new file mode 100644
--- /dev/null
+++ b/gfx/2d/Box.h
@@ -0,0 +1,125 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef MOZILLA_GFX_BOX_H_
+#define MOZILLA_GFX_BOX_H_
+
+#include <algorithm>
+#include <cstdint>
+
+#include "mozilla/Attributes.h"
+#include "Rect.h"
+#include "Types.h"
+
+namespace mozilla {
+
+template <typename> struct IsPixel;
+
+namespace gfx {
+
+/**
+ * A Box is similar to a Rect (see BaseRect.h), but represented as
+ * (x1, y1, x2, y2) instead of (x, y, width, height).
+ *
+ * Unless otherwise indicated, methods on this class correspond
+ * to methods on BaseRect.
+ *
+ * The API is currently very bare-bones; it may be extended as needed.
+ *
+ * Do not use this class directly. Subclass it, pass that subclass as the
+ * Sub parameter, and only use that subclass.
+ */
+template <class T, class Sub, class Rect>
+struct BaseBox {
+protected:
+  T x1, y1, x2, y2;
+
+public:
+  BaseBox() : x1(0), y1(0), x2(0), y2(0) {}
+  BaseBox(T aX1, T aY1, T aX2, T aY2) :
+    x1(aX1), y1(aY1), x2(aX2), y2(aY2) {}
+
+  MOZ_ALWAYS_INLINE T X() const { return x1; }
+  MOZ_ALWAYS_INLINE T Y() const { return y1; }
+  MOZ_ALWAYS_INLINE T Width() const { return x2 - x1; }
+  MOZ_ALWAYS_INLINE T Height() const { return y2 - y1; }
+  MOZ_ALWAYS_INLINE T XMost() const { return x2; }
+  MOZ_ALWAYS_INLINE T YMost() const { return y2; }
+
+  MOZ_ALWAYS_INLINE void SetBox(T aX1, T aY1, T aX2, T aY2)
+  {
+    x1 = aX1; y1 = aY1; x2 = aX2; y2 = aY2;
+  }
+  void SetLeftEdge(T aX1)
+  {
+    x1 = aX1;
+  }
+  void SetRightEdge(T aX2)
+  {
+    x2 = aX2;
+  }
+  void SetTopEdge(T aY1)
+  {
+    y1 = aY1;
+  }
+  void SetBottomEdge(T aY2)
+  {
+    y2 = aY2;
+  }
+
+  static Sub FromRect(const Rect& aRect)
+  {
+    return Sub(aRect.x, aRect.y, aRect.XMost(), aRect.YMost());
+  }
+
+  MOZ_MUST_USE Sub Intersect(const Sub& aBox) const
+  {
+    Sub result;
+    result.x1 = std::max<T>(x1, aBox.x1);
+    result.y1 = std::max<T>(y1, aBox.y1);
+    result.x2 = std::min<T>(x2, aBox.x2);
+    result.y2 = std::min<T>(y2, aBox.y2);
+    return result;
+  }
+
+  bool IsEqualEdges(const Sub& aBox) const
+  {
+    return x1 == aBox.x1 && y1 == aBox.y1 &&
+           x2 == aBox.x2 && y2 == aBox.y2;
+  }
+};
+
+template <class Units>
+struct IntBoxTyped :
+    public BaseBox<int32_t, IntBoxTyped<Units>, IntRectTyped<Units>>,
+    public Units {
+  static_assert(IsPixel<Units>::value,
+                "'units' must be a coordinate system tag");
+  typedef BaseBox<int32_t, IntBoxTyped<Units>, IntRectTyped<Units>> Super;
+  typedef IntParam<int32_t> ToInt;
+
+  IntBoxTyped() : Super() {}
+  IntBoxTyped(ToInt aX1, ToInt aY1, ToInt aX2, ToInt aY2) :
+      Super(aX1.value, aY1.value, aX2.value, aY2.value) {}
+};
+
+template <class Units>
+struct BoxTyped :
+    public BaseBox<Float, BoxTyped<Units>, RectTyped<Units>>,
+    public Units {
+  static_assert(IsPixel<Units>::value,
+                "'units' must be a coordinate system tag");
+  typedef BaseBox<Float, BoxTyped<Units>, RectTyped<Units>> Super;
+
+  BoxTyped() : Super() {}
+  BoxTyped(Float aX1, Float aY1, Float aX2, Float aY2) :
+      Super(aX1, aY1, aX2, aY2) {}
+};
+
+}
+}
+
+#endif /* MOZILLA_GFX_BOX_H_ */

--- a/gfx/2d/moz.build
+++ b/gfx/2d/moz.build
@@ -15,16 +15,17 @@ EXPORTS.mozilla.gfx += [
     'BasePoint.h',
     'BasePoint3D.h',
     'BasePoint4D.h',
     'BaseRect.h',
     'BaseSize.h',
     'BezierUtils.h',
     'Blur.h',
     'BorrowedContext.h',
+    'Box.h',
     'Coord.h',
     'CriticalSection.h',
     'DataSurfaceHelpers.h',
     'DrawEventRecorder.h',
     'DrawTargetRecording.h',
     'DrawTargetTiled.h',
     'DrawTargetWrapAndRecord.h',
     'Filters.h',