Struct gtk4::CellLayout[][src]

pub struct CellLayout(_);
Expand description

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 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 CellLayoutExt::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 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:

⚠️ The following code is in C ⚠️

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

Trait Implementations

Returns a copy of the value. Read more

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Feeds a slice of this type into the given Hasher. Read more

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

Instance specific initialization. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

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Restrict a value to a certain interval. Read more

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

This method tests for !=.

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

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

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

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

Returns the type identifier of Self.

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Gets the TypeId of self. Read more

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Upcasts an object to a superclass or interface T. Read more

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Tries to cast to reference to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more

Casts to T unconditionally. Read more

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Performs the conversion.

Performs the conversion.

Returns true if the object is an instance of (can be cast to) T.

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Same as connect but takes a SignalId instead of a signal name.

Same as connect_local but takes a SignalId instead of a signal name.

Same as connect_unsafe but takes a SignalId instead of a signal name.

Emit signal by signal id.

Same as emit but takes Value for the arguments.

Emit signal by its name.

Same as emit_by_name but takes Value for the arguments.

Emit signal with details by signal id.

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The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

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The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.