remove arrangement spacing (#2157)

* remove arrangement spacing

* snapshot test

* comment

* changelog

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Issue with parsing action strings whose arguments contained quoted closing parenthesis https://github.com/Textualize/textual/pull/2112
 - Issues with parsing action strings with tuple arguments https://github.com/Textualize/textual/pull/2112
 - Fix for tabs not invalidating https://github.com/Textualize/textual/issues/2125
+- Fixed scrollbar layers issue https://github.com/Textualize/textual/issues/1358
 - Fix for interaction between pseudo-classes and widget-level render caches https://github.com/Textualize/textual/pull/2155
 
 ### Changed

src/textual/_arrange.py

@@ -128,4 +128,4 @@ def arrange(
 
         placements.extend(layout_placements)
 
-    return DockArrangeResult(placements, arrange_widgets, scroll_spacing)
+    return DockArrangeResult(placements, arrange_widgets)

src/textual/_compositor.py

@@ -484,7 +484,6 @@ class Compositor:
                     # Arrange the layout
                     arrange_result = widget._arrange(child_region.size)
                     arranged_widgets = arrange_result.widgets
-                    spacing = arrange_result.spacing
                     widgets.update(arranged_widgets)
 
                     if visible_only:
@@ -513,9 +512,7 @@ class Compositor:
                         if fixed:
                             widget_region = sub_region + placement_offset
                         else:
-                            total_region = total_region.union(
-                                sub_region.grow(spacing + margin)
-                            )
+                            total_region = total_region.union(sub_region.grow(margin))
                             widget_region = sub_region + placement_scroll_offset
 
                         widget_order = order + (

src/textual/_layout.py

@@ -21,8 +21,6 @@ class DockArrangeResult:
     """A `WidgetPlacement` for every widget to describe it's location on screen."""
     widgets: set[Widget]
     """A set of widgets in the arrangement."""
-    spacing: Spacing
-    """Shared spacing around the widgets."""
 
     _spatial_map: SpatialMap[WidgetPlacement] | None = None
     """A Spatial map to query widget placements."""
@@ -113,7 +111,7 @@ class Layout(ABC):
         else:
             # Use a size of 0, 0 to ignore relative sizes, since those are flexible anyway
             arrangement = widget._arrange(Size(0, 0))
-            return arrangement.total_region.right + arrangement.spacing.right
+            return arrangement.total_region.right
         return width
 
     def get_content_height(
@@ -135,5 +133,5 @@ class Layout(ABC):
         else:
             # Use a height of zero to ignore relative heights
             arrangement = widget._arrange(Size(width, 0))
-            height = arrangement.total_region.bottom + arrangement.spacing.bottom
+            height = arrangement.total_region.bottom
         return height

tests/snapshot_tests/snapshot_apps/layer_fix.py

@@ -0,0 +1,48 @@
+from textual.app import App, ComposeResult
+from textual.containers import Vertical
+from textual.widgets import Header, Footer, Label
+from textual.binding import Binding
+
+
+class Dialog(Vertical):
+    def compose(self) -> ComposeResult:
+        """Compose the child widgets."""
+        yield Label("This should not cause a scrollbar to appear")
+
+
+class DialogIssueApp(App[None]):
+    CSS = """
+    Screen {
+        layers: base dialog;
+    }
+
+    .hidden {
+        display: none;
+    }
+
+    Dialog {
+        align: center middle;
+        border: round red;
+        width: 50%;
+        height: 50%;
+        layer: dialog;
+        offset: 50% 50%;
+    }
+    """
+
+    BINDINGS = [
+        Binding("d", "dialog", "Toggle the dialog"),
+    ]
+
+    def compose(self) -> ComposeResult:
+        yield Header()
+        yield Vertical()
+        yield Dialog(classes="hidden")
+        yield Footer()
+
+    def action_dialog(self) -> None:
+        self.query_one(Dialog).toggle_class("hidden")
+
+
+if __name__ == "__main__":
+    DialogIssueApp().run()

tests/snapshot_tests/test_snapshots.py

@@ -340,3 +340,8 @@ def test_scrollbar_thumb_height(snap_compare):
     assert snap_compare(
         SNAPSHOT_APPS_DIR / "scrollbar_thumb_height.py",
     )
+
+
+def test_layer_fix(snap_compare):
+    # Check https://github.com/Textualize/textual/issues/1358
+    assert snap_compare(SNAPSHOT_APPS_DIR / "layer_fix.py", press=["d"])

tests/test_arrange.py

@@ -12,7 +12,6 @@ def test_arrange_empty():
     result = arrange(container, [], Size(80, 24), Size(80, 24))
     assert result.placements == []
     assert result.widgets == set()
-    assert result.spacing == Spacing(0, 0, 0, 0)
 
 
 def test_arrange_dock_top():
@@ -31,7 +30,6 @@ def test_arrange_dock_top():
         WidgetPlacement(Region(0, 1, 80, 23), Spacing(), child, order=0, fixed=False),
     ]
     assert result.widgets == {child, header}
-    assert result.spacing == Spacing(1, 0, 0, 0)
 
 
 def test_arrange_dock_left():
@@ -49,7 +47,6 @@ def test_arrange_dock_left():
         WidgetPlacement(Region(10, 0, 70, 24), Spacing(), child, order=0, fixed=False),
     ]
     assert result.widgets == {child, header}
-    assert result.spacing == Spacing(0, 0, 0, 10)
 
 
 def test_arrange_dock_right():
@@ -67,7 +64,6 @@ def test_arrange_dock_right():
         WidgetPlacement(Region(0, 0, 70, 24), Spacing(), child, order=0, fixed=False),
     ]
     assert result.widgets == {child, header}
-    assert result.spacing == Spacing(0, 10, 0, 0)
 
 
 def test_arrange_dock_bottom():
@@ -85,7 +81,6 @@ def test_arrange_dock_bottom():
         WidgetPlacement(Region(0, 0, 80, 23), Spacing(), child, order=0, fixed=False),
     ]
     assert result.widgets == {child, header}
-    assert result.spacing == Spacing(0, 0, 1, 0)
 
 
 def test_arrange_dock_badly():