fix for scroll width issue

src/textual/_arrange.py

@@ -48,7 +48,7 @@ def arrange(
     _WidgetPlacement = WidgetPlacement
     top_z = TOP_Z
     scroll_spacing = Spacing()
-
+    null_spacing = Spacing()
     get_dock = attrgetter("styles.dock")
 
     for widgets in dock_layers.values():
@@ -94,7 +94,9 @@ def arrange(
                 (widget_width, widget_height), size
             )
             dock_region = dock_region.shrink(margin).translate(align_offset)
-            add_placement(_WidgetPlacement(dock_region, dock_widget, top_z, True))
+            add_placement(
+                _WidgetPlacement(dock_region, null_spacing, dock_widget, top_z, True)
+            )
 
         dock_spacing = Spacing(top, right, bottom, left)
         region = size.region.shrink(dock_spacing)
@@ -109,9 +111,9 @@ def arrange(
             if placement_offset:
                 layout_placements = [
                     _WidgetPlacement(
-                        _region + placement_offset, layout_widget, order, fixed
+                        _region + placement_offset, margin, layout_widget, order, fixed
                     )
-                    for _region, layout_widget, order, fixed in layout_placements
+                    for _region, margin, layout_widget, order, fixed in layout_placements
                 ]
 
         placements.extend(layout_placements)

src/textual/_compositor.py

@@ -400,17 +400,16 @@ class Compositor:
                     get_layer_index = layers_to_index.get
 
                     # Add all the widgets
-                    for sub_region, sub_widget, z, fixed in placements:
+                    for sub_region, margin, sub_widget, z, fixed in placements:
                         # Combine regions with children to calculate the "virtual size"
                         if fixed:
                             widget_region = sub_region + placement_offset
                         else:
-                            total_region = total_region.union(sub_region.grow(spacing))
+                            total_region = total_region.union(
+                                sub_region.grow(spacing + margin)
+                            )
                             widget_region = sub_region + placement_scroll_offset
 
-                        if sub_widget is None:
-                            continue
-
                         widget_order = order + (get_layer_index(sub_widget.layer, 0), z)
 
                         add_widget(

src/textual/_layout.py

@@ -25,7 +25,8 @@ class WidgetPlacement(NamedTuple):
     """The position, size, and relative order of a widget within its parent."""
 
     region: Region
-    widget: Widget | None = None  # A widget of None means empty space
+    margin: Spacing
+    widget: Widget
     order: int = 0
     fixed: bool = False
 

src/textual/layouts/center.py

@@ -17,7 +17,6 @@ class CenterLayout(Layout):
     ) -> ArrangeResult:
 
         placements: list[WidgetPlacement] = []
-        total_regions: list[Region] = []
 
         parent_size = parent.outer_size
         container_width, container_height = size
@@ -32,8 +31,6 @@ class CenterLayout(Layout):
             x = margin.left + max(0, (container_width - margin_width) // 2)
             y = margin.top + max(0, (container_height - margin_height) // 2)
             region = Region(x, y, int(width), int(height))
-            total_regions.append(region.grow(margin))
-            placements.append(WidgetPlacement(region, widget, 0))
+            placements.append(WidgetPlacement(region, margin, widget, 0))
 
-        placements.append(WidgetPlacement(Region.from_union(total_regions), None, 0))
         return placements, set(children)

src/textual/layouts/horizontal.py

@@ -61,11 +61,8 @@ class HorizontalLayout(Layout):
             max_height = max(
                 max_height, content_height + offset_y + box_model.margin.bottom
             )
-            add_placement(WidgetPlacement(region, widget, 0))
+            add_placement(WidgetPlacement(region, box_model.margin, widget, 0))
             x = next_x + margin
             max_width = x
 
-        total_region = Region(0, 0, int(max_width), int(max_height))
-        add_placement(WidgetPlacement(total_region, None, 0))
-
         return placements, set(displayed_children)

src/textual/layouts/table.py

@@ -6,7 +6,7 @@ from typing import TYPE_CHECKING, Iterable
 from .._layout import ArrangeResult, Layout, WidgetPlacement
 from .._resolve import resolve
 from ..css.scalar import Scalar
-from ..geometry import Region, Size
+from ..geometry import Region, Size, Spacing
 
 if TYPE_CHECKING:
     from ..widget import Widget
@@ -132,6 +132,7 @@ class TableLayout(Layout):
         add_widget = widgets.append
         max_column = len(columns) - 1
         max_row = len(rows) - 1
+        margin = Spacing()
         for widget, (column, row, column_span, row_span) in cell_size_map.items():
             x = columns[column][0]
             if row > max_row:
@@ -150,7 +151,7 @@ class TableLayout(Layout):
                 .shrink(margin)
                 .clip_size(cell_size)
             )
-            add_placement(WidgetPlacement(region, widget))
+            add_placement(WidgetPlacement(region, margin, widget))
             add_widget(widget)
 
         return (placements, set(widgets))

src/textual/layouts/vertical.py

@@ -54,10 +54,7 @@ class VerticalLayout(Layout):
             )
             next_y = y + content_height
             region = Region(offset_x, int(y), int(content_width), int(next_y) - int(y))
-            add_placement(WidgetPlacement(region, widget, 0))
+            add_placement(WidgetPlacement(region, box_model.margin, widget, 0))
             y = next_y + margin
 
-        total_region = Region(0, 0, size.width, int(y))
-        add_placement(WidgetPlacement(total_region, None, 0))
-
         return placements, set(children)