fix bug with layout updates

sandbox/will/center2.py

@@ -27,6 +27,10 @@ class CenterApp(App):
         margin: 2 4;  
     }
 
+    #sidebar.hidden {
+       width: 0;
+    }
+
     Static {        
         background: $panel;
         color: $text-panel;
@@ -35,6 +39,9 @@ class CenterApp(App):
     
     """
 
+    def on_mount(self) -> None:
+        self.bind("t", "toggle_class('#sidebar', 'hidden')")
+
     def compose(self):
         yield Static("Sidebar", id="sidebar")
         yield Vertical(
@@ -45,4 +52,4 @@ class CenterApp(App):
         )
 
 
-app = CenterApp()
+app = CenterApp(log_verbosity=3)

src/textual/_compositor.py

@@ -632,6 +632,7 @@ class Compositor:
             update_regions: set[Region] = set()
         else:
             update_regions = self._dirty_regions.copy()
+
             if screen_region in update_regions:
                 # If one of the updates is the entire screen, then we only need one update
                 full = True

src/textual/box_model.py

@@ -81,7 +81,7 @@ def get_box_model(
         )
         content_width = min(content_width, max_width)
 
-    content_width = max(Fraction(1), content_width)
+    content_width = max(Fraction(0), content_width)
 
     if styles.height is None:
         # No height specified, fill the available space

src/textual/screen.py

@@ -170,7 +170,6 @@ class Screen(Widget):
         self.update_timer.pause()
         try:
             hidden, shown, resized = self._compositor.reflow(self, size)
-
             Hide = events.Hide
             Show = events.Show
             for widget in hidden:

src/textual/widget.py

@@ -1040,7 +1040,9 @@ class Widget(DOMNode):
 
         if layout:
             self._layout_required = True
-            self._clear_arrangement_cache()
+            if isinstance(self._parent, Widget):
+                self._parent._clear_arrangement_cache()
+
         if repaint:
             self._set_dirty(*regions)
             self._content_width_cache = (None, 0)