grow height for scrollbar

Author: willmcgugan

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Input cursor will no longer jump to the end on focus https://github.com/Textualize/textual/pull/4773
 - Removed `Size.cip_size`, which was a clone of `crop_size`
+- Widgets with auto dimensions will now grow if there is a scrollbar
 
 ### Fixed
 

src/textual/widget.py

@@ -1236,7 +1236,9 @@ def _get_box_model(
             content_width = Fraction(
                 self.get_content_width(content_container - margin.totals, viewport)
             )
-            if styles.scrollbar_gutter == "stable" and styles.overflow_x == "auto":
+            if styles.overflow_x == "auto" and (
+                styles.scrollbar_gutter == "stable" or self.show_vertical_scrollbar
+            ):
                 content_width += styles.scrollbar_size_vertical
             if (
                 content_width < content_container.width
@@ -1286,8 +1288,11 @@ def _get_box_model(
             content_height = Fraction(
                 self.get_content_height(content_container, viewport, int(content_width))
             )
-            if styles.scrollbar_gutter == "stable" and styles.overflow_y == "auto":
+            if styles.overflow_y == "auto" and (
+                styles.scrollbar_gutter == "stable" or self.show_horizontal_scrollbar
+            ):
                 content_height += styles.scrollbar_size_horizontal
+
             if (
                 content_height < content_container.height
                 and self._has_relative_children_height

tests/snapshot_tests/__snapshots__/test_snapshots/test_auto_height_scrollbar.svg

@@ -0,0 +1,38 @@
+from textual.app import App, ComposeResult
+from textual.widgets import DataTable, Label
+
+LORUM_IPSUM = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
+
+
+class ExampleApp(App):
+    CSS = """
+    Screen {
+       
+        DataTable {
+            border: solid white;
+        }
+    }
+
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Label("automatic scrollbar")
+        yield DataTable(id="table1")
+        yield Label("no automatic scrollbar")
+        yield DataTable(id="table2")
+
+    def on_mount(self) -> None:
+        table = self.query_one("#table1", DataTable)
+        table.add_column("Column 1")
+        table.add_column("Column 2")
+        table.add_row(LORUM_IPSUM, LORUM_IPSUM)
+
+        table = self.query_one("#table2", DataTable)
+        table.add_column("Column 1")
+        table.add_column("Column 2")
+        table.add_row("Paul", "Jessica")
+
+
+if __name__ == "__main__":
+    app = ExampleApp()
+    app.run()

tests/snapshot_tests/snapshot_apps/data_table_auto_height.py

@@ -1400,3 +1400,8 @@ async def run_before(pilot: Pilot):
 def test_remove_tab_no_animation(snap_compare):
     """Regression test for https://github.com/Textualize/textual/issues/4814"""
     assert snap_compare(SNAPSHOT_APPS_DIR / "remove_tab.py", press=["space"])
+
+
+def test_auto_height_scrollbar(snap_compare):
+    """Regression test for https://github.com/Textualize/textual/issues/4778"""
+    assert snap_compare(SNAPSHOT_APPS_DIR / "data_table_auto_height.py")