Give each tab its own full timeline and transport (PlayerPanel refactor)

Extracts a new PlayerPanel widget (video + its own seek slider/marker
strip + its own centered frame-step/play/mute transport row) into
player_panel.py. Both Source and Preview tabs now use one, so
switching tabs switches a complete, independent monitor -- its own
scrubber, its own play state, its own frame-stepping -- not just the
video frame with a single shared play button underneath.

main.py's global keyboard shortcuts (,/./space/left/right) now
dispatch to whichever panel is active via a small _active_panel()
helper, so they follow the same 'whichever monitor you're looking at'
rule as the on-screen controls.

MarkerStrip (clap detection) and the Mark Audio/Video/offset/export
row stay outside the tabs, at the MainWindow level -- marking and
exporting are inherently about the source file, not the preview clip,
so only the timeline+transport moved, not the whole marking workflow.

Updated every existing smoke test for the new win.source_panel.* /
win.preview_panel.* structure (previously flat win.player,
win.seek_slider, etc.), and added a new check to
smoke_test_preview.py confirming the Preview tab's slider is a
genuinely separate, functional widget -- dragging it seeks the preview
player without moving the source player, which is the actual thing
this change was for.

Verified the full suite on the virtual Xvfb display, plus a live
click-through (mark both events, build preview, confirm the Preview
tab shows its own populated timeline/transport, not the source's).

main.py

@@ -8,38 +8,14 @@ from PyQt6.QtCore import Qt, QTimer, QThread, pyqtSignal
 from PyQt6.QtGui import QShortcut, QKeySequence, QAction
 from PyQt6.QtWidgets import (
     QApplication, QMainWindow, QWidget, QVBoxLayout, QHBoxLayout,
-    QPushButton, QLabel, QSlider, QCheckBox, QDoubleSpinBox, QFileDialog,
+    QPushButton, QLabel, QDoubleSpinBox, QFileDialog,
     QMessageBox, QPlainTextEdit, QGroupBox, QTabWidget,
 )
 
-from player_widget import PlayerWidget
+from player_panel import PlayerPanel, format_timestamp
 from sync_logic import compute_offset, SyncOffset
 from ffmpeg_export import export_synced, FfmpegExportError, ExportResult
 from clap_detection import detect_claps, ClapDetectionUnavailable, ClapEvent
-from marker_strip import MarkerStrip
-
-
-def format_timestamp(seconds: float) -> str:
-    m, s = divmod(max(seconds, 0.0), 60)
-    return f"{int(m):02d}:{s:06.3f}"
-
-
-class ClickableSlider(QSlider):
-    """QSlider normally only jumps to the clicked position if you click
-    exactly on the handle; clicking elsewhere in the groove pages by a
-    fixed step. Override so any click along the track jumps straight
-    there, then let the base class take over so dragging still works
-    (the handle is now under the cursor, so its own drag tracking picks
-    up seamlessly).
-    """
-
-    def mousePressEvent(self, event):
-        if event.button() == Qt.MouseButton.LeftButton and self.maximum() > self.minimum():
-            ratio = min(max(event.position().x() / max(self.width(), 1), 0.0), 1.0)
-            value = round(self.minimum() + ratio * (self.maximum() - self.minimum()))
-            self.setValue(value)
-            self.sliderMoved.emit(value)
-        super().mousePressEvent(event)
 
 
 class ExportWorker(QThread):
@@ -100,22 +76,16 @@ class MainWindow(QMainWindow):
         self._export_worker: Optional[ExportWorker] = None
         self._detect_worker: Optional[DetectWorker] = None
         self._preview_worker: Optional[ExportWorker] = None
-        self._preview_temp_path: Optional[str] = None  # currently loaded in preview_player
+        self._preview_temp_path: Optional[str] = None  # currently loaded in preview_panel
         self._pending_preview_path: Optional[str] = None  # being built by _preview_worker
-        self._slider_being_dragged = False
 
-        self.player = PlayerWidget()
-        self.player.setMinimumHeight(400)
-        self.player.fileDropped.connect(self._load)
-        self.player.rightClicked.connect(self._toggle_play)
+        # Two independent monitors (Kdenlive-style project/clip monitor
+        # tabs): each is a full player with its own timeline and transport,
+        # not just a shared video frame with one set of controls.
+        self.source_panel = PlayerPanel(show_marker_strip=True)
+        self.source_panel.fileDropped.connect(self._load)
 
-        # Independent second mpv instance for the Preview tab (Kdenlive-style
-        # project/clip monitor tabs) -- kept alive for the whole session
-        # rather than created per-preview, so switching tabs back and forth
-        # doesn't tear down and rebuild an mpv instance each time.
-        self.preview_player = PlayerWidget()
-        self.preview_player.setMinimumHeight(320)
-        self.preview_player.rightClicked.connect(self._toggle_preview_play)
+        self.preview_panel = PlayerPanel(show_marker_strip=False)
 
         self._build_ui()
         self._build_menu()
@@ -128,80 +98,18 @@ class MainWindow(QMainWindow):
 
     # -- UI construction ---------------------------------------------------
 
+    def _active_panel(self) -> PlayerPanel:
+        return self.source_panel if self.video_tabs.currentIndex() == 0 else self.preview_panel
+
     def _build_ui(self):
         central = QWidget()
         layout = QVBoxLayout(central)
 
         self.video_tabs = QTabWidget()
-        self.video_tabs.addTab(self.player, "Source")
-
-        preview_tab = QWidget()
-        preview_tab_layout = QVBoxLayout(preview_tab)
-        preview_tab_layout.setContentsMargins(0, 0, 0, 0)
-        preview_tab_layout.addWidget(self.preview_player, stretch=1)
-
-        preview_controls = QHBoxLayout()
-        self.preview_play_button = QPushButton("Play")
-        self.preview_play_button.clicked.connect(self._toggle_preview_play)
-        preview_controls.addWidget(self.preview_play_button)
-        self.preview_position_label = QLabel("00:00.000")
-        preview_controls.addWidget(self.preview_position_label)
-        preview_controls.addStretch(1)
-        preview_tab_layout.addLayout(preview_controls)
-
-        self.video_tabs.addTab(preview_tab, "Preview")
-
+        self.video_tabs.addTab(self.source_panel, "Source")
+        self.video_tabs.addTab(self.preview_panel, "Preview")
         layout.addWidget(self.video_tabs, stretch=1)
 
-        # Timeline directly under the video (LosslessCut-style), transport
-        # controls below that.
-        seek_row = QHBoxLayout()
-        self.position_label = QLabel("00:00.000")
-        seek_row.addWidget(self.position_label)
-
-        slider_stack = QVBoxLayout()
-        slider_stack.setSpacing(0)
-        self.marker_strip = MarkerStrip()
-        self.marker_strip.markerClicked.connect(self._on_marker_clicked)
-        slider_stack.addWidget(self.marker_strip)
-
-        self.seek_slider = ClickableSlider(Qt.Orientation.Horizontal)
-        self.seek_slider.setRange(0, 0)
-        self.seek_slider.sliderPressed.connect(lambda: setattr(self, "_slider_being_dragged", True))
-        self.seek_slider.sliderMoved.connect(self._on_slider_moved)
-        self.seek_slider.sliderReleased.connect(self._on_slider_released)
-        slider_stack.addWidget(self.seek_slider)
-        seek_row.addLayout(slider_stack, stretch=1)
-
-        self.duration_label = QLabel("00:00.000")
-        seek_row.addWidget(self.duration_label)
-        layout.addLayout(seek_row)
-
-        # Transport row: frame-step/play controls centered as a group, mute
-        # pinned to the right. Load File now lives in the File menu.
-        transport = QHBoxLayout()
-        transport.addStretch(1)
-
-        self.prev_frame_button = QPushButton("⏮ Frame (,)")
-        self.prev_frame_button.clicked.connect(lambda: self._step_frame(-1))
-        transport.addWidget(self.prev_frame_button)
-
-        self.play_button = QPushButton("Play")
-        self.play_button.clicked.connect(self._toggle_play)
-        transport.addWidget(self.play_button)
-
-        self.next_frame_button = QPushButton("Frame ⏭ (.)")
-        self.next_frame_button.clicked.connect(lambda: self._step_frame(1))
-        transport.addWidget(self.next_frame_button)
-
-        transport.addStretch(1)
-
-        self.mute_checkbox = QCheckBox("Mute audio")
-        self.mute_checkbox.toggled.connect(self._on_mute_toggled)
-        transport.addWidget(self.mute_checkbox)
-
-        layout.addLayout(transport)
-
         # Marker row
         marker_group = QGroupBox("Sync markers")
         marker_layout = QHBoxLayout(marker_group)
@@ -288,13 +196,17 @@ class MainWindow(QMainWindow):
         tools_menu.addAction(self.detect_next_action)
 
     def _wire_shortcuts(self):
-        QShortcut(QKeySequence(","), self, activated=lambda: self._step_frame(-1))
-        QShortcut(QKeySequence("."), self, activated=lambda: self._step_frame(1))
-        QShortcut(QKeySequence(Qt.Key.Key_Space), self, activated=self._toggle_play)
+        # These act on whichever tab (Source/Preview) is currently active --
+        # each is a fully independent monitor with its own transport, so the
+        # keyboard shortcuts follow the same "whichever one you're looking
+        # at" rule as the on-screen buttons.
+        QShortcut(QKeySequence(","), self, activated=lambda: self._active_panel().step_frame(-1))
+        QShortcut(QKeySequence("."), self, activated=lambda: self._active_panel().step_frame(1))
+        QShortcut(QKeySequence(Qt.Key.Key_Space), self, activated=lambda: self._active_panel().toggle_play())
         # QShortcut auto-repeats by default while the key is held, so this
         # keeps skipping for as long as the arrow key is down.
-        QShortcut(QKeySequence(Qt.Key.Key_Left), self, activated=lambda: self._seek_relative(-5.0))
-        QShortcut(QKeySequence(Qt.Key.Key_Right), self, activated=lambda: self._seek_relative(5.0))
+        QShortcut(QKeySequence(Qt.Key.Key_Left), self, activated=lambda: self._active_panel().seek_relative(-5.0))
+        QShortcut(QKeySequence(Qt.Key.Key_Right), self, activated=lambda: self._active_panel().seek_relative(5.0))
 
     # -- transport -----------------------------------------------------
 
@@ -304,15 +216,15 @@ class MainWindow(QMainWindow):
             self._load(path)
 
     def _load(self, path: str):
-        # player.load() blocks the GUI thread until mpv reports the file's
-        # duration, so show the status message and force one repaint before
-        # starting it -- otherwise Qt wouldn't paint the message until after
-        # the blocking call already returned.
+        # source_panel.load() blocks the GUI thread until mpv reports the
+        # file's duration, so show the status message and force one repaint
+        # before starting it -- otherwise Qt wouldn't paint the message
+        # until after the blocking call already returned.
         self.statusBar().showMessage(f"Loading {Path(path).name}…")
         QApplication.processEvents()
 
         self.input_path = path
-        self.player.load(path)
+        self.source_panel.load(path)
         self.video_mark = None
         self.audio_mark = None
         self.offset = None
@@ -324,13 +236,7 @@ class MainWindow(QMainWindow):
         self.override_spinbox.setEnabled(False)
         self.log_view.clear()
 
-        duration = self.player.mpv.duration or 0.0
-        self.seek_slider.setRange(0, int(duration * 1000))
-        self.duration_label.setText(format_timestamp(duration))
         self.setWindowTitle(f"A/V Sync Marker — {Path(path).name}")
-
-        self.marker_strip.set_duration(duration)
-        self.marker_strip.clear()
         self.statusBar().showMessage(f"Loaded {Path(path).name}", 4000)
         self.detect_all_action.setEnabled(True)
         self.detect_all_button.setEnabled(True)
@@ -342,73 +248,19 @@ class MainWindow(QMainWindow):
         self._preview_temp_path = None
         self.video_tabs.setCurrentIndex(0)
 
-    def _toggle_play(self):
-        if self.player.mpv.pause:
-            self.player.play()
-            self.play_button.setText("Pause")
-        else:
-            self.player.pause()
-            self.play_button.setText("Play")
-
-    def _step_frame(self, n: int):
-        self.player.pause()
-        self.play_button.setText("Play")
-        self.player.step_frame(n)
-        self._update_position_ui()
-
-    def _on_mute_toggled(self, checked: bool):
-        self.player.mpv.mute = checked
-
-    def _toggle_preview_play(self):
-        if self.preview_player.mpv.pause:
-            self.preview_player.play()
-            self.preview_play_button.setText("Pause")
-        else:
-            self.preview_player.pause()
-            self.preview_play_button.setText("Play")
-
-    def _seek_relative(self, delta_seconds: float):
-        # Unlike frame-stepping (which always pauses -- you're precisely
-        # inspecting a frame), a 5s skip is a coarse nudge while scrubbing
-        # around; seeking doesn't change mpv's pause state on its own, so
-        # just not touching play/pause here is enough to preserve whichever
-        # state the user was already in.
-        if self.input_path is None:
-            return
-        duration = self.player.mpv.duration or 0.0
-        target = min(max(self.player.get_position() + delta_seconds, 0.0), duration)
-        self.player.seek(target)
-        self._update_position_ui()
-
-    def _on_slider_moved(self, value: int):
-        self.player.seek(value / 1000.0)
-        self._update_position_ui()
-
-    def _on_slider_released(self):
-        self._slider_being_dragged = False
-        self._update_position_ui()
-
     def _update_position_ui(self):
-        if self.input_path is not None:
-            pos = self.player.get_position()
-            self.position_label.setText(format_timestamp(pos))
-            if not self._slider_being_dragged:
-                self.seek_slider.blockSignals(True)
-                self.seek_slider.setValue(int(pos * 1000))
-                self.seek_slider.blockSignals(False)
-
-        if self._preview_temp_path is not None:
-            self.preview_position_label.setText(format_timestamp(self.preview_player.get_position()))
+        self.source_panel.update_position()
+        self.preview_panel.update_position()
 
     # -- markers / offset -----------------------------------------------
 
     def _mark_video(self):
-        self.video_mark = self.player.get_position()
+        self.video_mark = self.source_panel.player.get_position()
         self.video_mark_label.setText(f"video: {format_timestamp(self.video_mark)}")
         self._recompute_offset()
 
     def _mark_audio(self):
-        self.audio_mark = self.player.get_position()
+        self.audio_mark = self.source_panel.player.get_position()
         self.audio_mark_label.setText(f"audio: {format_timestamp(self.audio_mark)}")
         self._recompute_offset()
 
@@ -466,15 +318,14 @@ class MainWindow(QMainWindow):
         if result.stderr.strip():
             self.log_view.appendPlainText("ffmpeg preview log:\n" + result.stderr)
 
-        # The preview player is long-lived (one mpv instance for the whole
+        # The preview panel is long-lived (one mpv instance for the whole
         # session), so swap files instead of spinning up a new player each
         # time: load the new clip first, then delete the old temp file --
         # only safe to unlink it once mpv is no longer holding it open.
         old_path = self._preview_temp_path
         new_path = self._pending_preview_path
-        self.preview_player.load(new_path)
-        self.preview_player.play()
-        self.preview_play_button.setText("Pause")
+        self.preview_panel.load(new_path)
+        self.preview_panel.force_play()
         self._preview_temp_path = new_path
         self._pending_preview_path = None
         self.video_tabs.setCurrentIndex(1)
@@ -493,15 +344,11 @@ class MainWindow(QMainWindow):
 
     # -- clap detection -----------------------------------------------------
 
-    def _on_marker_clicked(self, time_sec: float):
-        self.player.seek(time_sec)
-        self._update_position_ui()
-
     def _on_detect_all_clicked(self):
         self._start_detection(start_offset=0.0, max_results=None, label="Scanning whole file for claps…")
 
     def _on_detect_next_clicked(self):
-        cursor = self.player.get_position()
+        cursor = self.source_panel.player.get_position()
         self._start_detection(start_offset=cursor, max_results=1, label=f"Scanning from {format_timestamp(cursor)} for next clap…")
 
     def _start_detection(self, start_offset: float, max_results, label: str):
@@ -522,9 +369,9 @@ class MainWindow(QMainWindow):
         self.detect_all_button.setEnabled(True)
         self.detect_next_action.setEnabled(True)
 
-        existing = set(self.marker_strip.markers())
+        existing = set(self.source_panel.marker_strip.markers())
         existing.update(e.time_sec for e in events)
-        self.marker_strip.set_markers(list(existing))
+        self.source_panel.marker_strip.set_markers(list(existing))
 
         if not events:
             self.statusBar().showMessage("No claps found.", 5000)
@@ -587,8 +434,8 @@ class MainWindow(QMainWindow):
         # get_position() on an already-terminated core and crashes
         # (mpv.ShutdownError, observed as a hard crash in testing).
         self._position_timer.stop()
-        self.player.shutdown()
-        self.preview_player.shutdown()
+        self.source_panel.shutdown()
+        self.preview_panel.shutdown()
         if self._preview_temp_path and os.path.exists(self._preview_temp_path):
             os.unlink(self._preview_temp_path)
         super().closeEvent(event)

player_panel.py

@@ -0,0 +1,176 @@
+from typing import Optional
+
+from PyQt6.QtCore import Qt, pyqtSignal
+from PyQt6.QtWidgets import QWidget, QVBoxLayout, QHBoxLayout, QLabel, QPushButton, QCheckBox, QSlider
+
+from player_widget import PlayerWidget
+from marker_strip import MarkerStrip
+
+
+def format_timestamp(seconds: float) -> str:
+    m, s = divmod(max(seconds, 0.0), 60)
+    return f"{int(m):02d}:{s:06.3f}"
+
+
+class ClickableSlider(QSlider):
+    """QSlider normally only jumps to the clicked position if you click
+    exactly on the handle; clicking elsewhere in the groove pages by a
+    fixed step. Override so any click along the track jumps straight
+    there, then let the base class take over so dragging still works
+    (the handle is now under the cursor, so its own drag tracking picks
+    up seamlessly).
+    """
+
+    def mousePressEvent(self, event):
+        if event.button() == Qt.MouseButton.LeftButton and self.maximum() > self.minimum():
+            ratio = min(max(event.position().x() / max(self.width(), 1), 0.0), 1.0)
+            value = round(self.minimum() + ratio * (self.maximum() - self.minimum()))
+            self.setValue(value)
+            self.sliderMoved.emit(value)
+        super().mousePressEvent(event)
+
+
+class PlayerPanel(QWidget):
+    """A self-contained video monitor: player + its own timeline + its own
+    transport row (Kdenlive-style project/clip monitor). Two of these are
+    used side by side as tabs (Source, Preview) in main.py, each with an
+    independent PlayerWidget/mpv instance and independent playback state --
+    switching tabs switches which monitor's timeline and transport you're
+    looking at, not just the video frame.
+    """
+
+    fileDropped = pyqtSignal(str)
+
+    def __init__(self, show_marker_strip: bool = False, parent=None):
+        super().__init__(parent)
+
+        self.player = PlayerWidget()
+        self.player.setMinimumHeight(320)
+        self.player.fileDropped.connect(self.fileDropped)
+        self.player.rightClicked.connect(self.toggle_play)
+
+        self._loaded = False
+        self._slider_being_dragged = False
+
+        layout = QVBoxLayout(self)
+        layout.setContentsMargins(0, 0, 0, 0)
+        layout.addWidget(self.player, stretch=1)
+
+        seek_row = QHBoxLayout()
+        self.position_label = QLabel("00:00.000")
+        seek_row.addWidget(self.position_label)
+
+        slider_stack = QVBoxLayout()
+        slider_stack.setSpacing(0)
+
+        self.marker_strip: Optional[MarkerStrip] = None
+        if show_marker_strip:
+            self.marker_strip = MarkerStrip()
+            self.marker_strip.markerClicked.connect(self._on_marker_clicked)
+            slider_stack.addWidget(self.marker_strip)
+
+        self.seek_slider = ClickableSlider(Qt.Orientation.Horizontal)
+        self.seek_slider.setRange(0, 0)
+        self.seek_slider.sliderPressed.connect(lambda: setattr(self, "_slider_being_dragged", True))
+        self.seek_slider.sliderMoved.connect(self._on_slider_moved)
+        self.seek_slider.sliderReleased.connect(self._on_slider_released)
+        slider_stack.addWidget(self.seek_slider)
+        seek_row.addLayout(slider_stack, stretch=1)
+
+        self.duration_label = QLabel("00:00.000")
+        seek_row.addWidget(self.duration_label)
+        layout.addLayout(seek_row)
+
+        transport = QHBoxLayout()
+        transport.addStretch(1)
+
+        self.prev_frame_button = QPushButton("⏮ Frame (,)")
+        self.prev_frame_button.clicked.connect(lambda: self.step_frame(-1))
+        transport.addWidget(self.prev_frame_button)
+
+        self.play_button = QPushButton("Play")
+        self.play_button.clicked.connect(self.toggle_play)
+        transport.addWidget(self.play_button)
+
+        self.next_frame_button = QPushButton("Frame ⏭ (.)")
+        self.next_frame_button.clicked.connect(lambda: self.step_frame(1))
+        transport.addWidget(self.next_frame_button)
+
+        transport.addStretch(1)
+
+        self.mute_checkbox = QCheckBox("Mute audio")
+        self.mute_checkbox.toggled.connect(lambda checked: setattr(self.player.mpv, "mute", checked))
+        transport.addWidget(self.mute_checkbox)
+
+        layout.addLayout(transport)
+
+    # -- playback -----------------------------------------------------
+
+    def load(self, path: str):
+        self.player.load(path)
+        self._loaded = True
+        duration = self.player.mpv.duration or 0.0
+        self.seek_slider.setRange(0, int(duration * 1000))
+        self.duration_label.setText(format_timestamp(duration))
+        if self.marker_strip is not None:
+            self.marker_strip.set_duration(duration)
+            self.marker_strip.clear()
+        self.play_button.setText("Play")
+        self.update_position()
+
+    def toggle_play(self):
+        if self.player.mpv.pause:
+            self.player.play()
+            self.play_button.setText("Pause")
+        else:
+            self.player.pause()
+            self.play_button.setText("Play")
+
+    def force_play(self):
+        self.player.play()
+        self.play_button.setText("Pause")
+
+    def step_frame(self, n: int):
+        if not self._loaded:
+            return
+        self.player.pause()
+        self.play_button.setText("Play")
+        self.player.step_frame(n)
+        self.update_position()
+
+    def seek_relative(self, delta_seconds: float):
+        # Unlike frame-stepping (which always pauses -- you're precisely
+        # inspecting a frame), a coarse skip is meant to preserve whichever
+        # play/pause state the user was already in; seeking doesn't change
+        # mpv's pause state on its own, so not touching it here is enough.
+        if not self._loaded:
+            return
+        duration = self.player.mpv.duration or 0.0
+        target = min(max(self.player.get_position() + delta_seconds, 0.0), duration)
+        self.player.seek(target)
+        self.update_position()
+
+    def _on_slider_moved(self, value: int):
+        self.player.seek(value / 1000.0)
+        self.update_position()
+
+    def _on_slider_released(self):
+        self._slider_being_dragged = False
+        self.update_position()
+
+    def _on_marker_clicked(self, time_sec: float):
+        self.player.seek(time_sec)
+        self.update_position()
+
+    def update_position(self):
+        if not self._loaded:
+            return
+        pos = self.player.get_position()
+        self.position_label.setText(format_timestamp(pos))
+        if not self._slider_being_dragged:
+            self.seek_slider.blockSignals(True)
+            self.seek_slider.setValue(int(pos * 1000))
+            self.seek_slider.blockSignals(False)
+
+    def shutdown(self):
+        self.player.shutdown()

scripts/smoke_test_arrow_seek.py

@@ -51,39 +51,40 @@ def main():
     assert not win.toggle_log_action.isChecked()
     print("PASS: log panel hidden by default")
 
-    win.player.seek(5.0)
+    win.source_panel.player.seek(5.0)
     qapp.processEvents()
     QTest.keyClick(win, Qt.Key.Key_Right)
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    pos = win.player.get_position()
+    pos = win.source_panel.player.get_position()
     print(f"after Right arrow from 5.0s: pos={pos:.3f}s")
     assert abs(pos - 10.0) < 0.5, f"expected ~10.0s, got {pos:.3f}s"  # 10s clip, clamps at end
 
-    win.player.seek(5.0)
+    win.source_panel.player.seek(5.0)
     qapp.processEvents()
     QTest.keyClick(win, Qt.Key.Key_Left)
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    pos = win.player.get_position()
+    pos = win.source_panel.player.get_position()
     print(f"after Left arrow from 5.0s: pos={pos:.3f}s")
     assert abs(pos - 0.0) < 0.5, f"expected ~0.0s, got {pos:.3f}s"
 
-    win.player.seek(2.0)
+    win.source_panel.player.seek(2.0)
     qapp.processEvents()
     QTest.keyClick(win, Qt.Key.Key_Left)
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    pos = win.player.get_position()
+    pos = win.source_panel.player.get_position()
     print(f"after Left arrow from 2.0s (should clamp to 0, not go negative): pos={pos:.3f}s")
     assert 0.0 <= pos < 0.5, f"expected clamped to ~0.0s, got {pos:.3f}s"
 
     print("PASS: arrow keys skip 5s and clamp to file bounds")
 
-    win.player.shutdown()
+    win.source_panel.shutdown()
+    win.preview_panel.shutdown()
     print("\nARROW SEEK SMOKE TEST PASSED")
 
 

scripts/smoke_test_clap_detection.py

@@ -47,7 +47,7 @@ def main():
     ok = wait_for(lambda: win.detect_all_action.isEnabled(), qapp)
     assert ok, "detection did not finish in time"
 
-    markers = win.marker_strip.markers()
+    markers = win.source_panel.marker_strip.markers()
     print(f"detected markers: {markers}")
     assert len(markers) >= 1, "expected at least one clap marker"
     # ground truth beep is at t=5.350s in this fixture; onset detection has
@@ -59,12 +59,12 @@ def main():
     # Simulate a real mouse click on the marker to prove click-to-seek works
     # end to end, not just that the signal is wired.
     target_time = min(markers, key=lambda m: abs(m - 5.350))
-    strip = win.marker_strip
-    strip.resize(win.seek_slider.width(), strip.height())
+    strip = win.source_panel.marker_strip
+    strip.resize(win.source_panel.seek_slider.width(), strip.height())
     x = strip._x_for_time(target_time)
     click_pos = QPointF(x, 5)
 
-    before_pos = win.player.get_position()
+    before_pos = win.source_panel.player.get_position()
     event = QMouseEvent(
         QMouseEvent.Type.MouseButtonPress, click_pos, click_pos,
         Qt.MouseButton.LeftButton, Qt.MouseButton.LeftButton, Qt.KeyboardModifier.NoModifier,
@@ -74,11 +74,12 @@ def main():
     time.sleep(0.2)
     qapp.processEvents()
 
-    after_pos = win.player.get_position()
+    after_pos = win.source_panel.player.get_position()
     print(f"clicked marker at x={x:.1f} (t={target_time:.3f}s); player position before={before_pos:.3f}s after={after_pos:.3f}s")
     assert abs(after_pos - target_time) < 0.1, "clicking the marker should seek the player to that timestamp"
 
-    win.player.shutdown()
+    win.source_panel.shutdown()
+    win.preview_panel.shutdown()
     print("\nCLAP DETECTION SMOKE TEST PASSED")
 
 

scripts/smoke_test_interactions.py

@@ -50,7 +50,7 @@ def main():
         Qt.MouseButton.LeftButton, Qt.KeyboardModifier.NoModifier,
         QDropEvent.Type.Drop,
     )
-    win.player.dropEvent(drop_event)
+    win.source_panel.player.dropEvent(drop_event)
     qapp.processEvents()
     time.sleep(0.3)
     qapp.processEvents()
@@ -58,42 +58,43 @@ def main():
     print(f"PASS: drag-and-drop loaded {Path(win.input_path).name}")
 
     # -- Clicking directly on the slider track (not the handle) jumps there
-    duration_ms = win.seek_slider.maximum()
+    duration_ms = win.source_panel.seek_slider.maximum()
     assert duration_ms > 0
-    target_x = win.seek_slider.width() * 0.5
-    click_pos = QPointF(target_x, win.seek_slider.height() / 2)
+    target_x = win.source_panel.seek_slider.width() * 0.5
+    click_pos = QPointF(target_x, win.source_panel.seek_slider.height() / 2)
     press_event = QMouseEvent(
         QMouseEvent.Type.MouseButtonPress, click_pos, click_pos,
         Qt.MouseButton.LeftButton, Qt.MouseButton.LeftButton, Qt.KeyboardModifier.NoModifier,
     )
-    before = win.player.get_position()
-    win.seek_slider.mousePressEvent(press_event)
+    before = win.source_panel.player.get_position()
+    win.source_panel.seek_slider.mousePressEvent(press_event)
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    after = win.player.get_position()
+    after = win.source_panel.player.get_position()
     expected = 0.5 * (duration_ms / 1000.0)
     print(f"clicked slider track at 50%: before={before:.3f}s after={after:.3f}s expected~{expected:.3f}s")
     assert abs(after - expected) < 0.5, "clicking the track should jump the player near that position"
     print("PASS: click-anywhere-on-track seeking works")
 
     # -- Dragging (sliderMoved) seeks live, without waiting for release
-    win.seek_slider.sliderPressed.emit()
+    win.source_panel.seek_slider.sliderPressed.emit()
     qapp.processEvents()
     drag_value = int(0.2 * duration_ms)
-    win.seek_slider.setValue(drag_value)
-    win.seek_slider.sliderMoved.emit(drag_value)
+    win.source_panel.seek_slider.setValue(drag_value)
+    win.source_panel.seek_slider.sliderMoved.emit(drag_value)
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    live_pos = win.player.get_position()
+    live_pos = win.source_panel.player.get_position()
     expected_drag = drag_value / 1000.0
     print(f"dragged to 20% (still 'pressed', not released): live player position={live_pos:.3f}s expected~{expected_drag:.3f}s")
     assert abs(live_pos - expected_drag) < 0.5, "dragging should seek immediately, before release"
-    win.seek_slider.sliderReleased.emit()
+    win.source_panel.seek_slider.sliderReleased.emit()
     print("PASS: live-seek during drag works")
 
-    win.player.shutdown()
+    win.source_panel.shutdown()
+    win.preview_panel.shutdown()
     print("\nALL INTERACTION SMOKE TESTS PASSED")
 
 

scripts/smoke_test_preserve_play_state.py

@@ -1,14 +1,14 @@
 """Verifies arrow-key skips preserve whichever play/pause state the user
 was already in, instead of always forcing a pause.
 
-Calls the real MainWindow._seek_relative() method directly rather than
+Calls the real PlayerPanel.seek_relative() method directly rather than
 simulating the QShortcut keypress: QTest.keyClick against this shortcut was
 observed to be unreliable in this headless setup even with Qt's
 active-window state forced (see smoke_test_arrow_seek.py's note) --
 sometimes the simulated key silently doesn't reach the shortcut at all, and
 a debug script isolated that PlayerWidget.seek() itself works correctly
 while playing, so the flakiness is in the synthetic-keypress dispatch, not
-the app. The QShortcut -> _seek_relative wiring itself (a single line) was
+the app. The QShortcut -> seek_relative wiring itself (a single line) was
 already independently confirmed with real xdotool keypresses against a
 live window in an earlier session.
 """
@@ -37,37 +37,38 @@ def main():
     qapp.processEvents()
 
     # -- Case 1: paused before the skip -> stays paused after
-    assert win.player.mpv.pause is True
-    before_pos = win.player.get_position()
-    win._seek_relative(5.0)
+    assert win.source_panel.player.mpv.pause is True
+    before_pos = win.source_panel.player.get_position()
+    win.source_panel.seek_relative(5.0)
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    after_pos = win.player.get_position()
+    after_pos = win.source_panel.player.get_position()
     print(f"paused case: before={before_pos:.3f}s after={after_pos:.3f}s")
-    assert win.player.mpv.pause is True, "should still be paused after skip"
-    assert win.play_button.text() == "Play"
+    assert win.source_panel.player.mpv.pause is True, "should still be paused after skip"
+    assert win.source_panel.play_button.text() == "Play"
     assert after_pos > before_pos + 4.0, "should have actually skipped forward"
     print("PASS: stays paused across arrow-key skip when it started paused")
 
     # -- Case 2: playing before the skip -> stays playing after
-    win.player.seek(0.0)
-    win.player.play()
-    win.play_button.setText("Pause")
+    win.source_panel.player.seek(0.0)
+    win.source_panel.player.play()
+    win.source_panel.play_button.setText("Pause")
     qapp.processEvents()
     time.sleep(0.2)
-    before_pos = win.player.get_position()
-    win._seek_relative(5.0)
+    before_pos = win.source_panel.player.get_position()
+    win.source_panel.seek_relative(5.0)
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    assert win.player.mpv.pause is False, "should still be playing after skip"
-    assert win.play_button.text() == "Pause"
-    after_pos = win.player.get_position()
+    assert win.source_panel.player.mpv.pause is False, "should still be playing after skip"
+    assert win.source_panel.play_button.text() == "Pause"
+    after_pos = win.source_panel.player.get_position()
     print(f"playing case: before={before_pos:.3f}s after={after_pos:.3f}s (should have jumped ~5s and kept playing)")
     assert after_pos > before_pos + 4.0, "should have actually skipped forward"
 
-    win.player.shutdown()
+    win.source_panel.shutdown()
+    win.preview_panel.shutdown()
     print("\nPRESERVE PLAY STATE SMOKE TEST PASSED")
 
 

scripts/smoke_test_preview.py

@@ -38,7 +38,8 @@ def main():
     assert win.video_tabs.count() == 2
     assert win.video_tabs.tabText(0) == "Source"
     assert win.video_tabs.tabText(1) == "Preview"
-    assert win.video_tabs.widget(0) is win.player
+    assert win.video_tabs.widget(0) is win.source_panel
+    assert win.video_tabs.widget(1) is win.preview_panel
     print("PASS: video area has Source and Preview tabs")
 
     win._load(CLIP)
@@ -47,11 +48,11 @@ def main():
     qapp.processEvents()
     assert win.video_tabs.currentIndex() == 0, "loading a new source should land on the Source tab"
 
-    win.player.seek(5.000)
+    win.source_panel.player.seek(5.000)
     qapp.processEvents()
     win._mark_video()
 
-    win.player.seek(5.350)
+    win.source_panel.player.seek(5.350)
     qapp.processEvents()
     win._mark_audio()
 
@@ -77,21 +78,41 @@ def main():
     time.sleep(0.3)
     qapp.processEvents()
 
-    duration = win.preview_player.mpv.duration
+    duration = win.preview_panel.player.mpv.duration
     print(f"preview clip duration: {duration:.3f}s (expected ~{win.PREVIEW_DURATION_SEC}s, clamped to file bounds)")
     assert duration is not None and 0 < duration <= win.PREVIEW_DURATION_SEC + 0.5
-    assert win.preview_player.mpv.pause is False, "preview should auto-play"
-    assert win.preview_play_button.text() == "Pause"
+    assert win.preview_panel.player.mpv.pause is False, "preview should auto-play"
+    assert win.preview_panel.play_button.text() == "Pause"
+
+    # -- The Preview tab has its own functional timeline (not a static video
+    # + a single play button): its own seek slider, sized to the preview
+    # clip's own duration, that seeks the preview player independently of
+    # the Source tab's slider/player.
+    assert win.preview_panel.seek_slider is not win.source_panel.seek_slider
+    preview_duration_ms = win.preview_panel.seek_slider.maximum()
+    assert preview_duration_ms > 0
+    print(f"Preview tab's own seek slider range: 0..{preview_duration_ms}ms")
+    target_ms = int(preview_duration_ms * 0.7)
+    win.preview_panel.seek_slider.setValue(target_ms)
+    win.preview_panel.seek_slider.sliderMoved.emit(target_ms)
+    qapp.processEvents()
+    time.sleep(0.2)
+    qapp.processEvents()
+    preview_pos = win.preview_panel.player.get_position()
+    source_pos = win.source_panel.player.get_position()
+    print(f"dragged Preview tab's own slider to 70%: preview player now at {preview_pos:.3f}s, source player still at {source_pos:.3f}s")
+    assert abs(preview_pos - target_ms / 1000.0) < 0.5, "Preview tab's slider should seek the preview player"
+    print("PASS: Preview tab has its own independent, functional timeline")
 
     # -- Switching back to Source shouldn't disturb the main player, and the
     # preview player keeps running independently (two live mpv instances).
-    main_pos_before_switch = win.player.get_position()
+    main_pos_before_switch = win.source_panel.player.get_position()
     win.video_tabs.setCurrentIndex(0)
     qapp.processEvents()
-    main_pos_after_switch = win.player.get_position()
+    main_pos_after_switch = win.source_panel.player.get_position()
     print(f"main player position: before switch={main_pos_before_switch:.3f}s after={main_pos_after_switch:.3f}s")
     assert abs(main_pos_after_switch - main_pos_before_switch) < 0.1, "switching tabs shouldn't move the main player"
-    assert win.player.mpv.pause is True, "main player should still be paused (untouched by preview building)"
+    assert win.source_panel.player.mpv.pause is True, "main player should still be paused (untouched by preview building)"
     print("PASS: switching tabs doesn't disturb the main player")
 
     # -- Building a second preview swaps the file without leaking the first

scripts/smoke_test_rightclick_filemenu.py

@@ -42,24 +42,25 @@ def main():
     print("PASS: Load File lives in the File menu")
 
     # -- Right-click on the player toggles play/pause
-    assert win.player.mpv.pause is True, "should start paused"
-    win.player.mpv.command("keypress", "MBTN_RIGHT")
+    assert win.source_panel.player.mpv.pause is True, "should start paused"
+    win.source_panel.player.mpv.command("keypress", "MBTN_RIGHT")
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    assert win.player.mpv.pause is False, "right-click should have started playback"
-    assert win.play_button.text() == "Pause"
+    assert win.source_panel.player.mpv.pause is False, "right-click should have started playback"
+    assert win.source_panel.play_button.text() == "Pause"
     print("PASS: right-click on player started playback")
 
-    win.player.mpv.command("keypress", "MBTN_RIGHT")
+    win.source_panel.player.mpv.command("keypress", "MBTN_RIGHT")
     qapp.processEvents()
     time.sleep(0.2)
     qapp.processEvents()
-    assert win.player.mpv.pause is True, "second right-click should pause again"
-    assert win.play_button.text() == "Play"
+    assert win.source_panel.player.mpv.pause is True, "second right-click should pause again"
+    assert win.source_panel.play_button.text() == "Play"
     print("PASS: right-click on player paused again")
 
-    win.player.shutdown()
+    win.source_panel.shutdown()
+    win.preview_panel.shutdown()
     print("\nRIGHT-CLICK / FILE MENU SMOKE TEST PASSED")
 
 

scripts/smoke_test_ui.py

@@ -30,14 +30,14 @@ def main():
     qapp.processEvents()
     time.sleep(0.3)
     qapp.processEvents()
-    print(f"loaded: duration slider range = {win.seek_slider.maximum()}ms")
+    print(f"loaded: duration slider range = {win.source_panel.seek_slider.maximum()}ms")
 
-    win.player.seek(5.000)
+    win.source_panel.player.seek(5.000)
     qapp.processEvents()
     win._mark_video()
     print(f"video mark: {win.video_mark:.3f}s -> label: {win.video_mark_label.text()}")
 
-    win.player.seek(5.350)
+    win.source_panel.player.seek(5.350)
     qapp.processEvents()
     win._mark_audio()
     print(f"audio mark: {win.audio_mark:.3f}s -> label: {win.audio_mark_label.text()}")
@@ -85,7 +85,8 @@ def main():
     assert Path(EXPORT_OUT).exists()
     print(f"exported file exists: {EXPORT_OUT}, size={Path(EXPORT_OUT).stat().st_size} bytes")
 
-    win.player.shutdown()
+    win.source_panel.shutdown()
+    win.preview_panel.shutdown()
     print("\nUI SMOKE TEST PASSED")
 
 

scripts/smoke_test_view_menu.py

@@ -31,7 +31,8 @@ def main():
     qapp.processEvents()
     assert not win.log_view.isVisible()
 
-    win.player.shutdown()
+    win.source_panel.shutdown()
+    win.preview_panel.shutdown()
     print("PASS: View > Show ffmpeg Log toggles the log panel correctly")