Iced master merge (again)

src/multi_window/application.rs

@@ -148,6 +148,7 @@ pub trait Application: Sized {
     /// while a scale factor of `0.5` will shrink them to half their size.
     ///
     /// By default, it returns `1.0`.
+    #[allow(unused_variables)]
     fn scale_factor(&self, window: window::Id) -> f64 {
         1.0
     }