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>Container Widgets</H1
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><A
NAME="SEC-EVENTBOX"
>The EventBox</A
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><P
>Some GTK widgets don't have associated X windows, so they just draw on
their parents. Because of this, they cannot receive events and if they
are incorrectly sized, they don't clip so you can get messy
overwriting, etc. If you require more from these widgets, the EventBox
is for you.</P
><P
>At first glance, the EventBox widget might appear to be totally
useless. It draws nothing on the screen and responds to no
events. However, it does serve a function - it provides an X window
for its child widget. This is important as many GTK widgets do not
have an associated X window. Not having an X window saves memory and
improves performance, but also has some drawbacks. A widget without an
X window cannot receive events, and does not perform any clipping on
its contents. Although the name <I
CLASS="EMPHASIS"
>EventBox</I
> emphasizes the
event-handling function, the widget can also be used for clipping.
(and more, see the example below).</P
><P
>To create a new EventBox widget, use:</P
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>GtkWidget *gtk_event_box_new( void );</PRE
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>A child widget can then be added to this EventBox:</P
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> gtk_container_add (GTK_CONTAINER (event_box), child_widget);</PRE
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><P
>The following example demonstrates both uses of an EventBox - a label
is created that is clipped to a small box, and set up so that a
mouse-click on the label causes the program to exit. Resizing the
window reveals varying amounts of the label.</P
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CLASS="PROGRAMLISTING"
> #include <stdlib.h>
#include <gtk/gtk.h>
int main( int argc,
char *argv[] )
{
GtkWidget *window;
GtkWidget *event_box;
GtkWidget *label;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Event Box");
g_signal_connect (window, "destroy",
G_CALLBACK (exit), NULL);
gtk_container_set_border_width (GTK_CONTAINER (window), 10);
/* Create an EventBox and add it to our toplevel window */
event_box = gtk_event_box_new ();
gtk_container_add (GTK_CONTAINER (window), event_box);
gtk_widget_show (event_box);
/* Create a long label */
label = gtk_label_new ("Click here to quit, quit, quit, quit, quit");
gtk_container_add (GTK_CONTAINER (event_box), label);
gtk_widget_show (label);
/* Clip it short. */
gtk_widget_set_size_request (label, 110, 20);
/* And bind an action to it */
gtk_widget_set_events (event_box, GDK_BUTTON_PRESS_MASK);
g_signal_connect (event_box, "button_press_event",
G_CALLBACK (exit), NULL);
/* Yet one more thing you need an X window for ... */
gtk_widget_realize (event_box);
gdk_window_set_cursor (event_box->window, gdk_cursor_new (GDK_HAND1));
gtk_widget_show (window);
gtk_main ();
return 0;
}</PRE
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