layout/generic/AspectRatio.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_AspectRatio_h
   8 #define mozilla_AspectRatio_h
   9
  10 /* The aspect ratio of a box, in a "width / height" format. */
  11
  12 #include "mozilla/Attributes.h"
  13 #include "mozilla/Maybe.h"
  14 #include "nsCoord.h"
  15
  16 namespace mozilla {
  17
  18 struct AspectRatio {
  19   AspectRatio() : mRatio(0.0f) {}
  20   explicit AspectRatio(float aRatio) : mRatio(std::max(aRatio, 0.0f)) {}
  21
  22   static AspectRatio FromSize(float aWidth, float aHeight) {
  23     if (aWidth == 0.0f || aHeight == 0.0f) {
  24       return AspectRatio();
  25     }
  26     return AspectRatio(aWidth / aHeight);
  27   }
  28
  29   explicit operator bool() const { return mRatio != 0.0f; }
  30
  31   nscoord ApplyTo(nscoord aCoord) const {
  32     MOZ_DIAGNOSTIC_ASSERT(*this);
  33     return NSCoordSaturatingNonnegativeMultiply(aCoord, mRatio);
  34   }
  35
  36   // Inverts the ratio, in order to get the height / width ratio.
  37   MOZ_MUST_USE AspectRatio Inverted() const {
  38     return *this ? AspectRatio(1.0f / mRatio) : *this;
  39   }
  40
  41   bool operator==(const AspectRatio& aOther) const {
  42     return mRatio == aOther.mRatio;
  43   }
  44
  45   bool operator!=(const AspectRatio& aOther) const {
  46     return !(*this == aOther);
  47   }
  48
  49   bool operator<(const AspectRatio& aOther) const {
  50     return mRatio < aOther.mRatio;
  51   }
  52
  53  private:
  54   // 0.0f represents no aspect ratio.
  55   float mRatio;
  56 };
  57
  58 }  // namespace mozilla
  59
  60 #endif  // mozilla_AspectRatio_h