      // reset attributes back to their original values
      entry->SetTextAlign(talign);
      entry->SetTextAngle(tangle);
      entry->SetTextColor(tcolor);
      entry->SetTextFont(tfont);
      entry->SetTextSize(tsize);

      // define x,y as the center of the symbol for this entry
      Double_t xsym = x1 + margin/2.;
      Double_t ysym = ytext;

      TObject *eobj = entry->GetObject();

      // Draw fill pattern (in a box)

      if ( opt.Contains("f")) {
         if (eobj && eobj->InheritsFrom(TAttFill::Class())) {
            dynamic_cast<TAttFill*>(eobj)->Copy(*entry);
         }

         // box total height is yspace*0.7
         entry->TAttFill::Modify();
         Double_t xf[4],yf[4];
         xf[0] = xsym - boxw;
         yf[0] = ysym - yspace*0.35;
         xf[1] = xsym + boxw;
         yf[1] = yf[0];
         xf[2] = xf[1];
         yf[2] = ysym + yspace*0.35;
         xf[3] = xf[0];
         yf[3] = yf[2];
         for (Int_t i=0;i<4;i++) {
            xf[i] = gPad->GetX1() + xf[i]*(gPad->GetX2()-gPad->GetX1());
            yf[i] = gPad->GetY1() + yf[i]*(gPad->GetY2()-gPad->GetY1());
         }
         gPad->PaintFillArea(4,xf,yf);
      }

      // Draw line

      if ( opt.Contains("l") || opt.Contains("f")) {

         if (eobj && eobj->InheritsFrom(TAttLine::Class())) {
            dynamic_cast<TAttLine*>(eobj)->Copy(*entry);
         }
         // line total length (in x) is margin*0.8
         TLine entryline( xsym - boxw, ysym, xsym + boxw, ysym );
         entryline.SetBit(TLine::kLineNDC);
         entry->TAttLine::Copy(entryline);
         // if the entry is filled, then surround the box with the line instead
         if ( opt.Contains("f") && !opt.Contains("l")) {
            // box total height is yspace*0.7
            boxwidth = yspace*
               (gPad->GetX2()-gPad->GetX1())/(gPad->GetY2()-gPad->GetY1());
            if ( boxwidth > margin ) boxwidth = margin;

            entryline.PaintLineNDC( xsym - boxw, ysym + yspace*0.35,
                                 xsym + boxw, ysym + yspace*0.35);
            entryline.PaintLineNDC( xsym - boxw, ysym - yspace*0.35,
                                 xsym + boxw, ysym - yspace*0.35);
            entryline.PaintLineNDC( xsym + boxw, ysym - yspace*0.35,
                                 xsym + boxw, ysym + yspace*0.35);
            entryline.PaintLineNDC( xsym - boxw, ysym - yspace*0.35,
                                 xsym - boxw, ysym + yspace*0.35);
         } else {
            entryline.Paint();
            if (opt.Contains("e")) {
               entryline.PaintLineNDC( xsym, ysym - yspace*0.30,
                                       xsym, ysym + yspace*0.30);
            }
         }
      }

      // Draw error only

      if (opt.Contains("e") && !(opt.Contains("l") || opt.Contains("f"))) {
         if (eobj && eobj->InheritsFrom(TAttLine::Class())) {
            dynamic_cast<TAttLine*>(eobj)->Copy(*entry);
         }
         TLine entryline(xsym, ysym - yspace*0.30,
                         xsym, ysym + yspace*0.30);
         entryline.SetBit(TLine::kLineNDC);
         entry->TAttLine::Copy(entryline);
         entryline.Paint();
      }

      // Draw Polymarker

      if ( opt.Contains("p")) {

         if (eobj && eobj->InheritsFrom(TAttMarker::Class())) {
            dynamic_cast<TAttMarker*>(eobj)->Copy(*entry);
         }
         TMarker entrymarker( xsym, ysym, 0 );
         entrymarker.SetNDC();
         entry->TAttMarker::Copy(entrymarker);
         entrymarker.Paint();
      }
   }

   SetTextSize(save_textsize);
   delete [] columnWidths;
}

////////////////////////////////////////////////////////////////////////////////
/// Dump this TLegend and its contents.

void TLegend::Print( Option_t* option ) const
{
   TPave::Print( option );
   if (fPrimitives) fPrimitives->Print();
}

////////////////////////////////////////////////////////////////////////////////
/// Reset the legend entries pointing to "obj".

void TLegend::RecursiveRemove(TObject *obj)
{
   TIter next(fPrimitives);
   TLegendEntry *entry;
   while (( entry = (TLegendEntry *)next() )) {
      if (entry->GetObject() == obj) entry->SetObject((TObject*)0);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Save this legend as C++ statements on output stream out
/// to be used with the SaveAs .C option.

void TLegend::SavePrimitive(std::ostream &out, Option_t* )
{

   out << "   " << std::endl;
   char quote = '"';
   if ( gROOT->ClassSaved( TLegend::Class() ) ) {
      out << "   ";
   } else {
      out << "   TLegend *";
   }
   // note, we can always use NULL header, since its included in primitives
   out << "leg = new TLegend("<<GetX1NDC()<<","<<GetY1NDC()<<","
       <<GetX2NDC()<<","<<GetY2NDC()<<","
       << "NULL" << "," <<quote<< fOption <<quote<<");" << std::endl;
   if (fBorderSize != 4) {
      out<<"   leg->SetBorderSize("<<fBorderSize<<");"<<std::endl;
   }
   SaveTextAttributes(out,"leg",12,0,1,42,0);
   SaveLineAttributes(out,"leg",-1,-1,-1);
   SaveFillAttributes(out,"leg",-1,-1);
   if ( fPrimitives ) {
      TIter next(fPrimitives);
      TLegendEntry *entry;
      while (( entry = (TLegendEntry *)next() )) entry->SaveEntry(out,"leg");
   }
   out << "   leg->Draw();"<<std::endl;
}

////////////////////////////////////////////////////////////////////////////////
/// Edit the label of the entry pointed to by the mouse.

void TLegend::SetEntryLabel( const char* label )
{
   TLegendEntry* entry = GetEntry();   // get entry pointed by the mouse
   if ( entry ) entry->SetLabel( label );
}

////////////////////////////////////////////////////////////////////////////////
/// Edit the option of the entry pointed to by the mouse.

void TLegend::SetEntryOption( Option_t* option )
{
   TLegendEntry* entry = GetEntry();   // get entry pointed by the mouse
   if ( entry ) entry->SetOption( option );
}

////////////////////////////////////////////////////////////////////////////////
/// Sets the header, which is the "title" that appears at the top of the legend.
/// If `option` contains `C`, the title will be centered.

void TLegend::SetHeader( const char *header, Option_t* option )
{
   TString opt;

   if ( !fPrimitives ) fPrimitives = new TList;
   TIter next(fPrimitives);
   TLegendEntry *first;   // header is always the first entry
   if ((  first = (TLegendEntry*)next() )) {
      opt = first->GetOption();
      opt.ToLower();
      if ( opt.Contains("h") ) {
         first->SetLabel(header);
         opt = option;
         opt.ToLower();
         if ( opt.Contains("c") ) first->SetTextAlign(22);
         else                     first->SetTextAlign(0);
         return;
      }
   }
   first = new TLegendEntry( 0, header, "h" );
   opt = option;
   opt.ToLower();
   if ( opt.Contains("c") ) first->SetTextAlign(22);
   else                     first->SetTextAlign(0);
   first->SetTextAngle(0);
   first->SetTextColor(0);
   first->SetTextFont(GetTextFont()); // default font is TLegend font for the header
   first->SetTextSize(0);
   fPrimitives->AddFirst((TObject*)first);
}