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<HTML><HEAD><TITLE>An Upgraded Hello World</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.49"><LINKREL="HOME"TITLE="GTK+ 1.2 Tutorial"HREF="gtk-tut.html"><LINKREL="UP"TITLE="Moving On"HREF="ch-movingon.html"><LINKREL="PREVIOUS"TITLE="More on Signal Handlers"HREF="sec-moreonsignalhandlers.html"><LINKREL="NEXT"TITLE="Packing Widgets"HREF="ch-packingwidgets.html"></HEAD></head><body bgcolor="#FFFFFF" marginheight=0 marginwidth=0 width="100%"><table cellspacing=6 border=0 cellpadding=0 width="100%">  <tr>    <td bgcolor="#FFFFFF" valign=top nowrap>    <centeR><A HREF="/"><img src="/images/gtk-logo-rgb.gif" width=107 height=140 border=0></A>      <font face="helvetica,lucidia" color="#000000"><BR><BR><b>GTK+<BR>The GIMP Toolkit</b></center><BR><table width=100% cellspacing=0 cellpadding=2 border=0><tr><td bgcolor="#000000"><table width=100% cellspacing=0 cellpadding=4 border=0><tr><td bgcolor="#AAAAEE" nowrap><B>General</B></td></tr><tr><td bgcolor="#FFFFFF" nowrap><A HREF="/">Introduction</A><BR><A HREF="/screenshots/">Screenshots</A><br><A HREF="/download/">Download</A><br><A HREF="/mailinglists.html">Mailing Lists</A><BR><A HREF="/bindings.html">Language Bindings</A><BR><A HREF="http://gtk.themes.org/">Themes</A><BR><A HREF="/bugs.html">Bug Tracker</A><BR></td></tr></table></td></tr></table><BR>  <table width=100% cellspacing=0 cellpadding=2 border=0><tr><td bgcolor="#000000"><table width=100% cellspacing=0 cellpadding=4 border=0><tr><td bgcolor="#AAAAEE" nowrap><B>Documentation</B></td></tr><tr><td bgcolor="#FFFFFF" nowrap><A HREF="/faq/">FAQ</A><br><A HREF="/tutorial/">Tutorial</A><BR><A HREF="/api/">API Reference</A><br><A HREF="/books.html">Published Books</A><BR></td></tr></table></td></tr></table><BR>  <table width=100% cellspacing=0 cellpadding=2 border=0><tr><td bgcolor="#000000"><table width=100% cellspacing=0 cellpadding=4 border=0><tr><td bgcolor="#AAAAEE" nowrap><B>Projects</B></td></tr><tr><td bgcolor="#FFFFFF" nowrap><A HREF="http://www.pango.org/">Pango</A><BR><A HREF="http://sources.redhat.com/inti/">Inti</A><BR><A HREF="http://www.gnome.org/">GNOME</A><BR><A HREF="http://user.sgic.fi/~tml/gimp/win32/">GTK+ for Win32</A><br><A HREF="http://people.redhat.com/sopwith/gtkfb/">GtkFB (Framebuffer)</A><br><A HREF="http://www.directfb.org/gtk.xml">GTK+ on DirectFB</A><BR><A HREF="/beos/">GTK+ for BeOS</A></td></tr></table></td></tr></table><BR>  <table width=100% cellspacing=0 cellpadding=2 border=0><tr><td bgcolor="#000000"><table width=100% cellspacing=0 cellpadding=4 border=0><tr><td bgcolor="#AAAAEE" nowrap><B><B>Applications</B></B></td></tr><tr><td bgcolor="#FFFFFF" nowrap><A HREF="http://www.gimp.org/">GIMP</A><BR><A HREF="http://www.abiword.org/">Abiword</A><BR><A HREF="http://www.lysator.liu.se/~alla/dia/dia.html">Dia</A><BR><A HREF="http://glade.pn.org/">Glade</A><BR><A HREF="http://www.gnucash.org/">GnuCash</A><BR><A HREF="http://www.gnome.org/projects/gnumeric/">Gnumeric</A><BR><BR><A HREF="http://www.gnome.org/applist/">GNOME Software Map</A><br></td></tr></table></td></tr></table><BR>      </td>  <td bgcolor="#ffffff" valign=top width="99%"><font face="lucida,helvetica"><BODYCLASS="SECT1"BGCOLOR="#FFFFFF"TEXT="#000000"LINK="#0000FF"VLINK="#840084"ALINK="#0000FF"><DIVCLASS="NAVHEADER"><TABLEWIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">GTK+ 1.2 Tutorial</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><AHREF="sec-moreonsignalhandlers.html">&#60;&#60;&#60; Previous</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">Chapter 3. Moving On</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="ch-packingwidgets.html">Next &#62;&#62;&#62;</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1"><ANAME="SEC-ANUPGRADEDHELLOWORLD">3.3. An Upgraded Hello World</A></H1><P>Let's take a look at a slightly improved <ICLASS="EMPHASIS">helloworld</I> withbetter examples of callbacks. This will also introduce us to our nexttopic, packing widgets.</P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><PRECLASS="PROGRAMLISTING">/* example-start helloworld2 helloworld2.c */#include &#60;gtk/gtk.h&#62;/* Our new improved callback.  The data passed to this function * is printed to stdout. */void callback( GtkWidget *widget,               gpointer   data ){    g_print ("Hello again - %s was pressed\n", (char *) data);}/* another callback */gint delete_event( GtkWidget *widget,                   GdkEvent  *event,                   gpointer   data ){    gtk_main_quit();    return(FALSE);}int main( int   argc,          char *argv[] ){    /* GtkWidget is the storage type for widgets */    GtkWidget *window;    GtkWidget *button;    GtkWidget *box1;    /* This is called in all GTK applications. Arguments are parsed     * from the command line and are returned to the application. */    gtk_init (&#38;argc, &#38;argv);    /* Create a new window */    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);    /* This is a new call, which just sets the title of our     * new window to "Hello Buttons!" */    gtk_window_set_title (GTK_WINDOW (window), "Hello Buttons!");    /* Here we just set a handler for delete_event that immediately     * exits GTK. */    gtk_signal_connect (GTK_OBJECT (window), "delete_event",			GTK_SIGNAL_FUNC (delete_event), NULL);    /* Sets the border width of the window. */    gtk_container_set_border_width (GTK_CONTAINER (window), 10);    /* We create a box to pack widgets into.  This is described in detail     * in the "packing" section. The box is not really visible, it     * is just used as a tool to arrange widgets. */    box1 = gtk_hbox_new(FALSE, 0);    /* Put the box into the main window. */    gtk_container_add (GTK_CONTAINER (window), box1);    /* Creates a new button with the label "Button 1". */    button = gtk_button_new_with_label ("Button 1");        /* Now when the button is clicked, we call the "callback" function     * with a pointer to "button 1" as its argument */    gtk_signal_connect (GTK_OBJECT (button), "clicked",			GTK_SIGNAL_FUNC (callback), (gpointer) "button 1");    /* Instead of gtk_container_add, we pack this button into the invisible     * box, which has been packed into the window. */    gtk_box_pack_start(GTK_BOX(box1), button, TRUE, TRUE, 0);    /* Always remember this step, this tells GTK that our preparation for     * this button is complete, and it can now be displayed. */    gtk_widget_show(button);    /* Do these same steps again to create a second button */    button = gtk_button_new_with_label ("Button 2");    /* Call the same callback function with a different argument,     * passing a pointer to "button 2" instead. */    gtk_signal_connect (GTK_OBJECT (button), "clicked",			GTK_SIGNAL_FUNC (callback), (gpointer) "button 2");    gtk_box_pack_start(GTK_BOX(box1), button, TRUE, TRUE, 0);    /* The order in which we show the buttons is not really important, but I     * recommend showing the window last, so it all pops up at once. */    gtk_widget_show(button);    gtk_widget_show(box1);    gtk_widget_show (window);        /* Rest in gtk_main and wait for the fun to begin! */    gtk_main ();    return(0);}/* example-end */</PRE></TD></TR></TABLE><P>Compile this program using the same linking arguments as our firstexample.  You'll notice this time there is no easy way to exit theprogram, you have to use your window manager or command line to killit. A good exercise for the reader would be to insert a third "Quit"button that will exit the program. You may also wish to play with theoptions to gtk_box_pack_start() while reading the next section.  Tryresizing the window, and observe the behavior.</P><P>Just as a side note, there is another useful define forgtk_window_new() - <TTCLASS="LITERAL">GTK_WINDOW_DIALOG</TT>. This interacts with thewindow manager a little differently and should be used for transientwindows.</P></DIV><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLEWIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><AHREF="sec-moreonsignalhandlers.html">&#60;&#60;&#60; Previous</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="gtk-tut.html">Home</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><AHREF="ch-packingwidgets.html">Next &#62;&#62;&#62;</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">More on Signal Handlers</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="ch-movingon.html">Up</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">Packing Widgets</TD></TR></TABLE></DIV>        </td>    </tr></table>  </td>  </tr></table></body></BODY></HTML>
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