Mystify

mystify.c

#include <stdlib.h>

#include <cairo/cairo.h>
#include <gtk/gtk.h>
#include <gdk/gdk.h>

#define N_VERTS   5

#define WIN_WIDTH   1024
#define WIN_HEIGHT  768

struct tag_mystify_vert {
  int x, y;     /* x and y positions */
  int vx, vy;   /* x and y velocities */
  double r, g, b;  /* colour components */
};

typedef struct tag_mystify_vert mystify_vert;

mystify_vert verts[N_VERTS];

GtkWidget *darea;

void init_verts() {
  int n;

  for (n = 0; n < N_VERTS; n ++) {
    verts[n].x = rand() % WIN_WIDTH;
    verts[n].y = rand() % WIN_HEIGHT;
    verts[n].vx = 0;
    verts[n].vy = 0;

    while (verts[n].vx == 0) {
      verts[n].vx = 5 - rand() % 10;
    }

    while (verts[n].vy == 0) {
      verts[n].vy = 5 - rand() % 10;
    }

    verts[n].r = (rand() % 255) / 255.0;
    verts[n].g = (rand() % 255) / 255.0;
    verts[n].b = (rand() % 255) / 255.0;
  }

}

void animate_verts() {
  int n;

  for (n = 0; n < N_VERTS; n ++) {
    verts[n].x += verts[n].vx;

    if (verts[n].x < 0 || verts[n].x > WIN_WIDTH) {
      verts[n].vx *= -1;
      verts[n].x += (verts[n].vx * 2);
    }

    verts[n].y += verts[n].vy;

    if (verts[n].y < 0 || verts[n].y > WIN_HEIGHT) {
      verts[n].vy *= -1;
      verts[n].y += (verts[n].vy * 2);
    }

  }
}

gboolean mystify_animate(GtkWidget *window) {
  animate_verts();
  gtk_widget_queue_draw_area(window, 0, 0, WIN_WIDTH, WIN_HEIGHT);

  return TRUE;
}

static gboolean on_draw_event(GtkWidget *widget, cairo_t *cr, gpointer user_data) {
  int n;

  /* clear the background to black */
  cairo_set_source_rgb(cr, 0, 0, 0);
  cairo_paint(cr);

  for (n = 0; n < (N_VERTS - 1); n ++) {
    cairo_set_source_rgb(cr, verts[n].r, verts[n].g, verts[n].b);
    cairo_move_to (cr, verts[n].x, verts[n].y);
    cairo_line_to (cr, verts[n + 1].x, verts[n + 1].y);
    cairo_set_line_width (cr, 1);
    cairo_stroke (cr);
  }

  n = N_VERTS - 1;

  cairo_set_source_rgb(cr, verts[n].r, verts[n].g, verts[n].b);
  cairo_move_to (cr, verts[n].x, verts[n].y);
  cairo_line_to (cr, verts[0].x, verts[0].y);
  cairo_set_line_width (cr, 1);
  cairo_stroke (cr);

	return FALSE;
}

int main(int argc, char *argv[]) {
  GtkWidget *window;
  
  gtk_init(&argc, &argv);
  init_verts();

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  darea = gtk_drawing_area_new();
  gtk_container_add(GTK_CONTAINER(window), darea);
 
  g_signal_connect(G_OBJECT(darea), "draw", G_CALLBACK(on_draw_event), NULL); 
  g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);  
 
  gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
  gtk_window_set_default_size(GTK_WINDOW(window), WIN_WIDTH, WIN_HEIGHT); 
  gtk_window_set_title(GTK_WINDOW(window), "Lines");

  gtk_widget_show_all(window);

  (void)g_timeout_add(33, (GSourceFunc)mystify_animate, window);

  gtk_main();

  return 0;
}