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

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GtkBuilder

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Build an interface from an XML UI definition

<!-- ##### SECTION Long_Description ##### -->
<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. 
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. The function gtk_builder_connect_signals() 
and variants thereof can be used to connect handlers to the named signals 
in the description. 
</para>
<para>
A GtkBuilder holds a reference to all objects that it has constructed
and drops these references when it is finalized. To keep objects beyond
the lifespan of the builder, they must be fetched with gtk_builder_get_object()
and reffed with g_object_ref(). It is the responsibility of the user
to destroy all toplevel windows that have been constructed by a builder
(these are not automatically cleaned up when the builder is finalized, 
since GTK+ itself holds a reference to each toplevel window).
</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 >
<!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;.
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 can 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) 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.
</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 or nick), flags (can be specified by their name or nick, 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. GtkBuilder currently does not allow forward references
to objects &mdash; an object must be constructed before it can be used
as a property value. 
</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>
<example>
<title>A GtkBuilder UI Definition</title>
<programlisting><![CDATA[
<interface>
  <object class="GtkDialog" id="dialog1">
    <child internal-child="vbox">
      <object class="GtkVBox">
        <property name="border-width">10</property>
        <child internal-child="action_area">
          <object class="GtkHButtonBox">
            <property name="border-width">20</property>
            <child id="ok-button">
              <object class="GtkButton"/>
                <property name="label">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. 
<!-- FIXME: explain custom tags in <child> vs custom tags in  <object> --> 
These are explained in their own sections, 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>

<!-- ##### STRUCT GtkBuilderClass ##### -->
<para>

</para>

@get_type_from_name: Looks up a type by name. The default
  implementation applies heuristics to map type names to
  <function>_get_type</function> function names, e.g. 
  GtkHBox to gtk_hbox_get_type(). This virtual function
  is provided to allow language bindings to intercept the
  type resolution process.


<!-- ##### 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>