gtk2/docs/reference/gtk/tmpl/gtkbuilder.sgml

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GtkBuilder

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Build an interface from an XML UI definition

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<para>
A GtkBuilder is an auxiliary object that reads textual descriptions
of a user interface and instantiates the described objects. To pass a 
description to a GtkBuilder, call gtk_builder_add_from_file() or 
gtk_builder_add_from_string(). These functions can be called multiple
times; the builder merges the content of all descriptions. 
</para>
<para>
A GtkBuilder holds a reference to all objects that it has constructed
and drops these references when it is finalized. This finalization can 
cause the destruction of non-widget objects or widgets which are not 
contained in a toplevel window. For toplevel windows constructed by a 
builder, it is the responsibility of the user to call gtk_widget_destroy() 
to get rid of them and all the widgets they contain.
</para>
<para>
The functions gtk_builder_get_object() and gtk_builder_get_objects()
can be used to access the widgets in the interface by the names assigned 
to them inside the UI description. Toplevel windows returned by these
functions will stay around until the user explicitly destroys them
with gtk_widget_destroy(). Other widgets will either be part of a 
larger hierarchy constructed by the builder (in which case you should
not have to worry about their lifecycle), or without a parent, in which 
case they have to be added to some container to make use of them.  
Non-widget objects need to be reffed with g_object_ref() to keep them
beyond the lifespan of the builder.
</para>
<para>
The function gtk_builder_connect_signals() and variants thereof can be 
used to connect handlers to the named signals in the description. 
</para>

<refsect2 id="BUILDER-UI"><title>GtkBuilder UI Definitions</title>
<para>
GtkBuilder parses textual descriptions of user interfaces which 
are specified in an XML format which can be roughly described 
by the DTD below. We refer to these descriptions as 
<firstterm>GtkBuilder UI definitions</firstterm> or just
<firstterm>UI definitions</firstterm> if the context is clear.
Do not confuse GtkBuilder UI Definitions with 
<link linkend="XML-UI">GtkUIManager UI Definitions</link>, 
which are more limited in scope. 
</para>
<para>
<programlisting><![CDATA[
<!ELEMENT interface object* >
<!ELEMENT object    (property|signal|child|ANY)* >
<!ELEMENT property  PCDATA >
<!ELEMENT signal    EMPTY >
<!ELEMENT child     (object|ANY*) >

<!ATTLIST interface  domain         #IMPLIED >
<!ATTLIST object     id             #REQUIRED
                     class          #IMPLIED
                     type-func      #IMPLIED
                     constructor    #IMPLIED >
<!ATTLIST property   name           #REQUIRED
                     translatable   #IMPLIED 
                     comments       #IMPLIED
                     context        #IMPLIED >
<!ATTLIST signal     name           #REQUIRED
                     handler        #REQUIRED
                     after          #IMPLIED
                     swapped        #IMPLIED
                     object         #IMPLIED >
<!ATTLIST child      type           #IMPLIED
                     internal-child #IMPLIED >
]]></programlisting>
</para>
<para>
The toplevel element is &lt;interface&gt;.
It optionally takes a "domain" attribute, which will make
the builder look for translated strings using dgettext() in the
domain specified. This can also be done by calling
gtk_builder_set_translation_domain() on the builder.
Objects are described by &lt;object&gt; elements, which can
contain &lt;property&gt; elements to set properties, &lt;signal&gt;
elements which connect signals to handlers, and &lt;child&gt;
elements, which describe child objects (most often widgets
inside a container, but also e.g. actions in an action group,
or columns in a tree model). A &lt;child&gt; element contains
an &lt;object&gt; element which describes the child object.
</para>
<para>
Typically, the specific kind of object represented by an
&lt;object&gt; element is specified by the "class" attribute.
If the type has not been loaded yet, GTK+ tries to find the
<function>_get_type()</function> from the class name by applying 
heuristics. This works in most cases, but if necessary, it is
possible to specify the name of the <function>_get_type()</function> 
explictly with the "type-func" attribute. As a special case, 
GtkBuilder allows to use an object that has been constructed
by a #GtkUIManager in another part of the UI definition by
specifying the id of the #GtkUIManager in the "constructor"
attribute and the name of the object in the "id" attribute.
</para>
<para>
Objects must be given a name with the "id" attribute, which 
allows the application to retrieve them from the builder with 
gtk_builder_get_object(). An id is also necessary to use the 
object as property value in other parts of the UI definition.
</para>
<para>
Setting properties of objects is pretty straightforward with
the &lt;property&gt; element: the "name" attribute specifies
the name of the property, and the content of the element 
specifies the value. If the "translatable" attribute is 
set to a true value, GTK+ uses gettext() (or dgettext() if
the builder has a translation domain set) to find a translation 
for the value. This happens before the value is parsed, so
it can be used for properties of any type, but it is probably
most useful for string properties. It is also possible to
specify a context to disambiguate short strings, and comments
which may help the translators.
</para>
<para>
GtkBuilder can parse textual representations for the most
common property types: characters, strings, integers, floating-point
numbers, booleans (strings like "TRUE", "t", "yes", "y", "1" are
interpreted as %TRUE, strings like "FALSE, "f", "no", "n", "0" are
interpreted as %FALSE), enumerations (can be specified by their 
name, nick or integer value), flags (can be specified by their name, 
nick, integer value, optionally combined with "|", e.g. 
"GTK_VISIBLE|GTK_REALIZED")  and colors (in a format understood by 
gdk_color_parse()). Objects can be referred to by their name. 
Pixbufs can be specified as a filename of an image file to load.
In general, GtkBuilder allows forward references to objects &mdash; 
an object doesn't have to constructed before it can be referred to.
The exception to this rule is that an object has to be constructed
before it can be used as the value of a construct-only property. 
</para>
<para>
Signal handlers are set up with the &lt;signal&gt; element.
The "name" attribute specifies the name of the signal, and the
"handler" attribute specifies the function to connect to the signal.
By default, GTK+ tries to find the handler using g_module_symbol(),
but this can be changed by passing a custom #GtkBuilderConnectFunc
to gtk_builder_connect_signals_full(). The remaining attributes,
"after", "swapped" and "object", have the same meaning as the 
corresponding parameters of the g_signal_connect_object() or
g_signal_connect_data() functions.
</para>
<para>
Sometimes it is necessary to refer to widgets which have implicitly
been constructed by GTK+ as part of a composite widget, to set 
properties on them or to add further children (e.g. the @vbox 
of a #GtkDialog). This can be achieved by setting the "internal-child"
propery of the &lt;child&gt; element to a true value. Note that
GtkBuilder still requires an &lt;object&gt; element for the internal
child, even if it has already been constructed.
</para>
<para>
A number of widgets have different places where a child can be 
added (e.g. tabs vs. page content in notebooks). This can be reflected
in a UI definition by specifying the "type" attribute on a &lt;child&gt;
The possible values for the "type" attribute are described in 
the sections describing the widget-specific portions of UI definitions.
</para>
<example>
<title>A GtkBuilder UI Definition</title>
<programlisting><![CDATA[
<interface>
  <object class="GtkDialog" id="dialog1">
    <child internal-child="vbox">
      <object class="GtkVBox" id="vbox1">
        <property name="border-width">10</property>
        <child internal-child="action_area">
          <object class="GtkHButtonBox" id="hbuttonbox1">
            <property name="border-width">20</property>
            <child>
              <object class="GtkButton" id="ok_button">
                <property name="label">gtk-ok</property>
                <property name="use-stock">TRUE</property>
                <signal name="clicked" handler="ok_button_clicked"/>
              </object>
            </child>
          </object>
        </child>
      </object>
    </child>
  </object>
</interface>
]]></programlisting>
</example>
<para>
Beyond this general structure, several object classes define
their own XML DTD fragments for filling in the ANY placeholders
in the DTD above. Note that a custom element in a &lt;child&gt;
element gets parsed by the custom tag handler of the parent
object, while a custom element in an &lt;object&gt; element
gets parsed by the custom tag handler of the object. 
</para>
<para>
These XML fragments are explained in the documentation of the
respective objects, see 
<link linkend="GtkWidget-BUILDER-UI">GtkWidget</link>,
<link linkend="GtkContainer-BUILDER-UI">GtkContainer</link>,
<link linkend="GtkDialog-BUILDER-UI">GtkDialog</link>,
<link linkend="GtkCellLayout-BUILDER-UI">GtkCellLayout</link>,
<link linkend="GtkColorSelectionDialog-BUILDER-UI">GtkColorSelectionDialog</link>,
<link linkend="GtkFontSelectionDialog-BUILDER-UI">GtkFontSelectionDialog</link>,
<link linkend="GtkComboBoxEntry-BUILDER-UI">GtkComboBoxEntry</link>,
<link linkend="GtkExpander-BUILDER-UI">GtkExpander</link>,
<link linkend="GtkFrame-BUILDER-UI">GtkFrame</link>,
<link linkend="GtkListStore-BUILDER-UI">GtkListStore</link>,
<link linkend="GtkTreeStore-BUILDER-UI">GtkTreeStore</link>,
<link linkend="GtkNotebook-BUILDER-UI">GtkNotebook</link>,
<link linkend="GtkSizeGroup-BUILDER-UI">GtkSizeGroup</link>,
<link linkend="GtkTreeView-BUILDER-UI">GtkTreeView</link>,
<link linkend="GtkUIManager-BUILDER-UI">GtkUIManager</link>,
<link linkend="GtkActionGroup-BUILDER-UI">GtkActionGroup</link>.
</para>
</refsect2>

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<!-- ##### SECTION Stability_Level ##### -->


<!-- ##### STRUCT GtkBuilder ##### -->
<para>

</para>


<!-- ##### ARG GtkBuilder:translation-domain ##### -->
<para>

</para>

<!-- ##### USER_FUNCTION GtkBuilderConnectFunc ##### -->
<para>

</para>

@builder: 
@object: 
@signal_name: 
@handler_name: 
@connect_object: 
@flags: 
@user_data: 


<!-- ##### FUNCTION gtk_builder_new ##### -->
<para>

</para>

@Returns: 


<!-- ##### FUNCTION gtk_builder_add_from_file ##### -->
<para>

</para>

@builder: 
@filename: 
@error: 
@Returns: 


<!-- ##### FUNCTION gtk_builder_add_from_string ##### -->
<para>

</para>

@builder: 
@buffer: 
@length: 
@error: 
@Returns: 


<!-- ##### FUNCTION gtk_builder_get_object ##### -->
<para>

</para>

@builder: 
@name: 
@Returns: 


<!-- ##### FUNCTION gtk_builder_get_objects ##### -->
<para>

</para>

@builder: 
@Returns: 


<!-- ##### FUNCTION gtk_builder_connect_signals ##### -->
<para>

</para>

@builder: 
@user_data: 


<!-- ##### FUNCTION gtk_builder_connect_signals_full ##### -->
<para>

</para>

@builder: 
@func: 
@user_data: 


<!-- ##### FUNCTION gtk_builder_set_translation_domain ##### -->
<para>

</para>

@builder: 
@domain: 


<!-- ##### FUNCTION gtk_builder_get_translation_domain ##### -->
<para>

</para>

@builder: 
@Returns: 


<!-- ##### FUNCTION gtk_builder_get_type_from_name ##### -->
<para>

</para>

@builder: 
@type_name: 
@Returns: 


<!-- ##### FUNCTION gtk_builder_value_from_string ##### -->
<para>

</para>

@builder: 
@pspec: 
@string: 
@value: 
@error: 
@Returns: 


<!-- ##### FUNCTION gtk_builder_value_from_string_type ##### -->
<para>

</para>

@builder: 
@type: 
@string: 
@value: 
@error: 
@Returns: 


<!-- ##### MACRO GTK_BUILDER_WARN_INVALID_CHILD_TYPE ##### -->
<para>

</para>

@object: 
@type: 


<!-- ##### MACRO GTK_BUILDER_ERROR ##### -->
<para>

</para>