<book>
<bookinfo>
- <date>June 26th 2000</date>
+ <date>June 28th 2000</date>
<title>GTK+ FAQ</title>
<authorgroup>
<author>
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, "<MyApp>/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), &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>
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