Let the next dictation start while the last one is still working

Pressing the shortcut while a transcript was being transcribed or cleaned up
did nothing, and the thought you had while waiting was lost. The microphone is
free the moment a recording stops, so the next dictation can now be spoken at
once; the pipeline queues it and each one is finished, pasted and reported in
the order it was spoken. The corner indicator stays with the recording under
way rather than being wiped by the previous run's progress, and a stop that
lands behind an unfinished run says it is waiting its turn.

dikte/worker.py

@@ -6,6 +6,7 @@ whatever came of it: an answer to a question, or a sentence saying what was
 done.
 """
 
+import collections
 import os
 import shutil
 import sys
@@ -45,6 +46,13 @@ class Pipeline(QObject):
         self.conf = conf
         self._thread = None
         self._stop = threading.Event()
+        # Recordings waiting their turn, and whether a thread is working them
+        # off. The flag rather than the thread's own liveness, because a thread
+        # stays alive for a moment after deciding it is done, and a job arriving
+        # in that moment would be left in the queue with nobody coming back.
+        self._jobs = collections.deque()
+        self._draining = False
+        self._jobs_lock = threading.Lock()
 
     @property
     def busy(self):
@@ -53,17 +61,30 @@ class Pipeline(QObject):
     def run(self, wav_path, duration, rms_values=(), ask=False, paste=None):
         """`paste` overrides the setting for this one run, which is what a
         dictation asked for from a terminal wants: the text comes back down the
-        socket, and pasting it into whatever had focus is nobody's intention."""
-        if self.busy:
-            return
+        socket, and pasting it into whatever had focus is nobody's intention.
+
+        A run started while one is going waits its turn rather than being
+        dropped: the next dictation can be spoken while the last one is still
+        being cleaned up, and each one is finished, pasted and reported in the
+        order it was spoken."""
+        with self._jobs_lock:
+            self._jobs.append((wav_path, duration, list(rms_values), ask, paste))
+            if self._draining:
+                return
+            self._draining = True
         self._stop.clear()
-        self._thread = threading.Thread(
-            target=self._work,
-            args=(wav_path, duration, list(rms_values), ask, paste),
-            daemon=True,
-        )
+        self._thread = threading.Thread(target=self._drain, daemon=True)
         self._thread.start()
 
+    def _drain(self):
+        while True:
+            with self._jobs_lock:
+                if not self._jobs:
+                    self._draining = False
+                    return
+                job = self._jobs.popleft()
+            self._work(*job)
+
     def cancel(self):
         """Give up on a job already under way.