Package: gio

Interface g-list-model

Superclasses

g-object, common-lisp:standard-object, common-lisp:t

Documented Subclasses

Direct Slots

None

Details

The g-list-model interface is an interface that represents a mutable list of g-object instances. 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 g-list-model implementation 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 g-list-model instance are of, or derived from, the same type. The g-list-model-item-type function 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: the g-list-model-n-items function returns the number of items in the list and the g-list-model-item function 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 the g-list-model-item function until it returns nil.

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 in effect at the time that the model was created.

Signal Details

The "items-changed" signal
 lambda (list position removed added)    :run-last      
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 is not equal added, the positions of all later items in the model change.
list
The g-list-model instance that changed.
position
An unsigned integer with the position at which list changed.
removed
An unsigned integer with the number of items removed.
added
An unsigned integer with the number of items addes.
 

Inherited Slot Access Functions

See also

2021-11-15