What is it?

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


static gboolean
on_expose_event(GtkWidget *widget,
    GdkEventExpose *event,
    gpointer data)
{
  cairo_t *cr;

  cr = gdk_cairo_create (widget->window);

  cairo_set_source_rgba(cr, 0, 0, 0, 1);

  static const double dashed1[] = {4.0, 1.0};
  static int len1  = sizeof(dashed1) / sizeof(dashed1[0]);

  static const double dashed2[] = {4.0, 1.0, 4.0};
  static int len2  = sizeof(dashed2) / sizeof(dashed2[0]);

  static const double dashed3[] = {1.0};

  cairo_set_line_width(cr, 1.5);

  cairo_set_dash(cr, dashed1, len1, 0);

  cairo_move_to(cr, 40, 30);  
  cairo_line_to(cr, 200, 30);
  cairo_stroke(cr);

  cairo_set_dash(cr, dashed2, len2, 1);

  cairo_move_to(cr, 40, 50);  
  cairo_line_to(cr, 200, 50);
  cairo_stroke(cr);

  cairo_set_dash(cr, dashed3, 1, 0);

  cairo_move_to(cr, 40, 70);  
  cairo_line_to(cr, 200, 70);
  cairo_stroke(cr);

  cairo_destroy(cr);

  return FALSE;
}


int main (int argc, char *argv[])
{

  GtkWidget *window;
  GtkWidget *darea;  

  gtk_init(&argc, &argv);

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  darea = gtk_drawing_area_new();
  gtk_container_add(GTK_CONTAINER(window), darea);

  g_signal_connect(darea, "expose-event",
      G_CALLBACK (on_expose_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), 250, 100); 

  gtk_widget_show_all(window);

  gtk_main();

  return 0;
}