Adding upstream version 0.12.0.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tests/snapshot_tests/snapshot_apps/data_table_add_column.py

@@ -0,0 +1,36 @@
+from textual.app import App, ComposeResult
+from textual.binding import Binding
+from textual_fastdatatable import ArrowBackend, DataTable
+
+MOVIES = [
+    "Severance",
+    "Foundation",
+    "Dark",
+    "The Boys",
+    "The Last of Us",
+    "Lost in Space",
+    "Altered Carbon",
+]
+
+
+class AddColumn(App):
+    BINDINGS = [
+        Binding(key="c", action="add_column", description="Add Column"),
+    ]
+
+    def compose(self) -> ComposeResult:
+        backend = ArrowBackend.from_pydict({"Movies": MOVIES})
+        table = DataTable(backend=backend)
+
+        column_idx = table.add_column("No Default")
+        table.add_column("With Default", default="ABC")
+        table.add_column("Long Default", default="01234567890123456789")
+
+        # Ensure we can update a cell
+        table.update_cell(2, column_idx, "Hello!")
+        yield table
+
+
+app = AddColumn()
+if __name__ == "__main__":
+    app.run()