DataTable new rows can have auto height.

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Reactive callbacks are now scheduled on the message pump of the reactable that is watching instead of the owner of reactive attribute https://github.com/Textualize/textual/pull/3065
 - Callbacks scheduled with `call_next` will now have the same prevented messages as when the callback was scheduled https://github.com/Textualize/textual/pull/3065
 - Added `cursor_type` to the `DataTable` constructor.
+- `DataTable.add_row` accepts `height=None` to automatically compute optimal height for a row https://github.com/Textualize/textual/pull/3213
 
 ### Fixed
 

src/textual/widgets/_data_table.py

@@ -187,6 +187,7 @@ class Row:
     key: RowKey
     height: int
     label: Text | None = None
+    auto_height: bool = False
 
 
 class RowRenderables(NamedTuple):
@@ -1190,8 +1191,16 @@ def _update_column_widths(self, updated_cells: set[CellKey]) -> None:
         self._require_update_dimensions = True
 
     def _update_dimensions(self, new_rows: Iterable[RowKey]) -> None:
-        """Called to recalculate the virtual (scrollable) size."""
+        """Called to recalculate the virtual (scrollable) size.
+
+        This recomputes column widths and then checks if any of the new rows need
+        to have their height computed.
+
+        Args:
+            new_rows: The new rows that will affect the `DataTable` dimensions.
+        """
         console = self.app.console
+        auto_height_rows: list[tuple[Row, list[RenderableType]]] = []
         for row_key in new_rows:
             row_index = self._row_locations.get(row_key)
 
@@ -1201,6 +1210,7 @@ def _update_dimensions(self, new_rows: Iterable[RowKey]) -> None:
                 continue
 
             row = self.rows.get(row_key)
+            assert row is not None
 
             if row.label is not None:
                 self._labelled_row_exists = True
@@ -1215,6 +1225,22 @@ def _update_dimensions(self, new_rows: Iterable[RowKey]) -> None:
                 content_width = measure(console, renderable, 1)
                 column.content_width = max(column.content_width, content_width)
 
+            if row.auto_height:
+                auto_height_rows.append((row, cells_in_row))
+
+        for row, cells_in_row in auto_height_rows:
+            height = 0
+            for column, renderable in zip(self.ordered_columns, cells_in_row):
+                height = max(
+                    height,
+                    len(
+                        console.render_lines(
+                            renderable, console.options.update_width(column.width)
+                        )
+                    ),
+                )
+            row.height = height
+
         self._clear_caches()
 
         data_cells_width = sum(column.render_width for column in self.columns.values())
@@ -1373,21 +1399,22 @@ def add_column(
     def add_row(
         self,
         *cells: CellType,
-        height: int = 1,
+        height: int | None = 1,
         key: str | None = None,
         label: TextType | None = None,
     ) -> RowKey:
         """Add a row at the bottom of the DataTable.
 
         Args:
             *cells: Positional arguments should contain cell data.
-            height: The height of a row (in lines).
+            height: The height of a row (in lines). Use `None` to auto-detect the optimal
+                height.
             key: A key which uniquely identifies this row. If None, it will be generated
                 for you and returned.
             label: The label for the row. Will be displayed to the left if supplied.
 
         Returns:
-            Uniquely identifies this row. Can be used to retrieve this row regardless
+            Unique identifier for this row. Can be used to retrieve this row regardless
                 of its current location in the DataTable (it could have moved after
                 being added due to sorting or insertion/deletion of other rows).
         """
@@ -1407,7 +1434,12 @@ def add_row(
             for column, cell in zip_longest(self.ordered_columns, cells)
         }
         label = Text.from_markup(label) if isinstance(label, str) else label
-        self.rows[row_key] = Row(row_key, height, label)
+        self.rows[row_key] = Row(
+            row_key,
+            height if height is not None else 1,
+            label,
+            height is None,
+        )
         self._new_rows.add(row_key)
         self._require_update_dimensions = True
         self.cursor_coordinate = self.cursor_coordinate
@@ -1546,7 +1578,8 @@ async def _on_idle(self, _: events.Idle) -> None:
 
         if self._require_update_dimensions:
             # Add the new rows *before* updating the column widths, since
-            # cells in a new row may influence the final width of a column
+            # cells in a new row may influence the final width of a column.
+            # Only then can we compute optimal height of rows with "auto" height.
             self._require_update_dimensions = False
             new_rows = self._new_rows.copy()
             self._new_rows.clear()

tests/test_data_table.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import pytest
+from rich.panel import Panel
 from rich.text import Text
 
 from textual._wait import wait_for_idle
@@ -419,11 +420,11 @@ async def test_get_cell_coordinate_returns_coordinate():
         table.add_row("ValR2C1", "ValR2C2", "ValR2C3", key="R2")
         table.add_row("ValR3C1", "ValR3C2", "ValR3C3", key="R3")
 
-        assert table.get_cell_coordinate('R1', 'C1') == Coordinate(0, 0)
-        assert table.get_cell_coordinate('R2', 'C2') == Coordinate(1, 1)
-        assert table.get_cell_coordinate('R1', 'C3') == Coordinate(0, 2)
-        assert table.get_cell_coordinate('R3', 'C1') == Coordinate(2, 0)
-        assert table.get_cell_coordinate('R3', 'C2') == Coordinate(2, 1)
+        assert table.get_cell_coordinate("R1", "C1") == Coordinate(0, 0)
+        assert table.get_cell_coordinate("R2", "C2") == Coordinate(1, 1)
+        assert table.get_cell_coordinate("R1", "C3") == Coordinate(0, 2)
+        assert table.get_cell_coordinate("R3", "C1") == Coordinate(2, 0)
+        assert table.get_cell_coordinate("R3", "C2") == Coordinate(2, 1)
 
 
 async def test_get_cell_coordinate_invalid_row_key():
@@ -434,7 +435,7 @@ async def test_get_cell_coordinate_invalid_row_key():
         table.add_row("TargetValue", key="R1")
 
         with pytest.raises(CellDoesNotExist):
-            coordinate = table.get_cell_coordinate('INVALID_ROW', 'C1')
+            coordinate = table.get_cell_coordinate("INVALID_ROW", "C1")
 
 
 async def test_get_cell_coordinate_invalid_column_key():
@@ -445,7 +446,7 @@ async def test_get_cell_coordinate_invalid_column_key():
         table.add_row("TargetValue", key="R1")
 
         with pytest.raises(CellDoesNotExist):
-            coordinate = table.get_cell_coordinate('R1', 'INVALID_COLUMN')
+            coordinate = table.get_cell_coordinate("R1", "INVALID_COLUMN")
 
 
 async def test_get_cell_at_returns_value_at_cell():
@@ -531,9 +532,9 @@ async def test_get_row_index_returns_index():
         table.add_row("ValR2C1", "ValR2C2", key="R2")
         table.add_row("ValR3C1", "ValR3C2", key="R3")
 
-        assert table.get_row_index('R1') == 0
-        assert table.get_row_index('R2') == 1
-        assert table.get_row_index('R3') == 2
+        assert table.get_row_index("R1") == 0
+        assert table.get_row_index("R2") == 1
+        assert table.get_row_index("R3") == 2
 
 
 async def test_get_row_index_invalid_row_key():
@@ -544,7 +545,7 @@ async def test_get_row_index_invalid_row_key():
         table.add_row("TargetValue", key="R1")
 
         with pytest.raises(RowDoesNotExist):
-            index = table.get_row_index('InvalidRow')
+            index = table.get_row_index("InvalidRow")
 
 
 async def test_get_column():
@@ -591,19 +592,20 @@ async def test_get_column_at_invalid_index(index):
         with pytest.raises(ColumnDoesNotExist):
             list(table.get_column_at(index))
 
+
 async def test_get_column_index_returns_index():
     app = DataTableApp()
     async with app.run_test():
         table = app.query_one(DataTable)
         table.add_column("Column1", key="C1")
         table.add_column("Column2", key="C2")
         table.add_column("Column3", key="C3")
-        table.add_row("ValR1C1", "ValR1C2", "ValR1C3",  key="R1")
-        table.add_row("ValR2C1", "ValR2C2", "ValR2C3",  key="R2")
+        table.add_row("ValR1C1", "ValR1C2", "ValR1C3", key="R1")
+        table.add_row("ValR2C1", "ValR2C2", "ValR2C3", key="R2")
 
-        assert table.get_column_index('C1') == 0
-        assert table.get_column_index('C2') == 1
-        assert table.get_column_index('C3') == 2
+        assert table.get_column_index("C1") == 0
+        assert table.get_column_index("C2") == 1
+        assert table.get_column_index("C3") == 2
 
 
 async def test_get_column_index_invalid_column_key():
@@ -613,11 +615,10 @@ async def test_get_column_index_invalid_column_key():
         table.add_column("Column1", key="C1")
         table.add_column("Column2", key="C2")
         table.add_column("Column3", key="C3")
-        table.add_row("TargetValue1", "TargetValue2", "TargetValue3",  key="R1")
+        table.add_row("TargetValue1", "TargetValue2", "TargetValue3", key="R1")
 
         with pytest.raises(ColumnDoesNotExist):
-            index = table.get_column_index('InvalidCol')
-
+            index = table.get_column_index("InvalidCol")
 
 
 async def test_update_cell_cell_exists():
@@ -1161,3 +1162,24 @@ async def test_unset_hover_highlight_when_no_table_cell_under_mouse():
         # the widget, and the hover cursor is hidden
         await pilot.hover(DataTable, offset=Offset(42, 1))
         assert not table._show_hover_cursor
+
+
+@pytest.mark.parametrize(
+    ["cell", "height"],
+    [
+        ("hey there", 1),
+        (Text("hey there"), 1),
+        (Text("long string", overflow="fold"), 2),
+        (Panel.fit("Hello\nworld"), 4),
+        ("1\n2\n3\n4\n5\n6\n7", 7),
+    ],
+)
+async def test_add_row_auto_height(cell: RenderableType, height: int):
+    app = DataTableApp()
+    async with app.run_test() as pilot:
+        table = app.query_one(DataTable)
+        table.add_column("C", width=10)
+        row_key = table.add_row(cell, height=None)
+        row = table.rows.get(row_key)
+        await pilot.pause()
+        assert row.height == height