Merge pull request #6478 from Textualize/update-classes

Update classes

Author: willmcgugan

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
+
+### Added
+
+- Added `DOM.update_classes` https://github.com/Textualize/textual/pull/6478
+
 ## [8.2.3] - 2026-04-05 
 
 ### Changed

src/textual/dom.py

@@ -16,6 +16,7 @@
     Callable,
     ClassVar,
     Iterable,
+    Mapping,
     Sequence,
     Type,
     TypeVar,
@@ -1762,6 +1763,34 @@ def set_class(self, add: bool, *class_names: str, update: bool = True) -> Self:
             self.remove_class(*class_names, update=update)
         return self
 
+    def update_classes(
+        self, classes: Mapping[str, bool], update: bool = True, animate: bool = True
+    ) -> Self:
+        """Update classes in an atomic batch.
+
+        Args:
+            classes: A mapping of class name on to a boolean where `True` adds
+                to the current classes, and `False` removes.
+            update: Also update styles.
+            animate: Enable any CSS animation?
+
+        Returns:
+            Self
+        """
+
+        add_classes: set[str] = set()
+        remove_classes: set[str] = set()
+        adds = (remove_classes.add, add_classes.add)
+        for class_name, add in classes.items():
+            adds[add](class_name)
+
+        new_classes = (self._classes | add_classes) - remove_classes
+        if self._classes != new_classes:
+            self._classes = new_classes
+            if update:
+                self.update_node_styles(animate=animate)
+        return self
+
     def set_classes(self, classes: str | Iterable[str]) -> Self:
         """Replace all classes.
 

src/textual/layouts/grid.py

@@ -318,6 +318,8 @@ def apply_height_limits(widget: Widget, height: int) -> int:
         max_column = len(columns) - 1
         max_row = len(rows) - 1
 
+        stretch_height = self.stretch_height and len(children) > 1
+
         for widget, (column, row, column_span, row_span) in cell_size_map.items():
             x = columns[column][0]
             if row > max_row:
@@ -336,9 +338,8 @@ def apply_height_limits(widget: Widget, height: int) -> int:
                 greedy=greedy,
             )
 
-            if self.stretch_height and len(children) > 1:
-                if box_height <= cell_size.height:
-                    box_height = Fraction(cell_size.height)
+            if stretch_height and box_height <= cell_size.height:
+                box_height = Fraction(cell_size.height)
 
             region = (
                 Region(

src/textual/screen.py

@@ -1527,36 +1527,24 @@ async def _on_resize(self, event: events.Resize) -> None:
             else self.VERTICAL_BREAKPOINTS
         ) or []
 
-        width, height = event.size
-
         if horizontal_breakpoints or vertical_breakpoints:
+            width, height = event.size
+            breakpoints = {
+                breakpoint: False
+                for _, breakpoint in (horizontal_breakpoints + vertical_breakpoints)
+            }
 
-            remove_breakpoint_classes = {
-                breakpoint for _, breakpoint in horizontal_breakpoints
-            } | {breakpoint for _, breakpoint in vertical_breakpoints}
-            remove_breakpoint_classes = self._classes.intersection(
-                remove_breakpoint_classes
-            )
-
-            breakpoint_classes: set[str] = set()
+            for breakpoint in self._get_breakpoint_classes(
+                width, horizontal_breakpoints
+            ):
+                breakpoints[breakpoint] = True
 
-            if horizontal_breakpoints:
-                breakpoint_classes |= self._get_breakpoint_classes(
-                    width, horizontal_breakpoints
-                )
-            if vertical_breakpoints:
-                breakpoint_classes |= self._get_breakpoint_classes(
-                    height, vertical_breakpoints
-                )
+            for breakpoint in self._get_breakpoint_classes(
+                height, vertical_breakpoints
+            ):
+                breakpoints[breakpoint] = True
 
-            remove_breakpoint_classes -= breakpoint_classes
-            classes = self._classes.copy()
-            if remove_breakpoint_classes:
-                self._classes.difference_update(remove_breakpoint_classes)
-            if breakpoint_classes:
-                self._classes.update(breakpoint_classes)
-            if self._classes != classes:
-                self.update_node_styles(animate=False)
+            self.update_classes(breakpoints, animate=False)
 
     def _get_breakpoint_classes(
         self, dimension: int, breakpoints: list[tuple[int, str]]