Gtk.Builder¶

Subclasses:: None

Methods¶

Inherited:: GObject.Object (37)
Structs:: GObject.ObjectClass (5)

class	`new` ()
class	`new_from_file` (filename)
class	`new_from_resource` (resource_path)
class	`new_from_string` (string, length)
	`add_from_file` (filename)
	`add_from_resource` (resource_path)
	`add_from_string` (buffer)
	`add_objects_from_file` (filename, object_ids)
	`add_objects_from_resource` (resource_path, object_ids)
	`add_objects_from_string` (buffer, object_ids)
	`create_closure` (function_name, flags, object)
	`expose_object` (name, object)
	`extend_with_template` (object, template_type, buffer, length)
	`get_current_object` ()
	`get_object` (name)
	`get_objects` ()
	`get_scope` ()
	`get_translation_domain` ()
	`get_type_from_name` (type_name)
	`set_current_object` (current_object)
	`set_scope` (scope)
	`set_translation_domain` (domain)
	`value_from_string` (pspec, string)
	`value_from_string_type` (type, string)

Virtual Methods¶

Inherited:: GObject.Object (7)

Properties¶

Name	Type	Flags
`current-object`	`GObject.Object`	r/w
`scope`	`Gtk.BuilderScope`	r/w/c
`translation-domain`	`str`	r/w

Signals¶

Inherited:: GObject.Object (1)

Fields¶

Inherited:: GObject.Object (1)

Class Details¶

class Gtk.Builder(**kwargs)¶

Bases:: GObject.Object
Abstract:: No
Structure:: Gtk.BuilderClass

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

To create a GtkBuilder from a user interface description, call [ctor`Gtk`.Builder.new_from_file], [ctor`Gtk`.Builder.new_from_resource] or [ctor`Gtk`.Builder.new_from_string].

In the (unusual) case that you want to add user interface descriptions from multiple sources to the same GtkBuilder you can call [ctor`Gtk`.Builder.new] to get an empty builder and populate it by (multiple) calls to [method`Gtk`.Builder.add_from_file], [method`Gtk`.Builder.add_from_resource] or [method`Gtk`.Builder.add_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 [method`Gtk`.Window.destroy] to get rid of them and all the widgets they contain.

The functions [method`Gtk`.Builder.get_object] and [method`Gtk`.Builder.get_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 [method`Gtk`.Window.destroy]. 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 GObject.Object.ref() to keep them beyond the lifespan of the builder.

Gtk.Builder UI Definitions

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

### Structure of UI definitions

UI definition files are always encoded in UTF-8.

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 [method`Gtk`.Builder.set_translation_domain] on the builder. For example:

``xml <?xml version=”1.0” encoding=”UTF-8”> <interface domain=”your-app”>

…

</interface> ``

### Requirements

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. For example:

``xml <?xml version=”1.0” encoding=”UTF-8”> <interface domain=”your-app”>

<requires lib=”gtk” version=”4.0” />

</interface> ``

### Objects

Objects are defined as children of the <interface> element.

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() 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. If your UI definition is referencing internal types, you should make sure to call g_type_ensure() for each object type before parsing the UI definition.

Objects may be given a name with the “id” attribute, which allows the application to retrieve them from the builder with [method`Gtk`.Builder.get_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.

### Properties

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:

``xml <object class=”GtkButton”>

<property name=”label”>Hello, world</property>

</object> ``

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:

``xml <object class=”GtkButton”>

<property name=”label” translatable=”yes” context=”button”>Hello, world</property>

</object> ``

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 values, strings like “False”, “f”, “no”, “n”, “0” are interpreted as false values)
enumeration types (can be specified by their full C identifier their short name used when registering the enumeration type, or their integer value)
flag types (can be specified by their C identifier, short name, integer value, and optionally combined with “|” for bitwise OR, e.g. “Gtk.InputHints.EMOJI|:obj:Gtk.InputHints.LOWERCASE”, or “emoji|lowercase”)
colors (in a format understood by [method`Gdk`.RGBA.parse])
GVariant (can be specified in the format understood by [func`GLib`.Variant.parse])
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 [method`Gtk`.Builder.expose_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.

### Property bindings

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 [class`GObject`.Binding] objects.

For instance, in the example below the “label” property of the bottom_label widget is bound to the “label” property of the top_button widget:

``xml <object class=”GtkBox”>

<property name=”orientation”>vertical</property> <child>

<object class=”GtkButton” id=”top_button”>
<property name=”label”>Hello, world</property>

</object>

</child> <child>

<object class=”GtkLabel” id=”bottom_label”>

<property name=”label”
bind-source=”top_button” bind-property=”label” bind-flags=”sync-create” />

</object>

</child>

</object> ``

For more information, see the documentation of the [method`GObject`.Object.bind_property] method.

### Internal children

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.

### Specialized children

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.

``xml <object class=”GtkButton” id=”hello_button”>

<signal name=”clicked” handler=”hello_button__clicked” />

</object> ``

The remaining attributes, “after”, “swapped” and “object”, have the same meaning as the corresponding parameters of the [func`GObject`.signal_connect_object] or [func`GObject`.signal_connect_data] functions:

“after” matches the G_CONNECT_AFTER flag, and will ensure that the handler is called after the default class closure for the signal
“swapped” matches the G_CONNECT_SWAPPED flag, and will swap the instance and closure arguments when invoking the signal handler
“object” will bind the signal handler to the lifetime of the object referenced by the attribute

By default “swapped” will be set to “yes” if not specified otherwise, in the case where “object” is set, for convenience. A “last_modification_time” attribute is also allowed, but it does not have a meaning to the builder.

When compiling applications for Windows, you must declare signal callbacks with the G_MODULE_EXPORT decorator, or they will not be put in the symbol table:

``c G_MODULE_EXPORT void hello_button__clicked (GtkButton *button,

gpointer data)

{: // …

}¶

On Linux and Unix, this is not necessary; applications should instead be compiled with the -Wl,--export-dynamic argument inside their compiler flags, and linked against gmodule-export-2.0.

Example UI Definition

``xml <interface>

<object class=”GtkDialog” id=”dialog1”>

<child internal-child=”content_area”>

<object class=”GtkBox”>

<child internal-child=”action_area”>

<object class=”GtkBox”>

<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> ``

Using Gtk.Buildable for extending UI definitions

Objects can implement the [iface`Gtk`.Buildable] interface to add custom elements and attributes to the XML. Typically, any extension will be documented in each type that implements the interface.

Templates

When describing a [class`Gtk`.Widget], you can use the <template> tag to describe a UI bound to a specific widget type. GTK will automatically load the UI definition when instantiating the type, and bind children and signal handlers to instance fields and function symbols.

For more information, see the GtkWidget documentation for details.

classmethod new()[source]¶

Returns:: a new (empty) GtkBuilder object
Return type:: Gtk.Builder

Creates a new empty builder object.

This function is only useful if you intend to make multiple calls to [method`Gtk`.Builder.add_from_file], [method`Gtk`.Builder.add_from_resource] or [method`Gtk`.Builder.add_from_string] in order to merge multiple UI descriptions into a single builder.

classmethod new_from_file(filename)[source]¶

Parameters:: filename (str) – filename of user interface description file
Returns:: a GtkBuilder containing the described interface
Return type:: Gtk.Builder

Parses the UI definition in the file filename.

If there is an error opening the file or parsing the description then the program will be aborted. You should only ever attempt to parse user interface descriptions that are shipped as part of your program.

classmethod new_from_resource(resource_path)[source]¶

Parameters:: resource_path (str) – a GResource resource path
Returns:: a GtkBuilder containing the described interface
Return type:: Gtk.Builder

Parses the UI definition at resource_path.

If there is an error locating the resource or parsing the description, then the program will be aborted.

classmethod new_from_string(string, length)[source]¶

Parameters:

string (str) – a user interface (XML) description
length (int) – the length of string, or -1

Returns:

a GtkBuilder containing the interface described by string

Return type:

Gtk.Builder

Parses the UI definition in string.

If string is None-terminated, then length should be -1. If length is not -1, then it is the length of string.

If there is an error parsing string then the program will be aborted. You should not attempt to parse user interface description from untrusted sources.

add_from_file(filename)[source]¶

Parameters:: filename (str) – the name of the file to parse
Raises:: GLib.Error
Returns:: True on success, False if an error occurred
Return type:: bool

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

This function is useful if you need to call [method`Gtk`.Builder.set_current_object]) to add user data to callbacks before loading Gtk.Builder UI. Otherwise, you probably want [ctor`Gtk`.Builder.new_from_file] instead.

If an error occurs, 0 will be returned and error will be assigned a GError from the GTK_BUILDER_ERROR, G_MARKUP_ERROR or G_FILE_ERROR domains.

It’s not really reasonable to attempt to handle failures of this call. You should not use this function with untrusted files (ie: files that are not part of your application). Broken GtkBuilder files can easily crash your program, and it’s possible that memory was leaked leading up to the reported failure. The only reasonable thing to do when an error is detected is to call g_error().

add_from_resource(resource_path)[source]¶

Parameters:: resource_path (str) – the path of the resource file to parse
Raises:: GLib.Error
Returns:: True on success, False if an error occurred
Return type:: bool

Parses a resource file containing a UI definition and merges it with the current contents of self.

This function is useful if you need to call [method`Gtk`.Builder.set_current_object] to add user data to callbacks before loading Gtk.Builder UI. Otherwise, you probably want [ctor`Gtk`.Builder.new_from_resource] instead.

If an error occurs, 0 will be returned and error will be assigned a GError from the %GTK_BUILDER_ERROR, %G_MARKUP_ERROR or %G_RESOURCE_ERROR domain.

It’s not really reasonable to attempt to handle failures of this call. The only reasonable thing to do when an error is detected is to call g_error().

add_from_string(buffer)[source]¶

Parameters:

buffer (str) – the string to parse
length (int) – the length of buffer (may be -1 if buffer is nul-terminated)

Raises:

GLib.Error

Returns:

True on success, False if an error occurred

Return type:

bool

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

This function is useful if you need to call [method`Gtk`.Builder.set_current_object] to add user data to callbacks before loading GtkBuilder UI. Otherwise, you probably want [ctor`Gtk`.Builder.new_from_string] instead.

Upon errors False will be returned and error will be assigned a GError from the %GTK_BUILDER_ERROR, %G_MARKUP_ERROR or %G_VARIANT_PARSE_ERROR domain.

It’s not really reasonable to attempt to handle failures of this call. The only reasonable thing to do when an error is detected is to call g_error().

add_objects_from_file(filename, object_ids)[source]¶

Parameters:

filename (str) – the name of the file to parse
object_ids ([str]) – nul-terminated array of objects to build

Raises:

GLib.Error

Returns:

True on success, False if an error occurred

Return type:

bool

Parses a file containing a UI definition building only the requested objects and merges them with the current contents of self.

Upon errors, 0 will be returned and error will be assigned a GError from the %GTK_BUILDER_ERROR, %G_MARKUP_ERROR or %G_FILE_ERROR domain.

If you are adding an object that depends on an object that is not its child (for instance a GtkTreeView that depends on its GtkTreeModel), you have to explicitly list all of them in object_ids.

add_objects_from_resource(resource_path, object_ids)[source]¶

Parameters:

resource_path (str) – the path of the resource file to parse
object_ids ([str]) – nul-terminated array of objects to build

Raises:

GLib.Error

Returns:

True on success, False if an error occurred

Return type:

bool

Parses a resource file containing a UI definition, building only the requested objects and merges them with the current contents of self.

Upon errors, 0 will be returned and error will be assigned a GError from the %GTK_BUILDER_ERROR, %G_MARKUP_ERROR or %G_RESOURCE_ERROR domain.

If you are adding an object that depends on an object that is not its child (for instance a GtkTreeView that depends on its GtkTreeModel), you have to explicitly list all of them in object_ids.

add_objects_from_string(buffer, object_ids)[source]¶

Parameters:

buffer (str) – the string to parse
object_ids ([str]) – array of objects to build

Raises:

GLib.Error

Returns:

A positive value on success, 0 if an error occurred

Return type:

int

Parses a string containing a UI definition, building only the requested objects and merges them with the current contents of self.

Upon errors False will be returned and error will be assigned a GError from the %GTK_BUILDER_ERROR or %G_MARKUP_ERROR domain.

If you are adding an object that depends on an object that is not its child (for instance a GtkTreeView that depends on its GtkTreeModel), you have to explicitly list all of them in object_ids.

create_closure(function_name, flags, object)[source]¶

Parameters:

function_name (str) – name of the function to look up
flags (Gtk.BuilderClosureFlags) – closure creation flags
object (GObject.Object or None) – Object to create the closure with

Raises:

GLib.Error

Returns:

A new closure for invoking function_name

Return type:

GObject.Closure or None

Creates a closure to invoke the function called function_name.

This is using the create_closure() implementation of self's [iface`Gtk`.BuilderScope].

If no closure could be created, None will be returned and error will be set.

expose_object(name, object)[source]¶

Parameters:

name (str) – the name of the object exposed to the builder
object (GObject.Object) – the object to expose

Add object to the self object pool so it can be referenced just like any other object built by builder.

Only a single object may be added using name. However, it is not an error to expose the same object under multiple names. gtk_builder_get_object() may be used to determine if an object has already been added with name.

extend_with_template(object, template_type, buffer, length)[source]¶

Parameters:

object (GObject.Object) – the object that is being extended
template_type (GObject.GType) – the type that the template is for
buffer (str) – the string to parse
length (int) – the length of buffer (may be -1 if buffer is nul-terminated)

Raises:

GLib.Error

Returns:

A positive value on success, 0 if an error occurred

Return type:

bool

Main private entry point for building composite components from template XML.

Most likely you do not need to call this function in applications as templates are handled by GtkWidget.

get_current_object()[source]¶

Returns:: the current object
Return type:: GObject.Object or None

Gets the current object set via Gtk.Builder.set_current_object().

get_object(name)[source]¶

Parameters:: name (str) – name of object to get
Returns:: the object named name
Return type:: GObject.Object or None

Gets the object named name.

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

get_objects()[source]¶

Returns:: a newly-allocated GSList containing all the objects constructed by the GtkBuilder instance. It should be freed by g_slist_free()
Return type:: [GObject.Object]

Gets all objects that have been constructed by self.

Note that this function does not increment the reference counts of the returned objects.

get_scope()[source]¶

Returns:: the current scope
Return type:: Gtk.BuilderScope

Gets the scope in use that was set via Gtk.Builder.set_scope().

get_translation_domain()[source]¶

Returns:: the translation domain
Return type:: str or None

Gets the translation domain of self.

get_type_from_name(type_name)[source]¶

Parameters:: type_name (str) – type name to lookup
Returns:: the GType found for type_name or GObject.TYPE_INVALID if no type was found
Return type:: GObject.GType

Looks up a type by name.

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

set_current_object(current_object)[source]¶

Parameters:: current_object (GObject.Object or None) – the new current object

Sets the current object for the self.

The current object can be thought of as the this object that the builder is working for and will often be used as the default object when an object is optional.

[method`Gtk`.Widget.init_template] for example will set the current object to the widget the template is inited for. For functions like [ctor`Gtk`.Builder.new_from_resource], the current object will be None.

set_scope(scope)[source]¶

Parameters:: scope (Gtk.BuilderScope or None) – the scope to use

Sets the scope the builder should operate in.

If scope is None, a new [class`Gtk`.BuilderCScope] will be created.

set_translation_domain(domain)[source]¶

Parameters:: domain (str or None) – the translation domain

Sets the translation domain of self.

value_from_string(pspec, string)[source]¶

Parameters:

pspec (GObject.ParamSpec) – the GParamSpec for the property
string (str) – the string representation of the value

Raises:

GLib.Error

Returns:

True on success

value:: the GValue to store the result in

Return type:

(bool, value: GObject.Value)

Demarshals a value from a string.

This function calls GObject.Value.init() on the value argument, so it need not be initialised beforehand.

Can handle str, uchar, boolean, int, uint, long, ulong, enum, flags, float, double, string, GdkRGBA and GtkAdjustment type values.

Upon errors False will be returned and error will be assigned a GError from the %GTK_BUILDER_ERROR domain.

value_from_string_type(type, string)[source]¶

Parameters:

type (GObject.GType) – the GType of the value
string (str) – the string representation of the value

Raises:

GLib.Error

Returns:

True on success

value:: the GValue to store the result in

Return type:

(bool, value: GObject.Value)

Demarshals a value from a string.

Unlike [method`Gtk`.Builder.value_from_string], this function takes a GType instead of GParamSpec.

Calls GObject.Value.init() on the value argument, so it need not be initialised beforehand.

Upon errors False will be returned and error will be assigned a GError from the %GTK_BUILDER_ERROR domain.

Property Details¶

Gtk.Builder.props.current_object¶

Name:: current-object
Type:: GObject.Object
Default Value:: None
Flags:: READABLE, WRITABLE

The object the builder is evaluating for.

Gtk.Builder.props.scope¶

Name:: scope
Type:: Gtk.BuilderScope
Default Value:: None
Flags:: READABLE, WRITABLE, CONSTRUCT

The scope the builder is operating in

Gtk.Builder.props.translation_domain¶

Name:: translation-domain
Type:: str
Default Value:: None
Flags:: READABLE, WRITABLE

The translation domain used when translating property values that have been marked as translatable.

If the translation domain is None, GtkBuilder uses gettext(), otherwise GLib.dgettext().