Class GtkBuilder

java.lang.Object
org.javagi.base.ProxyInstance
org.gnome.gobject.TypeInstance
org.gnome.gobject.GObject
org.gnome.gtk.GtkBuilder
All Implemented Interfaces:
Proxy
@Generated("org.javagi.JavaGI") public class GtkBuilder extends GObject

Reads XML descriptions of a user interface and instantiates the described objects.

To create a GtkBuilder from a user interface description, call fromFile(String), fromResource(String) or fromString(String, long).

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

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 Window.destroy() to get rid of them and all the widgets they contain.

The functions getObject(String) and 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 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

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.

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 setTranslationDomain(String) 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>”. GtkBuilder 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 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 getObject(String). 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"
            comments="A classic">Hello, world</property>
</object>

The xgettext tool that is part of gettext can extract these strings, but note that it only looks for translatable="yes".

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)
  • string lists (separated by newlines)
  • 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 or short name, optionally combined with “|” for bitwise OR, or a single integer value e.g., “GTK_INPUT_HINT_EMOJI|GTK_INPUT_HINT_LOWERCASE”, or “emoji|lowercase” or 520).
  • colors (in the format understood by RGBA#parse)
  • transforms (in the format understood by Transform#parse)
  • Pango attribute lists (in the format understood by AttrList#toString)
  • Pango tab arrays (in the format understood by TabArray#toString)
  • Pango font descriptions (in the format understood by FontDescription#fromString)
  • GVariant (in the format understood by Variant#parse)
  • textures (can be specified as an object id, a resource path or a filename of an image file to load relative to the Builder file or the CWD if addFromString(String, long) was used)
  • GFile (like textures, can be specified as an object id, a URI or a filename of a file to load relative to the Builder file or the CWD if addFromString(String, long) was used)

Objects can be referred to by their name and by default refer to objects declared in the local XML fragment and objects exposed via exposeObject(String, GObject). 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.

Child objects

Many widgets have properties for child widgets, such as Gtk.Expander:child. 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 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 Buildable interface can specify how children may be added to it. Since many objects and widgets that are included with GTK already implement the GtkBuildable interface, typically child objects can be added using the <child> element without having to be concerned about the underlying implementation.

See the GtkWidget documentation for many examples of using GtkBuilder with widgets, including setting child objects using the <child> element.

A noteworthy special case to the general rule that only objects implementing GtkBuildable may specify how to handle the <child> element is that GtkBuilder provides special support for adding objects to a 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, GtkBuilder implements this using 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#bindProperty method.

Please note that another way to set up bindings between objects in .ui files is to use the GtkExpression methodology. See the GtkExpression 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 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.

<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 GObjects#signalConnectObject or GObjects#signalConnectData 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 Buildable interface to add custom elements and attributes to the XML. Typically, any extension will be documented in each type that implements the interface.

In addition to objects with properties that are created with <object> and <property> elements, GtkBuilder also allows to parse XML menu definitions as used by Menu when exporting menu models over D-Bus, and as described in the PopoverMenu documentation. Menus can be defined as toplevel elements, or as property values for properties of type GMenuModel.

Templates

When describing a 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.

  • Constructor Details

    • GtkBuilder

      public GtkBuilder(MemorySegment address)
      Create a GtkBuilder instance for the provided memory address.
      Parameters:
      address - the memory address of the native object

    • GtkBuilder

      public GtkBuilder()
      Create a new GtkBuilder.

  • Method Details

    • getType

      public static @Nullable Type getType()
      Get the GType of the GtkBuilder class.
      Returns:
      the GType

    • getMemoryLayout

      public static MemoryLayout getMemoryLayout()
      The memory layout of the native struct.
      Returns:
      the memory layout

    • asParent

      protected GtkBuilder asParent()
      Return this instance as if it were its parent type. Comparable to the Java super keyword, but ensures the parent typeclass is also used in native code.
      Overrides:
      asParent in class GObject
      Returns:
      the instance as if it were its parent type

    • fromFile

      public static GtkBuilder fromFile(String filename)

      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.

      Parameters:
      filename - filename of user interface description file
      Returns:
      a GtkBuilder containing the described interface

    • fromResource

      public static GtkBuilder fromResource(String resourcePath)

      Parses the UI definition at resourcePath.

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

      Parameters:
      resourcePath - a GResource resource path
      Returns:
      a GtkBuilder containing the described interface

    • fromString

      public static GtkBuilder fromString(String string, long length)

      Parses the UI definition in string.

      If string is null-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.

      Parameters:
      string - a user interface (XML) description
      length - the length of string, or -1
      Returns:
      a GtkBuilder containing the interface described by string

    • addFromFile

      public boolean addFromFile(String filename) throws GErrorException

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

      This function is useful if you need to call setCurrentObject(GObject)) to add user data to callbacks before loading GtkBuilder UI. Otherwise, you probably want fromFile(String) 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().

      Parameters:
      filename - the name of the file to parse
      Returns:
      true on success, false if an error occurred
      Throws:
      GErrorException - see GError

    • addFromResource

      public boolean addFromResource(String resourcePath) throws GErrorException

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

      This function is useful if you need to call setCurrentObject(GObject) to add user data to callbacks before loading GtkBuilder UI. Otherwise, you probably want fromResource(String) 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().

      Parameters:
      resourcePath - the path of the resource file to parse
      Returns:
      true on success, false if an error occurred
      Throws:
      GErrorException - see GError

    • addFromString

      public boolean addFromString(String buffer, long length) throws GErrorException

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

      This function is useful if you need to call setCurrentObject(GObject) to add user data to callbacks before loading GtkBuilder UI. Otherwise, you probably want fromString(String, long) 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().

      Parameters:
      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
      Throws:
      GErrorException - see GError

    • addObjectsFromFile

      public boolean addObjectsFromFile(String filename, @Nullable String @Nullable [] objectIds) throws GErrorException

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

      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 objectIds.

      Parameters:
      filename - the name of the file to parse
      objectIds - nul-terminated array of objects to build
      Returns:
      true on success, false if an error occurred
      Throws:
      GErrorException - see GError

    • addObjectsFromResource

      public boolean addObjectsFromResource(String resourcePath, @Nullable String @Nullable [] objectIds) throws GErrorException

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

      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 objectIds.

      Parameters:
      resourcePath - the path of the resource file to parse
      objectIds - nul-terminated array of objects to build
      Returns:
      true on success, false if an error occurred
      Throws:
      GErrorException - see GError

    • addObjectsFromString

      public boolean addObjectsFromString(String buffer, long length, @Nullable String @Nullable [] objectIds) throws GErrorException

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

      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 objectIds.

      Parameters:
      buffer - the string to parse
      length - the length of buffer (may be -1 if buffer is nul-terminated)
      objectIds - nul-terminated array of objects to build
      Returns:
      true on success, false if an error occurred
      Throws:
      GErrorException - see GError

    • createClosure

      public @Nullable Closure createClosure(String functionName, Set<BuilderClosureFlags> flags, @Nullable GObject object) throws GErrorException

      Creates a closure to invoke the function called functionName.

      This is using the create_closure() implementation of builder's BuilderScope.

      If no closure could be created, null will be returned and error will be set.

      Parameters:
      functionName - name of the function to look up
      flags - closure creation flags
      object - Object to create the closure with
      Returns:
      A new closure for invoking functionName
      Throws:
      GErrorException - see GError

    • createClosure

      public @Nullable Closure createClosure(String functionName, BuilderClosureFlags flags, @Nullable GObject object) throws GErrorException

      Creates a closure to invoke the function called functionName.

      This is using the create_closure() implementation of builder's BuilderScope.

      If no closure could be created, null will be returned and error will be set.

      Parameters:
      functionName - name of the function to look up
      flags - closure creation flags
      object - Object to create the closure with
      Returns:
      A new closure for invoking functionName
      Throws:
      GErrorException - see GError

    • exposeObject

      public void exposeObject(String name, GObject object)

      Add object to the this Builder 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.

      Parameters:
      name - the name of the object exposed to the builder
      object - the object to expose

    • extendWithTemplate

      public boolean extendWithTemplate(GObject object, Type templateType, String buffer, long length) throws GErrorException

      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.

      Parameters:
      object - the object that is being extended
      templateType - 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
      Throws:
      GErrorException - see GError

    • getCurrentObject

      public @Nullable GObject getCurrentObject()
      Gets the current object set via gtk_builder_set_current_object().
      Returns:
      the current object

    • getObject

      public @Nullable GObject getObject(String name)

      Gets the object named name.

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

      Parameters:
      name - name of object to get
      Returns:
      the object named name

    • getObjects

      public SList<GObject> getObjects()

      Gets all objects that have been constructed by builder.

      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()

    • getScope

      public BuilderScope getScope()
      Gets the scope in use that was set via gtk_builder_set_scope().
      Returns:
      the current scope

    • getTranslationDomain

      public @Nullable String getTranslationDomain()
      Gets the translation domain of builder.
      Returns:
      the translation domain

    • getTypeFromName

      public Type getTypeFromName(String typeName)

      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.

      Parameters:
      typeName - type name to lookup
      Returns:
      the GType found for typeName or G_TYPE_INVALID if no type was found

    • setCurrentObject

      public void setCurrentObject(@Nullable GObject currentObject)

      Sets the current object for the builder.

      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.

      Widget.initTemplate() for example will set the current object to the widget the template is inited for. For functions like fromResource(String), the current object will be null.

      Parameters:
      currentObject - the new current object

    • setScope

      public void setScope(@Nullable BuilderScope scope)

      Sets the scope the builder should operate in.

      If scope is null, a new BuilderCScope will be created.

      Parameters:
      scope - the scope to use

    • setTranslationDomain

      public void setTranslationDomain(@Nullable String domain)
      Sets the translation domain of builder.
      Parameters:
      domain - the translation domain

    • valueFromString

      public boolean valueFromString(ParamSpec pspec, String string, Value value) throws GErrorException

      Demarshals a value from a string.

      This function calls g_value_init() 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, GdkRGBA and GtkAdjustment type values.

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

      Parameters:
      pspec - the GParamSpec for the property
      string - the string representation of the value
      value - the GValue to store the result in
      Returns:
      true on success
      Throws:
      GErrorException - see GError

    • valueFromStringType

      public boolean valueFromStringType(Type type, String string, Value value) throws GErrorException

      Demarshals a value from a string.

      Unlike valueFromString(ParamSpec, String, Value), this function takes a GType instead of GParamSpec.

      Calls g_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.

      Parameters:
      type - the GType of the value
      string - the string representation of the value
      value - the GValue to store the result in
      Returns:
      true on success
      Throws:
      GErrorException - see GError

    • builder

      public static GtkBuilder.Builder<? extends GtkBuilder.Builder> builder()
      A GtkBuilder.Builder object constructs a GtkBuilder with the specified properties. Use the various set...() methods to set properties, and finish construction with GtkBuilder.Builder.build().
      Returns:
      the builder object