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.

1
2
3
4
5
6
7
8

<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.

1
2
3
4
5
6
7
8
9

<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

1

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).

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

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.

GtkCellLayout

typedef struct _GtkCellLayout GtkCellLayout;

struct GtkCellLayoutIface

struct GtkCellLayoutIface {
  GTypeInterface g_iface;

  /* Virtual Table */
  void (* pack_start)         (GtkCellLayout         *cell_layout,
                               GtkCellRenderer       *cell,
                               gboolean               expand);
  void (* pack_end)           (GtkCellLayout         *cell_layout,
                               GtkCellRenderer       *cell,
                               gboolean               expand);
  void (* clear)              (GtkCellLayout         *cell_layout);
  void (* add_attribute)      (GtkCellLayout         *cell_layout,
                               GtkCellRenderer       *cell,
                               const gchar           *attribute,
                               gint                   column);
  void (* set_cell_data_func) (GtkCellLayout         *cell_layout,
                               GtkCellRenderer       *cell,
                               GtkCellLayoutDataFunc  func,
                               gpointer               func_data,
                               GDestroyNotify         destroy);
  void (* clear_attributes)   (GtkCellLayout         *cell_layout,
                               GtkCellRenderer       *cell);
  void (* reorder)            (GtkCellLayout         *cell_layout,
                               GtkCellRenderer       *cell,
                               gint                   position);
  GList* (* get_cells)        (GtkCellLayout         *cell_layout);

  GtkCellArea *(* get_area)   (GtkCellLayout         *cell_layout);
};

GtkCellLayoutDataFunc ()

void                (*GtkCellLayoutDataFunc)            (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell,
                                                         GtkTreeModel *tree_model,
                                                         GtkTreeIter *iter,
                                                         gpointer data);

A function which should set the value of cell_layout's cell renderer(s) as appropriate.

gtk_cell_layout_pack_start ()

void                gtk_cell_layout_pack_start          (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell,
                                                         gboolean expand);

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.

Since 2.4

gtk_cell_layout_pack_end ()

void                gtk_cell_layout_pack_end            (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell,
                                                         gboolean expand);

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.

Since 2.4

gtk_cell_layout_get_area ()

GtkCellArea *       gtk_cell_layout_get_area            (GtkCellLayout *cell_layout);

Returns the underlying GtkCellArea which might be cell_layout if called on a GtkCellArea or might be NULL if no GtkCellArea is used by cell_layout.

Since 3.0

gtk_cell_layout_get_cells ()

GList *             gtk_cell_layout_get_cells           (GtkCellLayout *cell_layout);

Returns the cell renderers which have been added to cell_layout.

Since 2.12

gtk_cell_layout_reorder ()

void                gtk_cell_layout_reorder             (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell,
                                                         gint position);

Re-inserts cell at position.

Note that cell has already to be packed into cell_layout for this to function properly.

Since 2.4

gtk_cell_layout_clear ()

void                gtk_cell_layout_clear               (GtkCellLayout *cell_layout);

Unsets all the mappings on all renderers on cell_layout and removes all renderers from cell_layout.

Since 2.4

gtk_cell_layout_set_attributes ()

void                gtk_cell_layout_set_attributes      (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell,
                                                         ...);

Sets the attributes in list as the attributes of cell_layout.

The attributes should be in attribute/column order, as in gtk_cell_layout_add_attribute(). All existing attributes are removed, and replaced with the new attributes.

Since 2.4

gtk_cell_layout_add_attribute ()

void                gtk_cell_layout_add_attribute       (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell,
                                                         const gchar *attribute,
                                                         gint column);

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 parameter on cell to be set from the 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.

Since 2.4

gtk_cell_layout_set_cell_data_func ()

void                gtk_cell_layout_set_cell_data_func  (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell,
                                                         GtkCellLayoutDataFunc func,
                                                         gpointer func_data,
                                                         GDestroyNotify destroy);

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.

Since 2.4

gtk_cell_layout_clear_attributes ()

void                gtk_cell_layout_clear_attributes    (GtkCellLayout *cell_layout,
                                                         GtkCellRenderer *cell);

Clears all existing attributes previously set with gtk_cell_layout_set_attributes().

Since 2.4