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Start of Section 6.

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Wed Jun 28 13:31:55 BST 2000  Tony Gale <gale@gtk.org>

	* docs/faq/gtk-faq.sgml: Start of Section 6.
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Wed Jun 28 13:31:55 BST 2000 Tony Gale <gale@gtk.org>
* docs/faq/gtk-faq.sgml: Start of Section 6.
Mon Jun 26 19:37:04 2000 Owen Taylor <otaylor@redhat.com>
* configure.in: Put 1.3.1 in warning message, not 1.3.0.

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Wed Jun 28 13:31:55 BST 2000 Tony Gale <gale@gtk.org>
* docs/faq/gtk-faq.sgml: Start of Section 6.
Mon Jun 26 19:37:04 2000 Owen Taylor <otaylor@redhat.com>
* configure.in: Put 1.3.1 in warning message, not 1.3.0.

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ChangeLog.pre-2-10
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Wed Jun 28 13:31:55 BST 2000 Tony Gale <gale@gtk.org>
* docs/faq/gtk-faq.sgml: Start of Section 6.
Mon Jun 26 19:37:04 2000 Owen Taylor <otaylor@redhat.com>
* configure.in: Put 1.3.1 in warning message, not 1.3.0.

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ChangeLog.pre-2-2
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Wed Jun 28 13:31:55 BST 2000 Tony Gale <gale@gtk.org>
* docs/faq/gtk-faq.sgml: Start of Section 6.
Mon Jun 26 19:37:04 2000 Owen Taylor <otaylor@redhat.com>
* configure.in: Put 1.3.1 in warning message, not 1.3.0.

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ChangeLog.pre-2-4
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@ -1,3 +1,7 @@
Wed Jun 28 13:31:55 BST 2000 Tony Gale <gale@gtk.org>
* docs/faq/gtk-faq.sgml: Start of Section 6.
Mon Jun 26 19:37:04 2000 Owen Taylor <otaylor@redhat.com>
* configure.in: Put 1.3.1 in warning message, not 1.3.0.

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ChangeLog.pre-2-6
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Wed Jun 28 13:31:55 BST 2000 Tony Gale <gale@gtk.org>
* docs/faq/gtk-faq.sgml: Start of Section 6.
Mon Jun 26 19:37:04 2000 Owen Taylor <otaylor@redhat.com>
* configure.in: Put 1.3.1 in warning message, not 1.3.0.

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ChangeLog.pre-2-8
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@ -1,3 +1,7 @@
Wed Jun 28 13:31:55 BST 2000 Tony Gale <gale@gtk.org>
* docs/faq/gtk-faq.sgml: Start of Section 6.
Mon Jun 26 19:37:04 2000 Owen Taylor <otaylor@redhat.com>
* configure.in: Put 1.3.1 in warning message, not 1.3.0.

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<book>
<bookinfo>
<date>June 26th 2000</date>
<date>June 28th 2000</date>
<title>GTK+ FAQ</title>
<authorgroup>
<author>
@ -2091,6 +2091,414 @@ gint gtk_clist_prepend (GtkCList *clist,
gdk_pixmap_unref (pixmap_mask);
</programlisting>
</sect2>
</sect1>
</chapter>
<!-- ***************************************************************** -->
<chapter>
<title>Development with GTK+: widget specific questions</title>
<sect1>
<title></title>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How do I find out about the selection of a GtkList?</title>
<para>Get the selection something like this:</para>
<programlisting role="C">
GList *sel;
sel = GTK_LIST(list)->selection;
</programlisting>
<para>This is how GList is defined (quoting glist.h):</para>
<programlisting role="C">
typedef struct _GList GList;
struct _GList
{
gpointer data;
GList *next;
GList *prev;
};
</programlisting>
<para>A GList structure is just a simple structure for doubly
linked lists. there exist several g_list_*() functions to
modify a linked list in glib.h. However the
GTK_LIST(MyGtkList)->selection is maintained by the
gtk_list_*() functions and should not be modified.</para>
<para>The selection_mode of the GtkList determines the
selection facilities of a GtkList and therefore the contents
of GTK_LIST(AnyGtkList)->selection:</para>
<informaltable frame="all">
<tgroup cols="2">
<thead>
<row>
<entry><literal>selection_mode</literal></entry>
<entry><literal> GTK_LIST()->selection</literal>
contents</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>GTK_SELECTION_SINGLE</literal></entry>
<entry>selection is either NULL or contains a GList*
pointer for a single selected item.</entry>
</row>
<row>
<entry><literal>GTK_SELECTION_BROWSE</literal></entry>
<entry>selection is NULL if the list contains no
widgets, otherwise it contains a GList*
pointer for one GList structure.</entry>
</row>
<row>
<entry><literal>GTK_SELECTION_MULTIPLE</literal></entry>
<entry>selection is NULL if no listitems are selected
or a a GList* pointer for the first selected
item. that in turn points to a GList structure
for the second selected item and so
on.</entry>
</row>
<row>
<entry><literal>GTK_SELECTION_EXTENDED</literal></entry>
<entry>selection is NULL.</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>The data field of the GList structure
GTK_LIST(MyGtkList)->selection points to the first
GtkListItem that is selected. So if you would like to
determine which listitems are selected you should go like
this:</para>
<programlisting role="C">
{
gchar *list_items[]={
"Item0",
"Item1",
"foo",
"last Item",
};
guint nlist_items=sizeof(list_items)/sizeof(list_items[0]);
GtkWidget *list_item;
guint i;
list=gtk_list_new();
gtk_list_set_selection_mode(GTK_LIST(list), GTK_SELECTION_MULTIPLE);
gtk_container_add(GTK_CONTAINER(AnyGtkContainer), list);
gtk_widget_show (list);
for (i = 0; i < nlist_items; i++)
{
list_item=gtk_list_item_new_with_label(list_items[i]);
gtk_object_set_user_data(GTK_OBJECT(list_item), (gpointer)i);
gtk_container_add(GTK_CONTAINER(list), list_item);
gtk_widget_show(list_item);
}
}
</programlisting>
<para>To get known about the selection:</para>
<programlisting role="C">
{
GList *items;
items=GTK_LIST(list)->selection;
printf("Selected Items: ");
while (items) {
if (GTK_IS_LIST_ITEM(items->data))
printf("%d ", (guint)
gtk_object_get_user_data(items->data));
items=items->next;
}
printf("\n");
}
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How do I stop the column headings of a GtkCList
disappearing when the list is scrolled?</title>
<para>This happens when a GtkCList is packed into a
GtkScrolledWindow using the function
<literal>gtk_scroll_window_add_with_viewport()</literal>. The prefered
method of adding a CList to a scrolled window is to use the
function <literal>gtk_container_add</literal>, as in:</para>
<programlisting role="C">
GtkWidget *scrolled, *clist;
char *titles[] = { "Title1" , "Title2" };
scrolled = gtk_scrolled_window_new(NULL, NULL);
clist = gtk_clist_new_with_titles(2, titles);
gtk_container_add(GTK_CONTAINER(scrolled), clist);
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>I don't want the user of my applications to enter text
into a GtkCombo. Any idea?</title>
<para>A GtkCombo has an associated entry which can be accessed
using the following expression:</para>
<programlisting role="C">
GTK_COMBO(combo_widget)->entry
</programlisting>
<para>If you don't want the user to be able to modify the
content of this entry, you can use the
gtk_entry_set_editable() function:</para>
<programlisting role="C">
void gtk_entry_set_editable(GtkEntry *entry,
gboolean editable);
</programlisting>
<para>Set the editable parameter to FALSE to disable typing
into the entry.</para>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How do I catch a combo box change?</title>
<para>The entry which is associated to your GtkCombo send a
"changed" signal when:</para>
<itemizedlist>
<listitem><simpara>some text is typed in</simpara>
</listitem>
<listitem><simpara>the selection of the combo box is changed</simpara>
</listitem>
</itemizedlist>
<para>To catch any combo box change, simply connect your
signal handler with</para>
<programlisting role="C">
gtk_signal_connect(GTK_COMBO(cb)->entry,
"changed",
GTK_SIGNAL_FUNC(my_cb_change_handler),
NULL);
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How can I define a separation line in a menu?</title>
<para>See the <ulink
url="http://www.gtk.org/tutorial/">Tutorial</ulink> for
information on how to create menus. However, to create a
separation line in a menu, just insert an empty menu item:</para>
<programlisting role="C">
menuitem = gtk_menu_item_new();
gtk_menu_append(GTK_MENU(menu), menuitem);
gtk_widget_show(menuitem);
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How can I right justify a menu, such as Help?</title>
<para>Depending on if you use the MenuFactory or not, there
are two ways to proceed. With the MenuFactory, use something
like the following:</para>
<programlisting role="C">
menu_path = gtk_menu_factory_find (factory, "&lt;MyApp&gt;/Help");
gtk_menu_item_right_justify(menu_path->widget);
</programlisting>
<para>If you do not use the MenuFactory, you should simply
use:</para>
<programlisting role="C">
gtk_menu_item_right_justify(my_menu_item);
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How do I add some underlined accelerators to menu
items?</title>
<para>Damon Chaplin, the technical force behind the Glade
project, provided the following code sample (this code is an
output from Glade). It creates a small <GUIMenu>File</guimenu> menu item
with only one child (<guimenu>New</guimenu>). The F in <guimenu>File</guimenu> and the N
in <guimenu>New</guimenu> are underlined, and the relevant accelerators are
created.</para>
<programlisting role="C">
menubar1 = gtk_menu_bar_new ();
gtk_object_set_data (GTK_OBJECT (window1), "menubar1", menubar1);
gtk_widget_show (menubar1);
gtk_box_pack_start (GTK_BOX (vbox1), menubar1, FALSE, FALSE, 0);
file1 = gtk_menu_item_new_with_label ("");
tmp_key = gtk_label_parse_uline (GTK_LABEL (GTK_BIN (file1)->child),
_("_File"));
gtk_widget_add_accelerator (file1, "activate_item", accel_group,
tmp_key, GDK_MOD1_MASK, 0);
gtk_object_set_data (GTK_OBJECT (window1), "file1", file1);
gtk_widget_show (file1);
gtk_container_add (GTK_CONTAINER (menubar1), file1);
file1_menu = gtk_menu_new ();
file1_menu_accels = gtk_menu_ensure_uline_accel_group (GTK_MENU (file1_menu));
gtk_object_set_data (GTK_OBJECT (window1), "file1_menu", file1_menu);
gtk_menu_item_set_submenu (GTK_MENU_ITEM (file1), file1_menu);
new1 = gtk_menu_item_new_with_label ("");
tmp_key = gtk_label_parse_uline (GTK_LABEL (GTK_BIN (new1)->child),
_("_New"));
gtk_widget_add_accelerator (new1, "activate_item", file1_menu_accels,
tmp_key, 0, 0);
gtk_object_set_data (GTK_OBJECT (window1), "new1", new1);
gtk_widget_show (new1);
gtk_container_add (GTK_CONTAINER (file1_menu), new1);
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How can I retrieve the text from a GtkMenuItem?</title>
<para>You can usually retrieve the label of a specific
GtkMenuItem with:</para>
<programlisting role="C">
if (GTK_BIN (menu_item)->child)
{
GtkWidget *child = GTK_BIN (menu_item)->child;
/* do stuff with child */
if (GTK_IS_LABEL (child))
{
gchar *text;
gtk_label_get (GTK_LABEL (child), &amp;text);
g_print ("menu item text: %s\n", text);
}
}
</programlisting>
<para>To get the active menu item from a GtkOptionMenu you can
do:</para>
<programlisting role="C">
if (GTK_OPTION_MENU (option_menu)->menu_item)
{
GtkWidget *menu_item = GTK_OPTION_MENU (option_menu)->menu_item;
}
</programlisting>
<para>But, there's a catch. For this specific case, you can
<emphasis>not</emphasis> get the label widget from
<literal>menu_item</literal> with the above code, because the
option menu reparents the menu_item's child temporarily to
display the currently active contents. So to retrive the child
of the currently active menu_item of an option menu, you'll
have to do:</para>
<programlisting role="C">
if (GTK_BIN (option_menu)->child)
{
GtkWidget *child = GTK_BIN (option_menu)->child;
/* do stuff with child */
}
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How do I right (or otherwise) justify a
GtkLabel?</title>
<para>Are you sure you want to <emphasis>justify</emphasis>
the labels? The label class contains the
<literal>gtk_label_set_justify()</literal> function that is
used to control the justification of a multi-line
label.</para>
<para>What you probably want is to set the <emphasis>alignment</emphasis>
of the label, ie right align it, center it or left align
it. If you want to do this, you should use:</para>
<programlisting role="C">
void gtk_misc_set_alignment (GtkMisc *misc,
gfloat xalign,
gfloat yalign);
</programlisting>
<para>where the <literal>xalign</literal> and
<literal>yalign</literal> values are floats in
[0.00;1.00].</para>
<programlisting role="C">
GtkWidget *label;
/* horizontal : left align, vertical : top */
gtk_misc_set_alignment(GTK_MISK(label), 0.0f, 0.0f);
/* horizontal : centered, vertical : centered */
gtk_misc_set_alignment(GTK_MISK(label), 0.5f, 0.5f);
/* horizontal : right align, vertical : bottom */
gtk_misc_set_alignment(GTK_MISK(label), 1.0f, 1.0f);
</programlisting>
</sect2>
<!-- ----------------------------------------------------------------- -->
<sect2>
<title>How do I set the background color of a GtkLabel
widget?</title>
<para>The Gtklabel widget is one of a few GTK+ widgets that
don't create their own window to render themselves
into. Instead, they draw themselves directly onto their
parents window.</para>
<para>This means that in order to set the background color for
a GtkLabel widget, you need to change the background color of
its parent, i.e. the object that you pack it into.</para>
</sect2>
</sect1>
</chapter>