% gcc -o  timer timer.c `pkg-config --libs --cflags gtk+-3.0`

timer.c: In function ‘on_expose_event’:
timer.c:15:31: error: ‘GtkWidget’ has no member named ‘window’
   cr = gdk_cairo_create(widget->window);
                               ^
timer.c: In function ‘time_handler’:
timer.c:28:13: error: ‘GtkWidget’ has no member named ‘window’
   if (widget->window == NULL) return FALSE;
             ^

--------------------------------------------------------------------

% gcc -o  timer timer.c `pkg-config --libs --cflags gtk+-2.0`
Package gtk+-2.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `gtk+-2.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gtk+-2.0' found
timer.c:1:19: fatal error: cairo.h: Datei oder Verzeichnis nicht gefunden
 #include <cairo.h>
                   ^
compilation terminated.


Sourc-Code: 

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


static char buffer[256];

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

  cr = gdk_cairo_create(widget->window);

  cairo_move_to(cr, 30, 30);
  cairo_show_text(cr, buffer);

  cairo_destroy(cr);

  return FALSE;
}

static gboolean
time_handler(GtkWidget *widget)
{
  if (widget->window == NULL) return FALSE;

  time_t curtime;
  struct tm *loctime;

  curtime = time(NULL);
  loctime = localtime(&curtime);
  strftime(buffer, 256, "%T", loctime);

  gtk_widget_queue_draw(widget);
  return TRUE;
}

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), 170, 100);

  gtk_window_set_title(GTK_WINDOW(window), "timer");
  g_timeout_add(1000, (GSourceFunc) time_handler, (gpointer) window);
  gtk_widget_show_all(window);
  time_handler(window);

  gtk_main();

  return 0;
}