feat: read-only waveform strip + manual refresh in the Audio tab

main.py

@@ -3937,6 +3937,39 @@ def main():
     sys.exit(ret)
 
 
+class AudioWaveform(QWidget):
+    """Read-only waveform strip: paints normalized peak bars for the current
+    audio region. Populated on demand via manual refresh (no implicit UI-thread
+    decode)."""
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self._peaks: list[float] = []
+        self.setFixedHeight(48)
+        self.setToolTip("Waveform of the current audio area (↻ to refresh)")
+
+    def set_peaks(self, peaks: list[float]) -> None:
+        self._peaks = list(peaks or [])
+        self.update()
+
+    def clear(self) -> None:
+        self._peaks = []
+        self.update()
+
+    def paintEvent(self, _ev):
+        p = QPainter(self)
+        p.fillRect(self.rect(), QColor(30, 30, 30))
+        if not self._peaks:
+            return
+        w = self.width(); h = self.height(); mid = h / 2
+        n = len(self._peaks)
+        p.setPen(QPen(QColor(0, 220, 190)))
+        for i, v in enumerate(self._peaks):
+            x = int(i * w / n)
+            bar_h = v * (h - 4) / 2
+            p.drawLine(x, int(mid - bar_h), x, int(mid + bar_h))
+
+
 class MainWindow(QMainWindow):
     def __init__(self):
         super().__init__()
@@ -4495,6 +4528,11 @@ class MainWindow(QMainWindow):
         self._spn_gain.setSingleStep(0.5)
         self._spn_gain.setSuffix(" dB")
         self._spn_gain.setToolTip("Gain applied to the extracted audio (0 = unchanged)")
+        self._wave = AudioWaveform()
+        self._btn_wave_refresh = QPushButton("↻ Waveform")
+        self._btn_wave_refresh.setToolTip(
+            "Decode the current audio area and draw its waveform")
+        self._btn_wave_refresh.clicked.connect(self._on_wave_refresh)
         self._transport_row = transport_row
 
         # Row 1b — subcategory (subprofile) export buttons live on their own
@@ -4797,10 +4835,12 @@ class MainWindow(QMainWindow):
         g.addWidget(self._chk_normalize, 3, 0, 1, 2)
         g.addWidget(QLabel("Gain:"), 3, 2)
         g.addWidget(self._spn_gain, 3, 3)
-        # Row 4 reserved for the waveform strip (added in a later task).
+        # Row 4 — read-only waveform strip for the current audio area.
-        g.addWidget(self._btn_extract_audio, 5, 0, 1, 4)
+        g.addWidget(self._wave, 4, 0, 1, 4)
+        g.addWidget(self._btn_wave_refresh, 5, 0, 1, 2)
+        g.addWidget(self._btn_extract_audio, 6, 0, 1, 4)
         g.setColumnStretch(4, 1)   # spare gutter column clusters label/field pairs to the left
-        g.setRowStretch(6, 1)      # anchor content to the top (row 4 stays reserved for the waveform)
+        g.setRowStretch(7, 1)      # anchor content to the top
         tb.addItem(extract_page, "Extract & Edit")
 
         # ── Page 2: Scan / Classify (moved verbatim) ─────────────
@@ -6463,6 +6503,21 @@ class MainWindow(QMainWindow):
         start = self._cursor
         self._timeline.set_audio_region(start, start + self._spn_audio_len.value())
 
+    def _on_wave_refresh(self) -> None:
+        """Decode the current audio area and repaint the waveform strip."""
+        if not self._file_path:
+            self._wave.clear()
+            return
+        from core.waveform import load_region_samples, peaks
+        start = self._cursor
+        dur = self._spn_audio_len.value()
+        QApplication.setOverrideCursor(Qt.CursorShape.WaitCursor)
+        try:
+            samples = load_region_samples(self._file_path, start, dur)
+        finally:
+            QApplication.restoreOverrideCursor()
+        self._wave.set_peaks(peaks(samples))
+
     def _on_extract_audio(self) -> None:
         """Extract an exact-length audio slice starting at the playhead and
         prompt for where to save it (format follows the chosen extension)."""

tests/test_ui_structure.py

@@ -372,3 +372,17 @@ def test_extract_no_edits_passes_no_filters(win, monkeypatch, tmp_path):
     with pytest.raises(_Stop):
         win._on_extract_audio()
     assert seen["filters"] is None
+
+
+def test_waveform_strip_present_and_safe(win):
+    from PyQt6.QtWidgets import QPushButton
+    assert win._wave is not None
+    assert isinstance(win._btn_wave_refresh, QPushButton)
+    # set_peaks stores + doesn't crash
+    win._wave.set_peaks([0.1, 0.5, 0.9])
+    assert list(win._wave._peaks) == [0.1, 0.5, 0.9]
+    win._wave.clear()
+    assert win._wave._peaks == []
+    # refresh with no file loaded is a safe no-op
+    win._file_path = ""
+    win._on_wave_refresh()