gfx/2d/BaseMargin.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef MOZILLA_GFX_BASEMARGIN_H_
   7 #define MOZILLA_GFX_BASEMARGIN_H_
   8
   9 #include "Types.h"
  10
  11 namespace mozilla {
  12 namespace gfx {
  13
  14 /**
  15  * Do not use this class directly. Subclass it, pass that subclass as the
  16  * Sub parameter, and only use that subclass.
  17  */
  18 template <class T, class Sub>
  19 struct BaseMargin {
  20   typedef mozilla::css::Side SideT;
  21
  22   // Do not change the layout of these members; the Side() methods below
  23   // depend on this order.
  24   T top, right, bottom, left;
  25
  26   // Constructors
  27   BaseMargin() : top(0), right(0), bottom(0), left(0) {}
  28   BaseMargin(T aTop, T aRight, T aBottom, T aLeft) :
  29       top(aTop), right(aRight), bottom(aBottom), left(aLeft) {}
  30
  31   void SizeTo(T aTop, T aRight, T aBottom, T aLeft)
  32   {
  33     top = aTop; right = aRight; bottom = aBottom; left = aLeft;
  34   }
  35
  36   T LeftRight() const { return left + right; }
  37   T TopBottom() const { return top + bottom; }
  38
  39   T& Side(SideT aSide) {
  40     // This is ugly!
  41     return *(&top + aSide);
  42   }
  43   T Side(SideT aSide) const {
  44     // This is ugly!
  45     return *(&top + aSide);
  46   }
  47
  48   // Overloaded operators. Note that '=' isn't defined so we'll get the
  49   // compiler generated default assignment operator
  50   bool operator==(const Sub& aMargin) const {
  51     return top == aMargin.top && right == aMargin.right &&
  52            bottom == aMargin.bottom && left == aMargin.left;
  53   }
  54   bool operator!=(const Sub& aMargin) const {
  55     return !(*this == aMargin);
  56   }
  57   Sub operator+(const Sub& aMargin) const {
  58     return Sub(top + aMargin.top, right + aMargin.right,
  59                bottom + aMargin.bottom, left + aMargin.left);
  60   }
  61   Sub operator-(const Sub& aMargin) const {
  62     return Sub(top - aMargin.top, right - aMargin.right,
  63                bottom - aMargin.bottom, left - aMargin.left);
  64   }
  65   Sub& operator+=(const Sub& aMargin) {
  66     top += aMargin.top;
  67     right += aMargin.right;
  68     bottom += aMargin.bottom;
  69     left += aMargin.left;
  70     return *static_cast<Sub*>(this);
  71   }
  72 };
  73
  74 }
  75 }
  76
  77 #endif /* MOZILLA_GFX_BASEMARGIN_H_ */