Keep leftover shares inside scroll viewports

src/widget/position/scroll.rs

@@ -17,9 +17,9 @@ impl Widget for Scroll {
         let answer_len = painter
             .widget_at(&self.inner, whole, [Place::Fill(Part::All); 2])
             .len(self.axis);
-        let content = answer_len.apply_leftover();
+        let fixed = Len::from_parts(answer_len.rel, answer_len.px).to_px(container_len);
         self.container_len = container_len;
-        self.content_len = content.to_px(container_len);
+        self.content_len = fixed.max(container_len);
 
         if self.snap_end {
             self.amt = self.content_len - self.container_len;
@@ -32,9 +32,9 @@ impl Widget for Scroll {
         // the drawing holds for that length alone. One scrolled part way sits
         // where it is until the box shrinks past what is left of it. Kept to
         // the end, it moves with every length.
-        let fixed_len = content.rel == Rel::ZERO;
+        let fixed_len = answer_len.rel == Rel::ZERO && answer_len.leftover == Weight::ZERO;
         if fixed_len && self.content_len <= self.container_len && align == AxisAlign::NEG {
-            painter.holds(self.axis, self.content_len..=Px::MAX);
+            painter.holds(self.axis, fixed..=Px::MAX);
         } else if fixed_len && !self.snap_end {
             let left = self.content_len - self.amt;
             painter.holds(self.axis, Px::MIN..=left);