feat: Merge sequence — add (file/selection), reorder, remove

main.py

@@ -4544,6 +4544,7 @@ class MainWindow(QMainWindow):
         self._merge_list.setSelectionMode(
             QAbstractItemView.SelectionMode.SingleSelection)
         self._merge_list.setToolTip("Clips to merge, top to bottom")
+        self._merge_temps: set[str] = set()
         self._spn_crossfade = QDoubleSpinBox()
         self._spn_crossfade.setRange(0.0, 10.0)
         self._spn_crossfade.setDecimals(2)
@@ -6579,17 +6580,74 @@ class MainWindow(QMainWindow):
         start = self._cursor
         self._timeline.set_audio_region(start, start + self._spn_audio_len.value())
 
-    def _on_merge_add_selection(self) -> None:
-        pass   # implemented in M3
+    def _merge_add_paths(self, paths: list[str]) -> None:
+        QApplication.setOverrideCursor(Qt.CursorShape.WaitCursor)
+        try:
+            for p in paths:
+                ap = os.path.abspath(p)
+                dur = probe_duration(ap)
+                text = (f"{os.path.basename(ap)}  ({dur:.2f}s)"
+                        if dur is not None else os.path.basename(ap))
+                item = QListWidgetItem(text)
+                item.setData(Qt.ItemDataRole.UserRole, ap)
+                item.setData(Qt.ItemDataRole.UserRole + 1, dur)
+                self._merge_list.addItem(item)
+        finally:
+            QApplication.restoreOverrideCursor()
 
     def _on_merge_add_file(self) -> None:
-        pass   # implemented in M3
+        default_dir = (self._settings.value("audio_extract_dir", "")
+                       or os.path.dirname(self._file_path or ""))
+        paths, _sel = QFileDialog.getOpenFileNames(
+            self, "Add audio file(s)", default_dir,
+            "Audio (*.wav *.mp3 *.flac *.m4a *.ogg *.opus *.aac);;All files (*)")
+        if paths:
+            self._merge_add_paths(paths)
+
+    def _on_merge_add_selection(self) -> None:
+        if not self._file_path:
+            self._show_status("Load a video first", 3000)
+            return
+        import tempfile
+        start = self._cursor
+        dur = self._spn_audio_len.value()
+        fd, tmp = tempfile.mkstemp(suffix=".wav", prefix="8cut_merge_")
+        os.close(fd)
+        self._show_status("Rendering selection…")
+        QApplication.setOverrideCursor(Qt.CursorShape.WaitCursor)
+        try:
+            cmd = build_audio_clip_command(self._file_path, start, dur, tmp,
+                                           filters=self._current_edit_filters() or None)
+            proc = subprocess.run(cmd, capture_output=True, timeout=120)
+        except Exception:
+            proc = None
+        finally:
+            QApplication.restoreOverrideCursor()
+        if proc is not None and proc.returncode == 0 and os.path.exists(tmp):
+            self._merge_temps.add(tmp)
+            self._merge_add_paths([tmp])
+        else:
+            try:
+                os.remove(tmp)
+            except OSError:
+                pass
+            self._show_status("Could not render selection", 3000)
 
     def _merge_move(self, delta: int) -> None:
-        pass   # implemented in M3
+        row = self._merge_list.currentRow()
+        if row < 0:
+            return
+        new = row + delta
+        if new < 0 or new >= self._merge_list.count():
+            return
+        item = self._merge_list.takeItem(row)
+        self._merge_list.insertItem(new, item)
+        self._merge_list.setCurrentRow(new)
 
     def _merge_remove_selected(self) -> None:
-        pass   # implemented in M3
+        row = self._merge_list.currentRow()
+        if row >= 0:
+            self._merge_list.takeItem(row)
 
     def _on_merge_preview(self) -> None:
         pass   # implemented in M4