Copyright | Will Thompson and Iñaki García Etxebarria |
---|---|
License | LGPL-2.1 |
Maintainer | Iñaki García Etxebarria |
Safe Haskell | None |
Language | Haskell2010 |
GListModel
is an interface that represents a mutable list of
Object
. 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 Object::notify signal). Taken together with the ListModel::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 GListModel
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 GListModel
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 listModelGetItem
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
listModelGetItem
until it returns NULL
.
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 facilitate 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 (see
mainContextPushThreadDefault
) in effect at the time that the
model was created.
Over time, it has established itself as good practice for list model
implementations to provide properties item-type
and n-items
to
ease working with them. While it is not required, it is recommended
that implementations provide these two properties. They should return
the values of listModelGetItemType
and
listModelGetNItems
respectively and be defined as such:
c code
properties[PROP_ITEM_TYPE] = g_param_spec_gtype ("item-type", NULL, NULL, G_TYPE_OBJECT, G_PARAM_CONSTRUCT_ONLY | G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS); properties[PROP_N_ITEMS] = g_param_spec_uint ("n-items", NULL, NULL, 0, G_MAXUINT, 0, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);
Synopsis
- newtype ListModel = ListModel (ManagedPtr ListModel)
- class (GObject o, IsDescendantOf ListModel o) => IsListModel o
- toListModel :: (MonadIO m, IsListModel o) => o -> m ListModel
- listModelGetItem :: (HasCallStack, MonadIO m, IsListModel a) => a -> Word32 -> m (Maybe Object)
- listModelGetItemType :: (HasCallStack, MonadIO m, IsListModel a) => a -> m GType
- listModelGetNItems :: (HasCallStack, MonadIO m, IsListModel a) => a -> m Word32
- listModelItemsChanged :: (HasCallStack, MonadIO m, IsListModel a) => a -> Word32 -> Word32 -> Word32 -> m ()
- type ListModelItemsChangedCallback = Word32 -> Word32 -> Word32 -> IO ()
- afterListModelItemsChanged :: (IsListModel a, MonadIO m) => a -> ((?self :: a) => ListModelItemsChangedCallback) -> m SignalHandlerId
- onListModelItemsChanged :: (IsListModel a, MonadIO m) => a -> ((?self :: a) => ListModelItemsChangedCallback) -> m SignalHandlerId
Exported types
Memory-managed wrapper type.
Instances
Eq ListModel Source # | |
GObject ListModel Source # | |
Defined in GI.Gio.Interfaces.ListModel | |
ManagedPtrNewtype ListModel Source # | |
Defined in GI.Gio.Interfaces.ListModel | |
TypedObject ListModel Source # | |
Defined in GI.Gio.Interfaces.ListModel | |
HasParentTypes ListModel Source # | |
Defined in GI.Gio.Interfaces.ListModel | |
IsGValue (Maybe ListModel) Source # | Convert |
Defined in GI.Gio.Interfaces.ListModel | |
type ParentTypes ListModel Source # | |
Defined in GI.Gio.Interfaces.ListModel type ParentTypes ListModel = '[Object] |
class (GObject o, IsDescendantOf ListModel o) => IsListModel o Source #
Type class for types which can be safely cast to ListModel
, for instance with toListModel
.
Instances
(GObject o, IsDescendantOf ListModel o) => IsListModel o Source # | |
Defined in GI.Gio.Interfaces.ListModel |
toListModel :: (MonadIO m, IsListModel o) => o -> m ListModel Source #
Methods
Click to display all available methods, including inherited ones
Methods
bindProperty, bindPropertyFull, forceFloating, freezeNotify, getv, isFloating, itemsChanged, notify, notifyByPspec, ref, refSink, runDispose, stealData, stealQdata, thawNotify, unref, watchClosure.
Getters
getData, getItem, getItemType, getNItems, getProperty, getQdata.
Setters
getItem
:: (HasCallStack, MonadIO m, IsListModel a) | |
=> a |
|
-> Word32 |
|
-> m (Maybe Object) | Returns: the object at |
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.
This function is meant to be used by language bindings in place
of g_list_model_get_item()
.
See also: listModelGetNItems
Since: 2.44
getItemType
:: (HasCallStack, MonadIO m, IsListModel a) | |
=> a |
|
-> m GType | Returns: the |
Gets the type of the items in list
.
All items returned from g_list_model_get_item()
are of the type
returned by this function, or a subtype, or if the type is an
interface, they 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
:: (HasCallStack, MonadIO m, IsListModel a) | |
=> a |
|
-> m Word32 | Returns: the number of items in |
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 Source #
:: (HasCallStack, MonadIO m, IsListModel a) | |
=> a |
|
-> Word32 |
|
-> Word32 |
|
-> Word32 |
|
-> m () |
Emits the ListModel::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 ListModelItemsChangedCallback Source #
= Word32 |
|
-> Word32 |
|
-> Word32 |
|
-> IO () |
This signal is emitted whenever items were added to or removed
from list
. At position
, removed
items were removed and added
items were added in their place.
Note: If removed != added
, the positions of all later items
in the model change.
Since: 2.44
afterListModelItemsChanged :: (IsListModel a, MonadIO m) => a -> ((?self :: a) => ListModelItemsChangedCallback) -> m SignalHandlerId Source #
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
By default the object invoking the signal is not passed to the callback.
If you need to access it, you can use the implit ?self
parameter.
Note that this requires activating the ImplicitParams
GHC extension.
onListModelItemsChanged :: (IsListModel a, MonadIO m) => a -> ((?self :: a) => ListModelItemsChangedCallback) -> m SignalHandlerId Source #
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