Measure container children without intermediate placement

src/widget/position/span.rs

@@ -37,10 +37,7 @@ impl Widget for Span {
             // from the cursor, because a text has to wrap at the width
             // actually there.
             let room = axis.pair(Some(along(cursor, far)), None);
-            let len = match painter.known_len(child, axis, region, room) {
-                Some(len) => len,
-                None => painter.widget_at(child, region, room).len(axis),
-            };
+            let len = painter.measure_len(child, axis, region, room);
             cursor.px += len.px + self.gap;
             cursor.rel += len.rel;
             lens.push(len);