GtkBuilder UI Definitions

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 GtkBuilder UI definitions or just UI definitions if the context is clear. Do not confuse GtkBuilder UI Definitions with GtkUIManager UI Definitions, which are more limited in scope.

<!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          	    #REQUIRED
                     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
                     last_modification_time #IMPLIED >
<!ATTLIST child      type           	    #IMPLIED
                     internal-child 	    #IMPLIED >

The toplevel element is <interface>. 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 <object> elements, which can contain <property> elements to set properties, <signal> elements which connect signals to handlers, and <child> 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 <child> element contains an <object> element which describes the child object.

Typically, the specific kind of object represented by an <object> element is specified by the "class" attribute. If the type has not been loaded yet, GTK+ tries to find the _get_type() from the class name by applying heuristics. This works in most cases, but if necessary, it is possible to specify the name of the _get_type() 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.

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.

Setting properties of objects is pretty straightforward with the <property> 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.

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 — 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.

Signal handlers are set up with the <signal> 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. A "last_modification_time" attribute is also allowed, but it does not have a meaning to the builder.

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 <child> element to a true value. Note that GtkBuilder still requires an <object> element for the internal child, even if it has already been constructed.

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 <child> The possible values for the "type" attribute are described in the sections describing the widget-specific portions of UI definitions.

<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>

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 <child> element gets parsed by the custom tag handler of the parent object, while a custom element in an <object> element gets parsed by the custom tag handler of the object.

These XML fragments are explained in the documentation of the respective objects, see GtkWidget, GtkContainer, GtkDialog, GtkCellLayout, GtkColorSelectionDialog, GtkFontSelectionDialog, GtkComboBoxEntry, GtkExpander, GtkFrame, GtkListStore, GtkTreeStore, GtkNotebook, GtkSizeGroup, GtkTreeView, GtkUIManager, GtkActionGroup.

GtkBuilder

typedef struct _GtkBuilder GtkBuilder;

GtkBuilderConnectFunc ()

void                (*GtkBuilderConnectFunc)            (GtkBuilder *builder,
                                                         GObject *object,
                                                         const gchar *signal_name,
                                                         const gchar *handler_name,
                                                         GObject *connect_object,
                                                         GConnectFlags flags,
                                                         gpointer user_data);

This is the signature of a function used to connect signals. It is used by the gtk_builder_connect_signals() and gtk_builder_connect_signals_full() methods. It is mainly intended for interpreted language bindings, but could be useful where the programmer wants more control over the signal connection process.

Since 2.12

enum GtkBuilderError

typedef enum
{
  GTK_BUILDER_ERROR_INVALID_TYPE_FUNCTION,
  GTK_BUILDER_ERROR_UNHANDLED_TAG,
  GTK_BUILDER_ERROR_MISSING_ATTRIBUTE,
  GTK_BUILDER_ERROR_INVALID_ATTRIBUTE,
  GTK_BUILDER_ERROR_INVALID_TAG,
  GTK_BUILDER_ERROR_MISSING_PROPERTY_VALUE,
  GTK_BUILDER_ERROR_INVALID_VALUE
} GtkBuilderError;

gtk_builder_new ()

GtkBuilder*         gtk_builder_new                     (void);

Creates a new builder object.

Since 2.12

gtk_builder_add_from_file ()

guint               gtk_builder_add_from_file           (GtkBuilder *builder,
                                                         const gchar *filename,
                                                         GError **error);

Parses a file containing a GtkBuilder UI definition and merges it with the current contents of builder.

Since 2.12

gtk_builder_add_from_string ()

guint               gtk_builder_add_from_string         (GtkBuilder *builder,
                                                         const gchar *buffer,
                                                         gsize length,
                                                         GError **error);

Parses a string containing a GtkBuilder UI definition and merges it with the current contents of builder.

Since 2.12

gtk_builder_get_object ()

GObject*            gtk_builder_get_object              (GtkBuilder *builder,
                                                         const gchar *name);

Gets the object named name. Note that this function does not increment the reference count of the returned object.

Since 2.12

gtk_builder_get_objects ()

GSList*             gtk_builder_get_objects             (GtkBuilder *builder);

Gets all objects that have been constructed by builder. Note that this function does not increment the reference counts of the returned objects.

Since 2.12

gtk_builder_connect_signals ()

void                gtk_builder_connect_signals         (GtkBuilder *builder,
                                                         gpointer user_data);

This method is a simpler variation of gtk_builder_connect_signals_full(). It uses GModule's introspective features (by opening the module NULL) to look at the application's symbol table. From here it tries to match the signal handler names given in the interface description with symbols in the application and connects the signals.

Note that this function will not work correctly if GModule is not supported on the platform.

Since 2.12

gtk_builder_connect_signals_full ()

void                gtk_builder_connect_signals_full    (GtkBuilder *builder,
                                                         GtkBuilderConnectFunc func,
                                                         gpointer user_data);

This function can be thought of the interpreted language binding version of gtk_builder_connect_signals(), except that it does not require GModule to function correctly.

Since 2.12

gtk_builder_set_translation_domain ()

void                gtk_builder_set_translation_domain  (GtkBuilder *builder,
                                                         const gchar *domain);

Sets the translation domain of builder. See "translation-domain".

Since 2.12

gtk_builder_get_translation_domain ()

const gchar*        gtk_builder_get_translation_domain  (GtkBuilder *builder);

Gets the translation domain of builder.

Since 2.12

gtk_builder_get_type_from_name ()

GType               gtk_builder_get_type_from_name      (GtkBuilder *builder,
                                                         const char *type_name);

Looks up a type by name, using the virtual function that GtkBuilder has for that purpose. This is mainly used when implementing the GtkBuildable interface on a type.

Since 2.12

gtk_builder_value_from_string ()

gboolean            gtk_builder_value_from_string       (GtkBuilder *builder,
                                                         GParamSpec *pspec,
                                                         const gchar *string,
                                                         GValue *value,
                                                         GError **error);

This function demarshals a value from a string. This function calls g_value_init() on the value argument, so it need not be initialised beforehand.

This function can handle char, uchar, boolean, int, uint, long, ulong, enum, flags, float, double, string, GdkColor and GtkAdjustment type values. Support for GtkWidget type values is still to come.

Since 2.12

gtk_builder_value_from_string_type ()

gboolean            gtk_builder_value_from_string_type  (GtkBuilder *builder,
                                                         GType type,
                                                         const gchar *string,
                                                         GValue *value,
                                                         GError **error);

Like gtk_builder_value_from_string(), this function demarshals a value from a string, but takes a GType instead of GParamSpec. This function calls g_value_init() on the value argument, so it need not be initialised beforehand.

Since 2.12

GTK_BUILDER_WARN_INVALID_CHILD_TYPE()

#define             GTK_BUILDER_WARN_INVALID_CHILD_TYPE(object, type)

GTK_BUILDER_ERROR

#define GTK_BUILDER_ERROR                (gtk_builder_error_quark ())

The "translation-domain" property

  "translation-domain"       gchar*                : Read / Write

The translation domain used when translating property values that have been marked as translatable in interface descriptions. If the translation domain is NULL, GtkBuilder uses gettext(), otherwise dgettext().

Default value: NULL

Since 2.12