maybe fix relative len for sized span

src/layout/painter.rs

@@ -158,7 +158,6 @@ impl<'a> Painter<'a> {
 
     pub fn size_ctx(&mut self) -> SizeCtx {
         SizeCtx {
-            screen_size: self.screen_size,
             size: self.region().in_size(self.screen_size),
             text: self.text,
             textures: self.textures,