polytest1.C: This macro is testing new "compacting" algorithm in TPadPainter

//Author: Timur Pocheptsov, 20.01.2014.
//
//This macro is testing new "compacting" algorithm in TPadPainter
//(it reduces the number of polygon's vertices using actual pixel coordinates).
//It's not really usefull, but just to test that the resulting polygon
//is still reasonable. Initial number of points is 1000000, after "compression"
//it's 523904 (with default canvas size, before you tried to resize it) - so almost half of
//vertices were removed but you can still see the reasonable shape. If you resize
//a canvas to a smaller size, the number of vertices after compression can be something like 5000 and even less.
//It's easy to 'fool' this algorithm though in this particular case (ellipse is a kind of fringe case,
//you can easily have a sequence of almost unique vertices (at a pixel level).
//

//Includes for ACLiC.
#include <cassert>
#include <vector>

#include "TRandom.h"
#include "TCanvas.h"
#include "TError.h"
#include "Rtypes.h"
#include "TNamed.h"
#include "TMath.h"

class PolyTest1 : public TNamed, public TAttLine, public TAttFill {
public:
   PolyTest1(unsigned nVertices);

   void Paint(const Option_t *notUsed);
   void Reset(unsigned nVertices);

private:
   enum {
      kNPointsDefault = 10000//minimal number of points.
   };

   std::vector<Double_t> fXs;
   std::vector<Double_t> fYs;
};

//_____________________________________________________________
PolyTest1::PolyTest1(unsigned nVertices)
               : TNamed("polygon_compression_test1", "polygon_compression_test1")
{
   Reset(nVertices);
}

//_____________________________________________________________
void PolyTest1::Reset(unsigned nVertices)
{
   //Some canvas must already exist by this point.
   assert(gPad != 0 && "Reset, gPad is null");
   //We need a gRandom to exist.
   assert(gRandom != 0 && "Reset, gRandom is null");

   if (nVertices < kNPointsDefault) {
      Warning("Reset", "resetting nVertices parameter to %u", unsigned(kNPointsDefault));
      nVertices = kNPointsDefault;
   }

   fXs.resize(nVertices);
   fYs.resize(nVertices);

   Double_t xMin = 0., xMax = 0., yMin = 0., yMax = 0.;
   gPad->GetRange(xMin, yMin, xMax, yMax);
   assert(xMax - xMin > 0 && yMax - yMin > 0 && "Reset, invalid canvas' ranges");

   const Double_t xCentre = xMin + 0.5 * (xMax - xMin);
   const Double_t yCentre = yMin + 0.5 * (yMax - yMin);

   const Double_t r = TMath::Min(xMax - xMin, yMax - yMin) * 0.8 / 2;
   const Double_t angle = TMath::TwoPi() / (nVertices - 1);

   for (unsigned i = 0; i < nVertices - 1; ++i) {
      const Double_t currR = r + gRandom->Rndm() * r * 0.01;
      fXs[i] = xCentre + currR * TMath::Cos(angle * i);
      fYs[i] = yCentre + currR * TMath::Sin(angle * i);
   }

   fXs[nVertices - 1] = fXs[0];
   fYs[nVertices - 1] = fYs[0];
}

//_____________________________________________________________
void PolyTest1::Paint(const Option_t * /*notUsed*/)
{
   assert(gPad != 0 && "Paint, gPad is null");

   TAttFill::Modify();
   gPad->PaintFillArea((Int_t)fXs.size(), &fXs[0], &fYs[0]);

   TAttLine::Modify();
   gPad->PaintPolyLine((Int_t)fXs.size(), &fXs[0], &fYs[0]);
}

void polytest1()
{
   TCanvas * const cnv = new TCanvas;
   cnv->cd();

   PolyTest1 * polygon = new PolyTest1(1000000);
   polygon->SetLineColor(kBlue);
   polygon->SetFillColor(kRed);
   polygon->SetLineWidth(1);
   polygon->Draw();//Attach a polygon to a canvas.
}