RE: Question about GtkButton->event_window.

["Tom Liu" <tom liu flextrade com>]

Check this Gtk+ source code:(gtkbutton.cpp) 

static void gtk_button_realize (GtkWidget *widget)
{
[snip]
  attributes.event_mask = gtk_widget_get_events (widget);
  attributes.event_mask |= (GDK_EXPOSURE_MASK |
                            GDK_BUTTON_PRESS_MASK |
                            GDK_BUTTON_RELEASE_MASK |
                            GDK_ENTER_NOTIFY_MASK |
                            GDK_LEAVE_NOTIFY_MASK);
[snip]
  button->event_window = gdk_window_new (gtk_widget_get_parent_window
(widget),
                                         &attributes, attributes_mask);
  gdk_window_set_user_data (button->event_window, button);
[snip]
}

We can see GtkButton->event_window has GDK_EXPOSURE_MASK, means it will
fire the expose event? But I tried to hook the widget->expose_event, and
the GtkButton->event_window didn't send the "expose-event".

Thanks.
Tom





> -----Original Message-----
> From: gtk-app-devel-list-admin gnome org [mailto:gtk-app-devel-list-
> admin gnome org] On Behalf Of Tristan Van Berkom
> Sent: Wednesday, February 18, 2004 2:12 PM
> To: Tom Liu
> Cc: gtk-app-devel-list gnome org
> Subject: Re: Question about GtkButton->event_window.
>
> Tom Liu wrote:
>  > I still confuse:
> [snip]
>
>  > 3: the GtkButton need a gdk window,
>  > (GTK_WIDGET_FLAGS(GTK_WIDGET(button)) & GTK_NO_WINDOW) should
return
>  > FALSE.
>
> I have here a gtk+-2.2.2 source (didn't go through another
> download just to write an email...)
>
> and this is my version of gtkbutton.c:
> ========================
> static void
> gtk_button_init (GtkButton *button)
> {
>    GTK_WIDGET_SET_FLAGS (button, GTK_CAN_FOCUS |
GTK_RECEIVES_DEFAULT);
>    GTK_WIDGET_SET_FLAGS (button, GTK_NO_WINDOW);
> ...
> ========================
>
> That means that a gtkbutton is `GTK_NO_WINDOW', meaning that it
> uses the GdkWindow of its parent (container) widget to draw on.
>
>  > 2: The GtkButton->event_window covers the area of button in
>  > GtkWidget->window, All the draw on GtkWidget->window should be
covered.
> Its called an event_window for a reason, its there to recieve events
> (you can not draw on an "event window", only recieve events from X).
>
> since the event_window is only as big as the gtkbutton, it is
practicle
> to recieve enter/leave notify (because if it used the parent, it would
> have to calculate its position relative to its parent every
> "motion-notify" to emulate a mouse-over)
>
>
> I hope this clarifies things,
>                                                           -Tristan
>
>
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