#include <gtk/gtk.h>

typedef struct
{
    gdouble x, y;
    gdouble old_x, old_y;
    gdouble r, g, b;
    GdkEventSequence *seq;
} TouchData;

GList *touch_list = NULL;
cairo_surface_t *image = NULL;
cairo_t *icr;
GRand *randseed;

gboolean
on_touch (GtkWidget     *widget,
          GdkEventTouch *event,
          gpointer       user_data)
{
  static gint count = 0;
  GList *lst;
  TouchData *data;
  GdkEventMotion *mevent = (GdkEventMotion *) event;

  g_printerr ("on_touch: event type %d\n", event->type);

  switch (event->type)
    {
      case GDK_TOUCH_BEGIN:
        data = g_malloc (sizeof (TouchData));
        data->old_x = event->axes[0];
        data->old_y = event->axes[1];
        data->x = event->axes[0];
        data->y = event->axes[1];
        data->r = g_rand_double (randseed);
        data->g = g_rand_double (randseed);
        data->b = g_rand_double (randseed);
        data->seq = event->sequence;
        touch_list = g_list_append (touch_list, data);
        // g_printerr ("touch begin: %.2f, %.2f (%p, %p)\n", event->axes[0], event->axes[1], event->device, event->sequence);
        count ++;
        break;

      case GDK_TOUCH_UPDATE:
        lst = touch_list;
        while (lst)
          {
            data = (TouchData*) lst->data;
            if (data->seq == event->sequence)
              {
                data->old_x = data->x;
                data->old_y = data->y;
                data->x = event->axes[0];
                data->y = event->axes[1];

                g_printerr ("%.2f, %.2f\n", data->x, data->y);

                cairo_set_line_width (icr, 30);
                cairo_set_source_rgb (icr, data->r, data->g, data->b);
                cairo_move_to (icr, data->old_x, data->old_y);
                cairo_line_to (icr, data->x, data->y);
                cairo_stroke (icr);

                break;
              }
            lst = lst->next;
          }

        cairo_surface_flush (image);
        gtk_widget_queue_draw (widget);
        break;

      case GDK_TOUCH_END:
      case GDK_TOUCH_CANCEL:
        lst = touch_list;
        while(lst)
          {
            data = (TouchData*) lst->data;
            if (data->seq == event->sequence)
              {
                touch_list = g_list_remove (touch_list, data);
                g_free (data);
                break;
              }
            lst = lst->next;
          }
        count--;
        break;

      case GDK_MOTION_NOTIFY:
        // return FALSE;

        cairo_set_source_rgb (icr, 1.0, 1.0, 1.0);
        cairo_set_line_width (icr, event->axes[2] * 100);
        cairo_move_to (icr, event->axes[0], event->axes[1]);
        cairo_line_to (icr, event->axes[0] + 0.0001, event->axes[1]);
        cairo_stroke (icr);
        cairo_surface_flush (image);
        gtk_widget_queue_draw (widget);

        break;

      default:
        g_printerr ("Unknown touch type %d\n", event->type);
    }

  // g_printerr ("%d\n", count);
  return TRUE;
}


gboolean
on_draw (GtkWidget *widget,
         cairo_t   *cr)
{
  cairo_set_source_surface (cr, image, 0, 0);
  cairo_paint (cr);
  return FALSE;
}


void
list_devices ()
{
  GdkDisplay *display;
  GdkDeviceManager *manager;
  GList *l, *devices;

  display = gdk_display_get_default ();
  manager = gdk_display_get_device_manager (display);

  devices = gdk_device_manager_list_devices (manager, GDK_DEVICE_TYPE_SLAVE);

  for (l = devices; l; l = g_list_next (l))
    {
      GdkDevice *device = l->data;

      g_printerr ("%s (type %d, %d)\n",
                  gdk_device_get_name (device),
                  gdk_device_get_source (device),
                  gdk_device_get_mode (device)
                  );
      if (gdk_device_get_source (device) == GDK_SOURCE_PEN ||
          gdk_device_get_source (device) == GDK_SOURCE_ERASER ||
          gdk_device_get_source (device) == GDK_SOURCE_TOUCHSCREEN)
        {
          gdk_device_set_mode (device, GDK_MODE_SCREEN);
        }
    }
}


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

  gtk_init (&argc, &argv);

  list_devices ();
  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

  gtk_widget_set_events (window,
                         GDK_POINTER_MOTION_MASK |
                         GDK_BUTTON_PRESS_MASK   |
                         GDK_TOUCH_MASK);

  image = cairo_image_surface_create (CAIRO_FORMAT_RGB24, 1820, 980);
  icr = cairo_create (image);
  cairo_set_source_rgb (icr, 0.0, 0.0, 0.0);
  cairo_paint (icr);
  cairo_set_line_width (icr, 30);
  cairo_set_line_cap (icr, CAIRO_LINE_CAP_ROUND);
  cairo_surface_flush (image);

  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
  g_signal_connect (window, "touch-event", G_CALLBACK (on_touch), NULL);
  g_signal_connect (window, "button-press-event", G_CALLBACK (on_touch), NULL);
  g_signal_connect (window, "button-release-event", G_CALLBACK (on_touch), NULL);
  g_signal_connect (window, "motion-notify-event", G_CALLBACK (on_touch), NULL);
  g_signal_connect (window, "draw", G_CALLBACK (on_draw), NULL);

  gtk_window_set_default_size (GTK_WINDOW (window), 1820, 980);
  gtk_widget_set_app_paintable (window, TRUE);

  randseed = g_rand_new ();

  gtk_widget_show (window);
  gtk_main ();

  return 0;
}