Builder

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

To create a gtk.builder.Builder from a user interface description, call gtk.builder.Builder.newFromFile, gtk.builder.Builder.newFromResource or gtk.builder.Builder.newFromString.

In the (unusual) case that you want to add user interface descriptions from multiple sources to the same gtk.builder.Builder you can call gtk.builder.Builder.new_ to get an empty builder and populate it by (multiple) calls to gtk.builder.Builder.addFromFile, gtk.builder.Builder.addFromResource or gtk.builder.Builder.addFromString.

A gtk.builder.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.Window.destroy to get rid of them and all the widgets they contain.

The functions gtk.builder.Builder.getObject and gtk.builder.Builder.getObjects 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.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.ObjectG.ref_ to keep them beyond the lifespan of the builder.

GtkBuilder UI Definitions

gtk.builder.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.

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 gtk.builder.Builder.setTranslationDomain on the builder. For example:

<?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>”. gtk.builder.Builder will error out if the version requirements are not met. For example:

<?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.

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 [gobject.global.typeEnsure] 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 gtk.builder.Builder.getObject. 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:

<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:

<object class="GtkButton">
  <property name="label" translatable="yes" context="button">Hello, world</property>
</object>

gtk.builder.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 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_INPUT_HINT_EMOJI|GTK_INPUT_HINT_LOWERCASE”, or “emoji|lowercase”)
colors (in a format understood by gdk.rgba.RGBA.parse)
glib.variant.VariantG (can be specified in the format understood by glib.variant.VariantG.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 gtk.builder.Builder.exposeObject. In general, gtk.builder.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.

Child objects

Many widgets have properties for child widgets, such as gtk.expander.Expander.Widget. In this case, the preferred way to specify the child widget in a ui file is to simply set the property:

<object class="GtkExpander">
  <property name="child">
    <object class="GtkLabel">
    ...
    </object>
  </property>
</object>

Generic containers that can contain an arbitrary number of children, such as gtk.box.Box instead use the <child> element. A <child> element contains an <object> element which describes the child object. Most often, child objects are widgets inside a container, but they can also be, e.g., actions in an action group, or columns in a tree model.

Any object type that implements the gtk.buildable.Buildable interface can specify how children may be added to it. Since many objects and widgets that are included with GTK already implement the gtk.buildable.Buildable interface, typically child objects can be added using the <child> element without having to be concerned about the underlying implementation.

See the [gtk.widget.Widget] documentation for many examples of using gtk.builder.Builder with widgets, including setting child objects using the <child> element.

A noteworthy special case to the general rule that only objects implementing gtk.buildable.Buildable may specify how to handle the <child> element is that gtk.builder.Builder provides special support for adding objects to a gio.list_store.ListStore by using the <child> element. For instance:

<object class="GListStore">
  <property name="item-type">MyObject</property>
  <child>
    <object class="MyObject" />
  </child>
  ...
</object>

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, gtk.builder.Builder implements this using gobject.binding.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:

<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 gobject.object.ObjectG.bindProperty method.

Please note that another way to set up bindings between objects in .ui files is to use the gtk.expression.Expression methodology. See the [gtk.expression.Expression] documentation

for more information.

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 gtk.dialog.Dialog). This can be achieved by setting the “internal-child” property of the <child> element to a true value. Note that gtk.builder.Builder 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.

<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:

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

<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 GtkBuildable for extending UI definitions

Objects can implement the gtk.buildable.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 gtk.widget.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 [gtk.widget.Widget] documentation for details.

class Builder : ObjectG {

this();

static gtk.builder.Builder newFromFile(string filename);

static gtk.builder.Builder newFromResource(string resourcePath);

static gtk.builder.Builder newFromString(string string_);

bool addFromFile(string filename);

bool addFromResource(string resourcePath);

bool addFromString(string buffer, ptrdiff_t length);

bool addObjectsFromFile(string filename, string[] objectIds);

bool addObjectsFromResource(string resourcePath, string[] objectIds);

bool addObjectsFromString(string buffer, ptrdiff_t length, string[] objectIds);

gobject.closure.Closure createClosure(string functionName, gtk.types.BuilderClosureFlags flags, gobject.object.ObjectG object);

void exposeObject(string name, gobject.object.ObjectG object);

bool extendWithTemplate(gobject.object.ObjectG object, gobject.types.GType templateType, string buffer, ptrdiff_t length);

gobject.object.ObjectG getCurrentObject();

gobject.object.ObjectG getObject(string name);

gobject.object.ObjectG[] getObjects();

gtk.builder_scope.BuilderScope getScope();

string getTranslationDomain();

gobject.types.GType getTypeFromName(string typeName);

void setCurrentObject(gobject.object.ObjectG currentObject);

void setScope(gtk.builder_scope.BuilderScope scope_);

void setTranslationDomain(string domain);

bool valueFromString(gobject.param_spec.ParamSpec pspec, string string_, gobject.value.Value value);

bool valueFromStringType(gobject.types.GType type, string string_, gobject.value.Value value);

}

Constructors

this this(): Creates a new empty builder object.

Members

Functions

addFromFile bool addFromFile(string filename): Parses a file containing a UI definition and merges it with the current contents of builder.
addFromResource bool addFromResource(string resourcePath): Parses a resource file containing a UI definition and merges it with the current contents of builder.
addFromString bool addFromString(string buffer, ptrdiff_t length): Parses a string containing a UI definition and merges it with the current contents of builder.
addObjectsFromFile bool addObjectsFromFile(string filename, string[] objectIds): Parses a file containing a UI definition building only the requested objects and merges them with the current contents of builder.
addObjectsFromResource bool addObjectsFromResource(string resourcePath, string[] objectIds): Parses a resource file containing a UI definition, building only the requested objects and merges them with the current contents of builder.
addObjectsFromString bool addObjectsFromString(string buffer, ptrdiff_t length, string[] objectIds): Parses a string containing a UI definition, building only the requested objects and merges them with the current contents of builder.
createClosure gobject.closure.Closure createClosure(string functionName, gtk.types.BuilderClosureFlags flags, gobject.object.ObjectG object): Creates a closure to invoke the function called function_name.
exposeObject void exposeObject(string name, gobject.object.ObjectG object): Add object to the builder object pool so it can be referenced just like any other object built by builder.
extendWithTemplate bool extendWithTemplate(gobject.object.ObjectG object, gobject.types.GType templateType, string buffer, ptrdiff_t length): Main private entry point for building composite components from template XML.
getCurrentObject gobject.object.ObjectG getCurrentObject(): Gets the current object set via gtk.builder.Builder.setCurrentObject.
getObject gobject.object.ObjectG getObject(string name): Gets the object named name.
getObjects gobject.object.ObjectG[] getObjects(): Gets all objects that have been constructed by builder.
getScope gtk.builder_scope.BuilderScope getScope(): Gets the scope in use that was set via gtk.builder.Builder.setScope.
getTranslationDomain string getTranslationDomain(): Gets the translation domain of builder.
getTypeFromName gobject.types.GType getTypeFromName(string typeName): Looks up a type by name.
setCurrentObject void setCurrentObject(gobject.object.ObjectG currentObject): Sets the current object for the builder.
setScope void setScope(gtk.builder_scope.BuilderScope scope_): Sets the scope the builder should operate in.
setTranslationDomain void setTranslationDomain(string domain): Sets the translation domain of builder.
valueFromString bool valueFromString(gobject.param_spec.ParamSpec pspec, string string_, gobject.value.Value value): Demarshals a value from a string.
valueFromStringType bool valueFromStringType(gobject.types.GType type, string string_, gobject.value.Value value): Demarshals a value from a string.

Static functions

newFromFile gtk.builder.Builder newFromFile(string filename): Parses the UI definition in the file filename.
newFromResource gtk.builder.Builder newFromResource(string resourcePath): Parses the UI definition at resource_path.
newFromString gtk.builder.Builder newFromString(string string_): Parses the UI definition in string.

Inherited Members

From ObjectG

setGObject void setGObject(void* cObj, Flag!"Take" take): Set the GObject of a D ObjectG wrapper.
cPtr void* cPtr(Flag!"Dup" dup): Get a pointer to the underlying C object.
ref_ void* ref_(void* gObj): Calls g_object_ref() on a GObject.
unref unref(void* gObj): Calls g_object_unref() on a GObject.
getType GType getType(): Get the GType of an object.
gType GType gType [@property getter]: GObject GType property.
self ObjectG self(): Convenience method to return this cast to a type. For use in D with statements.
getDObject T getDObject(void* cptr, Flag!"Take" take): Template to get the D object from a C GObject and cast it to the given D object type.
connectSignalClosure ulong connectSignalClosure(string signalDetail, DClosure closure, Flag!"After" after): Connect a D closure to an object signal.
setProperty void setProperty(string propertyName, T val): Template for setting a GObject property.
getProperty T getProperty(string propertyName): Template for getting a GObject property.
compatControl size_t compatControl(size_t what, void* data)
bindProperty gobject.binding.Binding bindProperty(string sourceProperty, gobject.object.ObjectG target, string targetProperty, gobject.types.BindingFlags flags): Creates a binding between source_property on source and target_property on target.
bindPropertyFull gobject.binding.Binding bindPropertyFull(string sourceProperty, gobject.object.ObjectG target, string targetProperty, gobject.types.BindingFlags flags, gobject.closure.Closure transformTo, gobject.closure.Closure transformFrom): Creates a binding between source_property on source and target_property on target, allowing you to set the transformation functions to be used by the binding.
forceFloating void forceFloating(): This function is intended for #GObject implementations to re-enforce a floating[floating-ref] object reference. Doing this is seldom required: all #GInitiallyUnowneds are created with a floating reference which usually just needs to be sunken by calling gobject.object.ObjectG.refSink.
freezeNotify void freezeNotify(): Increases the freeze count on object. If the freeze count is non-zero, the emission of "notify" signals on object is stopped. The signals are queued until the freeze count is decreased to zero. Duplicate notifications are squashed so that at most one #GObject::notify signal is emitted for each property modified while the object is frozen.
getData void* getData(string key): Gets a named field from the objects table of associations (see gobject.object.ObjectG.setData).
getProperty void getProperty(string propertyName, gobject.value.Value value): Gets a property of an object.
getQdata void* getQdata(glib.types.Quark quark): This function gets back user data pointers stored via gobject.object.ObjectG.setQdata.
getv void getv(string[] names, gobject.value.Value[] values): Gets n_properties properties for an object. Obtained properties will be set to values. All properties must be valid. Warnings will be emitted and undefined behaviour may result if invalid properties are passed in.
isFloating bool isFloating(): Checks whether object has a floating[floating-ref] reference.
notify void notify(string propertyName): Emits a "notify" signal for the property property_name on object.
notifyByPspec void notifyByPspec(gobject.param_spec.ParamSpec pspec): Emits a "notify" signal for the property specified by pspec on object.
refSink gobject.object.ObjectG refSink(): Increase the reference count of object, and possibly remove the floating[floating-ref] reference, if object has a floating reference.
runDispose void runDispose(): Releases all references to other objects. This can be used to break reference cycles.
setData void setData(string key, void* data): Each object carries around a table of associations from strings to pointers. This function lets you set an association.
setProperty void setProperty(string propertyName, gobject.value.Value value): Sets a property on an object.
stealData void* stealData(string key): Remove a specified datum from the object's data associations, without invoking the association's destroy handler.
stealQdata void* stealQdata(glib.types.Quark quark): This function gets back user data pointers stored via gobject.object.ObjectG.setQdata and removes the data from object without invoking its destroy() function (if any was set). Usually, calling this function is only required to update user data pointers with a destroy notifier, for example:
thawNotify void thawNotify(): Reverts the effect of a previous call to gobject.object.ObjectG.freezeNotify. The freeze count is decreased on object and when it reaches zero, queued "notify" signals are emitted.
watchClosure void watchClosure(gobject.closure.Closure closure): This function essentially limits the life time of the closure to the life time of the object. That is, when the object is finalized, the closure is invalidated by calling gobject.closure.Closure.invalidate on it, in order to prevent invocations of the closure with a finalized (nonexisting) object. Also, gobject.object.ObjectG.ref_ and gobject.object.ObjectG.unref are added as marshal guards to the closure, to ensure that an extra reference count is held on object during invocation of the closure. Usually, this function will be called on closures that use this object as closure data.
connectNotify ulong connectNotify(string detail, T callback, Flag!"After" after): Connect to Notify signal.

gtk builder classes

Builder