# RGB color chart [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 13 Exercise 7
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

```Output:

```

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 13 Exercise 7

#define _USE_MATH_DEFINES
#include "Simple_window.h"
#include "Graph.h"
#include <cmath>

using namespace Graph_lib;

/*
template<class T> class Vector_ref {
public:
void push_back(T&); //add a named object
void push_back(T*); //add a unnamed object

T& operator[](int i); //subscripting: read and write access
const T& operator[](int i) const;

int size() const;
};
*/

int main()
try
{
int xcount = 13;
int ycount = 9;
int cellSize = 20;

Point tl(100, 100);
Simple_window win(tl, 720, 400, "Simple Window");

Vector_ref<Graph_lib::Rectangle> vr;

for (int i = 0; i < 6; ++i) {
for (int j = 0; j < 6; ++j) {
for (int k = 0; k < 6; ++k) {
vr.push_back(new Graph_lib::Rectangle(Point(i * 6 * cellSize + j*cellSize, k*cellSize), cellSize, cellSize));
vr[vr.size() – 1].set_fill_color(fl_rgb_color(51 * i, 51 * j, 51 * k));
vr[vr.size() – 1].set_color(Color(Color::black, Color::invisible));
win.attach(vr[vr.size() – 1]);
}
}
}

win.wait_for_button();
}
catch (exception& e) {
cout << e.what() << endl;
return 1;
}
catch (…) {
cout << "Exiting" << endl;
return 2;
}
[/code]