JLegend.hh

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#ifndef __JGIZMO__JLEGEND__
#define __JGIZMO__JLEGEND__
 
#include <string>
 
#include "TLegend.h"
#include "TPad.h"
#include "TStyle.h"
 
 
/**
 * \author mdejong
 */
 
namespace JGIZMO {}
namespace JPP { using namespace JGIZMO; }
 
namespace JGIZMO {
 
  /**
   * Wrapper class for ROOT TLegend.
   */
  class JLegend :
    public TLegend
  {
  public:
    /**
     * Constructor.
     *
     * \param  width        width    [characters]
     * \param  height       height   [lines]
     * \param  option       position [TR TL BL BR]
     */
    JLegend(const Int_t       width,
            const Int_t       height,
            const std::string option = "TR") :
      TLegend()
    {
      using namespace std;
      
      gPad->Update();
 
      //SetFillStyle(4000);
      SetFillColor(kWhite);
      SetBorderSize(0);
      SetTextAlign(12);
      SetTextFont(gStyle->GetStatFont());
      SetTextSize(gStyle->GetStatFontSize());
 
      const Double_t X1  = 0.0 + gPad->GetLeftMargin();
      const Double_t X2  = 1.0 - gPad->GetRightMargin();
      const Double_t Y1  = 0.0 + gPad->GetBottomMargin();
      const Double_t Y2  = 1.0 - gPad->GetTopMargin();
 
      const Double_t w   = gPad->XtoPixel(gPad->GetX2());
      const Double_t h   = gPad->YtoPixel(gPad->GetY1());
      const Double_t ch  = gStyle->GetStatFontSize() * (w < h ? w : h);
      
      const Double_t fx  = 0.70 * ch/w;            // estimated fonst size  [NDC]
      const Double_t fy  = 1.10 * ch/h;            // estimated fonst size  [NDC]
      const Double_t eps = 0.002;                  // extra space [NDC]
      const Int_t    nc  = 3;                      // number of characters reserved for margin
 
      Int_t wd = width;
      
      if (wd < 2) {
        wd = 2;
      }
      
      SetMargin((Double_t) nc / (Double_t) (wd + nc));
      
      Double_t W  =  (wd + nc) * fx;               // width  [NDC]
      Double_t H  =  (height)  * fy;               // height [NDC]
 
      Double_t fc = 1.0;                           // scaling factor
      
      if (fc * W > X2 - X1 - 2*eps) {
        fc *= (X2 - X1 - 2*eps) / W;
      }
 
      if (fc * H > Y2 - Y1 - 2*eps) {
        fc *= (Y2 - Y1 - 2*eps) / H;
      }
      
      SetTextSize(GetTextSize() * fc);
      
      W *= fc;
      H *= fc;
      
      // default position is top-right
 
      Double_t x1  = X2 - W - eps;
      Double_t y1  = Y2 - H - eps;
      Double_t x2  = X2     - eps;
      Double_t y2  = Y2     - eps;
 
      int halign = 2;
      int valign = 2;
      
      if (option.find('T') != string::npos && option.find('B') == string::npos) {   // top
 
        y1  = Y2 - H - eps;
        y2  = Y2     - eps;
 
        //valign = 1;
      }
 
      if (option.find('B') != string::npos && option.find('T') == string::npos) {   // bottom
 
        y1  = Y1     + eps;
        y2  = Y1 + H + eps;
 
        //valign = 3;
      }
 
      if (option.find('R') != string::npos && option.find('L') == string::npos) {   // right
 
        x1  = X2 - W - eps;
        x2  = X2     - eps;
 
        halign = 1;
      }
 
      if (option.find('L') != string::npos && option.find('R') == string::npos) {   // left
 
        x1  = X1     + eps;
        x2  = X1 + W + eps;
 
        halign = 1;
      }
 
      SetTextAlign(halign*10 + valign);
      SetX1NDC(x1);
      SetY1NDC(y1);
      SetX2NDC(x2);
      SetY2NDC(y2);
    }
  };
}
 
#endif