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Interface Gtk.CellLayout

Import line: Gtk = imports.gi.Gtk;
GIR File: Gtk-3.0.gir
C documentation: GtkCellLayout
Interface : CellLayout
Implementations: GWeather.TimezoneMenu, Gtk.AppChooserButton, Gtk.CellArea, Gtk.CellAreaBox, Gtk.CellView, Gtk.ComboBox, Gtk.ComboBoxText, Gtk.EntryCompletion, Gtk.IconView, Gtk.TreeViewColumn
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, GtkComboBoxEntry,
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.

A UI definition fragment specifying attributes




0

"

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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.

A UI definition fragment specifying cell properties




True
False

"

]]>




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

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.
Properties
None
Methods / Constructors
Method / Constructor Defined By
Events
None
Documentation generated by Introspection Doc Generator Loosely Based on JsDoc Toolkit on Sat Apr 16 2011 17:14:41 GMT+0800 (HKT)