Add retained paints and shared text selection

src/widget/position/lazy_span.rs

@@ -741,6 +741,10 @@ impl Scrollable for LazySpan {
 }
 
 impl Widget for LazySpan {
+    fn child_order(&self) -> ChildOrder {
+        ChildOrder::Axis(self.dir.axis)
+    }
+
     /// A lazy span animates exactly one thing, its fling -- and it drives
     /// its own rather than being handed deltas by a `ScrollArea` around
     /// it, since which rows exist at all is a function of where it is
@@ -842,7 +846,7 @@ mod tests {
     }
 
     fn fixed_row(rsc: &mut TestRsc, height: f32) -> (WeakWidget<Sized>, StrongWidget) {
-        let rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
+        let rect = rsc.ui.widgets.add_strong(Rect::new(PaintId::WHITE));
         let sized = rsc.ui.widgets.add_strong(Sized {
             inner: rect.any(),
             x: None,
@@ -1054,9 +1058,9 @@ mod tests {
         rsc: &mut TestRsc,
         height: f32,
     ) -> (WidgetId, WeakWidget<Sized>, StrongWidget) {
-        let bg = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
+        let bg = rsc.ui.widgets.add_strong(Rect::new(PaintId::WHITE));
         let bg_id = bg.id();
-        let fg_rect = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
+        let fg_rect = rsc.ui.widgets.add_strong(Rect::new(PaintId::WHITE));
         let fg = rsc.ui.widgets.add_strong(Sized {
             inner: fg_rect.any(),
             x: None,