g-object, common-lisp:standard-object, common-lisp:t

None

A gtk-builder object is an auxiliary object that reads textual descriptions of a user interface and instantiates the described objects. To create a gtk-builder object from a user interface description, call the gtk-builder-new-from-file, gtk-builder-new-from-resource or gtk-builder-new-from-string functions.

In the (unusual) case that you want to add user interface descriptions from multiple sources to the same gtk-builder object you can call the gtk-builder-new function to get an empty builder and populate it by (multiple) calls to the gtk-builder-add-from-file, gtk-builder-add-from-resource or gtk-builder-add-from-string functions.

A gtk-builder object 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 the gtk-widget-destroy function to get rid of them and all the widgets they contain.

The gtk-builder-object and gtk-builder-objects functions 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 the gtk-widget-destroy function. 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 life cycle, or without a parent, in which case they have to be added to some container to make use of them.

The gtk-builder-connect-signals function and variants thereof can be used to connect handlers to the named signals in the UI description.

GtkBuilder UI Definitions

The gtk-builder implementation parses textual descriptions of user interfaces which are specified in an XML format which can be roughly described by the RELAX NG schema below. We refer to these descriptions as gtk-builder UI definitions or just UI definitions if the context is clear. Do not confuse gtk-builder UI Definitions with the deprecated gtk-ui-manager UI Definitions, which are more limited in scope. It is common to use .ui as the filename extension for files containing gtk-builder UI definitions.

 start = element interface {
   attribute domain { text } ?,
   ( requires | object | menu ) *
 }


 requires = element requires {
   attribute lib { text },
   attribute version { text }
 }


 object = element object {
   attribute id { xsd:ID },
   attribute class { text },
   attribute type-func { text } ?,
   attribute constructor { text } ?,
   (property | signal | child | ANY) *
 }


 template = element template {
   attribute class { text },
   attribute parent { text },
   (property | signal | child | ANY) *
 }


 property = element property {
   attribute name { text },
   attribute translatable { "yes" | "no" } ?,
   attribute comments { text } ?,
   attribute context { text } ?,
   text ?
 }


 signal = element signal {
   attribute name { text },
   attribute handler { text },
   attribute after { text } ?,
   attribute swapped { text } ?,
   attribute object { text } ?,
   attribute last_modification_time { text } ?,
   empty
 }


 child = element child {
   attribute type { text } ?,
   attribute internal-child { text } ?,
   (object | ANY)*
 }


 menu = element menu {
   attribute id { xsd:ID },
   attribute domain { text } ?,
   (item | submenu | section) *
 }


 item = element item {
   attribute id { xsd:ID } ?,
   (attribute_ | link) *
 }


 attribute_ = element attribute {
   attribute name { text },
   attribute type { text } ?,
   attribute translatable { "yes" | "no" } ?,
   attribute context { text } ?,
   attribute comments { text } ?,
   text ?
 }


 link = element link {
   attribute id { xsd:ID } ?,
   attribute name { text },
   item *
 }


 submenu = element submenu {
   attribute id { xsd:ID } ?,
   (attribute_ | item | submenu | section) *
 }


 section = element section {
   attribute id { xsd:ID } ?,
   (attribute_ | item | submenu | section) *
 }


 ANY = element * - (interface | requires | object | property | signal
                              | child | menu | item | attribute | link
                              | submenu | section) {
   attribute * { text } *,
   (ALL * & text ?)
 }
 ALL = element * {
   attribute * { text } *,
   (ALL * & text ?)
 }  

The toplevel element is <interface>. It optionally takes a "domain" attribute, which will make the builder look for translated strings using GNU gettext in the domain specified. This can also be done by calling the gtk-builder-translation-domain function 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. The target toolkit version(s) are described by <requires> elements, the "lib" attribute specifies the widget library in question, (currently the only supported value is "gtk+" and the "version" attribute specifies the target version in the form "<major>.<minor>". The builder will error out if the version requirements are not met.

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, the gtk-builder implementation allows to use an object that has been constructed by a gtk-ui-manager object in another part of the UI definition by specifying the ID of the gtk-ui-manager object 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 the gtk-builder-object function. An ID is also necessary to use the object as property value in other parts of the UI definition.

Note

Prior to 2.20, the gtk-builder implementation was setting the "name" property of constructed widgets to the "id" attribute. In GTK 2.20 or newer, you have to use the gtk-buildable-name function instead of the gtk-widget-name function to obtain the "id", or set the "name" property in your 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 GNU gettext 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.

The gtk-builder implementation 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 the gdk-rgba-parse function. Objects can be referred to by their name. Pixbufs can be specified as a filename of an image file to load. In general, the gtk-builder implementation allows forward references to objects - an object does not have to be 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 the g_module_symbol() function, but this can be changed by passing a custom GtkBuilderConnectFunc callback function to the gtk-builder-connect-signals-full function. 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 gtk-dialog widget. This can be achieved by setting the "internal-child" propery of the <child> element to a true value. Note that a gtk-builder object 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 versus 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.

Example: A gtk-builder UI Definition

<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.

Additionally, since 3.10 a special <template> tag has been added to the format allowing one to define a widget class's components.

Embedding other XML

Apart from the language for UI descriptions that has been explained in the previous section, the gtk-builder implementation can also parse XML fragments of GMenu markup. The resulting g-menu object and its named submenus are available via the gtk-builder-object function like other constructed objects.