Learner problem with key_press_event and key_release_event

[Andrew Blucher <andrew blucher monash edu au>]

Hi Folks.

I am new to GTK, and have been trying to add key_press_event and 
key_release_event to the scribble-simple.c example program.

I expect that I have missed something blindingly obvious in the 
tutorial and reference materials ... can you help me please?

The full code is below.  In summary, I have started with 
scribble-simple.c and added a few output messages like:

  g_message("button_press_event\n");    /* I see this message */

And added two new functions:

  static gint
  key_press_event (GtkWidget *widget, GdkEventKey *event) 
  { 
    g_message("key_press_event\n");       /* I *don't* see this message
*/
    
    return TRUE;    
  }

  static gint
  key_release_event (GtkWidget *widget, GdkEventKey *event) 
  {
    g_message("key_release_event\n");     /* I *don't* see this message
*/

    return TRUE;    
  }

Connected the signals:

  /* Events I added */
  gtk_signal_connect (GTK_OBJECT (drawing_area), "key_press_event", 
                      (GtkSignalFunc) key_press_event, NULL);
  gtk_signal_connect (GTK_OBJECT (drawing_area), "key_release_event", 
                      (GtkSignalFunc) key_release_event, NULL);

And set the events:

  gtk_widget_set_events (drawing_area, GDK_EXPOSURE_MASK
                         | GDK_LEAVE_NOTIFY_MASK
                         | GDK_BUTTON_PRESS_MASK
                         | GDK_KEY_PRESS_MASK      /* Events I added */
                         | GDK_KEY_RELEASE_MASK    /* Events I added */
                         | GDK_POINTER_MOTION_MASK
                         | GDK_POINTER_MOTION_HINT_MASK);

But when I compile and run I do not see the messages from the new 
functions when I press keys on the keyboard.  I have tried using
gtk_widget_set_events_after, gtk_widget_add_events, grabbing the
keyboard, 
grabbing the focus, setting GdkWindowAttr.wclass = GDK_INPUT_OUTPUT,
etc. 

I figure I must be missing something fundamental!

TIA,
Andy.
----------------------------- Full code follows
-----------------------------
/* scribblek modified from scribble-simple.c to trial key_*_event
handling */

#include <gtk/gtk.h>

/* Backing pixmap for drawing area */
static GdkPixmap *pixmap = NULL;

/* Create a new backing pixmap of the appropriate size */
static gint configure_event( GtkWidget         *widget,
                             GdkEventConfigure *event )
{
  g_message("configure_event\n");       /* I see this message */

  if (pixmap)
    gdk_pixmap_unref(pixmap);

  pixmap = gdk_pixmap_new(widget->window,
                          widget->allocation.width,
                          widget->allocation.height,
                          -1);
  gdk_draw_rectangle (pixmap,
                      widget->style->white_gc,
                      TRUE,
                      0, 0,
                      widget->allocation.width,
                      widget->allocation.height);

  return TRUE;
}

/* Redraw the screen from the backing pixmap */
static gint expose_event( GtkWidget      *widget,
                          GdkEventExpose *event )
{
  g_message("expose_event\n");          /* I see this message */

  gdk_draw_pixmap(widget->window,
                  widget->style->fg_gc[GTK_WIDGET_STATE (widget)],
                  pixmap,
                  event->area.x, event->area.y,
                  event->area.x, event->area.y,
                  event->area.width, event->area.height);

  return FALSE;
}

/* Draw a rectangle on the screen */
static void draw_brush( GtkWidget *widget,
                        gdouble    x,
                        gdouble    y)
{
  GdkRectangle update_rect;

  update_rect.x = x - 5;
  update_rect.y = y - 5;
  update_rect.width = 10;
  update_rect.height = 10;
  gdk_draw_rectangle (pixmap,
                      widget->style->black_gc,
                      TRUE,
                      update_rect.x, update_rect.y,
                      update_rect.width, update_rect.height);

  gtk_widget_draw (widget, &update_rect);
}

static gint button_press_event( GtkWidget      *widget,
                                GdkEventButton *event )
{
  g_message("button_press_event\n");    /* I see this message */

  if (event->button == 1 && pixmap != NULL)
    draw_brush (widget, event->x, event->y);

  return TRUE;
}

static gint
key_press_event (GtkWidget *widget, GdkEventKey *event) 
{
  g_message("key_press_event\n");       /* I *don't* see this message */

  return TRUE;    
}

static gint
key_release_event (GtkWidget *widget, GdkEventKey *event) 
{
  g_message("key_release_event\n");     /* I *don't* see this message */

  return TRUE;    
}

static gint motion_notify_event( GtkWidget *widget,
                                 GdkEventMotion *event )
{
  int x, y;
  GdkModifierType state;

  if (event->is_hint)
    gdk_window_get_pointer (event->window, &x, &y, &state);
  else
    {
      x = event->x;
      y = event->y;
      state = event->state;
    }
    
  if (state & GDK_BUTTON1_MASK && pixmap != NULL)
    draw_brush (widget, x, y);
  
  return TRUE;
}

void quit ()
{
   gtk_main_quit();                     /* modified */
}

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

  GtkWidget *button;

  gtk_init (&argc, &argv);

  g_message("scribblek started\n");     /* I see this message */

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  gtk_widget_set_name (window, "Test Input");

  vbox = gtk_vbox_new (FALSE, 0);
  gtk_container_add (GTK_CONTAINER (window), vbox);
  gtk_widget_show (vbox);

  gtk_signal_connect (GTK_OBJECT (window), "destroy",
                      GTK_SIGNAL_FUNC (quit), NULL);

  /* Create the drawing area */

  drawing_area = gtk_drawing_area_new ();
  gtk_drawing_area_size (GTK_DRAWING_AREA (drawing_area), 200, 200);
  gtk_box_pack_start (GTK_BOX (vbox), drawing_area, TRUE, TRUE, 0);

  gtk_widget_show (drawing_area);

  /* Signals used to handle backing pixmap */

  gtk_signal_connect (GTK_OBJECT (drawing_area), "expose_event",
                      (GtkSignalFunc) expose_event, NULL);
  gtk_signal_connect (GTK_OBJECT(drawing_area),"configure_event",
                      (GtkSignalFunc) configure_event, NULL);

  /* Event signals */

  gtk_signal_connect (GTK_OBJECT (drawing_area), "motion_notify_event",
                      (GtkSignalFunc) motion_notify_event, NULL);
  gtk_signal_connect (GTK_OBJECT (drawing_area), "button_press_event",
                      (GtkSignalFunc) button_press_event, NULL);

  /* Events I added */
  gtk_signal_connect (GTK_OBJECT (drawing_area), "key_press_event", 
                      (GtkSignalFunc) key_press_event, NULL);
  gtk_signal_connect (GTK_OBJECT (drawing_area), "key_release_event", 
                      (GtkSignalFunc) key_release_event, NULL);

  gtk_widget_set_events (drawing_area, GDK_EXPOSURE_MASK
                         | GDK_LEAVE_NOTIFY_MASK
                         | GDK_BUTTON_PRESS_MASK
                         | GDK_KEY_PRESS_MASK      /* Events I added */
                         | GDK_KEY_RELEASE_MASK    /* Events I added */
                         | GDK_POINTER_MOTION_MASK
                         | GDK_POINTER_MOTION_HINT_MASK);

  /* .. And a quit button */
  button = gtk_button_new_with_label ("Quit");
  gtk_box_pack_start (GTK_BOX (vbox), button, FALSE, FALSE, 0);

  gtk_signal_connect_object (GTK_OBJECT (button), "clicked",
                             GTK_SIGNAL_FUNC (gtk_widget_destroy),
                             GTK_OBJECT (window));
  gtk_widget_show (button);

  gtk_widget_show (window);

  gtk_main ();

  g_message("scribblek ended\n");       /* I see this message */

  return 0;
}
/* example-end */