110 lines
3.5 KiB
Python
110 lines
3.5 KiB
Python
# -*- coding: utf-8 -*-
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from time import perf_counter
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import weakref
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from .Qt import QtCore
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from . import ThreadsafeTimer
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from .functions import SignalBlock
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__all__ = ['SignalProxy']
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class SignalProxy(QtCore.QObject):
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"""Object which collects rapid-fire signals and condenses them
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into a single signal or a rate-limited stream of signals.
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Used, for example, to prevent a SpinBox from generating multiple
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signals when the mouse wheel is rolled over it.
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Emits sigDelayed after input signals have stopped for a certain period of
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time.
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"""
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sigDelayed = QtCore.Signal(object)
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def __init__(self, signal, delay=0.3, rateLimit=0, slot=None):
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"""Initialization arguments:
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signal - a bound Signal or pyqtSignal instance
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delay - Time (in seconds) to wait for signals to stop before emitting (default 0.3s)
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slot - Optional function to connect sigDelayed to.
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rateLimit - (signals/sec) if greater than 0, this allows signals to stream out at a
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steady rate while they are being received.
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"""
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QtCore.QObject.__init__(self)
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self.delay = delay
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self.rateLimit = rateLimit
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self.args = None
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self.timer = ThreadsafeTimer.ThreadsafeTimer()
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self.timer.timeout.connect(self.flush)
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self.lastFlushTime = None
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self.signal = signal
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self.signal.connect(self.signalReceived)
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if slot is not None:
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self.blockSignal = False
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self.sigDelayed.connect(slot)
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self.slot = weakref.ref(slot)
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else:
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self.blockSignal = True
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self.slot = None
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def setDelay(self, delay):
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self.delay = delay
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def signalReceived(self, *args):
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"""Received signal. Cancel previous timer and store args to be
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forwarded later."""
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if self.blockSignal:
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return
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self.args = args
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if self.rateLimit == 0:
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self.timer.stop()
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self.timer.start(int(self.delay * 1000) + 1)
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else:
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now = perf_counter()
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if self.lastFlushTime is None:
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leakTime = 0
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else:
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lastFlush = self.lastFlushTime
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leakTime = max(0, (lastFlush + (1.0 / self.rateLimit)) - now)
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self.timer.stop()
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self.timer.start(int(min(leakTime, self.delay) * 1000) + 1)
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def flush(self):
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"""If there is a signal queued up, send it now."""
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if self.args is None or self.blockSignal:
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return False
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args, self.args = self.args, None
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self.timer.stop()
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self.lastFlushTime = perf_counter()
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self.sigDelayed.emit(args)
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return True
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def disconnect(self):
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self.blockSignal = True
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try:
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self.signal.disconnect(self.signalReceived)
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except:
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pass
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try:
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# XXX: This is a weakref, however segfaulting on PySide and
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# Python 2. We come back later
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self.sigDelayed.disconnect(self.slot)
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except:
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pass
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finally:
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self.slot = None
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def connectSlot(self, slot):
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"""Connect the `SignalProxy` to an external slot"""
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assert self.slot is None, "Slot was already connected!"
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self.slot = weakref.ref(slot)
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self.sigDelayed.connect(slot)
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self.blockSignal = False
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def block(self):
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"""Return a SignalBlocker that temporarily blocks input signals to
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this proxy.
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"""
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return SignalBlock(self.signal, self.signalReceived)
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