# drawing a diagram from 12.6 [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 13 Exercise 6
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

```Output:

```

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 13 Exercise 6

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

using namespace Graph_lib;

Point operator+(Point& a, Point& b)
{
return Point(a.x + b.x, a.y + b.y);
}

Point operator-(Point& a, Point& b)
{
return Point(a.x – b.x, a.y – b.y);
}

//ARROW CLASS—————————————–START

double pointVecMag(Point vec) {
return sqrt(pow(vec.x, 2) + pow(vec.y, 2));;
}

struct MyArrow : public Shape
{
MyArrow(Point start, Point end, bool s, bool e, int size, Fl_Color arrowColor)
:start(start), end(end), s(s), e(e), size(size), aColor(arrowColor)
{
if (s) {
//end-start vector: c
c = Point(end.x – start.x, end.y – start.y);
cMag = pointVecMag(c);
cUnit = Point(c.x / cMag * size, c.y / cMag * size);
cTrans = Point(cUnit.x, cUnit.y);

cPerp = Point(-cTrans.y, cTrans.x);
arrowhead01 = Point(start.x + cPerp.x + cTrans.x, start.y + cPerp.y + cTrans.y);
arrowhead02 = Point(start.x – cPerp.x + cTrans.x, start.y – cPerp.y + cTrans.y);
}
if (e) {
//start-end vector: d
d = Point(start.x – end.x, start.y – end.y);
dMag = pointVecMag(d);
dUnit = Point(d.x / dMag * size, d.y / dMag * size);
dTrans = Point(dUnit.x, dUnit.y);

dPerp = Point(-dTrans.y, dTrans.x);
arrowhead03 = Point(end.x + dPerp.x + dTrans.x, end.y + dPerp.y + dTrans.y);
arrowhead04 = Point(end.x – dPerp.x + dTrans.x, end.y – dPerp.y + dTrans.y);
}
};

void draw_lines() const;

private:
Fl_Color aColor;
//Line
Point start;
Point end;

Point c;
Point cUnit;
Point cTrans;
Point cPerp;
double cMag;

Point d;
Point dUnit;
Point dTrans;
Point dPerp;
double dMag;

bool s;
bool e;
int size;
};

void MyArrow::draw_lines() const {

if (color().visibility()) {
fl_color(aColor);
//Line
fl_line(start.x, start.y, end.x, end.y);
if (s) {
}
if (e) {
}
}
}

//ARROW CLASS—————————————–END

//BOX ROUNDED CORNERS CLASS—————————START

struct boxRoundCorners : public Shape
{
boxRoundCorners(Fl_Color boxColor, Point origin, int width, int height, int radius, Fl_Color textColor, string s)
:
bc(boxColor), // box color
o(origin), // box origin
w(width), // box width
h(height), // box height
tc(textColor), // text color
label(s) // text
{
// defining points for box
a1 = Point(o.x + r, o.y);
a2 = Point(o.x, o.y + r);
a3 = Point(o.x + r, o.y + r);

b1 = Point(o.x + w – r, o.y);
b2 = Point(o.x + w, o.y + r);
b3 = Point(o.x + w – r, o.y + r);

c1 = Point(o.x + w, o.y + h – r);
c2 = Point(o.x + w – r, o.y + h);
c3 = Point(o.x + w – r, o.y + h – r);

d1 = Point(o.x + r, o.y + h);
d2 = Point(o.x, o.y + h – r);
d3 = Point(o.x + r, o.y + h – r);

set_fill_color(Color::red);

textPt = Point(o.x + r, o.y + h / 2 + r); // text point
};

Point get_textPt() { return textPt; }
Point get_north() { return Point(o.x + w / 2, o.y); }
Point get_east() { return Point(o.x + w, o.y + h / 2); }
Point get_south() { return Point(o.x + w / 2, o.y + h); }
Point get_west() { return Point(o.x, o.y + h / 2); }

int get_width() { return w; }
int get_height() { return h; }

void draw_lines() const {
if (color().visibility()) {
// DRAWING TEXT
fl_color(tc); // setting text color
fl_draw(label.c_str(), point(0).x, point(0).y); // drawing text

// DRAWING BOX
fl_color(bc); // setting box color

/*
// defining box lines
fl_line(a1.x, a1.y, b1.x, b1.y);
fl_line(b2.x, b2.y, c1.x, c1.y);
fl_line(c2.x, c2.y, d1.x, d1.y);
fl_line(d2.x, d2.y, a2.x, a2.y);
// defining box arcs
fl_arc(o.x, o.y, r + r, r + r, 90, 180);
fl_arc(o.x + w – (r + r), o.y, r + r, r + r, 360, 90);
fl_arc(o.x + w – (r + r), o.y + h – (r + r), r + r, r + r, 270, 360);
fl_arc(o.x, o.y + h – (r + r), r + r, r + r, 180, 270);
*/

fl_begin_complex_polygon();
fl_arc(o.x, o.y, r + r, r + r, 90, 180);
fl_gap();
fl_line(a1.x, a1.y, b1.x, b1.y);
fl_gap();
fl_arc(o.x + w – (r + r), o.y, r + r, r + r, 360, 90);
fl_gap();
fl_line(b2.x, b2.y, c1.x, c1.y);
fl_gap();
fl_arc(o.x + w – (r + r), o.y + h – (r + r), r + r, r + r, 270, 360);
fl_gap();
fl_line(c2.x, c2.y, d1.x, d1.y);
fl_gap();
fl_arc(o.x, o.y + h – (r + r), r + r, r + r, 180, 270);
fl_gap();
fl_line(d2.x, d2.y, a2.x, a2.y);
fl_end_complex_polygon();
}
}

private:
// BOX
Point o;
Point a1, a2, b1, b2, c1, c2, d1, d2;
Point a3, b3, c3, d3;
Point north, east, south, west;
Fl_Color bc;
int w, h, r;

// LABEL
Point textPt;
string label; // label
Fl_Color tc;
};

//BOX ROUNDED CORNERS CLASS—————————END

int main()
try
{
Point tl(100, 100);
Simple_window win(tl, 600, 400, "Simple Window");

Fl_Color boxColor = Color::black;
Fl_Color textColor = Color::black;
Fl_Color arrowColor = Color::black;

boxRoundCorners box_Window(boxColor, Point(200, 100), 60, 20, 5, textColor, "Window");
boxRoundCorners box_Line_style(boxColor, Point(300, 100), 80, 20, 5, textColor, "Line_style");
boxRoundCorners box_Color(boxColor, Point(400, 100), 60, 20, 5, textColor, "Color");

boxRoundCorners box_Simple_window(boxColor, Point(175, 200), 105, 20, 5, textColor, "Simple_window");
boxRoundCorners box_Shape(boxColor, Point(310, 200), 60, 20, 5, textColor, "Shape");
boxRoundCorners box_Point(boxColor, Point(400, 200), 60, 20, 5, textColor, "Point");

boxRoundCorners box_Line(boxColor, Point(150, 300), 40, 20, 5, textColor, "Line");
boxRoundCorners box_Lines(boxColor, Point(200, 300), 40, 20, 5, textColor, "Lines");
boxRoundCorners box_Polygon(boxColor, Point(250, 300), 60, 20, 5, textColor, "Polygon");
boxRoundCorners box_Axis(boxColor, Point(325, 300), 40, 20, 5, textColor, "Axis");
boxRoundCorners box_Rectangle(boxColor, Point(375, 300), 70, 20, 5, textColor, "Rectangle");
boxRoundCorners box_Text(boxColor, Point(450, 300), 40, 20, 5, textColor, "Text");
boxRoundCorners box_Image(boxColor, Point(500, 300), 45, 20, 5, textColor, "Image");

MyArrow arrow_Sw_W(box_Simple_window.get_north(), box_Window.get_south(), false, true, 5, arrowColor);
MyArrow arrow_L_S(box_Line.get_north(), Point(box_Shape.get_south().x – box_Shape.get_width() / 2, box_Shape.get_south().y), false, true, 5, arrowColor);
MyArrow arrow_Ls_S(box_Lines.get_north(), Point(box_Shape.get_south().x – box_Shape.get_width() / 4, box_Shape.get_south().y), false, true, 5, arrowColor);
MyArrow arrow_P_S(box_Polygon.get_north(), Point(box_Shape.get_south().x – box_Shape.get_width() / 6, box_Shape.get_south().y), false, true, 5, arrowColor);
MyArrow arrow_A_S(box_Axis.get_north(), box_Shape.get_south(), false, true, 5, arrowColor);
MyArrow arrow_R_S(box_Rectangle.get_north(), Point(box_Shape.get_south().x + box_Shape.get_width() / 6, box_Shape.get_south().y), false, true, 5, arrowColor);
MyArrow arrow_T_S(box_Text.get_north(), Point(box_Shape.get_south().x + box_Shape.get_width() / 4, box_Shape.get_south().y), false, true, 5, arrowColor);
MyArrow arrow_I_S(box_Image.get_north(), Point(box_Shape.get_south().x + box_Shape.get_width() / 2, box_Shape.get_south().y), false, true, 5, arrowColor);

//ATTACH BOXES
win.attach(box_Window);
win.attach(box_Line_style);
win.attach(box_Color);

win.attach(box_Simple_window);
win.attach(box_Shape);
win.attach(box_Point);

win.attach(box_Line);
win.attach(box_Lines);
win.attach(box_Polygon);
win.attach(box_Axis);
win.attach(box_Rectangle);
win.attach(box_Text);
win.attach(box_Image);

//ATTACH ARROWS
win.attach(arrow_Sw_W);
win.attach(arrow_L_S);
win.attach(arrow_Ls_S);
win.attach(arrow_P_S);
win.attach(arrow_A_S);
win.attach(arrow_R_S);
win.attach(arrow_T_S);
win.attach(arrow_I_S);

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