Introduce a new class, EventEmitter, which implements signal
handling for pure JavaScript classes. EventEmitter still
utilizes GJS' addSignalMethods internally.
EventEmitter allows static typechecking to understand the
structure of event-emitting JS classes and makes creating
child classes simpler.
The name 'EventEmitter' mirrors a common name for this pattern
in Node and in JS libraries.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2043>
We currently assume that any '::destroy' signal on a GObject type
has the semantics of the ClutterActor/GtkWidget signal, and should
therefore result in all signals being disconnected.
But we already have a case where the assumption doesn't hold: ShellWM
uses '::destroy' for the closing animation of windows, and the ShellWM
object itself remains very valid after the emission.
So rather than making assumptions about '::destroy', check objects
against a list of destroyable types that are explicitly registered
as such.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2226>
There are cases where we want to connect to a number of signals
for the lifetime of an object, but also other signals for a
limited period (say: between show and hide).
It is currently not possible to use disconnectObject() for the
latter, because it will disconnect all signals.
To address this use case, add a small class that can be used as
a transient signal holder, while still benefiting from autocleanup
by proxying the real owner.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2221>
The 'destroy' signal currently doesn't work with connectObject(),
because the handler is only connected after the signal tracker's
own destroy handler, which disconnects all handlers.
Address this by using connect_after for the cleanup handler, so
that other destroy handlers run before it (unless they also use
ConnectFlags.AFTER, but well *shrug*).
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2221>
The module exports a `addObjectSignalMethods()` method that extends
the provided prototype with `connectObject()` and `disconnectObject()`
methods.
In its simplest form, `connectObject()` looks like the regular
`connect()` method, except for an additional parameter:
```js
this._button.connectObject('clicked',
() => this._onButtonClicked(), this);
```
The additional object can be used to disconnect all handlers on the
instance that were connected with that object, similar to
`g_signal_handlers_disconnect_by_data()` (which cannot be used
from introspection).
For objects that are subclasses of Clutter.Actor, that will happen
automatically when the actor is destroyed, similar to
`g_signal_connect_object()`.
Finally, `connectObject()` allows to conveniently connect multiple
signals at once, similar to `g_object_connect()`:
```js
this._toggleButton.connect(
'clicked', () => this._onClicked(),
'notify::checked', () => this._onChecked(), this);
```
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1953>
