Current File : //snap/core20/current/usr/lib/python3/dist-packages/urwid/__pycache__/signals.cpython-38.pyc
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register the list of signals in the class variable signals,
including signals in superclasses.
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:param sig_class: the class of an object that will be sending signals
:type sig_class: class
:param signals: a list of signals that may be sent, typically each
signal is represented by a string
:type signals: signal names
This function must be called for a class before connecting any
signal callbacks or emitting any signals from that class' objects
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:param obj: the object sending a signal
:type obj: object
:param name: the signal to listen for, typically a string
:type name: signal name
:param callback: the function to call when that signal is sent
:type callback: function
:param user_arg: deprecated additional argument to callback (appended
after the arguments passed when the signal is
emitted). If None no arguments will be added.
Don't use this argument, use user_args instead.
:param weak_args: additional arguments passed to the callback
(before any arguments passed when the signal
is emitted and before any user_args).
These arguments are stored as weak references
(but converted back into their original value
before passing them to callback) to prevent
any objects referenced (indirectly) from
weak_args from being kept alive just because
they are referenced by this signal handler.
Use this argument only as a keyword argument,
since user_arg might be removed in the future.
:type weak_args: iterable
:param user_args: additional arguments to pass to the callback,
(before any arguments passed when the signal
is emitted but after any weak_args).
Use this argument only as a keyword argument,
since user_arg might be removed in the future.
:type user_args: iterable
When a matching signal is sent, callback will be called. The
arguments it receives will be the user_args passed at connect
time (as individual arguments) followed by all the positional
parameters sent with the signal.
As an example of using weak_args, consider the following snippet:
>>> import urwid
>>> debug = urwid.Text('')
>>> def handler(widget, newtext):
... debug.set_text("Edit widget changed to %s" % newtext)
>>> edit = urwid.Edit('')
>>> key = urwid.connect_signal(edit, 'change', handler)
If you now build some interface using "edit" and "debug", the
"debug" widget will show whatever you type in the "edit" widget.
However, if you remove all references to the "debug" widget, it
will still be kept alive by the signal handler. This because the
signal handler is a closure that (implicitly) references the
"edit" widget. If you want to allow the "debug" widget to be
garbage collected, you can create a "fake" or "weak" closure
(it's not really a closure, since it doesn't reference any
outside variables, so it's just a dynamic function):
>>> debug = urwid.Text('')
>>> def handler(weak_debug, widget, newtext):
... weak_debug.set_text("Edit widget changed to %s" % newtext)
>>> edit = urwid.Edit('')
>>> key = urwid.connect_signal(edit, 'change', handler, weak_args=[debug])
Here the weak_debug parameter in print_debug is the value passed
in the weak_args list to connect_signal. Note that the
weak_debug value passed is not a weak reference anymore, the
signals code transparently dereferences the weakref parameter
before passing it to print_debug.
Returns a key associated by this signal handler, which can be
used to disconnect the signal later on using
urwid.disconnect_signal_by_key. Alternatively, the signal
handler can also be disconnected by calling
urwid.disconnect_signal, which doesn't need this key.
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:param obj: the object to disconnect the signal from
:type obj: object
:param name: the signal to disconnect, typically a string
:type name: signal name
:param callback: the callback function passed to connect_signal
:type callback: function
:param user_arg: the user_arg parameter passed to connect_signal
:param weak_args: the weak_args parameter passed to connect_signal
:param user_args: the weak_args parameter passed to connect_signal
This function will remove a callback from the list connected
to a signal with connect_signal(). The arguments passed should
be exactly the same as those passed to connect_signal().
If the callback is not connected or already disconnected, this
function will simply do nothing.
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:param obj: the object to disconnect the signal from
:type obj: object
:param name: the signal to disconnect, typically a string
:type name: signal name
:param key: the key for this signal handler, as returned by
connect_signal().
:type key: Key
This function will remove a callback from the list connected
to a signal with connect_signal(). The key passed should be the
value returned by connect_signal().
If the callback is not connected or already disconnected, this
function will simply do nothing.
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:param obj: the object sending a signal
:type obj: object
:param name: the signal to send, typically a string
:type name: signal name
:param \*args: zero or more positional arguments to pass to the signal
callback functions
This function calls each of the callbacks connected to this signal
with the args arguments as positional parameters.
This function returns True if any of the callbacks returned True.
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