Added random color generation to the polygons, also made so that the

color of the vector indicating speed is the same as the color of the
polygon, but a little lighter

Makefile

@@ -11,7 +11,7 @@ CXXFLAGS=-Wall -g -O2 $(PROFILING_CFLAGS) $(GTK_CFLAGS)
 LIBS=$(GTK_LIBS) -lm
 
 PROGS=balls
-OBJS=balls.o c_index.o game.o gravity.o spaceship.o main.o polygons.o polygon_generator.o collisions.o
+OBJS=balls.o c_index.o game.o gravity.o spaceship.o main.o polygons.o polygon_generator.o collisions.o color.o
 
 # dependencies (gcc -MM *.cc)
 balls.o: balls.cc game.h balls.h vec2d.h gravity.h
@@ -21,9 +21,10 @@ gravity.o: gravity.cc gravity.h balls.h vec2d.h game.h
 main.o: main.cc game.h balls.h vec2d.h c_index.h gravity.h spaceship.h
 spaceship.o: spaceship.cc balls.h vec2d.h game.h
 stats.o: stats.cc
-polygons.o: polygons.cc polygons.h vec2d.h polygon_generator.h
+polygons.o: polygons.cc polygons.h vec2d.h polygon_generator.h color.h
 polygon_generator.o: polygon_generator.cc polygon_generator.h
 collisions.o: collisions.cc collisions.h vec2d.h
+color.o: color.cc color.h
 
 
 .PHONY: run

color.cc

@@ -0,0 +1,102 @@
+#include "color.h"
+
+// taken from
+// https://stackoverflow.com/questions/3018313/algorithm-to-convert-rgb-to-hsv-and-hsv-to-rgb-in-range-0-255-for-both
+hsv_t rgb2hsv(color_t in) {
+    hsv_t out;
+    double min, max, delta;
+
+    min = in.red < in.green ? in.red : in.green;
+    min = min < in.blue ? min : in.blue;
+
+    max = in.red > in.green ? in.red : in.green;
+    max = max > in.blue ? max : in.blue;
+
+    out.val = max; // v
+    delta = max - min;
+    if (delta < 0.00001) {
+        out.sat = 0;
+        out.hue = 0; // undefined, maybe nan?
+        return out;
+    }
+    if (max > 0.0) { // NOTE: if Max is == 0, this divide would cause a crash
+        out.sat = (delta / max); // s
+    } else {
+        // if max is 0, then r = g = b = 0
+        // s = 0, h is undefined
+        out.sat = 0.0;
+        out.hue = NAN; // its now undefined
+        return out;
+    }
+    if (in.red >= max) // > is bogus, just keeps compilor happy
+        out.hue = (in.green - in.blue) / delta; // between yellow & magenta
+    else if (in.green >= max)
+        out.hue = 2.0 + (in.blue - in.red) / delta; // between cyan & yellow
+    else
+        out.hue = 4.0 + (in.red - in.green) / delta; // between magenta & cyan
+
+    out.hue *= 60.0; // degrees
+
+    if (out.hue < 0.0)
+        out.hue += 360.0;
+
+    return out;
+}
+
+color_t hsv2rgb(hsv_t in) {
+    double hh, p, q, t, ff;
+    long i;
+    color_t out;
+
+    if (in.sat <= 0.0) { // < is bogus, just shuts up warnings
+        out.red = in.val;
+        out.green = in.val;
+        out.blue = in.val;
+        return out;
+    }
+    hh = in.hue;
+    if (hh >= 360.0)
+        hh = 0.0;
+    hh /= 60.0;
+    i = (long) hh;
+    ff = hh - i;
+    p = in.val * (1.0 - in.sat);
+    q = in.val * (1.0 - (in.sat * ff));
+    t = in.val * (1.0 - (in.sat * (1.0 - ff)));
+
+    switch (i) {
+    case 0:
+        out.red = in.val;
+        out.green = t;
+        out.blue = p;
+        break;
+    case 1:
+        out.red = q;
+        out.green = in.val;
+        out.blue = p;
+        break;
+    case 2:
+        out.red = p;
+        out.green = in.val;
+        out.blue = t;
+        break;
+
+    case 3:
+        out.red = p;
+        out.green = q;
+        out.blue = in.val;
+        break;
+    case 4:
+        out.red = t;
+        out.green = p;
+        out.blue = in.val;
+        break;
+    case 5:
+    default:
+        out.red = in.val;
+        out.green = p;
+        out.blue = q;
+        break;
+    }
+    return out;
+}

color.h

@@ -0,0 +1,17 @@
+#ifndef COLOR_H_INCLUDED
+#define COLOR_H_INCLUDED
+
+#include <cmath>
+
+struct color_t {
+    double red, green, blue;
+};
+
+struct hsv_t {
+    double hue, sat, val;
+};
+
+extern hsv_t rgb2hsv(color_t in);
+extern color_t hsv2rgb(hsv_t in);
+
+#endif

main.cc

@@ -213,6 +213,10 @@ gint keyboard_input(GtkWidget* widget, GdkEventKey* event) {
     case GDK_KEY_p:
         game_animation_on_off();
         return TRUE;
+    case GDK_KEY_S:
+    case GDK_KEY_s:
+        draw_speed = !draw_speed;
+        return TRUE;
     case GDK_KEY_Q:
     case GDK_KEY_q:
         gtk_main_quit();

polygons.cc

@@ -13,9 +13,28 @@
 #include <iostream>
 #include <utility>
 
+#define ARROW_VAL_RATIO 1.7
+
+
+bool draw_speed = true;
+
 polygon* polygons = nullptr;
 uint n_polygons = 0;
 
+static double to_rad(double angle_in_deg) {
+    static double PI_180 = M_PI / 180.;
+    return angle_in_deg * PI_180;
+}
+
+static double to_deg(double angle_in_rad) {
+    static double PI_180 = 180. / M_PI;
+    return angle_in_rad * PI_180;
+}
+
+static double random_color_component() {
+    return 1.0 * (rand() % 200 + 56) / 255;
+};
+
 void polygons_init_state() {
     n_polygons = 20;
     polygons = new polygon[n_polygons];
@@ -38,12 +57,19 @@ void polygons_init_state() {
                         .set_mass(INFINITY)
                         .set_center({width + wall_thickness / 2., height / 2.});
 
-    // middle wall
-    polygons[n++] = poly_generate::rectangle(50, height / 2.)
+    // top triangle wall
+    polygons[n++] = poly_generate::triangle(height / 4., height / 4., 90)
                         .set_mass(INFINITY)
-                        .set_center({25 + width * 1. / 2, height / 2.})
-                        .set_angle(30);
+                        .set_center({width / 2., height / 17.})
+                        .set_angle(-135);
+    // bottom triangle wall
+    polygons[n++] = poly_generate::triangle(height / 4., height / 4., 90)
+                        .set_mass(INFINITY)
+                        .set_center({width / 2., height - height / 17.})
+                        .set_angle(45);
 
+
+    // ---------- Shapes flying around start here ----------
     polygons[n++] = poly_generate::regular(100, 3)
                         .set_center({100, 400})
                         .set_angle(0)
@@ -64,24 +90,37 @@ void polygons_init_state() {
     polygons[n++] = poly_generate::rectangle(100, 150).set_center({600, 200});
     polygons[n++] = poly_generate::regular(50, 5)
                         .set_center({150, 150})
-                        .set_speed({50, -50});
-    polygons[n++] =
-        poly_generate::general({{0, 0}, {50, 80}, {0, 160}, {-50, 80}})
-            .set_center({700, 700})
-            .set_speed({0, -100});
+                        .set_speed({100, 0});
+
+    polygons[n++] = poly_generate::general({{40, 20},
+                                            {40, 40},
+                                            {80, 40},
+                                            {80, -40},
+                                            {40, -40},
+                                            {40, -20},
+                                            {-40, -20},
+                                            {-40, -40},
+                                            {-80, -40},
+                                            {-80, 40},
+                                            {-40, 40},
+                                            {-40, 20}})
+                        .set_center({700, 700})
+                        .set_speed({0, -100});
 
     assert(n <= n_polygons);
     n_polygons = n;
-}
 
-static double to_rad(double angle_in_deg) {
-    static double PI_180 = M_PI / 180.;
-    return angle_in_deg * PI_180;
-}
-
-static double to_deg(double angle_in_rad) {
-    static double PI_180 = 180. / M_PI;
-    return angle_in_rad * PI_180;
+    // Set the color of the polygons to random
+    for (polygon* p = polygons; p != polygons + n_polygons; ++p) {
+        p->color = {
+            random_color_component(),
+            random_color_component(),
+            random_color_component()};
+        hsv_t hsv = rgb2hsv(p->color);
+        if (hsv.val > 0.95)
+            hsv.val *= .7;
+        p->color = hsv2rgb(hsv);
+    }
 }
 
 static bool is_point_inside_rect(rect rect, vec2d point) {
@@ -252,15 +291,31 @@ void polygon::draw(cairo_t* cr) const {
         cairo_line_to(cr, point.x, point.y);
 
     cairo_line_to(cr, this->global_points[0].x, this->global_points[0].y);
-    cairo_stroke(cr);
-
+    if (mass == INFINITY) {
+        cairo_set_source_rgb(cr, .5, .5, .5);
+        cairo_fill(cr);
+    } else {
+        cairo_set_source_rgb(
+            cr,
+            this->color.red,
+            this->color.green,
+            this->color.blue
+        );
+        cairo_fill(cr);
+    }
 
     // draw centroid
     vec2d centroid = this->centroid();
     draw_circle(cr, centroid, 1);
 
+
     // draw speed
-    (delta * this->speed).draw(cr, centroid);
+    if (draw_speed && this->mass != INFINITY) {
+        hsv_t hsv = rgb2hsv(this->color);
+        hsv.val = hsv.val * ARROW_VAL_RATIO;
+        color_t arrow_color = hsv2rgb(hsv);
+        (delta * this->speed).draw(cr, centroid, arrow_color);
+    }
 }
 
 void polygons_draw(cairo_t* cr) {

polygons.h

@@ -1,6 +1,7 @@
 #ifndef POLYGONS_H_INCLUDED
 #define POLYGONS_H_INCLUDED
 
+#include "color.h"
 #include "vec2d.h"
 
 #include <cmath>
@@ -22,6 +23,7 @@ class polygon {
     double mass;
     std::string label;
 
+    color_t color;
     std::vector<vec2d> global_points = points;
 
     vec2d speed;
@@ -118,6 +120,8 @@ class polygon {
 extern polygon* polygons;
 extern uint n_polygons;
 
+extern bool draw_speed;
+
 extern void polygons_init_state();
 extern void polygons_update_state();
 extern void polygons_draw(cairo_t* cr);

vec2d.h

@@ -2,6 +2,7 @@
 #define VEC2D_H_INCLUDED
 
 #include "cairo.h"
+#include "color.h"
 
 #include <cmath>
 #include <iostream>
@@ -74,7 +75,7 @@ class vec2d {
         return {-y, x};
     }
 
-    void draw(cairo_t* cr, vec2d p) const {
+    void draw(cairo_t* cr, vec2d p, color_t color) const {
         double arrow_lenght_ = 10 * vec2d::norm(*this);
         double arrow_degrees_ = .5;
 
@@ -90,7 +91,7 @@ class vec2d {
         double x2 = end.x + head_length * cos(angle + arrow_degrees_);
         double y2 = end.y + head_length * sin(angle + arrow_degrees_);
 
-        cairo_set_source_rgb(cr, 255, 0, 0);
+        cairo_set_source_rgb(cr, color.red, color.green, color.blue);
 
         cairo_move_to(cr, p.x, p.y);
         cairo_line_to(cr, end.x, end.y);