Add basic controls to layout example

style/src/container.rs

@@ -1,5 +1,5 @@
 //! Change the appearance of a container.
-use iced_core::{Background, BorderRadius, Color};
+use crate::core::{Background, BorderRadius, Color, Pixels};
 
 /// The appearance of a container.
 #[derive(Debug, Clone, Copy)]
@@ -16,6 +16,30 @@ pub struct Appearance {
     pub border_color: Color,
 }
 
+impl Appearance {
+    /// Derives a new [`Appearance`] with a border of the given [`Color`] and
+    /// `width`.
+    pub fn with_border(
+        self,
+        color: impl Into<Color>,
+        width: impl Into<Pixels>,
+    ) -> Self {
+        Self {
+            border_color: color.into(),
+            border_width: width.into().0,
+            ..self
+        }
+    }
+
+    /// Derives a new [`Appearance`] with the given [`Background`].
+    pub fn with_background(self, background: impl Into<Background>) -> Self {
+        Self {
+            background: Some(background.into()),
+            ..self
+        }
+    }
+}
+
 impl std::default::Default for Appearance {
     fn default() -> Self {
         Self {