GI.Gio.Interfaces.ListModel

ListModel is an interface that represents a mutable list of GObjects. Its main intention is as a model for various widgets in user interfaces, such as list views, but it can also be used as a convenient method of returning lists of data, with support for updates.

Each object in the list may also report changes in itself via some mechanism (normally the notify signal). Taken together with the itemsChanged signal, this provides for a list that can change its membership, and in which the members can change their individual properties.

A good example would be the list of visible wireless network access points, where each access point can report dynamic properties such as signal strength.

It is important to note that the ListModel itself does not report changes to the individual items. It only reports changes to the list membership. If you want to observe changes to the objects themselves then you need to connect signals to the objects that you are interested in.

All items in a ListModel are of (or derived from) the same type. listModelGetItemType returns that type. The type may be an interface, in which case all objects in the list must implement it.

The semantics are close to that of an array: listModelGetNItems returns the number of items in the list and g_list_model_get_item() returns an item at a (0-based) position. In order to allow implementations to calculate the list length lazily, you can also iterate over items: starting from 0, repeatedly call g_list_model_get_item() until it returns Nothing.

An implementation may create objects lazily, but must take care to return the same object for a given position until all references to it are gone.

On the other side, a consumer is expected only to hold references on objects that are currently "user visible", in order to faciliate the maximum level of laziness in the implementation of the list and to reduce the required number of signal connections at a given time.

This interface is intended only to be used from a single thread. The thread in which it is appropriate to use it depends on the particular implementation, but typically it will be from the thread that owns the [thread-default main context][g-main-context-push-thread-default] in effect at the time that the model was created.

Exported types

newtype ListModel

Memory-managed wrapper type.

Constructors

ListModel (ManagedPtr ListModel)

Instances

Eq ListModel

Defined in GI.Gio.Interfaces.ListModel

Methods

(==) :: ListModel -> ListModel -> Bool

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

GObject ListModel

Defined in GI.Gio.Interfaces.ListModel

Methods

gobjectType :: IO GType

IsGValue ListModel

Convert ListModel to and from GValue with toGValue and fromGValue.

Defined in GI.Gio.Interfaces.ListModel

Methods

toGValue :: ListModel -> IO GValue

fromGValue :: GValue -> IO ListModel

HasParentTypes ListModel

Defined in GI.Gio.Interfaces.ListModel

type ParentTypes ListModel

Defined in GI.Gio.Interfaces.ListModel

type ParentTypes ListModel = '[Object]

noListModel :: Maybe ListModel

A convenience alias for Nothing :: Maybe ListModel.

class (GObject o, IsDescendantOf ListModel o) => IsListModel o

Type class for types which can be safely cast to ListModel, for instance with toListModel.

Instances

(GObject o, IsDescendantOf ListModel o) => IsListModel o

Defined in GI.Gio.Interfaces.ListModel

toListModel :: (MonadIO m, IsListModel o) => o -> m ListModel

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

Methods

Overloaded methods

getItem

listModelGetItem

Arguments

:: (HasCallStack, MonadIO m, IsListModel a)

=> a

list: a ListModel

-> Word32

position: the position of the item to fetch

-> m (Maybe Object)

Returns: the object at position.

Get the item at position. If position is greater than the number of items in list, Nothing is returned.

Nothing is never returned for an index that is smaller than the length of the list. See listModelGetNItems.

Since: 2.44

getItemType

listModelGetItemType

Arguments

:: (HasCallStack, MonadIO m, IsListModel a)

=> a

list: a ListModel

-> m GType

Returns: the GType of the items contained in list.

Gets the type of the items in list. All items returned from g_list_model_get_type() are of that type or a subtype, or are an implementation of that interface.

The item type of a ListModel can not change during the life of the model.

Since: 2.44

getNItems

listModelGetNItems

Arguments

:: (HasCallStack, MonadIO m, IsListModel a)

=> a

list: a ListModel

-> m Word32

Returns: the number of items in list.

Gets the number of items in list.

Depending on the model implementation, calling this function may be less efficient than iterating the list with increasing values for position until g_list_model_get_item() returns Nothing.

Since: 2.44

itemsChanged

listModelItemsChanged

Arguments

:: (HasCallStack, MonadIO m, IsListModel a)

=> a

list: a ListModel

-> Word32

position: the position at which list changed

-> Word32

removed: the number of items removed

-> Word32

added: the number of items added

-> m ()

Emits the itemsChanged signal on list.

This function should only be called by classes implementing ListModel. It has to be called after the internal representation of list has been updated, because handlers connected to this signal might query the new state of the list.

Implementations must only make changes to the model (as visible to its consumer) in places that will not cause problems for that consumer. For models that are driven directly by a write API (such as ListStore), changes can be reported in response to uses of that API. For models that represent remote data, changes should only be made from a fresh mainloop dispatch. It is particularly not permitted to make changes in response to a call to the ListModel consumer API.

Stated another way: in general, it is assumed that code making a series of accesses to the model via the API, without returning to the mainloop, and without calling other code, will continue to view the same contents of the model.

Since: 2.44

Signals

itemsChanged

type C_ListModelItemsChangedCallback = Ptr () -> Word32 -> Word32 -> Word32 -> Ptr () -> IO ()

Type for the callback on the (unwrapped) C side.

type ListModelItemsChangedCallback

Arguments

 = Word32

position: the position at which list changed

-> Word32

removed: the number of items removed

-> Word32

added: the number of items added

-> IO ()

This signal is emitted whenever items were added or removed to list. At position, removed items were removed and added items were added in their place.

Since: 2.44

afterListModelItemsChanged :: (IsListModel a, MonadIO m) => a -> ListModelItemsChangedCallback -> m SignalHandlerId

Connect a signal handler for the itemsChanged signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after listModel #itemsChanged callback

genClosure_ListModelItemsChanged :: MonadIO m => ListModelItemsChangedCallback -> m (GClosure C_ListModelItemsChangedCallback)

Wrap the callback into a GClosure.

mk_ListModelItemsChangedCallback :: C_ListModelItemsChangedCallback -> IO (FunPtr C_ListModelItemsChangedCallback)

Generate a function pointer callable from C code, from a C_ListModelItemsChangedCallback.

noListModelItemsChangedCallback :: Maybe ListModelItemsChangedCallback

A convenience synonym for Nothing :: Maybe ListModelItemsChangedCallback.

onListModelItemsChanged :: (IsListModel a, MonadIO m) => a -> ListModelItemsChangedCallback -> m SignalHandlerId

Connect a signal handler for the itemsChanged signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on listModel #itemsChanged callback

wrap_ListModelItemsChangedCallback :: ListModelItemsChangedCallback -> C_ListModelItemsChangedCallback

Wrap a ListModelItemsChangedCallback into a C_ListModelItemsChangedCallback.