## GtkBuildable GtkBuildable — Interface for objects that can be built by GtkBuilder |

## Functions

const char * | gtk_buildable_get_buildable_id ()
const char * | gtk_buildable_parse_context_get_element ()
GPtrArray * | gtk_buildable_parse_context_get_element_stack ()
void | gtk_buildable_parse_context_get_position ()
gpointer | gtk_buildable_parse_context_pop ()
void | gtk_buildable_parse_context_push ()

## Types and Values

| GtkBuildable
struct | GtkBuildableIface
struct | GtkBuildableParser

## Object Hierarchy

        GInterface
        ╰── GtkBuildable

## Prerequisites

GtkBuildable requires GObject.

## Known Implementations

GtkBuildable is implemented by GtkAboutDialog, GtkActionBar, GtkAnyFilter, GtkAppChooserButton, GtkAppChooserDialog, GtkAppChooserWidget, GtkApplicationWindow, GtkAspectFrame, GtkAssistant, GtkBox, GtkButton, GtkCalendar, GtkCellArea, GtkCellAreaBox, GtkCellView, GtkCenterBox, GtkCheckButton, GtkColorButton, GtkColorChooserDialog, GtkColorChooserWidget, GtkColumnView, GtkComboBox, GtkComboBoxText, GtkConstraintLayout, GtkDialog, GtkDragIcon, GtkDrawingArea, GtkDropDown, GtkEditableLabel, GtkEmojiChooser, GtkEntry, GtkEntryCompletion, GtkEveryFilter, GtkExpander, GtkFileChooserDialog, GtkFileChooserWidget, GtkFileFilter, GtkFixed, GtkFlowBox, GtkFlowBoxChild, GtkFontButton, GtkFontChooserDialog, GtkFontChooserWidget, GtkFrame, GtkGLArea, GtkGrid, GtkGridView, GtkHeaderBar, GtkIconView, GtkImage, GtkInfoBar, GtkLabel, GtkLevelBar, GtkLinkButton, GtkListBox, GtkListBoxRow, GtkListStore, GtkListView, GtkLockButton, GtkMediaControls, GtkMenuButton, GtkMessageDialog, GtkMultiFilter, GtkMultiSorter, GtkNotebook, GtkOverlay, GtkPageSetupUnixDialog, GtkPaned, GtkPasswordEntry, GtkPicture, GtkPopover, GtkPopoverMenu, GtkPopoverMenuBar, GtkPrintUnixDialog, GtkProgressBar, GtkRange, GtkRevealer, GtkScale, GtkScaleButton, GtkScrollbar, GtkScrolledWindow, GtkSearchBar, GtkSearchEntry, GtkSeparator, GtkShortcutController, GtkShortcutLabel, GtkShortcutsGroup, GtkShortcutsSection, GtkShortcutsShortcut, GtkShortcutsWindow, GtkSizeGroup, GtkSpinButton, GtkSpinner, GtkStack, GtkStackSidebar, GtkStackSwitcher, GtkStatusbar, GtkStringList, GtkSwitch, GtkText, GtkTextTagTable, GtkTextView, GtkToggleButton, GtkTreeExpander, GtkTreeStore, GtkTreeView, GtkTreeViewColumn, GtkVideo, GtkViewport, GtkVolumeButton, GtkWidget, GtkWindow, GtkWindowControls and GtkWindowHandle.

## Includes

    #include <gtk/gtk.h>

## Description

GtkBuildable allows objects to extend and customize their deserialization from GtkBuilder UI descriptions. The interface includes methods for setting names and properties of objects, parsing custom tags and constructing child objects.

The GtkBuildable interface is implemented by all widgets and many of the non-widget objects that are provided by GTK. The main user of this interface is GtkBuilder. There should be very little need for applications to call any of these functions directly.

An object only needs to implement this interface if it needs to extend the GtkBuilder format or run any extra routines at deserialization time.

## Functions

### gtk_buildable_get_buildable_id ()

    const char *
    gtk_buildable_get_buildable_id (GtkBuildable *buildable);

Gets the ID of the `buildable` object.

GtkBuilder sets the name based on the GtkBuilder UI definition used to construct the `buildable` .

#### Parameters

buildable | a GtkBuildable |

#### Returns

the ID set with `gtk_buildable_set_buildable_id()`

### gtk_buildable_parse_context_get_element ()

    const char *
    gtk_buildable_parse_context_get_element
                                   (GtkBuildableParseContext *context);

Retrieves the name of the currently open element.

If called from the start_element or end_element handlers this will give the element_name as passed to those functions. For the parent elements, see `gtk_buildable_parse_context_get_element_stack()`.

#### Parameters

context | a GtkBuildablParseContext |

#### Returns

the name of the currently open element, or `NULL`.

[nullable]

### gtk_buildable_parse_context_get_element_stack ()

    GPtrArray *
    gtk_buildable_parse_context_get_element_stack
                                   (GtkBuildableParseContext *context);

Retrieves the element stack from the internal state of the parser.

The returned GPtrArray is an array of strings where the last item is the currently open tag (as would be returned by `gtk_buildable_parse_context_get_element()`) and the previous item is its immediate parent.

This function is intended to be used in the start_element and end_element handlers where `gtk_buildable_parse_context_get_element()` would merely return the name of the element that is being processed.

#### Parameters

context | a GtkBuildableParseContext |

#### Returns

the element stack, which must not be modified.

[transfer none][element-type utf8]

### gtk_buildable_parse_context_get_position ()

    void
    gtk_buildable_parse_context_get_position
                                   (GtkBuildableParseContext *context,
                                    int *line_number,
                                    int *char_number);

Retrieves the current line number and the number of the character on that line. Intended for use in error messages; there are no strict semantics for what constitutes the "current" line number other than "the best number we could come up with for error messages."

#### Parameters

context | a GtkBuildableParseContext |
line_number | return location for a line number, or `NULL`. | [out][optional]
char_number | return location for a char-on-line number, or `NULL`. | [out][optional]

### gtk_buildable_parse_context_pop ()

    gpointer
    gtk_buildable_parse_context_pop (GtkBuildableParseContext *context);

Completes the process of a temporary sub-parser redirection.

This function exists to collect the user_data allocated by a matching call to `gtk_buildable_parse_context_push()`. It must be called in the end_element handler corresponding to the start_element handler during which `gtk_buildable_parse_context_push()` was called. You must not call this function from the error callback -- the `user_data` is provided directly to the callback in that case.

This function is not intended to be directly called by users interested in invoking subparsers. Instead, it is intended to be used by the subparsers themselves to implement a higher-level interface.

#### Parameters

context | a GtkBuildableParseContext |

#### Returns

the user data passed to `gtk_buildable_parse_context_push()`

### gtk_buildable_parse_context_push ()

    void
    gtk_buildable_parse_context_push (GtkBuildableParseContext *context,
                                      const GtkBuildableParser *parser,
                                      gpointer user_data);

Temporarily redirects markup data to a sub-parser.

This function may only be called from the start_element handler of a GtkBuildableParser. It must be matched with a corresponding call to `gtk_buildable_parse_context_pop()` in the matching end_element handler (except in the case that the parser aborts due to an error).

All tags, text and other data between the matching tags is redirected to the subparser given by `parser` . `user_data` is used as the user_data for that parser. `user_data` is also passed to the error callback in the event that an error occurs. This includes errors that occur in subparsers of the subparser.

The end tag matching the start tag for which this call was made is handled by the previous parser (which is given its own user_data) which is why `gtk_buildable_parse_context_pop()` is provided to allow "one last access" to the `user_data` provided to this function. In the case of error, the `user_data` provided here is passed directly to the error callback of the subparser and `gtk_buildable_parse_context_pop()` should not be called. In either case, if `user_data` was allocated then it ought to be freed from both of these locations.

This function is not intended to be directly called by users interested in invoking subparsers. Instead, it is intended to be used by the subparsers themselves to implement a higher-level interface.

For an example of how to use this, see `g_markup_parse_context_push()` which has the same kind of API.

#### Parameters

context | a GtkBuildableParseContext |
parser | a GtkBuildableParser |
user_data | user data to pass to GtkBuildableParser functions |

## Types and Values

### GtkBuildable

    typedef struct _GtkBuildable GtkBuildable;

### struct GtkBuildableIface

    struct GtkBuildableIface {
      GTypeInterface g_iface;

      /* virtual table */
      void          (* set_id)                 (GtkBuildable       *buildable,
                                                const char         *id);
      const char *  (* get_id)                 (GtkBuildable       *buildable);

      /**
       * GtkBuildableIface::add_child:
       * @buildable: a #GtkBuildable
       * @builder: a #GtkBuilder
       * @child: child to add
       * @type: (nullable): kind of child or %NULL
       *
       * Adds a child to @buildable. @type is an optional string
       * describing how the child should be added.
       */
      void          (* add_child)              (GtkBuildable       *buildable,
                                                GtkBuilder         *builder,
                                                GObject            *child,
                                                const char         *type);
      void          (* set_buildable_property) (GtkBuildable       *buildable,
                                                GtkBuilder         *builder,
                                                const char         *name,
                                                const GValue       *value);
      GObject *     (* construct_child)        (GtkBuildable       *buildable,
                                                GtkBuilder         *builder,
                                                const char         *name);

      /**
       * GtkBuildableIface::custom_tag_start:
       * @buildable: a #GtkBuildable
       * @builder: a #GtkBuilder used to construct this object
       * @child: (nullable): child object or %NULL for non-child tags
       * @tagname: name of tag
       * @parser: (out): a #GtkBuildableParser to fill in
       * @data: (out): return location for user data that will be passed in
       *   to parser functions
       *
       * Called for each unknown element under `<child>`.
       *
       * Returns: %TRUE if an object has a custom implementation, %FALSE
       *   if it doesn't.
       */
      gboolean      (* custom_tag_start)       (GtkBuildable       *buildable,
                                                GtkBuilder         *builder,
                                                GObject            *child,
                                                const char         *tagname,
                                                GtkBuildableParser *parser,
                                                gpointer           *data);
      /**
       * GtkBuildableIface::custom_tag_end:
       * @buildable: A #GtkBuildable
       * @builder: #GtkBuilder used to construct this object
       * @child: (nullable): child object or %NULL for non-child tags
       * @tagname: name of tag
       * @data: user data that will be passed in to parser functions
       *
       * Called at the end of each custom element handled by
       * the buildable.
       */
      void          (* custom_tag_end)         (GtkBuildable       *buildable,
                                                GtkBuilder         *builder,
                                                GObject            *child,
                                                const char         *tagname,
                                                gpointer            data);
       /**
        * GtkBuildableIface::custom_finished:
        * @buildable: a #GtkBuildable
        * @builder: a #GtkBuilder
        * @child: (nullable): child object or %NULL for non-child tags
        * @tagname: the name of the tag
        * @data: user data created in custom_tag_start
        *
        * Similar to gtk_buildable_parser_finished() but is
        * called once for each custom tag handled by the @buildable.
        */
      void          (* custom_finished)        (GtkBuildable       *buildable,
                                                GtkBuilder         *builder,
                                                GObject            *child,
                                                const char         *tagname,
                                                gpointer            data);
      void          (* parser_finished)        (GtkBuildable       *buildable,
                                                GtkBuilder         *builder);

      /**
       * GtkBuildableIface::get_internal_child:
       * @buildable: a #GtkBuildable
       * @builder: a #GtkBuilder
       * @childname: name of child
       *
       * Retrieves the internal child called @childname of the @buildable object.
       *
       * Returns: (transfer none): the internal child of the buildable object
       */
      GObject *     (* get_internal_child)     (GtkBuildable       *buildable,
                                                GtkBuilder         *builder,
                                                const char         *childname);
    };

The GtkBuildableIface interface contains method that are necessary to allow GtkBuilder to construct an object from a GtkBuilder UI definition.

#### Members

`set_id` () | Stores the id attribute given in the GtkBuilder UI definition. GtkWidget stores the name as object data. Implement this method if your object has some notion of “ID” and it makes sense to map the XML id attribute to it. |
`get_id` () | The getter corresponding to `set_id` . Implement this if you implement `set_id` . |
`add_child` () | Adds a child. The `type` parameter can be used to differentiate the kind of child. GtkWidget implements this to add event controllers to the widget, GtkNotebook uses the `type` to distinguish between page labels (of type "page-label") and normal children. |
`set_buildable_property` () | Sets a property of a buildable object. It is normally not necessary to implement this, `g_object_set_property()` is used by default. GtkWindow implements this to delay showing itself (i.e. setting the “visible” property) until the whole interface is created. |
`construct_child` () | Constructs a child of a buildable that has been specified as “constructor” in the UI definition. This can be used to reference a widget created in a <ui> tag which is outside of the normal GtkBuilder UI definition hierarchy. A reference to the constructed object is returned and becomes owned by the caller. |
`custom_tag_start` () | Implement this if the buildable needs to parse content below <child>. To handle an element, the implementation must fill in the `parser` and `user_data` and return `TRUE`. GtkWidget implements this to parse accessible attributes specified in <accessibility> elements. Note that `user_data` must be freed in `custom_tag_end` or `custom_finished` . |
`custom_tag_end` () | Called for the end tag of each custom element that is handled by the buildable (see `custom_tag_start` ). |
`custom_finished` () | Called for each custom tag handled by the buildable when the builder finishes parsing (see `custom_tag_start` ) |
`parser_finished` () | Called when a builder finishes the parsing of a UI definition. It is normally not necessary to implement this, unless you need to perform special cleanup actions. GtkWindow sets the “visible” property here. |
`get_internal_child` () | Returns an internal child of a buildable. GtkDialog implements this to give access to its `vbox` , making it possible to add children to the vbox in a UI definition. Implement this if the buildable has internal children that may need to be accessed from a UI definition. |

### struct GtkBuildableParser

    struct GtkBuildableParser {
      /* Called for open tags <foo bar="baz"> */
      void (*start_element)  (GtkBuildableParseContext *context,
                              const char               *element_name,
                              const char              **attribute_names,
                              const char              **attribute_values,
                              gpointer                  user_data,
                              GError                  **error);

      /* Called for close tags </foo> */
      void (*end_element)    (GtkBuildableParseContext *context,
                              const char               *element_name,
                              gpointer                  user_data,
                              GError                  **error);

      /* Called for character data */
      /* text is not nul-terminated */
      void (*text)           (GtkBuildableParseContext *context,
                              const char               *text,
                              gsize                     text_len,
                              gpointer                  user_data,
                              GError                  **error);

      /* Called on error, including one set by other
       * methods in the vtable. The GError should not be freed.
       */
      void (*error)          (GtkBuildableParseContext *context,
                              GError                   *error,
                              gpointer                 user_data);
    };

A sub-parser for GtkBuildable implementations.

#### Members

`start_element` () | function called for open elements |
`end_element` () | function called for close elements |
`text` () | function called for character data |
`error` () | function called on error |