v0.20.6: one press, sixteen hundred songs

A single Right-arrow press skipped 1,676 tracks in 81 s and hard-froze the
desktop. On Wayland key repeat is generated by the client until the
compositor delivers the release, and the key filter treated every repeat as
a new press. Each skip sent gnome-shell an MPRIS Metadata whose xesam:artist
was a plain Python list, which marshals as "av" instead of "as". gnome-shell
logged an error for every one (50k/min) and reloaded the cover, and that load
is what kept it from ever delivering the release.

Space/Left/Right now act once per press and swallow the repeats.
xesam:artist goes out through mpris.string_array, which build_properties_changed
now shares for invalidated_properties. The new test round-trips the signal
into GDBus, which is what gnome-shell validates with, and fails 'av' == 'as'
against the old code.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CLAUDE.md

@@ -283,7 +283,13 @@ persistence) → GUI (Qt widgets that read the manager and connect to its signal
 
 - **`lintunes/mpris.py`** — registers `org.mpris.MediaPlayer2.lintunes` over D-Bus
   so the desktop's media keys / now-playing popup control playback. Spacebar and
-  arrow keys are handled locally via `MainWindow.eventFilter`.
+  arrow keys are handled locally via `MainWindow.eventFilter`, which **ignores
+  auto-repeat**: on Wayland repeats are generated client-side until the
+  compositor delivers the release, and a busy gnome-shell turned one held
+  arrow into 1,676 track skips (Round 56). Every list sent over D-Bus must be
+  a typed `QDBusArgument` (`mpris.string_array`) — a plain Python list goes
+  out as `av`, which GDBus rejects. That was `xesam:artist`, and the error
+  flood it caused is what kept gnome-shell busy.
 
 - **`lintunes/trash.py`** — freedesktop.org Trash spec 1.0, hand-rolled (no new
   dep). The trash is **per-filesystem**: music usually lives on a mounted volume,

lintunes/__init__.py

@@ -1,3 +1,3 @@
 """LinTunes — iTunes-style music library manager and player for Linux."""
 
-__version__ = "0.20.5"
+__version__ = "0.20.6"

lintunes/gui/main_window.py

@@ -1626,6 +1626,15 @@ class MainWindow(QMainWindow):
                                   QAbstractSpinBox, QComboBox)):
                 return False
             key = event.key()
+            if key in (Qt.Key.Key_Space, Qt.Key.Key_Right, Qt.Key.Key_Left) \
+                    and event.isAutoRepeat():
+                # On Wayland key repeat is generated client-side until the
+                # compositor delivers the release — and a compositor busy
+                # with our own MPRIS churn delivers it late, so one held
+                # arrow became 1,676 track skips (Round 56). A transport key
+                # acts once per press; the repeats are swallowed so they
+                # don't fall through and move the table's cursor either.
+                return True
             if key == Qt.Key.Key_Space:
                 self._log_key(event, "space")
                 self.play_pause()

lintunes/mpris.py

@@ -259,7 +259,7 @@ class MprisPlayerAdaptor(QDBusAbstractAdaptor):
         meta = {
             "mpris:trackid": QDBusObjectPath(f"/org/lintunes/track/{track.track_id}"),
             "xesam:title": track.name or "",
-            "xesam:artist": [track.artist or ""],
+            "xesam:artist": string_array([track.artist or ""]),
             "xesam:album": track.album or "",
         }
         if track.total_time:
@@ -275,17 +275,31 @@ class MprisPlayerAdaptor(QDBusAbstractAdaptor):
         QDBusConnection.sessionBus().send(build_properties_changed(changed))
 
 
+def string_array(values) -> QDBusArgument:
+    """A D-Bus string array ("as"). A plain Python list of str marshals as
+    "av", which GDBus consumers validate and reject — see
+    build_properties_changed and xesam:artist in _metadata."""
+    string_id = QMetaType(QMetaType.Type.QString.value).id()
+    arg = QDBusArgument()
+    arg.beginArray(string_id)
+    for value in values:
+        arg.add(value, string_id)
+    arg.endArray()
+    return arg
+
+
 def build_properties_changed(changed: dict) -> QDBusMessage:
     """A spec-correct Properties.PropertiesChanged signal for the Player
     interface. invalidated_properties must be marshalled as a D-Bus string
     array ("as"); a plain Python [] goes over as "av", and GDBus consumers —
     including gsd-media-keys, which keys its media-key MRU on seeing
     PlaybackStatus change — validate the signature and drop the signal.
-    (Same pitfall as reveal_paths in track_table.)"""
+    (Same pitfall as reveal_paths in track_table, and as xesam:artist inside
+    Metadata: sent as "av", gnome-shell logged an error and reloaded the
+    cover per track change, and during a runaway key repeat that flood is
+    what froze the desktop — Round 56.)"""
     msg = QDBusMessage.createSignal(
         OBJECT_PATH, "org.freedesktop.DBus.Properties", "PropertiesChanged")
-    invalidated = QDBusArgument()
-    invalidated.beginArray(QMetaType(QMetaType.Type.QString.value).id())
-    invalidated.endArray()
-    msg.setArguments(["org.mpris.MediaPlayer2.Player", changed, invalidated])
+    msg.setArguments(["org.mpris.MediaPlayer2.Player", changed,
+                      string_array([])])
     return msg

tasks-done.md

@@ -1,5 +1,25 @@
 ## Done
 
+### Round 56 (2026-09-17) — one press, sixteen hundred songs (v0.20.6)
+
+One Right-arrow press skipped 1,676 tracks in 81 s and hard-froze GNOME badly
+enough to need SysRq (incident log `~/claude-diag/logs/issue-log-2026-09-17.md`).
+It was a feedback loop, and both halves were ours.
+
+- [x] **Transport keys act once per press.** On Wayland key repeat is
+      generated by the *client* until the compositor delivers the release, and
+      `MainWindow.eventFilter` treated every repeat as a new press. Space, Left
+      and Right now swallow auto-repeats (swallow, not pass through, so a held
+      Right doesn't walk the table cursor instead).
+- [x] **`xesam:artist` goes out as `as`.** A plain `[str]` inside `Metadata`
+      marshals as `av`; gnome-shell logged an error for it (32k–50k/min during
+      the incident) and reloaded the cover per track change. That load is what
+      kept it from delivering the key release, so the repeats never stopped.
+      `mpris.string_array` builds the typed array, shared with
+      `build_properties_changed`'s `invalidated_properties` (Round 17's same
+      pitfall). The test round-trips the signal into GDBus, which is what
+      gnome-shell validates with, and fails `'av' == 'as'` on the old code.
+
 ### Round 55 (2026-09-14) — the song that wasn't there (v0.20.4, andTunes 0.2.2)
 
 trav couldn't play the first track of his playlist: shuffle off gave him song

tests/test_round56.py

@@ -0,0 +1,129 @@
+"""Round 56: one held arrow key hard-froze the desktop.
+
+Incident 2026-09-17: a single Right press became 1,676 track skips in 81 s.
+On Wayland key repeat is generated by the *client* until the compositor
+delivers the release, and every skip sent gnome-shell an MPRIS Metadata whose
+xesam:artist was typed "av" rather than "as" — an error plus a cover reload
+per skip, which kept gnome-shell too busy to deliver that release. Both halves
+are pinned here: transport keys act once per press, and xesam:artist goes out
+as a real string array.
+"""
+import threading
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+import pytest
+from PyQt6.QtCore import QCoreApplication, QEvent, Qt
+from PyQt6.QtGui import QKeyEvent
+
+from lintunes.gui import main_window
+from lintunes.gui.main_window import MainWindow
+
+
+# ---- transport keys ignore auto-repeat ----
+
+def _window_stub():
+    return SimpleNamespace(
+        isActiveWindow=lambda: True,
+        play_pause=MagicMock(),
+        player=MagicMock(),
+        _log_key=MagicMock(),
+    )
+
+
+def _press(key, repeat):
+    return QKeyEvent(QEvent.Type.KeyPress, key,
+                     Qt.KeyboardModifier.NoModifier, "", repeat)
+
+
+@pytest.fixture
+def no_focus_widget(monkeypatch):
+    monkeypatch.setattr(main_window.QApplication, "focusWidget",
+                        staticmethod(lambda: None))
+
+
+@pytest.mark.parametrize("key, action", [
+    (Qt.Key.Key_Right, lambda w: w.player.next),
+    (Qt.Key.Key_Left, lambda w: w.player.previous),
+    (Qt.Key.Key_Space, lambda w: w.play_pause),
+])
+def test_held_key_acts_once(qapp, no_focus_widget, key, action):
+    win = _window_stub()
+    assert MainWindow.eventFilter(win, None, _press(key, repeat=False))
+    for _ in range(50):
+        # Swallowed, not passed through: a held Right mustn't walk the
+        # table's cursor instead.
+        assert MainWindow.eventFilter(win, None, _press(key, repeat=True))
+    assert action(win).call_count == 1
+    assert win._log_key.call_count == 1
+
+
+def test_separate_presses_each_act(qapp, no_focus_widget):
+    win = _window_stub()
+    for _ in range(3):
+        MainWindow.eventFilter(win, None, _press(Qt.Key.Key_Right, False))
+    assert win.player.next.call_count == 3
+
+
+# ---- xesam:artist is "as" ----
+
+def _adaptor_metadata(monkeypatch):
+    from lintunes import mpris
+    monkeypatch.setattr(mpris, "export_artwork", lambda track: None)
+    track = SimpleNamespace(track_id=7, name="I Know", artist="Dionne Farris",
+                            album="Wild Seed — Wild Flower", total_time=229000,
+                            location="/music/i-know.mp3", persistent_id="AB12")
+    adaptor = SimpleNamespace(_player=SimpleNamespace(current_track=track))
+    return mpris.MprisPlayerAdaptor._metadata(adaptor)
+
+
+def test_artist_is_typed_string_array(qapp, monkeypatch):
+    # A plain [str] is what went out as "av"; only a typed QDBusArgument
+    # carries "as". (The wire type itself is checked over the bus below.)
+    from PyQt6.QtDBus import QDBusArgument
+    meta = _adaptor_metadata(monkeypatch)
+    assert isinstance(meta["xesam:artist"], QDBusArgument)
+
+
+def test_gdbus_receives_artist_as_string_array(qapp, monkeypatch):
+    """Round-trip over the real session bus into GDBus — the same library
+    gnome-shell validates with — and check the type it actually sees."""
+    Gio = pytest.importorskip("gi.repository.Gio")
+    GLib = pytest.importorskip("gi.repository.GLib")
+    from PyQt6.QtDBus import QDBusConnection
+    from lintunes.mpris import OBJECT_PATH, build_properties_changed
+
+    bus = QDBusConnection.sessionBus()
+    if not bus.isConnected():
+        pytest.skip("no D-Bus session bus in this environment")
+    try:
+        gbus = Gio.bus_get_sync(Gio.BusType.SESSION, None)
+    except GLib.Error:
+        pytest.skip("GDBus can't reach the session bus")
+
+    received = []
+    sub = gbus.signal_subscribe(
+        bus.baseService(), "org.freedesktop.DBus.Properties",
+        "PropertiesChanged", OBJECT_PATH, None, Gio.DBusSignalFlags.NONE,
+        lambda *args: received.append(args[5]))
+    try:
+        meta = _adaptor_metadata(monkeypatch)
+        assert bus.send(build_properties_changed({"Metadata": meta}))
+        ctx = GLib.MainContext.default()
+        for _ in range(200):
+            QCoreApplication.processEvents()
+            while ctx.iteration(False):
+                pass
+            if received:
+                break
+            threading.Event().wait(0.01)
+    finally:
+        gbus.signal_unsubscribe(sub)
+
+    assert received, "signal was not delivered over the bus"
+    params = received[0]
+    assert params.get_type_string() == "(sa{sv}as)"
+    metadata = params.get_child_value(1).lookup_value("Metadata", None)
+    artist = metadata.lookup_value("xesam:artist", None)
+    assert artist.get_type_string() == "as"
+    assert artist.unpack() == ["Dionne Farris"]