GtkBuilder
Build an interface from an XML UI definition
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.
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).
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.
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The toplevel element is <interface>.
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 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.
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) 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.
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 — an object must be constructed before it can be used
as a property value.
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.
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 GtkBuilder UI Definition
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Beyond this general structure, several object classes define
their own XML DTD fragments for filling in the ANY placeholders
in the DTD above.
These are explained in their own sections, see
GtkWidget,
GtkContainer,
GtkDialog,
GtkCellLayout,
GtkColorSelectionDialog,
GtkFontSelectionDialog,
GtkComboBoxEntry,
GtkExpander,
GtkFrame,
GtkListStore,
GtkTreeStore,
GtkNotebook,
GtkSizeGroup,
GtkTreeView,
GtkUIManager,
GtkActionGroup.
@get_type_from_name: Looks up a type by name. The default
implementation applies heuristics to map type names to
_get_type 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.
@builder:
@object:
@signal_name:
@handler_name:
@connect_object:
@flags:
@user_data:
@Returns:
@builder:
@filename:
@error:
@Returns:
@builder:
@buffer:
@length:
@error:
@Returns:
@builder:
@name:
@Returns:
@builder:
@Returns:
@builder:
@user_data:
@builder:
@func:
@user_data:
@builder:
@domain:
@builder:
@Returns:
@builder:
@type_name:
@Returns:
@builder:
@pspec:
@string:
@value:
@error:
@Returns:
@builder:
@type:
@string:
@value:
@error:
@Returns:
@object:
@type: