Re: gtkmm custom widget problem

[Daniel Elstner <daniel kitta googlemail com>]

Am Freitag, den 19.01.2007, 15:54 -0800 schrieb Trigve Siver:
> Hi,
> 
> I have made custom gtkmm widget with embeded Ogre render
> window...everything is looking good except that I have some problem
> with motion event...I only get GdkEventMotion when I move my mouse
> pointer from OUTSIDE the GtkOgre widget TO GtkOgre widget and when I'm
> moving inside the widget I don't receive any motion event...BUT when
> I'm pressing the mouse button and moving with mouse inside GtkOgre
> widget I receive motion events...  
> 
> Anybody could help somehow?

Use
    add_events(Gdk::POINTER_MOTION_MASK)
or
    add_events(Gdk::POINTER_MOTION_MASK | Gdk::POINTER_MOTION_HINT_MASK)

in order to receive pointer motion events.  If HINT_MASK is used, the
motion events are only hints, and Gdk::Window::get_pointer() has to be
called to receive further events.  This has the advantage of avoiding
congestion if you can't handle the motion events fast enough.  On the
other hand it involves a round-trip to the X server and thus adds
latency.  You'll have to decide what's best for your application.

Preferably, the motion event handler should be able to deal with both
models.  Here's a bit of sample code ripped from one of my projects:

bool CubeScene::on_motion_notify_event(GdkEventMotion* event)
{
  reset_hide_cursor_timeout();

  int x = TRACK_UNSET;
  int y = TRACK_UNSET;

  Gdk::ModifierType state = Gdk::ModifierType(event->state);

  if (event->is_hint)
  {
    get_window()->get_pointer(x, y, state);
  }
  else
  {
    x = Math::clamp_to_int(event->x);
    y = Math::clamp_to_int(event->y);
  }

  // Test both the event state and the more recent one from get_pointer(),
  // so that we do not end up processing motion events before the initial
  // button press event has been received.

  if ((state & event->state & GDK_BUTTON1_MASK) != 0 && x != TRACK_UNSET && y != TRACK_UNSET)
  {
    // If the track position has been invalidated due to an allocation change,
    // completely ignore any further button motion events until the next button
    // press event.  This avoids all sorts of problems due to the uncertainty
    // of whether we will receive a button release event or not.

    if (track_last_x_ != TRACK_UNSET && track_last_y_ != TRACK_UNSET)
    {
      process_track_motion(x, y);

      track_last_x_ = x;
      track_last_y_ = y;
    }
  }

  return GL::Scene::on_motion_notify_event(event);
}

Hope this helps,
--Daniel