Merge pull request #1803 from Textualize/datatable-scrollbar-show-header-refresh

Ensure scrollbars update when show_header toggles

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased
+
+### Fixed
+
+- DataTable scrollbars resize correctly when header is toggled https://github.com/Textualize/textual/pull/1803
+
 ## [0.11.0] - 2023-02-15
 
 ### Added

src/textual/widgets/_data_table.py

@@ -786,7 +786,11 @@ class DataTable(ScrollView, Generic[CellType], can_focus=True):
             elif self.cursor_type == "column":
                 self._highlight_column(self.cursor_column)
 
-    def watch_show_header(self) -> None:
+    def watch_show_header(self, show: bool) -> None:
+        width, height = self.virtual_size
+        height_change = self.header_height if show else -self.header_height
+        self.virtual_size = Size(width, height + height_change)
+        self._scroll_cursor_into_view()
         self._clear_caches()
 
     def watch_fixed_rows(self) -> None: