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import weakref
from time import perf_counter
from .functions import SignalBlock
from .Qt import QtCore
from .ThreadsafeTimer import ThreadsafeTimer
__all__ = ['SignalProxy']
class SignalProxy(QtCore.QObject):
"""Object which collects rapid-fire signals and condenses them
into a single signal or a rate-limited stream of signals.
Used, for example, to prevent a SpinBox from generating multiple
signals when the mouse wheel is rolled over it.
Emits sigDelayed after input signals have stopped for a certain period of
time.
"""
sigDelayed = QtCore.Signal(object)
def __init__(self, signal, delay=0.3, rateLimit=0, slot=None, *, threadSafe=True):
"""Initialization arguments:
signal - a bound Signal or pyqtSignal instance
delay - Time (in seconds) to wait for signals to stop before emitting (default 0.3s)
slot - Optional function to connect sigDelayed to.
rateLimit - (signals/sec) if greater than 0, this allows signals to stream out at a
steady rate while they are being received.
threadSafe - Specify if thread-safety is required. For backwards compatibility, it
defaults to True.
"""
QtCore.QObject.__init__(self)
self.delay = delay
self.rateLimit = rateLimit
self.args = None
Timer = ThreadsafeTimer if threadSafe else QtCore.QTimer
self.timer = Timer()
self.timer.timeout.connect(self.flush)
self.lastFlushTime = None
self.signal = signal
self.signal.connect(self.signalReceived)
if slot is not None:
self.blockSignal = False
self.sigDelayed.connect(slot)
self.slot = weakref.ref(slot)
else:
self.blockSignal = True
self.slot = None
def setDelay(self, delay):
self.delay = delay
def signalReceived(self, *args):
"""Received signal. Cancel previous timer and store args to be
forwarded later."""
if self.blockSignal:
return
self.args = args
if self.rateLimit == 0:
self.timer.stop()
self.timer.start(int(self.delay * 1000) + 1)
else:
now = perf_counter()
if self.lastFlushTime is None:
leakTime = 0
else:
lastFlush = self.lastFlushTime
leakTime = max(0, (lastFlush + (1.0 / self.rateLimit)) - now)
self.timer.stop()
self.timer.start(int(min(leakTime, self.delay) * 1000) + 1)
def flush(self):
"""If there is a signal queued up, send it now."""
if self.args is None or self.blockSignal:
return False
args, self.args = self.args, None
self.timer.stop()
self.lastFlushTime = perf_counter()
self.sigDelayed.emit(args)
return True
def disconnect(self):
self.blockSignal = True
try:
self.signal.disconnect(self.signalReceived)
except:
pass
try:
slot = self.slot()
if slot is not None:
self.sigDelayed.disconnect(slot)
except:
pass
finally:
self.slot = None
def connectSlot(self, slot):
"""Connect the `SignalProxy` to an external slot"""
assert self.slot is None, "Slot was already connected!"
self.slot = weakref.ref(slot)
self.sigDelayed.connect(slot)
self.blockSignal = False
def block(self):
"""Return a SignalBlocker that temporarily blocks input signals to
this proxy.
"""
return SignalBlock(self.signal, self.signalReceived)
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