vibefpmgui.background

 1"""Blocking calls (a program run to completion, a slow server) on a pool
 2thread, so the window never waits for them; the result comes back in the
 3GUI thread."""
 4
 5from __future__ import annotations
 6
 7from collections.abc import Callable
 8
 9from qtpy.QtCore import QObject, QRunnable, QThreadPool, Signal
10
11
12class _Receiver(QObject):
13    """Brings a background call's result to the GUI thread (it lives there,
14    so its signal is delivered there) and hands it to ``then``."""
15
16    done = Signal(object)
17
18    def __init__(self, then, parent=None):
19        super().__init__(parent)
20        self._then = then
21        self.done.connect(self._deliver)
22
23    def _deliver(self, result):
24        self.deleteLater()
25        self._then(result)
26
27
28class _Call(QRunnable):
29    def __init__(self, fn, receiver: _Receiver):
30        super().__init__()
31        self.fn, self.receiver = fn, receiver
32
33    def run(self):
34        result = self.fn()
35        try:
36            self.receiver.done.emit(result)
37        except RuntimeError:
38            pass  # (the window that asked has closed)
39
40
41def call_in_background(fn: Callable[[], object], then: Callable[[object], None], parent: QObject):
42    """Run ``fn()`` on a pool thread, then ``then(result)`` in the GUI thread
43    (not at all if ``parent`` is gone by then)."""
44    QThreadPool.globalInstance().start(_Call(fn, _Receiver(then, parent)))