1 files changed, 98 insertions, 0 deletions
diff --git a/gfx/2d/ScaleFactor.h b/gfx/2d/ScaleFactor.h
new file mode 100644
index 0000000000..4d7346d200
--- /dev/null
+++ b/gfx/2d/ScaleFactor.h
@@ -0,0 +1,98 @@
+/* -*- 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_SCALEFACTOR_H_
+#define MOZILLA_GFX_SCALEFACTOR_H_
+
+#include <ostream>
+
+#include "mozilla/Attributes.h"
+
+#include "gfxPoint.h"
+
+namespace mozilla {
+namespace gfx {
+
+/*
+ * This class represents a scaling factor between two different pixel unit
+ * systems. This is effectively a type-safe float, intended to be used in
+ * combination with the known-type instances of gfx::Point, gfx::Rect, etc.
+ *
+ * This class is meant to be used in cases where a single scale applies to
+ * both the x and y axes. For cases where two diferent scales apply, use
+ * ScaleFactors2D.
+ */
+template <class Src, class Dst>
+struct ScaleFactor {
+  float scale;
+
+  constexpr ScaleFactor() : scale(1.0) {}
+  constexpr ScaleFactor(const ScaleFactor<Src, Dst>& aCopy)
+      : scale(aCopy.scale) {}
+  explicit constexpr ScaleFactor(float aScale) : scale(aScale) {}
+
+  ScaleFactor<Dst, Src> Inverse() { return ScaleFactor<Dst, Src>(1 / scale); }
+
+  ScaleFactor<Src, Dst>& operator=(const ScaleFactor<Src, Dst>&) = default;
+
+  bool operator==(const ScaleFactor<Src, Dst>& aOther) const {
+    return scale == aOther.scale;
+  }
+
+  bool operator!=(const ScaleFactor<Src, Dst>& aOther) const {
+    return !(*this == aOther);
+  }
+
+  bool operator<(const ScaleFactor<Src, Dst>& aOther) const {
+    return scale < aOther.scale;
+  }
+
+  bool operator<=(const ScaleFactor<Src, Dst>& aOther) const {
+    return scale <= aOther.scale;
+  }
+
+  bool operator>(const ScaleFactor<Src, Dst>& aOther) const {
+    return scale > aOther.scale;
+  }
+
+  bool operator>=(const ScaleFactor<Src, Dst>& aOther) const {
+    return scale >= aOther.scale;
+  }
+
+  template <class Other>
+  ScaleFactor<Other, Dst> operator/(
+      const ScaleFactor<Src, Other>& aOther) const {
+    return ScaleFactor<Other, Dst>(scale / aOther.scale);
+  }
+
+  template <class Other>
+  ScaleFactor<Src, Other> operator/(
+      const ScaleFactor<Other, Dst>& aOther) const {
+    return ScaleFactor<Src, Other>(scale / aOther.scale);
+  }
+
+  template <class Other>
+  ScaleFactor<Src, Other> operator*(
+      const ScaleFactor<Dst, Other>& aOther) const {
+    return ScaleFactor<Src, Other>(scale * aOther.scale);
+  }
+
+  template <class Other>
+  ScaleFactor<Other, Dst> operator*(
+      const ScaleFactor<Other, Src>& aOther) const {
+    return ScaleFactor<Other, Dst>(scale * aOther.scale);
+  }
+
+  friend std::ostream& operator<<(std::ostream& aStream,
+                                  const ScaleFactor<Src, Dst>& aSF) {
+    return aStream << aSF.scale;
+  }
+};
+
+}  // namespace gfx
+}  // namespace mozilla
+
+#endif /* MOZILLA_GFX_SCALEFACTOR_H_ */