DataTable - Message emitted when header selected

CHANGELOG.md

@@ -35,6 +35,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added `DataTable.get_row_at` to retrieve the values from a row by index https://github.com/Textualize/textual/pull/1786
 - Added `DataTable.get_column` to retrieve the values from a column by key https://github.com/Textualize/textual/pull/1786
 - Added `DataTable.get_column_at` to retrieve the values from a column by index https://github.com/Textualize/textual/pull/1786
+- Added `DataTable.HeaderSelected` which is posted when header label clicked https://github.com/Textualize/textual/pull/1788
 - Added `DOMNode.watch` and `DOMNode.is_attached` methods  https://github.com/Textualize/textual/pull/1750
 - Added `DOMNode.css_tree` which is a renderable that shows the DOM and CSS https://github.com/Textualize/textual/pull/1778
 - Added `DOMNode.children_view` which is a view on to a nodes children list, use for querying https://github.com/Textualize/textual/pull/1778

docs/widgets/data_table.md

@@ -48,6 +48,8 @@ The example below populates a table with CSV data.
 
 ### ::: textual.widgets.DataTable.ColumnSelected
 
+### ::: textual.widgets.DataTable.HeaderSelected
+
 ## Bindings
 
 The data table widget defines directly the following bindings:

src/textual/message.py

@@ -10,7 +10,6 @@
 
 if TYPE_CHECKING:
     from .message_pump import MessagePump
-    from .widget import Widget
 
 
 @rich.repr.auto

src/textual/widgets/_data_table.py

@@ -445,6 +445,29 @@ def __rich_repr__(self) -> rich.repr.Result:
             yield "cursor_column", self.cursor_column
             yield "column_key", self.column_key
 
+    class HeaderSelected(Message, bubble=True):
+        """Posted when a column header/label is clicked."""
+
+        def __init__(
+            self,
+            sender: DataTable,
+            column_key: ColumnKey,
+            column_index: int,
+            label: Text,
+        ):
+            self.column_key = column_key
+            """The key for the column."""
+            self.column_index = column_index
+            """The index for the column."""
+            self.label = label
+            """The text of the label."""
+            super().__init__(sender)
+
+        def __rich_repr__(self) -> rich.repr.Result:
+            yield "sender", self.sender
+            yield "column_key", self.column_key
+            yield "label", self.label.plain
+
     def __init__(
         self,
         *,
@@ -1334,8 +1357,7 @@ def _render_cell(
         column_key = self._column_locations.get_key(column_index)
         cell_cache_key = (row_key, column_key, style, cursor, hover, self._update_count)
         if cell_cache_key not in self._cell_render_cache:
-            if not is_header_row:
-                style += Style.from_meta({"row": row_index, "column": column_index})
+            style += Style.from_meta({"row": row_index, "column": column_index})
             height = self.header_height if is_header_row else self.rows[row_key].height
             cell = self._get_row_renderables(row_index)[column_index]
             lines = self.app.console.render_lines(
@@ -1650,14 +1672,26 @@ def _set_hover_cursor(self, active: bool) -> None:
 
     def on_click(self, event: events.Click) -> None:
         self._set_hover_cursor(True)
-        if self.show_cursor and self.cursor_type != "none":
+        meta = self.get_style_at(event.x, event.y).meta
+        if not meta:
+            return
+
+        row_index = meta["row"]
+        column_index = meta["column"]
+        is_header_click = self.show_header and row_index == -1
+        if is_header_click:
+            # Header clicks work even if cursor is off, and doesn't move the cursor.
+            column = self.ordered_columns[column_index]
+            message = DataTable.HeaderSelected(
+                self, column.key, column_index, label=column.label
+            )
+            self.post_message_no_wait(message)
+        elif self.show_cursor and self.cursor_type != "none":
             # Only post selection events if there is a visible row/col/cell cursor.
-            meta = self.get_style_at(event.x, event.y).meta
-            if meta:
-                self.cursor_coordinate = Coordinate(meta["row"], meta["column"])
-                self._post_selected_message()
-                self._scroll_cursor_into_view(animate=True)
-                event.stop()
+            self.cursor_coordinate = Coordinate(row_index, column_index)
+            self._post_selected_message()
+            self._scroll_cursor_into_view(animate=True)
+            event.stop()
 
     def action_cursor_up(self) -> None:
         self._set_hover_cursor(False)