gtk-tut.sgml

linux下电话本所依赖的一些图形库

                                        gpointer  data );
</programlisting>

</sect1>

<!-- ----------------------------------------------------------------- -->
<sect1 id="sec-AnUpgradedHelloWorld">
<title>An Upgraded Hello World</title>

<para>Let's take a look at a slightly improved <emphasis>helloworld</emphasis> with
better examples of callbacks. This will also introduce us to our next
topic, packing widgets.</para>

<para>
<inlinemediaobject>
<imageobject>
<imagedata fileref="images/helloworld2.png" format="png">
</imageobject>
</inlinemediaobject>
</para>

<programlisting role="C">
<!-- example-start helloworld2 helloworld2.c -->

#include &lt;gtk/gtk.h&gt;

/* Our new improved callback.  The data passed to this function
 * is printed to stdout. */
static void callback( GtkWidget *widget,
                      gpointer   data )
{
    g_print ("Hello again - %s was pressed\n", (gchar *) data);
}

/* another callback */
static gboolean 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 (&amp;argc, &amp;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. */
    g_signal_connect (G_OBJECT (window), "delete_event",
		      G_CALLBACK (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 */
    g_signal_connect (G_OBJECT (button), "clicked",
		      G_CALLBACK (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. */
    g_signal_connect (G_OBJECT (button), "clicked",
		      G_CALLBACK (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 -->
</programlisting>

<para>Compile this program using the same linking arguments as our first
example.  You'll notice this time there is no easy way to exit the
program, you have to use your window manager or command line to kill
it. 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 the
options to gtk_box_pack_start() while reading the next section.  Try
resizing the window, and observe the behavior.</para>

</sect1>
</chapter>

<!-- ***************************************************************** -->
<chapter id="ch-PackingWidgets">
<title>Packing Widgets</title>

<para>When creating an application, you'll want to put more than one widget
inside a window. Our first <emphasis>helloworld</emphasis> example only used one
widget so we could simply use a gtk_container_add() call to "pack" the
widget into the window. But when you want to put more than one widget
into a window, how do you control where that widget is positioned?
This is where packing comes in.</para>

<!-- ----------------------------------------------------------------- -->
<sect1 id="sec-TheoryOfPackingBoxes">
<title>Theory of Packing Boxes</title>

<para>Most packing is done by creating boxes. These
are invisible widget containers that we can pack our widgets into
which come in two forms, a horizontal box, and a vertical box. When
packing widgets into a horizontal box, the objects are inserted
horizontally from left to right or right to left depending on the call
used. In a vertical box, widgets are packed from top to bottom or vice
versa. You may use any combination of boxes inside or beside other
boxes to create the desired effect.</para>

<para>To create a new horizontal box, we use a call to gtk_hbox_new(), and
for vertical boxes, gtk_vbox_new(). The gtk_box_pack_start() and
gtk_box_pack_end() functions are used to place objects inside of these
containers. The gtk_box_pack_start() function will start at the top
and work its way down in a vbox, and pack left to right in an hbox.
gtk_box_pack_end() will do the opposite, packing from bottom to top in
a vbox, and right to left in an hbox. Using these functions allows us
to right justify or left justify our widgets and may be mixed in any
way to achieve the desired effect. We will use gtk_box_pack_start() in
most of our examples. An object may be another container or a
widget. In fact, many widgets are actually containers themselves,
including the button, but we usually only use a label inside a button.</para>

<para>By using these calls, GTK knows where you want to place your widgets
so it can do automatic resizing and other nifty things. There are also
a number of options as to how your widgets should be packed. As you
can imagine, this method gives us a quite a bit of flexibility when
placing and creating widgets.</para>

</sect1>

<!-- ----------------------------------------------------------------- -->
<sect1 id="sec-DetailsOfBoxes">
<title>Details of Boxes</title>

<para>Because of this flexibility, packing boxes in GTK can be confusing at
first. There are a lot of options, and it's not immediately obvious how
they all fit together. In the end, however, there are basically five
different styles.</para>

<para>
<inlinemediaobject>
<imageobject>
<imagedata fileref="images/packbox1.png" format="png">
</imageobject>
</inlinemediaobject>
</para>

<para>Each line contains one horizontal box (hbox) with several buttons. The
call to gtk_box_pack is shorthand for the call to pack each of the
buttons into the hbox. Each of the buttons is packed into the hbox the
same way (i.e., same arguments to the gtk_box_pack_start() function).</para>

<para>This is the declaration of the gtk_box_pack_start() function.</para>

<programlisting role="C">
void gtk_box_pack_start( GtkBox    *box,
                         GtkWidget *child,
                         gboolean   expand,
                         gboolean   fill,
                         guint      padding );
</programlisting>

<para>The first argument is the box you are packing the object into, the
second is the object. The objects will all be buttons for now, so
we'll be packing buttons into boxes.</para>

<para>The expand argument to gtk_box_pack_start() and gtk_box_pack_end()
controls whether the widgets are laid out in the box to fill in all
the extra space in the box so the box is expanded to fill the area
allotted to it (TRUE); or the box is shrunk to just fit the widgets
(FALSE). Setting expand to FALSE will allow you to do right and left
justification of your widgets.  Otherwise, they will all expand to fit
into the box, and the same effect could be achieved by using only one
of gtk_box_pack_start() or gtk_box_pack_end().</para>

<para>The fill argument to the gtk_box_pack functions control whether the
extra space is allocated to the objects themselves (TRUE), or as extra
padding in the box around these objects (FALSE). It only has an effect
if the expand argument is also TRUE.</para>

<para>When creating a new box, the function looks like this:</para>

<programlisting role="C">
GtkWidget *gtk_hbox_new ( gboolean homogeneous,
                          gint     spacing );
</programlisting>

<para>The homogeneous argument to gtk_hbox_new() (and the same for
gtk_vbox_new()) controls whether each object in the box has the same
size (i.e., the same width in an hbox, or the same height in a
vbox). If it is set, the gtk_box_pack() routines function essentially
as if the <literal>expand</literal> argument was always turned on.</para>

<para>What's the difference between spacing (set when the box is created)
and padding (set when elements are packed)? Spacing is added between
objects, and padding is added on either side of an object. The
following figure should make it clearer:</para>

<para>
<inlinemediaobject>
<imageobject>
<imagedata fileref="images/packbox2.png" format="png">
</imageobject>
</inlinemediaobject>
</para>

<para>Here is the code used to create the above images. I've commented it
fairly heavily so I hope you won't have any problems following
it. Compile it yourself and play with it.</para>

</sect1>

<!-- ----------------------------------------------------------------- -->
<sect1 id="sec-PackingDemonstrationProgram">
<title>Packing Demonstration Program</title>

<programlisting role="C">
/* example-start packbox packbox.c */

#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include "gtk/gtk.h"

static gboolean delete_event( GtkWidget *widget,
                              GdkEvent  *event,
                              gpointer   data )
{
    gtk_main_quit ();
    return FALSE;
}

/* Make a new hbox filled with button-labels. Arguments for the 
 * variables we're interested are passed in to this function. 
 * We do not show the box, but do show everything inside. */
static GtkWidget *make_box( gboolean homogeneous,
                            gint     spacing,
                            gboolean expand,
                            gboolean fill,
                            guint    padding ) 
{
    GtkWidget *box;
    GtkWidget *button;
    char padstr[80];
    
    /* Create a new hbox with the appropriate homogeneous
     * and spacing settings */
    box = gtk_hbox_new (homogeneous, spacing);
    
    /* Create a series of buttons with the appropriate settings */
    button = gtk_button_new_with_label ("gtk_box_pack");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);
    
    button = gtk_button_new_with_label ("(box,");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);
    
    button = gtk_button_new_with_label ("button,");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);
    
    /* Create a button with the label depending on the value of
     * expand. */
    if (expand == TRUE)
	    button = gtk_button_new_with_label ("TRUE,");
    else
	    button = gtk_button_new_with_label ("FALSE,");
    
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);
    
    /* This is the same as the button creation for "expand"
     * above, but uses the shorthand form. */
    button = gtk_button_new_with_label (fill ? "TRUE," : "FALSE,");
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);
    
    sprintf (padstr, "%d);", padding);
    
    button = gtk_button_new_with_label (padstr);
    gtk_box_pack_start (GTK_BOX (box), button, expand, fill, padding);
    gtk_widget_show (button);
    
    return box;
}

int main( int   argc,
          char *argv[]) 
{
    GtkWidget *window;
    GtkWidget *button;
    GtkWidget *box1;
    GtkWidget *box2;
    GtkWidget *separator;
    GtkWidget *label;
    GtkWidget *quitbox;
    int which;
    
    /* Our init, don't forget this! :) */
    gtk_init (&amp;argc, &amp;argv);
    
    if (argc != 2) {
	fprintf (stderr, "usage: packbox num, where num is 1, 2, or 3.\n");