Gtk.CellLayout

Gtk.CellLayout — An interface for packing cells

Object Hierarchy:

    GInterface
    ╰── Gtk.CellLayout

Functions:

Description:

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

One of the notable features provided by implementations of Gtk.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.CellLayout::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.CellLayout::set_cell_data_func() that is called to determine the value of the attribute for each cell that is rendered.

Gtk.CellLayouts as Gtk.Buildable

Implementations of Gtk.CellLayout which also implement the GtkBuildable interface (Gtk.CellView, GtkIconView, GtkComboBox, Gtk.EntryCompletion, GtkTreeViewColumn) accept GtkCellRenderer objects as \ elements in UI definitions. They support a custom \ element for their children, which can contain multiple \ elements. Each \ 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 Gtk.CellLayout that use a GtkCellArea to lay out cells (all Gtk.CellLayouts in GTK+ use a GtkCellArea) [cell properties][cell-properties] can also be defined in the format by specifying the custom \ attribute which can contain multiple \ 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 Gtk.CellLayout implementations

When subclassing a widget that implements Gtk.CellLayout like Gtk.IconView or GtkComboBox, there are some considerations related to the fact that these widgets internally use a Gtk.CellArea.

The cell area is exposed as a construct-only property by these widgets. This means that it is possible to e.g. do

    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).

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.

Function Details:

pack_start()

pack_start (self, cell:Gtk.CellRenderer, expand:bool)

Packs the cell into the beginning of cell_layout. If expand is FALSE,then the cell is allocated no more space than it needs. Any unused spaceis divided evenly between cells for which expand is True. Note that reusing the same cell renderer is not supported.

  • Since: 2.4

pack_end()

pack_end (self, cell:Gtk.CellRenderer, expand:bool)

Adds the cell to the end of cell_layout. If expand is FALSE, then thecell is allocated no more space than it needs. Any unused space isdivided evenly between cells for which expand is True. Note that reusing the same cell renderer is not supported.

  • Since: 2.4

get_area()

get_area (self) -> Gtk.CellArea or None

Returns the underlying Gtk.CellArea which might be cell_layoutif called on a Gtk.CellArea or might be None if no Gtk.CellAreais used by cell_layout.

  • Returns: the cell area used by cell_layout,or None in case no cell area is used.

  • Since: 3.0

get_cells()

get_cells (self) -> list

Returns the cell renderers which have been added to cell_layout.

  • Returns: a list of cell renderers. The list, but not the renderers hasbeen newly allocated and should be freed with g_list_free()when no longer needed.

  • Since: 2.12

reorder()

reorder (self, cell:Gtk.CellRenderer, position:int)

Re-inserts cell at position. Note that cell has already to be packed into cell_layoutfor this to function properly.

  • Since: 2.4

clear()

clear (self)

Unsets all the mappings on all renderers on cell_layout andremoves all renderers from cell_layout.

  • Since: 2.4

add_attribute()

add_attribute (self, cell:Gtk.CellRenderer, attribute:str, column:int)

Adds an attribute mapping to the list in cell_layout. The column is the column of the model to get a value from, and theattribute is the parameter on cell to be set from the value. So forexample if column 2 of the model contains strings, you could have the“text” attribute of a Gtk.CellRendererText get its values from column 2.

  • Since: 2.4

set_cell_data_func()

set_cell_data_func (self, cell:Gtk.CellRenderer, func:Gtk.CellLayoutDataFunc=None, func_data=None)

Sets the Gtk.CellLayoutDataFunc to use for cell_layout. This function is used instead of the standard attributes mappingfor setting the column value, and should set the value of cell_layout’scell renderer(s) as appropriate. func may be None to remove a previously set function.

  • Since: 2.4

clear_attributes()

clear_attributes (self, cell:Gtk.CellRenderer)

Clears all existing attributes previously set withGtk.CellLayout:set_attributes().

  • Since: 2.4

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