radialgradients.C

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/// \file
/// \ingroup tutorial_cocoa
/// This tutorial demonstrates how to use radial gradients,
/// custom colors, transparency.
/// Requires ROOT built for OS X with --enable-cocoa.
///
/// \macro_code
///
/// \author Timur Pocheptsov
 
// Includes for ACLiC:
#include <cassert>
#include <cstdlib>
 
#include "TColorGradient.h"
#include "TVirtualX.h"
#include "TEllipse.h"
#include "TRandom.h"
#include "TCanvas.h"
#include "TError.h"
 
// Cocoa aux. functions.
#include "customcolor.h"
 
namespace {
 
// Just some colors (rgba) to build our
// fancy gradients from.
const Double_t basicColors[][4] = {{1., 0., 0., 1.},
                                   {1., 0.3, 0., 1.},
                                   {0., 0., 1., 1.},
                                   {1., 1., 0., 1.},
                                   {1., 0., 1., 1.},
                                   {0., 1., 1., 1.},
                                   {0., 1., 0., 1.},
                                   {0., 0.5, 0., 1.},
                                   // transparent colors:
                                   {1., 0., 0., 0.5},
                                   {1., 0.3, 0., 0.5},
                                   {0., 0., 1., 0.5},
                                   {1., 1., 0., 0.5},
                                   {1., 0., 1., 0.5},
                                   {0., 1., 1., 0.5},
                                   {0., 1., 0., 0.5},
                                   {0., 0.5, 0., 0.5},
                                   // and even more transparent:
                                   {1., 0., 0., 0.2},
                                   {1., 0.3, 0., 0.2},
                                   {0., 0., 1., 0.2},
                                   {1., 1., 0., 0.2},
                                   {1., 0., 1., 0.2},
                                   {0., 1., 1., 0.2},
                                   {0., 1., 0., 0.2},
                                   {0., 0.5, 0., 0.2}};
 
const unsigned nBasicColors = sizeof basicColors / sizeof basicColors[0];
 
//______________________________________________________________________
Color_t CreateRandomGradientFill()
{
   Color_t idx[1] = {};
   if (ROOT::CocoaTutorials::FindFreeCustomColorIndices(idx) != 1)
      return -1;
 
   const Double_t *const fromRGBA = basicColors[(std::rand() % (nBasicColors / 2))];
   // With odd number of colors the last one is never selected :)
   const Double_t *const toRGBA = basicColors[nBasicColors / 2 + (std::rand() % (nBasicColors / 2))];
 
   const Double_t locations[] = {0., 1.};
   const Double_t rgbas[] = {fromRGBA[0], fromRGBA[1], fromRGBA[2], fromRGBA[3],
                             toRGBA[0],   toRGBA[1],   toRGBA[2],   toRGBA[3]};
 
   TRadialGradient *const grad = new TRadialGradient(idx[0], 2, locations, rgbas);
   grad->SetRadialGradient(TColorGradient::Point(0.5, 0.5), 0.5);
 
   return idx[0];
}
 
//______________________________________________________________________
bool add_ellipse(const Double_t xC, const Double_t yC, const Double_t r)
{
   assert(gPad != nullptr && "add_ellipse, no pad to add ellipse");
 
   const Color_t newColor = CreateRandomGradientFill();
   if (newColor == -1) {
      ::Error("add_ellipse", "failed to find a new color index for a gradient fill");
      return false;
   }
 
   TEllipse *const newEllipse = new TEllipse(xC, yC, r, r);
   newEllipse->SetFillColor(newColor);
   newEllipse->Draw();
 
   return true;
}
 
} // namespace
 
//______________________________________________________________________
void radialgradients()
{
   gRandom->SetSeed(4357); //;)
 
   TCanvas *const cnv = new TCanvas("radial gradients", "radial gradients", 800, 800);
   if (gVirtualX && !gVirtualX->InheritsFrom("TGCocoa")) {
      ::Error("radialgradients", "this demo requires OS X and ROOT built with --enable-cocoa");
      delete cnv;
      return;
   }
 
   for (unsigned i = 0; i < 100; ++i)
      if (!add_ellipse(gRandom->Rndm(), gRandom->Rndm(), 0.5 * gRandom->Rndm()))
         break;
 
   cnv->Modified();
   cnv->Update();
}