diff --git a/core/src/lib.rs b/core/src/lib.rs
index 18c672b..f3cf313 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -14,3 +14,8 @@ pub type Perhaps<T> = Result<Option<T>, Box<dyn Error>>;
         }
     };
 }
+
+pub trait Has<T>: Send + Sync {
+    fn get     (&self) -> &T;
+    fn get_mut (&mut self) -> &mut T;
+}
diff --git a/output/src/space/measure.rs b/output/src/space/measure.rs
index 2a1e415..9ea4765 100644
--- a/output/src/space/measure.rs
+++ b/output/src/space/measure.rs
@@ -3,13 +3,17 @@ use std::sync::{Arc, atomic::{AtomicUsize, Ordering::Relaxed}};
 
 pub trait HasSize<E: Output> {
     fn size (&self) -> &Measure<E>;
+    fn width (&self) -> usize {
+        self.size().w()
+    }
+    fn height (&self) -> usize {
+        self.size().w()
+    }
 }
 
-#[macro_export] macro_rules! has_size {
-    (<$E:ty>|$self:ident:$Struct:ident$(<$($L:lifetime),*$($T:ident$(:$U:path)?),*>)?|$cb:expr) => {
-        impl $(<$($L),*$($T $(: $U)?),*>)? HasSize<$E> for $Struct $(<$($L),*$($T),*>)? {
-            fn size (&$self) -> &Measure<$E> { $cb }
-        }
+impl<E: Output, T: Has<Measure<E>>> HasSize<E> for T {
+    fn size (&self) -> &Measure<E> {
+        self.get()
     }
 }