Greatly simplifed drag and drop code

app/playlists.py

@@ -189,8 +189,7 @@ class PlaylistTab(QTableWidget):
             self.resizeRowsToContents)
 
         # Drag and drop setup
-        # TODO: fix drag and drop for qt6
-        self.setAcceptDrops(False)
+        self.setAcceptDrops(True)
         self.viewport().setAcceptDrops(True)
         self.setDragDropOverwriteMode(False)
         self.setDropIndicatorShown(True)
@@ -232,41 +231,37 @@ class PlaylistTab(QTableWidget):
         if not event.source() == self:
             return  # We don't accept external drops
 
-        drop_row: int = self._drop_on(event)
-
-        rows: List = sorted(set(item.row() for item in self.selectedItems()))
-        rows_to_move = [
-            [QTableWidgetItem(
-                self.item(row_index, column_index)    # type: ignore
-            ) for
-             column_index in range(self.columnCount())]
-            for row_index in rows
-        ]
-        for row_index in reversed(rows):
-            self.removeRow(row_index)
-            if row_index < drop_row:
-                drop_row -= 1
-
-        for row_index, data in enumerate(rows_to_move):
-            row_index += drop_row
-            self.insertRow(row_index)
-            for column_index, column_data in enumerate(data):
-                self.setItem(row_index, column_index, column_data)
+        row_set = set([mi.row() for mi in self.selectedIndexes()])
+        targetRow = self.indexAt(event.position().toPoint()).row()
+        row_set.discard(targetRow)
+        rows = list(sorted(row_set))
+        if not rows:
+            return
+        if targetRow == -1:
+            targetRow = self.rowCount()
+        for _ in range(len(rows)):
+            self.insertRow(targetRow)
+        rowMapping = dict()  # Src row to target row.
+        for idx, row in enumerate(rows):
+            if row < targetRow:
+                rowMapping[row] = targetRow + idx
+            else:
+                rowMapping[row + len(rows)] = targetRow + idx
+        colCount = self.columnCount()
+        for srcRow, tgtRow in sorted(rowMapping.items()):
+            for col in range(0, colCount):
+                self.setItem(tgtRow, col, self.takeItem(srcRow, col))
+        for row in reversed(sorted(rowMapping.keys())):
+            self.removeRow(row)
         event.accept()
-        # The above doesn't handle column spans, which we use in note
-        # rows. Check and fix:
-        for row in range(drop_row, drop_row + len(rows_to_move)):
-            if not self._get_row_track_id(row):
-                self.setSpan(row, HEADER_NOTES_COLUMN, 1, len(columns))
 
         # Scroll to drop zone
-        self.scrollToItem(self.item(row, 1))
+        self.scrollToItem(self.item(targetRow, 1),
+                          QAbstractItemView.ScrollHint.PositionAtCenter)
 
         # Reset drag mode to allow row selection by dragging
         self.setDragEnabled(False)
 
-        super().dropEvent(event)
-
         with Session() as session:
             self.save_playlist(session)
             self._update_start_end_times(session)
@@ -291,8 +286,7 @@ class PlaylistTab(QTableWidget):
         """
 
         if self.selectedItems():
-            # TODO: fix drag and drop
-            self.setDragEnabled(False)
+            self.setDragEnabled(True)
         else:
             self.setDragEnabled(False)
         super().mouseReleaseEvent(event)
@@ -1152,19 +1146,6 @@ class PlaylistTab(QTableWidget):
 
             self._update_start_end_times(session)
 
-    def _drop_on(self, event):
-        """
-        https://stackoverflow.com/questions/26227885/drag-and-drop-rows-within-qtablewidget
-        """
-
-        position = event.position().toPoint()
-        index = self.indexAt(position)
-        if not index.isValid():
-            return self.rowCount()
-
-        return (index.row() + 1 if self._is_below(position, index)
-                else index.row())
-
     def _find_next_track_row(self, session: scoped_session,
                              starting_row: Optional[int] = None) \
             -> Optional[int]:
@@ -1416,23 +1397,6 @@ class PlaylistTab(QTableWidget):
         info.setDefaultButton(QMessageBox.StandardButton.Cancel)
         info.exec()
 
-    def _is_below(self, pos, index):   # review
-        """
-        https://stackoverflow.com/questions/26227885/drag-and-drop-rows-within-qtablewidget
-        """
-
-        rect = self.visualRect(index)
-        margin = 2
-        if pos.y() - rect.top() < margin:
-            return False
-        elif rect.bottom() - pos.y() < margin:
-            return True
-        return (
-                rect.contains(pos, True) and not
-        (int(self.model().flags(index)) & Qt.ItemIsDropEnabled)
-                and pos.y() >= rect.center().y()  # noqa W503
-        )
-
     def _look_up_row(self, website: str) -> None:
         """
         If there is a selected row and it is a track row,