wurf-02.c

#include <gtk/gtk.h>

#define WIDTH 1024
#define HEIGHT 768

double x = 137;
double y = 255;

static void draw (GtkDrawingArea *drawing_area, cairo_t *c,
                  int width, int height, gpointer user_data)
{
  GdkRGBA blue = { 0.0, 0.5, 1.0, 1.0 };

  gdk_cairo_set_source_rgba (c, &blue);
  cairo_arc (c, x, y, 10, 0, 2 * G_PI);
  cairo_fill (c);
}

gboolean timer (GtkWidget *widget)
{
  x += 3;
  y += 2;
  gtk_widget_queue_draw (widget);
  g_timeout_add (50, (GSourceFunc) timer, widget);
  return FALSE;
}

static void activate (GtkApplication *app, gpointer user_data)
{
  GtkWidget *window = gtk_application_window_new (app);
  gtk_window_set_title (GTK_WINDOW (window), "Hello");

  GtkWidget *vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 5);
  gtk_window_set_child (GTK_WINDOW (window), vbox);

  GtkWidget *drawing_area = gtk_drawing_area_new ();
  gtk_widget_set_size_request (drawing_area, WIDTH, HEIGHT);
  gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (drawing_area), draw, NULL, NULL);
  gtk_box_append (GTK_BOX (vbox), drawing_area);

  GtkWidget *quit_button = gtk_button_new_with_label ("Quit");
  g_signal_connect_swapped (quit_button, "clicked", G_CALLBACK (gtk_window_destroy), window);
  gtk_box_append (GTK_BOX (vbox), quit_button);

  g_timeout_add (50, (GSourceFunc) timer, drawing_area);

  gtk_window_present (GTK_WINDOW (window));
}

int main (int argc, char **argv)
{
  GtkApplication *app = gtk_application_new ("de.hs-bochum.cvh.hp.hello-gtk", G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  int status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);
  return status;
}