1 files changed, 151 insertions, 0 deletions
diff --git a/gfx/2d/Coord.h b/gfx/2d/Coord.h
new file mode 100644
index 000000000..0d2cdd6a6
--- /dev/null
+++ b/gfx/2d/Coord.h
@@ -0,0 +1,151 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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_COORD_H_
+#define MOZILLA_GFX_COORD_H_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/TypeTraits.h" // For IsSame
+#include "Types.h"
+#include "BaseCoord.h"
+
+#include <cmath>
+
+namespace mozilla {
+
+template <typename> struct IsPixel;
+
+namespace gfx {
+
+template <class units> struct IntCoordTyped;
+template <class units, class F = Float> struct CoordTyped;
+
+// CommonType<coord, primitive> is a metafunction that returns the type of the
+// result of an arithmetic operation on the underlying type of a strongly-typed
+// coordinate type 'coord', and a primitive type 'primitive'. C++ rules for
+// arithmetic conversions are designed to avoid losing information - for
+// example, the result of adding an int and a float is a float - and we want
+// the same behaviour when mixing our coordinate types with primitive types.
+// We get C++ to compute the desired result type using 'decltype'.
+
+template <class coord, class primitive>
+struct CommonType;
+
+template <class units, class primitive>
+struct CommonType<IntCoordTyped<units>, primitive> {
+    typedef decltype(int32_t() + primitive()) type;
+};
+
+template <class units, class F, class primitive>
+struct CommonType<CoordTyped<units, F>, primitive> {
+    typedef decltype(F() + primitive()) type;
+};
+
+// This is a base class that provides mixed-type operator overloads between
+// a strongly-typed Coord and a primitive value. It is needed to avoid
+// ambiguities at mixed-type call sites, because Coord classes are implicitly
+// convertible to their underlying value type. As we transition more of our code
+// to strongly-typed classes, we may be able to remove some or all of these
+// overloads.
+
+template <bool B, class coord, class primitive>
+struct CoordOperatorsHelper {
+  // Using SFINAE (Substitution Failure Is Not An Error) to suppress redundant
+  // operators
+};
+
+template <class coord, class primitive>
+struct CoordOperatorsHelper<true, coord, primitive> {
+  friend bool operator==(coord aA, primitive aB) {
+    return aA.value == aB;
+  }
+  friend bool operator==(primitive aA, coord aB) {
+    return aA == aB.value;
+  }
+  friend bool operator!=(coord aA, primitive aB) {
+    return aA.value != aB;
+  }
+  friend bool operator!=(primitive aA, coord aB) {
+    return aA != aB.value;
+  }
+
+  typedef typename CommonType<coord, primitive>::type result_type;
+
+  friend result_type operator+(coord aA, primitive aB) {
+    return aA.value + aB;
+  }
+  friend result_type operator+(primitive aA, coord aB) {
+    return aA + aB.value;
+  }
+  friend result_type operator-(coord aA, primitive aB) {
+    return aA.value - aB;
+  }
+  friend result_type operator-(primitive aA, coord aB) {
+    return aA - aB.value;
+  }
+  friend result_type operator*(coord aCoord, primitive aScale) {
+    return aCoord.value * aScale;
+  }
+  friend result_type operator*(primitive aScale, coord aCoord) {
+    return aScale * aCoord.value;
+  }
+  friend result_type operator/(coord aCoord, primitive aScale) {
+    return aCoord.value / aScale;
+  }
+  // 'scale / coord' is intentionally omitted because it doesn't make sense.
+};
+
+// Note: 'IntCoordTyped<units>' and 'CoordTyped<units>' do not derive from
+// 'units' to work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61959.
+
+template<class units>
+struct IntCoordTyped :
+  public BaseCoord< int32_t, IntCoordTyped<units> >,
+  public CoordOperatorsHelper< true, IntCoordTyped<units>, float >,
+  public CoordOperatorsHelper< true, IntCoordTyped<units>, double > {
+  static_assert(IsPixel<units>::value,
+                "'units' must be a coordinate system tag");
+
+  typedef BaseCoord< int32_t, IntCoordTyped<units> > Super;
+
+  constexpr IntCoordTyped() : Super() {}
+  constexpr MOZ_IMPLICIT IntCoordTyped(int32_t aValue) : Super(aValue) {}
+};
+
+template<class units, class F>
+struct CoordTyped :
+  public BaseCoord< F, CoordTyped<units, F> >,
+  public CoordOperatorsHelper< !IsSame<F, int32_t>::value, CoordTyped<units, F>, int32_t >,
+  public CoordOperatorsHelper< !IsSame<F, uint32_t>::value, CoordTyped<units, F>, uint32_t >,
+  public CoordOperatorsHelper< !IsSame<F, double>::value, CoordTyped<units, F>, double >,
+  public CoordOperatorsHelper< !IsSame<F, float>::value, CoordTyped<units, F>, float > {
+  static_assert(IsPixel<units>::value,
+                "'units' must be a coordinate system tag");
+
+  typedef BaseCoord< F, CoordTyped<units, F> > Super;
+
+  constexpr CoordTyped() : Super() {}
+  constexpr MOZ_IMPLICIT CoordTyped(F aValue) : Super(aValue) {}
+  explicit constexpr CoordTyped(const IntCoordTyped<units>& aCoord) : Super(F(aCoord.value)) {}
+
+  void Round() {
+    this->value = floor(this->value + 0.5);
+  }
+  void Truncate() {
+    this->value = int32_t(this->value);
+  }
+
+  IntCoordTyped<units> Rounded() const {
+    return IntCoordTyped<units>(int32_t(floor(this->value + 0.5)));
+  }
+  IntCoordTyped<units> Truncated() const {
+    return IntCoordTyped<units>(int32_t(this->value));
+  }
+};
+
+} // namespace gfx
+} // namespace mozilla
+
+#endif /* MOZILLA_GFX_COORD_H_ */