CellLayout

open class CellLayout : CellLayoutProtocol

An interface for packing cells

GtkCellLayout is an interface to be implemented by all objects which want to provide a GtkTreeViewColumn like API for packing cells, setting attributes and data funcs.

One of the notable features provided by implementations of GtkCellLayout are attributes. Attributes let you set the properties in flexible ways. They can just be set to constant values like regular properties. But they can also be mapped to a column of the underlying tree model with gtk_cell_layout_set_attributes(), which means that the value of the attribute can change from cell to cell as they are rendered by the cell renderer. Finally, it is possible to specify a function with gtk_cell_layout_set_cell_data_func() that is called to determine the value of the attribute for each cell that is rendered.

GtkCellLayouts as GtkBuildable

Implementations of GtkCellLayout which also implement the GtkBuildable interface (GtkCellView, GtkIconView, GtkComboBox, GtkEntryCompletion, GtkTreeViewColumn) accept GtkCellRenderer objects as <child> elements in UI definitions. They support a custom <attributes> element for their children, which can contain multiple <attribute> elements. Each <attribute> element has a name attribute which specifies a property of the cell renderer; the content of the element is the attribute value.

This is an example of a UI definition fragment specifying attributes:

<object class="GtkCellView">
  <child>
    <object class="GtkCellRendererText"/>
    <attributes>
      <attribute name="text">0</attribute>
    </attributes>
  </child>"
</object>

Furthermore for implementations of GtkCellLayout that use a GtkCellArea to lay out cells (all GtkCellLayouts in GTK use a GtkCellArea) cell properties can also be defined in the format by specifying the custom <cell-packing> attribute which can contain multiple <property> elements defined in the normal way.

Here is a UI definition fragment specifying cell properties:

<object class="GtkTreeViewColumn">
  <child>
    <object class="GtkCellRendererText"/>
    <cell-packing>
      <property name="align">True</property>
      <property name="expand">False</property>
    </cell-packing>
  </child>"
</object>

Subclassing GtkCellLayout implementations

When subclassing a widget that implements GtkCellLayout like GtkIconView or GtkComboBox, there are some considerations related to the fact that these widgets internally use a GtkCellArea. The cell area is exposed as a construct-only property by these widgets. This means that it is possible to e.g. do

(C Language Example):

combo = g_object_new (GTK_TYPE_COMBO_BOX, "cell-area", my_cell_area, NULL);

to use a custom cell area with a combo box. But construct properties are only initialized after instance init() functions have run, which means that using functions which rely on the existence of the cell area in your subclass’ init() function will cause the default cell area to be instantiated. In this case, a provided construct property value will be ignored (with a warning, to alert you to the problem).

(C Language Example):

static void
my_combo_box_init (MyComboBox *b)
{
  GtkCellRenderer *cell;

  cell = gtk_cell_renderer_pixbuf_new ();
  // The following call causes the default cell area for combo boxes,
  // a GtkCellAreaBox, to be instantiated
  gtk_cell_layout_pack_start (GTK_CELL_LAYOUT (b), cell, FALSE);
  ...
}

GtkWidget *
my_combo_box_new (GtkCellArea *area)
{
  // This call is going to cause a warning about area being ignored
  return g_object_new (MY_TYPE_COMBO_BOX, "cell-area", area, NULL);
}

If supporting alternative cell areas with your derived widget is not important, then this does not have to concern you. If you want to support alternative cell areas, you can do so by moving the problematic calls out of init() and into a constructor() for your class.

The CellLayout type acts as an owner of an underlying GtkCellLayout instance. It provides the methods that can operate on this data type through CellLayoutProtocol conformance. Use CellLayout as a strong reference or owner of a GtkCellLayout instance.

  • ptr
    Untyped pointer to the underlying `GtkCellLayout` instance.
    

    For type-safe access, use the generated, typed pointer cell_layout_ptr property instead.

    Declaration

    Swift

    public let ptr: UnsafeMutableRawPointer!
  • Designated initialiser from the underlying C data type. This creates an instance without performing an unbalanced retain i.e., ownership is transferred to the CellLayout instance.

    Declaration

    Swift

    @inlinable
    public init(_ op: UnsafeMutablePointer<GtkCellLayout>)

    Parameters

    op

    pointer to the underlying object

  • Designated initialiser from a constant pointer to the underlying C data type. This creates an instance without performing an unbalanced retain i.e., ownership is transferred to the CellLayout instance.

    Declaration

    Swift

    @inlinable
    public init(_ op: UnsafePointer<GtkCellLayout>)

    Parameters

    op

    pointer to the underlying object

  • Optional initialiser from a non-mutating gpointer to the underlying C data type. This creates an instance without performing an unbalanced retain i.e., ownership is transferred to the CellLayout instance.

    Declaration

    Swift

    @inlinable
    public init!(gpointer op: gpointer?)

    Parameters

    op

    gpointer to the underlying object

  • Optional initialiser from a non-mutating gconstpointer to the underlying C data type. This creates an instance without performing an unbalanced retain i.e., ownership is transferred to the CellLayout instance.

    Declaration

    Swift

    @inlinable
    public init!(gconstpointer op: gconstpointer?)

    Parameters

    op

    pointer to the underlying object

  • Optional initialiser from a constant pointer to the underlying C data type. This creates an instance without performing an unbalanced retain i.e., ownership is transferred to the CellLayout instance.

    Declaration

    Swift

    @inlinable
    public init!(_ op: UnsafePointer<GtkCellLayout>?)

    Parameters

    op

    pointer to the underlying object

  • Optional initialiser from the underlying C data type. This creates an instance without performing an unbalanced retain i.e., ownership is transferred to the CellLayout instance.

    Declaration

    Swift

    @inlinable
    public init!(_ op: UnsafeMutablePointer<GtkCellLayout>?)

    Parameters

    op

    pointer to the underlying object

  • Designated initialiser from the underlying C data type. GtkCellLayout does not allow reference counting, so despite the name no actual retaining will occur. i.e., ownership is transferred to the CellLayout instance.

    Declaration

    Swift

    @inlinable
    public init(retaining op: UnsafeMutablePointer<GtkCellLayout>)

    Parameters

    op

    pointer to the underlying object

  • Reference intialiser for a related type that implements CellLayoutProtocol GtkCellLayout does not allow reference counting.

    Declaration

    Swift

    @inlinable
    public init<T>(_ other: T) where T : CellLayoutProtocol

    Parameters

    other

    an instance of a related type that implements CellLayoutProtocol

  • Unsafe typed initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public init<T>(cPointer p: UnsafeMutablePointer<T>)

    Parameters

    cPointer

    pointer to the underlying object

  • Unsafe typed, retaining initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public init<T>(retainingCPointer cPointer: UnsafeMutablePointer<T>)

    Parameters

    cPointer

    pointer to the underlying object

  • Unsafe untyped initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public init(raw p: UnsafeRawPointer)

    Parameters

    p

    raw pointer to the underlying object

  • Unsafe untyped, retaining initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public init(retainingRaw raw: UnsafeRawPointer)
  • Unsafe untyped initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public required init(raw p: UnsafeMutableRawPointer)

    Parameters

    p

    mutable raw pointer to the underlying object

  • Unsafe untyped, retaining initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public init(retainingRaw raw: UnsafeMutableRawPointer)

    Parameters

    raw

    mutable raw pointer to the underlying object

  • Unsafe untyped initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public init(opaquePointer p: OpaquePointer)

    Parameters

    p

    opaque pointer to the underlying object

  • Unsafe untyped, retaining initialiser. Do not use unless you know the underlying data type the pointer points to conforms to CellLayoutProtocol.

    Declaration

    Swift

    @inlinable
    public init(retainingOpaquePointer p: OpaquePointer)

    Parameters

    p

    opaque pointer to the underlying object