Try catalog theming approach with Button

core/src/closure.rs

@@ -0,0 +1,33 @@
+//! Box closures with ease.
+//!
+//! These are just a bunch of types that wrap boxed closures with
+//! blanket [`From`] implementations for easy conversions.
+//!
+//! Mainly, it allows functions to take `Into<T>` where `T` may end
+//! up being a boxed closure.
+
+/// A boxed closure that takes `A` by reference and produces `O`.
+#[allow(missing_debug_implementations)]
+pub struct Unary<'a, A, O>(pub Box<dyn Fn(&A) -> O + 'a>);
+
+impl<'a, A, O, T> From<T> for Unary<'a, A, O>
+where
+    T: Fn(&A) -> O + 'a,
+{
+    fn from(f: T) -> Self {
+        Self(Box::new(f))
+    }
+}
+
+/// A boxed closure that takes `A` by reference and `B` by value and produces `O`.
+#[allow(missing_debug_implementations)]
+pub struct Binary<'a, A, B, O>(pub Box<dyn Fn(&A, B) -> O + 'a>);
+
+impl<'a, A, B, O, T> From<T> for Binary<'a, A, B, O>
+where
+    T: Fn(&A, B) -> O + 'a,
+{
+    fn from(f: T) -> Self {
+        Self(Box::new(f))
+    }
+}

core/src/lib.rs

@@ -19,6 +19,7 @@
 pub mod alignment;
 pub mod border;
 pub mod clipboard;
+pub mod closure;
 pub mod event;
 pub mod font;
 pub mod gradient;