Make alignment a widget property

src/widget/trait_fns.rs

@@ -12,14 +12,23 @@ widget_trait! {
         }
     }
 
-    fn align(self, align: impl Into<Align>) -> impl WidgetFn<Rsc, Aligned> {
-        move |state| Aligned {
-            inner: self.add_strong(state),
-            align: align.into(),
+    fn align(self, align: impl Into<Align>) -> impl WidgetIdFn<Rsc, WL::Widget> {
+        // An axis left out keeps whatever it had, which is centered unless
+        // something else set it.
+        let align = align.into();
+        move |state| {
+            let id = self.add(state);
+            let widgets = &mut state.ui_mut().widgets;
+            for (axis, align) in [(Axis::X, align.x), (Axis::Y, align.y)] {
+                if let Some(align) = align {
+                    widgets.set_alignment(id, axis, align);
+                }
+            }
+            id
         }
     }
 
-    fn center(self) -> impl WidgetFn<Rsc, Aligned> {
+    fn center(self) -> impl WidgetIdFn<Rsc, WL::Widget> {
         self.align(Align::CENTER)
     }