null visual

src/textual/visual.py

@@ -258,6 +258,31 @@ class Visual(ABC):
         return strips
 
 
+@rich.repr.auto
+class NullVisual(Visual):
+    """A visual with no size, which therefore renders nothing.
+
+    This is a placeholder for when a Widget has been reduced to zero area.
+    """
+
+    def __rich_repr__(self) -> rich.repr.Result:
+        yield from ()
+
+    def render_strips(
+        self, width: int, height: int | None, style: Style, options: RenderOptions
+    ) -> list[Strip]:
+        return []
+
+    def get_optimal_width(self, rules: RulesMap, container_width: int) -> int:
+        return 0
+
+    def get_minimal_width(self, rules: RulesMap) -> int:
+        return 0
+
+    def get_height(self, rules: RulesMap, width: int) -> int:
+        return 0
+
+
 @rich.repr.auto
 class RichVisual(Visual):
     """A Visual to wrap a Rich renderable."""

src/textual/widget.py

@@ -90,7 +90,7 @@ from textual.rlock import RLock
 from textual.selection import Selection
 from textual.strip import Strip
 from textual.style import Style as VisualStyle
-from textual.visual import Visual, VisualType, visualize
+from textual.visual import NullVisual, Visual, VisualType, visualize
 
 if TYPE_CHECKING:
     from textual.app import App, ComposeResult
@@ -4322,7 +4322,10 @@ class Widget(DOMNode):
         if cached_visual is not None:
             assert isinstance(cached_visual, Visual)
             return cached_visual
-        visual = visualize(self, self.render(), markup=self._render_markup)
+        if self.size.width:
+            visual = visualize(self, self.render(), markup=self._render_markup)
+        else:
+            visual = NullVisual()
         self._layout_cache[cache_key] = visual
         return visual
 

src/textual/widgets/_progress_bar.py

@@ -121,7 +121,7 @@ class Bar(Widget, can_focus=False):
         total_imaginary_width = width + highlighted_bar_width
         start: float
         end: float
-        if self.app.animation_level == "none" or width == 0:
+        if self.app.animation_level == "none":
             start = 0
             end = width
         else: