fix stack error

Author: willmcgugan

src/textual/app.py

@@ -1565,6 +1565,14 @@ def size(self) -> Size:
             width, height = self.console.size
         return Size(width, height)
 
+    @property
+    def viewport_size(self) -> Size:
+        """Get the viewport size (size of the screen)."""
+        try:
+            return self.screen.size
+        except (ScreenStackError, NoScreen):
+            return self.size
+
     def _get_inline_height(self) -> int:
         """Get the inline height (height when in inline mode).
 

src/textual/layouts/grid.py

@@ -60,7 +60,7 @@ def arrange(
                     table_size_columns -= 1
 
         table_size_rows = styles.grid_size_rows
-        viewport = parent.screen.size
+        viewport = parent.app.viewport_size
         keyline_style, _keyline_color = styles.keyline
         offset = (0, 0)
         gutter_spacing: Spacing | None

src/textual/layouts/horizontal.py

@@ -25,7 +25,7 @@ def arrange(
         parent.pre_layout(self)
         placements: list[WidgetPlacement] = []
         add_placement = placements.append
-        viewport = parent.screen.size
+        viewport = parent.app.viewport_size
 
         child_styles = [child.styles for child in children]
         box_margins: list[Spacing] = [

src/textual/layouts/stream.py

@@ -37,7 +37,7 @@ def arrange(
         parent.pre_layout(self)
         if not children:
             return []
-        viewport = parent.screen.size
+        viewport = parent.app.viewport_size
 
         _Region = Region
         _WidgetPlacement = WidgetPlacement

src/textual/layouts/vertical.py

@@ -23,7 +23,7 @@ def arrange(
         parent.pre_layout(self)
         placements: list[WidgetPlacement] = []
         add_placement = placements.append
-        viewport = parent.screen.size
+        viewport = parent.app.viewport_size
 
         child_styles = [child.styles for child in children]
         box_margins: list[Spacing] = [