added center layout

sandbox/will/center2.py

@@ -0,0 +1,48 @@
+from textual.app import App
+from textual.layout import Vertical, Center
+from textual.widgets import Static
+
+
+class CenterApp(App):
+    CSS = """
+
+    #sidebar {
+        dock: left;
+        width: 32;
+        height: 100%;
+        border-right: vkey $primary;
+    }
+
+    #bottombar {
+        dock: bottom;
+        height: 12;
+        width: 100%;
+        border-top: hkey $primary;
+    }
+
+    #hello {
+        border: wide $primary;
+        width: 40;
+        height: 16;      
+        margin: 2 4;  
+    }
+
+    Static {        
+        background: $panel;
+        color: $text-panel;
+        content-align: center middle;
+    }
+    
+    """
+
+    def compose(self):
+        yield Static("Sidebar", id="sidebar")
+        yield Vertical(
+            Static("Bottom bar", id="bottombar"),
+            Center(
+                Static("Hello World!", id="hello"),
+            ),
+        )
+
+
+app = CenterApp()

src/textual/layout.py

@@ -21,3 +21,15 @@ class Horizontal(Widget):
         overflow: auto;
     }    
     """
+
+
+class Center(Widget):
+    """A container widget to align children in the center."""
+
+    CSS = """
+    Center {
+        layout: center;
+        overflow: auto;
+    }
+    
+    """