remove arrangement spacing (#2157)

* remove arrangement spacing

* snapshot test

* comment

* changelog

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"])