layout: Perform text decoration propagation per CSS 2.1 § 16.3.1 without

going to the DOM.

src/components/gfx/macros.rs

@@ -0,0 +1,22 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#[macro_escape];
+
+macro_rules! bitfield(
+    ($bitfieldname:ident, $getter:ident, $setter:ident, $value:expr) => (
+        impl $bitfieldname {
+            #[inline]
+            pub fn $getter(self) -> bool {
+                (*self & $value) != 0
+            }
+
+            #[inline]
+            pub fn $setter(&mut self, value: bool) {
+                *self = $bitfieldname((**self & !$value) | (if value { $value } else { 0 }))
+            }
+        }
+    )
+)
+