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GTK+编程

GTK(GIMP Toolkit)是一个生成GUI的库，按LGPL发布。最初是为GIMP写的，但目前已发展为一个功能强大、设计灵活的一个通用工具。特别是被GNOME选中使得GTK+广为流传，大有取代Motif成为X上GUI开发的标准库的趋势。当然GTK+并不要求必须在X上，事实上，目前GTK+已经有了成功的windows版本。

毫无疑问，GIMP的作者就是GTK+的作者。

• Peter Mattis: petm@xcf.berkeley.edu


• Spencer Kimball: spencer@xcf.berkeley.edu


• Josh MacDonald: jmacd@xcf.berkeley.edu

GTK虽然是用C写的，即只提供C的函数调用接口，您可以使用你熟悉的语言了使用GTK，因为GTK+已经被绑定到几乎所有流行的语言上，如：C++, Guile, Perl, Python, TOM, Ada95, Objective C, Free Pascal, and Eiffel.

GTK+程序举例

#include 

/* This is a callback function. The data arguments are ignored
 * in this example. More on callbacks below. */
void hello( GtkWidget *widget,
            gpointer   data )
{
    g_print ("Hello World\n");
}

gint delete_event( GtkWidget *widget,
                   GdkEvent  *event,
                   gpointer   data )
{
    /* If you return FALSE in the "delete_event" signal handler,
     * GTK will emit the "destroy" signal. Returning TRUE means
     * you don't want the window to be destroyed.
     * This is useful for popping up 'are you sure you want to quit?'
     * type dialogs. */

    g_print ("delete event occurred\n");

    /* Change TRUE to FALSE and the main window will be destroyed with
     * a "delete_event". */

    return(TRUE);
}

/* Another callback */
void destroy( GtkWidget *widget,
              gpointer   data )
{
    gtk_main_quit();
}

int main( int   argc,
          char *argv[] )
{
    /* GtkWidget is the storage type for widgets */
    GtkWidget *window;
    GtkWidget *button;
    
    /* This is called in all GTK applications. Arguments are parsed
     * from the command line and are returned to the application. */
    gtk_init(&argc, &argv);
    
    /* create a new window */
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    
    /* When the window is given the "delete_event" signal (this is given
     * by the window manager, usually by the "close" option, or on the
     * titlebar), we ask it to call the delete_event () function
     * as defined above. The data passed to the callback
     * function is NULL and is ignored in the callback function. */
    gtk_signal_connect (GTK_OBJECT (window), "delete_event",
                        GTK_SIGNAL_FUNC (delete_event), NULL);
    
    /* Here we connect the "destroy" event to a signal handler.  
     * This event occurs when we call gtk_widget_destroy() on the window,
     * or if we return FALSE in the "delete_event" callback. */
    gtk_signal_connect (GTK_OBJECT (window), "destroy",
                        GTK_SIGNAL_FUNC (destroy), NULL);
    
    /* Sets the border width of the window. */
    gtk_container_set_border_width (GTK_CONTAINER (window), 10);
    
    /* Creates a new button with the label "Hello World". */
    button = gtk_button_new_with_label ("Hello World");
    
    /* When the button receives the "clicked" signal, it will call the
     * function hello() passing it NULL as its argument.  The hello()
     * function is defined above. */
    gtk_signal_connect (GTK_OBJECT (button), "clicked",
                        GTK_SIGNAL_FUNC (hello), NULL);
    
    /* This will cause the window to be destroyed by calling
     * gtk_widget_destroy(window) when "clicked".  Again, the destroy
     * signal could come from here, or the window manager. */
    gtk_signal_connect_object (GTK_OBJECT (button), "clicked",
                               GTK_SIGNAL_FUNC (gtk_widget_destroy),
                               GTK_OBJECT (window));
    
    /* This packs the button into the window (a gtk container). */
    gtk_container_add (GTK_CONTAINER (window), button);
    
    /* The final step is to display this newly created widget. */
    gtk_widget_show (button);
    
    /* and the window */
    gtk_widget_show (window);
    
    /* All GTK applications must have a gtk_main(). Control ends here
     * and waits for an event to occur (like a key press or
     * mouse event). */
    gtk_main ();
    
    return(0);
}
/* example-end */

GTK+的事件与信号处理

GTK是一个事件驱动的工具集，一个GTK应用通常在gtk_main上休眠直到一个事件发生，这时控制被传递给合适的函数。

信号绑定

gint gtk_signal_connect( GtkObject *object,
                         gchar *name,
                         GtkSignalFunc func,
                         gpointer func_data );


void gtk_signal_disconnect( GtkObject *object,
                            gint id );


void gtk_signal_handler_block( GtkObject *object,
                               guint      handler_id );
                               
                               
void gtk_signal_handler_unblock( GtkObject *object,
                                 guint      handler_id );

信号被处理的过程

信号发出

• 信号发出(signal emission)特指GTK为一个特定的对象和一个特定的信号执行所有的处理程序的过程；


• 绑定在一个信号上的所有处理程序的执行顺序与它们被设置的次序一致；


• 一次信号发出的返回值是最后一个被执行的处理程序的返回值；


• 由于所有的事件信号都是GTK_RUN_LAST类型，因此它将是最后执行的缺省处理程序，除非你使用gtk_signal_connect_after()；

信号传播

• 从事件发生的那个控件开始；


• 发出一个普通的事件“event”。如果它的信号处理程序返回TRUE，则停止一切处理；


• 否则，发出一个特定的"button_press_event"信号。如果返回TRUE，则停止处理；


• 否则，将控制转移到这个控件的父亲那里，继续上面的两步；


• 持续进行，直到某个处理程序返回TRUE，和到达顶级控件。

注意事项

1. 当有一个缺省处理程序时，您的处理程序的返回值可能不产生任何作用，除非您使用gtk_signal_connect_after()来绑定它；

2. 为阻止缺省处理程序执行，您需要：

• 用gtk_signal_connect()来绑定；


• 用gtk_signal_emit_stop_by_name()来停止信号继续传播。

3. 当GTK+不够用时，可以考虑使用GDK等库。

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