Initial commit

app/workers.py

@@ -0,0 +1,72 @@
+"""Run long operations off the GUI thread, with progress messages and cancel."""
+import traceback
+
+from PySide6.QtCore import QObject, QRunnable, QThreadPool, Signal
+
+
+class Cancelled(Exception):
+    pass
+
+
+class _Signals(QObject):
+    done = Signal(object)
+    failed = Signal(object, str)
+    progress = Signal(str)
+
+
+class Job(QRunnable):
+    """fn(job) -> result. Inside fn call job.report(msg) and job.check() (raises Cancelled)."""
+
+    def __init__(self, fn):
+        super().__init__()
+        self.fn = fn
+        self.signals = _Signals()
+        self.cancelled = False
+
+    def report(self, msg):
+        self.check()
+        self.signals.progress.emit(str(msg))
+
+    def check(self):
+        if self.cancelled:
+            raise Cancelled()
+
+    def cancel(self):
+        self.cancelled = True
+
+    def run(self):
+        try:
+            r = self.fn(self)
+        except Cancelled:
+            self.signals.failed.emit(Cancelled(), "cancelled")
+        except Exception as e:  # noqa: BLE001 - shown to the user
+            self.signals.failed.emit(e, traceback.format_exc())
+        else:
+            self.signals.done.emit(r)
+
+
+class Runner:
+    """Starts jobs on a thread pool (or inline when `sync`, used by the GUI tests)."""
+
+    def __init__(self, sync=False):
+        self.sync = sync
+        self.pool = QThreadPool.globalInstance()
+        self.active = set()  # keep Python references until the queued result signal is delivered
+
+    def start(self, fn, on_done=None, on_failed=None, on_progress=None):
+        job = Job(fn)
+        job.setAutoDelete(False)
+        self.active.add(job)
+        job.signals.done.connect(lambda *_: self.active.discard(job))
+        job.signals.failed.connect(lambda *_: self.active.discard(job))
+        if on_done:
+            job.signals.done.connect(on_done)
+        if on_failed:
+            job.signals.failed.connect(on_failed)
+        if on_progress:
+            job.signals.progress.connect(on_progress)
+        if self.sync:
+            job.run()
+        else:
+            self.pool.start(job)
+        return job