Gtk.Builder – gtk4 Reference Manual

Builder

Object Hierarchy:

Description:

[ CCode ( type_id = "gtk_builder_get_type ()" ) ]
public class Builder : Object

A `GtkBuilder` reads XML descriptions of a user interface and instantiates the described objects.

To create a `GtkBuilder` from a user interface description, call [[email protected]_from_file], [[email protected]_from_resource] or [[email protected]_from_string].

In the (unusual) case that you want to add user interface descriptions from multiple sources to the same `GtkBuilder` you can call [ [email protected]] to get an empty builder and populate it by (multiple) calls to [[email protected]_from_file], [ [email protected]_from_resource] or [[email protected]_from_string].

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 [[email protected]] to get rid of them and all the widgets they contain.

The functions [[email protected]_object] and [[email protected]_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 [[email protected]]. 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 @ref to keep them beyond the lifespan of the builder.

GtkBuilder UI Definitions

`GtkBuilder` parses textual descriptions of user interfaces which are specified in XML format. We refer to these descriptions as “GtkBuilder UI definitions” or just “UI definitions” if the context is clear.

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 [[email protected]_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.

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>`”. `GtkBuilder` 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()` 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 `get_type()` function explicitly with the "type-func" attribute.

Objects may be given a name with the “id” attribute, which allows the application to retrieve them from the builder with [ [email protected]_object]. An id is also necessary to use the object as property value in other parts of the UI definition. GTK reserves ids starting and ending with `___` (three consecutive underscores) for its own purposes.

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_INPUT_HINT_EMOJI|GTK_INPUT_HINT_LOWERCASE”) and colors (in a format understood by [[email protected]]).

`GVariant`s can be specified in the format understood by parse, and pixbufs can be specified as a filename of an image file to load.

Objects can be referred to by their name and by default refer to objects declared in the local XML fragment and objects exposed via [ [email protected]_object]. In general, `GtkBuilder` allows forward references to objects — declared in the local XML; an object doesn’t 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.

It is also possible to bind a property value to another object's property value using the attributes "bind-source" to specify the source object of the binding, and optionally, "bind-property" and "bind-flags" to specify the source property and source binding flags respectively. Internally, `GtkBuilder` implements this using `GBinding` objects. For more information see g_object_bind_property.

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 content area of a `GtkDialog`). This can be achieved by setting the “internal-child” property 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.

Signal handlers and function pointers

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. The remaining attributes, “after”, “swapped” and “object”, have the same meaning as the corresponding parameters of the connect_object or connect_data functions. A “last_modification_time” attribute is also allowed, but it does not have a meaning to the builder.

If you rely on `GModule` support to lookup callbacks in the symbol table, the following details should be noted:

When compiling applications for Windows, you must declare signal callbacks with g_module_export, or they will not be put in the symbol table. On Linux and Unix, this is not necessary; applications should instead be compiled with the -Wl,--export-dynamic `CFLAGS`, and linked against `gmodule-export-2.0`.

A GtkBuilder UI Definition

```xml <interface> <object class="GtkDialog" id="dialog1"> <child internal-child="content_area"> <object class="GtkBox" id="vbox1"> <child internal-child="action_area"> <object class="GtkBox" id="hbuttonbox1"> <child> <object class="GtkButton" id="ok_button"> <property name="label" translatable="yes">_Ok</property> <property name="use-underline">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.

A `<template>` tag can be used to define a widget class’s components. See the [GtkWidget documentation]( class.Widget.html#building-composite-widgets-from-template-xml) for details.

Namespace: Gtk

Package: gtk4

Content:

Properties:

public Object current_object { get; set; }
The object the builder is evaluating for.
public BuilderScope scope { get; set construct; }
The scope the builder is operating in
public string translation_domain { get; set; }
The translation domain used when translating property values that have been marked as translatable.

Creation methods:

public Builder ()
Creates a new empty builder object.
public Builder.from_file (string filename)
Parses the UI definition in the file filename.
public Builder.from_resource (string resource_path)
Parses the UI definition at resource_path.
public Builder.from_string (string str, ssize_t length)
Parses the UI definition in string.

Methods:

public bool add_from_file (string filename) throws Error
Parses a file containing a UI definition and merges it with the current contents of this.
public bool add_from_resource (string resource_path) throws Error
Parses a resource file containing a UI definition and merges it with the current contents of this.
public bool add_from_string (string buffer, ssize_t length) throws Error
Parses a string containing a UI definition and merges it with the current contents of this.
public bool add_objects_from_file (string filename, string[] object_ids) throws Error
Parses a file containing a UI definition building only the requested objects and merges them with the current contents of this.
public bool add_objects_from_resource (string resource_path, string[] object_ids) throws Error
Parses a resource file containing a UI definition, building only the requested objects and merges them with the current contents of this.
public bool add_objects_from_string (string buffer, ssize_t length, string[] object_ids) throws Error
Parses a string containing a UI definition, building only the requested objects and merges them with the current contents of this.
public Closure? create_closure (string function_name, BuilderClosureFlags flags, Object? object) throws Error
Creates a closure to invoke the function called function_name.
public void expose_object (string name, Object object)
Add object to the this object pool so it can be referenced just like any other object built by builder.
public bool extend_with_template (Object object, Type template_type, string buffer, ssize_t length) throws Error
Main private entry point for building composite components from template XML.
public unowned Object? get_current_object ()
Gets the current object set via set_current_object.
public unowned Object? get_object (string name)
Gets the object named name.
public SList<unowned Object> get_objects ()
Gets all objects that have been constructed by this.
public unowned BuilderScope get_scope ()
Gets the scope in use that was set via set_scope.
public unowned string? get_translation_domain ()
Gets the translation domain of this.
public Type get_type_from_name (string type_name)
Looks up a type by name.
public void set_current_object (Object? current_object)
Sets the current object for the this .
public void set_scope (BuilderScope? scope)
Sets the scope the builder should operate in.
public void set_translation_domain (string? domain)
Sets the translation domain of this.
public bool value_from_string (ParamSpec pspec, string str, out Value value) throws Error
Demarshals a value from a string.
public bool value_from_string_type (Type type, string str, out Value value) throws Error
Demarshals a value from a string.

Inherited Members:

All known members inherited from class GLib.Object

@get
@new
@ref
@set
add_toggle_ref
add_weak_pointer
bind_property
connect
constructed
disconnect
dispose
dup_data
dup_qdata
force_floating
freeze_notify
get_class
get_data

get_property
get_qdata
get_type
getv
interface_find_property
interface_install_property
interface_list_properties
is_floating
new_valist
new_with_properties
newv
notify
notify_property
ref_count
ref_sink
remove_toggle_ref
remove_weak_pointer

replace_data
replace_qdata
set_data
set_data_full
set_property
set_qdata
set_qdata_full
set_valist
setv
steal_data
steal_qdata
thaw_notify
unref
watch_closure
weak_ref
weak_unref

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