GI.Gtk.Objects.LayoutManager

Layout managers are delegate classes that handle the preferred size and the allocation of a container widget.

You typically subclass LayoutManager if you want to implement a layout policy for the children of a widget, or if you want to determine the size of a widget depending on its contents.

Each Widget can only have a LayoutManager instance associated to it at any given time; it is possible, though, to replace the layout manager instance using widgetSetLayoutManager.

Layout properties

A layout manager can expose properties for controlling the layout of each child, by creating an object type derived from LayoutChild and installing the properties on it as normal GObject properties.

Each LayoutChild instance storing the layout properties for a specific child is created through the layoutManagerGetLayoutChild method; a LayoutManager controls the creation of its LayoutChild instances by overriding the GtkLayoutManagerClass.create_layout_child() virtual function. The typical implementation should look like:

C code

static GtkLayoutChild *
create_layout_child (GtkLayoutManager *manager,
                     GtkWidget        *container,
                     GtkWidget        *child)
{
  return g_object_new (your_layout_child_get_type (),
                       "layout-manager", manager,
                       "child-widget", child,
                       NULL);
}

The LayoutChild:layout-manager and LayoutChild:child-widget properties on the newly created LayoutChild instance are mandatory. The LayoutManager will cache the newly created LayoutChild instance until the widget is removed from its parent, or the parent removes the layout manager.

Each LayoutManager instance creating a LayoutChild should use layoutManagerGetLayoutChild every time it needs to query the layout properties; each LayoutChild instance should call layoutManagerLayoutChanged every time a property is updated, in order to queue a new size measuring and allocation.

Exported types

newtype LayoutManager

Memory-managed wrapper type.

Constructors

LayoutManager (ManagedPtr LayoutManager)

Instances

Eq LayoutManager

Defined in GI.Gtk.Objects.LayoutManager

Methods

(==) :: LayoutManager -> LayoutManager -> Bool

(/=) :: LayoutManager -> LayoutManager -> Bool

IsGValue LayoutManager

Convert LayoutManager to and from GValue with toGValue and fromGValue.

Defined in GI.Gtk.Objects.LayoutManager

Methods

toGValue :: LayoutManager -> IO GValue

fromGValue :: GValue -> IO LayoutManager

ManagedPtrNewtype LayoutManager

Defined in GI.Gtk.Objects.LayoutManager

Methods

toManagedPtr :: LayoutManager -> ManagedPtr LayoutManager

TypedObject LayoutManager

Defined in GI.Gtk.Objects.LayoutManager

Methods

glibType :: IO GType

GObject LayoutManager

Defined in GI.Gtk.Objects.LayoutManager

HasParentTypes LayoutManager

Defined in GI.Gtk.Objects.LayoutManager

type ParentTypes LayoutManager

Defined in GI.Gtk.Objects.LayoutManager

type ParentTypes LayoutManager = '[Object]

class (GObject o, IsDescendantOf LayoutManager o) => IsLayoutManager o

Type class for types which can be safely cast to LayoutManager, for instance with toLayoutManager.

Instances

(GObject o, IsDescendantOf LayoutManager o) => IsLayoutManager o

Defined in GI.Gtk.Objects.LayoutManager

toLayoutManager :: (MonadIO m, IsLayoutManager o) => o -> m LayoutManager

Cast to LayoutManager, for types for which this is known to be safe. For general casts, use castTo.

Methods

Overloaded methods

allocate

layoutManagerAllocate

Arguments

:: (HasCallStack, MonadIO m, IsLayoutManager a, IsWidget b)

=> a

manager: a LayoutManager

-> b

widget: the Widget using manager

-> Int32

width: the new width of the widget

-> Int32

height: the new height of the widget

-> Int32

baseline: the baseline position of the widget, or -1

-> m ()

This function assigns the given width, height, and baseline to a widget, and computes the position and sizes of the children of the widget using the layout management policy of manager.

getLayoutChild

layoutManagerGetLayoutChild

Arguments

:: (HasCallStack, MonadIO m, IsLayoutManager a, IsWidget b)

=> a

manager: a LayoutManager

-> b

child: a Widget

-> m LayoutChild

Returns: a LayoutChild

Retrieves a LayoutChild instance for the LayoutManager, creating one if necessary.

The child widget must be a child of the widget using manager.

The LayoutChild instance is owned by the LayoutManager, and is guaranteed to exist as long as child is a child of the Widget using the given LayoutManager.

getRequestMode

layoutManagerGetRequestMode

Arguments

:: (HasCallStack, MonadIO m, IsLayoutManager a)

=> a

manager: a LayoutManager

-> m SizeRequestMode

Returns: a SizeRequestMode

Retrieves the request mode of manager.

getWidget

layoutManagerGetWidget

Arguments

:: (HasCallStack, MonadIO m, IsLayoutManager a)

=> a

manager: a LayoutManager

-> m (Maybe Widget)

Returns: a Widget

Retrieves the Widget using the given LayoutManager.

layoutChanged

layoutManagerLayoutChanged

Arguments

:: (HasCallStack, MonadIO m, IsLayoutManager a)

=> a

manager: a LayoutManager

-> m ()

Queues a resize on the Widget using manager, if any.

This function should be called by subclasses of LayoutManager in response to changes to their layout management policies.

measure

layoutManagerMeasure

Arguments

:: (HasCallStack, MonadIO m, IsLayoutManager a, IsWidget b)

=> a

manager: a LayoutManager

-> b

widget: the Widget using manager

-> Orientation

orientation: the orientation to measure

-> Int32

forSize: Size for the opposite of orientation; for instance, if the orientation is OrientationHorizontal, this is the height of the widget; if the orientation is OrientationVertical, this is the width of the widget. This allows to measure the height for the given width, and the width for the given height. Use -1 if the size is not known

-> m (Int32, Int32, Int32, Int32)

Measures the size of the widget using manager, for the given orientation and size.

See [GtkWidget's geometry management section][geometry-management] for more details.