Description
GListModel 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 “items-changed” 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.
g_list_model_get_item_type() 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:
g_list_model_get_n_items() 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 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 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
in effect at the time that the model was created.
Functions
g_list_model_get_item_type ()
GType
g_list_model_get_item_type (GListModel *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 GListModel can not change during the life of the
model.
Returns
the GType of the items contained in list
.
Since: 2.44
g_list_model_get_n_items ()
guint
g_list_model_get_n_items (GListModel *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 NULL.
Returns
the number of items in list
.
Since: 2.44
g_list_model_get_item ()
gpointer
g_list_model_get_item (GListModel *list,
guint position);
Get the item at position
. If position
is greater than the number of
items in list
, NULL is returned.
NULL is never returned for an index that is smaller than the length
of the list. See g_list_model_get_n_items().
[skip]
Returns
the item at position
.
[transfer full][nullable]
Since: 2.44
g_list_model_get_object ()
GObject *
g_list_model_get_object (GListModel *list,
guint position);
Get the item at position
. If position
is greater than the number of
items in list
, NULL is returned.
NULL is never returned for an index that is smaller than the length
of the list. See g_list_model_get_n_items().
[rename-to g_list_model_get_item]
Returns
the object at position
.
[transfer full][nullable]
Since: 2.44
g_list_model_items_changed ()
void
g_list_model_items_changed (GListModel *list,
guint position,
guint removed,
guint added);
Emits the “items-changed” signal on list
.
This function should only be called by classes implementing
GListModel. 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 GListStore), 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 GListModel
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
Signal Details
The “items-changed” signal
void
user_function (GListModel *list,
guint position,
guint removed,
guint added,
gpointer user_data)
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.
Flags: Run Last
Since: 2.44