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:
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 `GtkCellLayout`s in GTK use a
`GtkCellArea`) [cell properties](class.CellArea.htmlcell-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:
```xml <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 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).
```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.
<group>Trees and Lists</group>
<gtkada_demo>create_cell_view.adb</gtkada_demo>
function "+" (W : Gtk_Cell_Layout) return Gtk_Cell_Layout
procedure Add_Attribute
(Self : Gtk_Cell_Layout;
Cell : not null access Gtk.Cell_Renderer.Gtk_Cell_Renderer_Record'Class;
Attribute : UTF8_String;
Column : Glib.Gint)
Adds an attribute mapping to the list in Cell_Layout. The Column is the column of the model to get a value from, and the Attribute is the property on Cell to be set from that value. So for example if column 2 of the model contains strings, you could have the "text" attribute of a GtkCellRendererText get its values from column 2. In this context "attribute" and "property" are used interchangeably. Deprecated since 4.10, 1
a GtkCellRenderer
a property on the renderer
the column position on the model to get the attribute from
procedure Clear (Self : Gtk_Cell_Layout)
Unsets all the mappings on all renderers on Cell_Layout and removes all renderers from Cell_Layout. Deprecated since 4.10, 1
procedure Clear_Attributes
(Self : Gtk_Cell_Layout;
Cell : not null access Gtk.Cell_Renderer.Gtk_Cell_Renderer_Record'Class)
Clears all existing attributes previously set with gtk_cell_layout_set_attributes. Deprecated since 4.10, 1
a GtkCellRenderer to clear the attribute mapping on
function Get_Cells
(Self : Gtk_Cell_Layout)
return Gtk.Cell_Renderer.Cell_Renderer_List.Glist
Returns the cell renderers which have been added to Cell_Layout. Deprecated since 4.10, 1
a list of cell renderers. The list, but not the renderers has been newly allocated and should be freed with g_list_free when no longer needed.
function Get_Type return Glib.GType
type Gtk_Cell_Layout is new Glib.Types.GType_Interface;
type Gtk_Cell_Layout_Data_Func is access procedure
(Cell_Layout : Gtk_Cell_Layout;
Cell : not null access Gtk.Cell_Renderer.Gtk_Cell_Renderer_Record'Class;
Tree_Model : Gtk.Tree_Model.Gtk_Tree_Model;
Iter : Gtk.Tree_Model.Gtk_Tree_Iter);
A function which should set the value of Cell_Layout's cell renderer(s) as appropriate.
a GtkCellLayout
the cell renderer whose value is to be set
the model
a GtkTreeIter indicating the row to set the value for
Null_Gtk_Cell_Layout : constant Gtk_Cell_Layout;
procedure Pack_End
(Self : Gtk_Cell_Layout;
Cell : not null access Gtk.Cell_Renderer.Gtk_Cell_Renderer_Record'Class;
Expand : Boolean)
Adds the Cell to the end of Cell_Layout. If Expand is False, then the Cell is allocated no more space than it needs. Any unused space is divided evenly between cells for which Expand is True. Note that reusing the same cell renderer is not supported. Deprecated since 4.10, 1
a GtkCellRenderer
True if Cell is to be given extra space allocated to Cell_Layout
procedure Pack_Start
(Self : Gtk_Cell_Layout;
Cell : not null access Gtk.Cell_Renderer.Gtk_Cell_Renderer_Record'Class;
Expand : Boolean)
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 space is divided evenly between cells for which Expand is True. Note that reusing the same cell renderer is not supported. Deprecated since 4.10, 1
a GtkCellRenderer
True if Cell is to be given extra space allocated to Cell_Layout
procedure Reorder
(Self : Gtk_Cell_Layout;
Cell : not null access Gtk.Cell_Renderer.Gtk_Cell_Renderer_Record'Class;
Position : Glib.Gint)
Re-inserts Cell at Position. Note that Cell has already to be packed into Cell_Layout for this to function properly. Deprecated since 4.10, 1
a GtkCellRenderer to reorder
new position to insert Cell at
procedure Set_Cell_Data_Func
(Self : Gtk_Cell_Layout;
Cell : not null access Gtk.Cell_Renderer.Gtk_Cell_Renderer_Record'Class;
Func : Gtk_Cell_Layout_Data_Func)
Sets the GtkCellLayoutDataFunc to use for Cell_Layout. This function is used instead of the standard attributes mapping for setting the column value, and should set the value of Cell_Layout's cell renderer(s) as appropriate. Func may be null to remove a previously set function. Deprecated since 4.10, 1
a GtkCellRenderer
the GtkCellLayoutDataFunc to use