Struct gtk4::CellLayout

#[repr(transparent)]
pub struct CellLayout { /* private fields */ }

An interface for packing cells

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

One of the notable features provided by implementations of CellLayout 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 (CellView, IconView, ComboBox, EntryCompletion, TreeViewColumn) accept CellRenderer 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 CellLayout that use a CellArea to lay out cells (all CellLayouts in GTK use a CellArea) cell properties can also be defined in the format by specifying the custom <cell-packing> attribute which can contain multiple <property> elements.

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 CellLayout like IconView or ComboBox, there are some considerations related to the fact that these widgets internally use a CellArea. The cell area is exposed as a construct-only property by these widgets. This means that it is possible to e.g. do

⚠️ The following code is in c ⚠️

GtkWIdget *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).

⚠️ The following code is in c ⚠️

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.

Implements

CellLayoutExt, CellLayoutExtManual

Implementations

impl CellLayout

pub const NONE: Option<&'static CellLayout> = None

Trait Implementations

impl Clone for CellLayout

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for CellLayout

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for CellLayout

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for CellLayout

fn hash<H>(&self, state: &mut H)where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T: CellLayoutImpl> IsImplementable<T> for CellLayout

fn interface_init(iface: &mut Interface<Self>)

Override the virtual methods of this interface for the given subclass and do other interface initialization.

fn instance_init(_instance: &mut InitializingObject<T>)

Instance specific initialization.

impl Ord for CellLayout

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl<OT: ObjectType> PartialEq<OT> for CellLayout

fn eq(&self, other: &OT) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for CellLayout

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for CellLayout

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for CellLayout

impl IsA<CellLayout> for CellArea

impl IsA<CellLayout> for CellAreaBox

impl IsA<CellLayout> for CellView

impl IsA<CellLayout> for ComboBox

impl IsA<CellLayout> for ComboBoxText

impl IsA<CellLayout> for EntryCompletion

impl IsA<CellLayout> for IconView

impl IsA<CellLayout> for TreeViewColumn