Struct gtk4::Builder[][src]

pub struct Builder(_);
Expand description

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

To create a Builder from a user interface description, call from_file(), from_resource() or from_string().

In the (unusual) case that you want to add user interface descriptions from multiple sources to the same Builder you can call new() to get an empty builder and populate it by (multiple) calls to add_from_file(), add_from_resource() or add_from_string().

A Builder 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 Gtk::Window::destroy()`` to get rid of them and all the widgets they contain.

The functions object() and 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 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 g_object_ref() to keep them beyond the lifespan of the builder.

GtkBuilder UI Definitions

Builder 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 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.

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>”. 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() 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 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.

Builder 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 [gdk::RGBA::parse()``][crate::gdk::RGBA::parse()]).

GVariants can be specified in the format understood by g_variant_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 expose_object(). In general, Builder 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, Builder implements this using GBinding objects. For more information see [ObjectExtManual::bind_property()][crate::glib::prelude::ObjectExtManual::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 Dialog). This can be achieved by setting the “internal-child” property of the <child> element to a true value. Note that Builder 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 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.

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

<interface>
  <object class="GtkDialog" id="dialog1">
    <child internal-child="vbox">
      <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">gtk-ok</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 for details.

Implements

glib::ObjectExt

Implementations

Creates a new empty builder object.

This function is only useful if you intend to make multiple calls to add_from_file(), add_from_resource() or add_from_string() in order to merge multiple UI descriptions into a single builder.

Returns

a new (empty) Builder object

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.

resource_path

a GResource resource path

Returns

a Builder containing the described interface

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.

string

a user interface (XML) description

length

the length of string, or -1

Returns

a Builder containing the interface described by string

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 set_current_object() to add user data to callbacks before loading GtkBuilder UI. Otherwise, you probably want 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().

resource_path

the path of the resource file to parse

Returns

true on success, false if an error occurred

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 set_current_object() to add user data to callbacks before loading Builder UI. Otherwise, you probably want 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().

buffer

the string to parse

length

the length of buffer (may be -1 if buffer is nul-terminated)

Returns

true on success, false if an error occurred

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 TreeView that depends on its TreeModel), you have to explicitly list all of them in object_ids.

filename

the name of the file to parse

object_ids

nul-terminated array of objects to build

Returns

true on success, false if an error occurred

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 TreeView that depends on its TreeModel), you have to explicitly list all of them in object_ids.

resource_path

the path of the resource file to parse

object_ids

nul-terminated array of objects to build

Returns

true on success, false if an error occurred

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 TreeView that depends on its TreeModel), you have to explicitly list all of them in object_ids.

buffer

the string to parse

length

the length of buffer (may be -1 if buffer is nul-terminated)

object_ids

nul-terminated array of objects to build

Returns

true on success, false if an error occurred

Creates a closure to invoke the function called function_name.

This is using the create_closure() implementation of self’s BuilderScope.

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

function_name

name of the function to look up

flags

closure creation flags

object

Object to create the closure with

Returns

A new closure for invoking function_name

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

name

the name of the object exposed to the builder

object

the object to expose

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

This is exported purely to let gtk-builder-tool validate templates, applications have no need to call this function.

object

the object that is being extended

template_type

the type that the template is for

buffer

the string to parse

length

the length of buffer (may be -1 if buffer is nul-terminated)

Returns

A positive value on success, 0 if an error occurred

Gets the current object set via set_current_object().

Returns

the current object

Gets all objects that have been constructed by self.

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

Returns

a newly-allocated GSList containing all the objects constructed by the GtkBuilder instance. It should be freed by g_slist_free()

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

Returns

the current scope

Gets the translation domain of self.

Returns

the translation domain or None. This string is owned by the builder object and must not be modified or freed.

Looks up a type by name.

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

type_name

type name to lookup

Returns

the GType found for type_name or G_TYPE_INVALID if no type was found

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.

WidgetExt::init_template() for example will set the current object to the widget the template is inited for. For functions like from_resource(), the current object will be None.

current_object

the new current object or None for none

Sets the scope the builder should operate in.

If scope is None a new Gtk::BuilderCScope will be created.

scope

the scope to use or None for the default

Sets the translation domain of self.

domain

the translation domain or None

Demarshals a value from a string.

Unlike value_from_string(), this function takes a GType instead of GParamSpec.

Calls glib::Value::from_type() 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.

type_

the GType of the value

string

the string representation of the value

Returns

true on success

value

the glib::Value to store the result in

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.

filename

filename of user interface description file

Returns

a Builder containing the described interface

Gets the object named name.

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

name

name of object to get

Returns

the object named name or None if it could not be found in the object tree.

Demarshals a value from a string.

This function calls glib::Value::from_type() on the value argument, so it need not be initialised beforehand.

Can handle char, uchar, boolean, int, uint, long, ulong, enum, flags, float, double, string, gdk::RGBA and Adjustment type values.

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

pspec

the GParamSpec for the property

string

the string representation of the value

Returns

true on success

value

the GValue to store the result in

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 set_current_object()) to add user data to callbacks before loading GtkBuilder UI. Otherwise, you probably want 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 Builder 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().

filename

the name of the file to parse

Returns

true on success, false if an error occurred

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