gfx/src/nsRegion.h
author Ryan VanderMeulen <ryanvm@gmail.com>
Fri, 01 Sep 2017 15:37:08 -0400
changeset 430269 1d02aa80f2f8c283428f0a8a6310e7d1fec3936c
parent 426548 df7cada96cecd58afc3d43d7d9b7c885c316803d
child 436117 05a55026189070733d22b0ff75c41d0ee313c550
permissions -rw-r--r--
Backed out 9 changesets (bug 1383880) for decision task bustage. Backed out changeset 53f5d47a7cb0 (bug 1383880) Backed out changeset a0abda41172a (bug 1383880) Backed out changeset 729a7e2091e8 (bug 1383880) Backed out changeset a33f5a14a471 (bug 1383880) Backed out changeset 5b10d321cfee (bug 1383880) Backed out changeset 8056488d8aed (bug 1383880) Backed out changeset e62c90e3c1e8 (bug 1383880) Backed out changeset 91f116ce6c2a (bug 1383880) Backed out changeset 045498bc36c4 (bug 1383880)

/* -*- 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 nsRegion_h__
#define nsRegion_h__

#include <stddef.h>                     // for size_t
#include <stdint.h>                     // for uint32_t, uint64_t
#include <sys/types.h>                  // for int32_t
#include <ostream>                      // for std::ostream
#include "nsCoord.h"                    // for nscoord
#include "nsError.h"                    // for nsresult
#include "nsPoint.h"                    // for nsIntPoint, nsPoint
#include "nsRect.h"                     // for mozilla::gfx::IntRect, nsRect
#include "nsMargin.h"                   // for nsIntMargin
#include "nsRegionFwd.h"                // for nsIntRegion
#include "nsStringGlue.h"               // for nsCString
#include "xpcom-config.h"               // for CPP_THROW_NEW
#include "mozilla/ArrayView.h"          // for ArrayView
#include "mozilla/Move.h"               // for mozilla::Move
#include "mozilla/gfx/MatrixFwd.h"      // for mozilla::gfx::Matrix4x4

#include "pixman.h"

/* For information on the internal representation look at pixman-region.c
 *
 * This replaces an older homebrew implementation of nsRegion. The
 * representation used here may use more rectangles than nsRegion however, the
 * representation is canonical.  This means that there's no need for an
 * Optimize() method because for a paticular region there is only one
 * representation. This means that nsIntRegion will have more predictable
 * performance characteristics than the old nsRegion and should not become
 * degenerate.
 *
 * The pixman region code originates from X11 which has spread to a variety of
 * projects including Qt, Gtk, Wine. It should perform reasonably well.
 */

enum class VisitSide {
	TOP,
	BOTTOM,
	LEFT,
	RIGHT
};

class nsRegion
{
public:
  typedef nsRect RectType;
  typedef nsPoint PointType;
  typedef nsMargin MarginType;

  nsRegion () { pixman_region32_init(&mImpl); }
  MOZ_IMPLICIT nsRegion (const nsRect& aRect) { pixman_region32_init_rect(&mImpl,
                                                                          aRect.x,
                                                                          aRect.y,
                                                                          aRect.Width(),
                                                                          aRect.Height()); }
  explicit nsRegion (mozilla::gfx::ArrayView<pixman_box32_t> aRects)
  {
    pixman_region32_init_rects(&mImpl, aRects.Data(), aRects.Length());
  }
  nsRegion (const nsRegion& aRegion) { pixman_region32_init(&mImpl); pixman_region32_copy(&mImpl,aRegion.Impl()); }
  nsRegion (nsRegion&& aRegion) { mImpl = aRegion.mImpl; pixman_region32_init(&aRegion.mImpl); }
  nsRegion& operator = (nsRegion&& aRegion) {
      pixman_region32_fini(&mImpl);
      mImpl = aRegion.mImpl;
      pixman_region32_init(&aRegion.mImpl);
      return *this;
  }
 ~nsRegion () { pixman_region32_fini(&mImpl); }
  nsRegion& operator = (const nsRect& aRect) { Copy (aRect); return *this; }
  nsRegion& operator = (const nsRegion& aRegion) { Copy (aRegion); return *this; }
  bool operator==(const nsRegion& aRgn) const
  {
    return IsEqual(aRgn);
  }
  bool operator!=(const nsRegion& aRgn) const
  {
    return !(*this == aRgn);
  }

  friend std::ostream& operator<<(std::ostream& stream, const nsRegion& m);

  void Swap(nsRegion* aOther)
  {
    pixman_region32_t tmp = mImpl;
    mImpl = aOther->mImpl;
    aOther->mImpl = tmp;
  }

  static
  nsresult InitStatic()
  {
    return NS_OK;
  }

  static
  void ShutdownStatic() {}

  void AndWith(const nsRegion& aOther)
  {
    And(*this, aOther);
  }
  void AndWith(const nsRect& aOther)
  {
    And(*this, aOther);
  }
  nsRegion& And(const nsRegion& aRgn1,   const nsRegion& aRgn2)
  {
    pixman_region32_intersect(&mImpl, aRgn1.Impl(), aRgn2.Impl());
    return *this;
  }
  nsRegion& And(const nsRect& aRect, const nsRegion& aRegion)
  {
    return And(aRegion, aRect);
  }
  nsRegion& And(const nsRegion& aRegion, const nsRect& aRect)
  {
    pixman_region32_intersect_rect(&mImpl, aRegion.Impl(), aRect.x, aRect.y, aRect.Width(), aRect.Height());
    return *this;
  }
  nsRegion& And(const nsRect& aRect1, const nsRect& aRect2)
  {
    nsRect TmpRect;

    TmpRect.IntersectRect(aRect1, aRect2);
    return Copy(TmpRect);
  }

  nsRegion& OrWith(const nsRegion& aOther)
  {
    return Or(*this, aOther);
  }
  nsRegion& OrWith(const nsRect& aOther)
  {
    return Or(*this, aOther);
  }
  nsRegion& Or(const nsRegion& aRgn1, const nsRegion& aRgn2)
  {
    pixman_region32_union(&mImpl, aRgn1.Impl(), aRgn2.Impl());
    return *this;
  }
  nsRegion& Or(const nsRegion& aRegion, const nsRect& aRect)
  {
    pixman_region32_union_rect(&mImpl, aRegion.Impl(), aRect.x, aRect.y, aRect.Width(), aRect.Height());
    return *this;
  }
  nsRegion& Or(const nsRect& aRect, const nsRegion& aRegion)
  {
    return  Or(aRegion, aRect);
  }
  nsRegion& Or(const nsRect& aRect1, const nsRect& aRect2)
  {
    Copy (aRect1);
    return Or (*this, aRect2);
  }

  nsRegion& XorWith(const nsRegion& aOther)
  {
    return Xor(*this, aOther);
  }
  nsRegion& XorWith(const nsRect& aOther)
  {
    return Xor(*this, aOther);
  }
  nsRegion& Xor(const nsRegion& aRgn1,   const nsRegion& aRgn2)
  {
    // this could be implemented better if pixman had direct
    // support for xoring regions.
    nsRegion p;
    p.Sub(aRgn1, aRgn2);
    nsRegion q;
    q.Sub(aRgn2, aRgn1);
    return Or(p, q);
  }
  nsRegion& Xor(const nsRegion& aRegion, const nsRect& aRect)
  {
    return Xor(aRegion, nsRegion(aRect));
  }
  nsRegion& Xor(const nsRect& aRect, const nsRegion& aRegion)
  {
    return Xor(nsRegion(aRect), aRegion);
  }
  nsRegion& Xor(const nsRect& aRect1, const nsRect& aRect2)
  {
    return Xor(nsRegion(aRect1), nsRegion(aRect2));
  }

  nsRegion ToAppUnits (nscoord aAppUnitsPerPixel) const;

  nsRegion& SubOut(const nsRegion& aOther)
  {
    return Sub(*this, aOther);
  }
  nsRegion& SubOut(const nsRect& aOther)
  {
    return Sub(*this, aOther);
  }
  nsRegion& Sub(const nsRegion& aRgn1, const nsRegion& aRgn2)
  {
    pixman_region32_subtract(&mImpl, aRgn1.Impl(), aRgn2.Impl());
    return *this;
  }
  nsRegion& Sub(const nsRegion& aRegion, const nsRect& aRect)
  {
    return Sub(aRegion, nsRegion(aRect));
  }
  nsRegion& Sub(const nsRect& aRect, const nsRegion& aRegion)
  {
    return Sub(nsRegion(aRect), aRegion);
  }
  nsRegion& Sub(const nsRect& aRect1, const nsRect& aRect2)
  {
    Copy(aRect1);
    return Sub(*this, aRect2);
  }

  /**
   * Returns true iff the given point is inside the region. A region
   * created from a rect (x=0, y=0, w=100, h=100) will NOT contain
   * the point x=100, y=100.
   */
  bool Contains (int aX, int aY) const
  {
    return pixman_region32_contains_point(Impl(), aX, aY, nullptr);
  }
  bool Contains (const nsRect& aRect) const
  {
    pixman_box32_t box = RectToBox(aRect);
    return pixman_region32_contains_rectangle(Impl(), &box) == PIXMAN_REGION_IN;
  }
  bool Contains (const nsRegion& aRgn) const;
  bool Intersects (const nsRect& aRect) const;

  void MoveBy (int32_t aXOffset, int32_t aYOffset)
  {
    MoveBy (nsPoint (aXOffset, aYOffset));
  }
  void MoveBy (nsPoint aPt) { pixman_region32_translate(&mImpl, aPt.x, aPt.y); }
  void SetEmpty ()
  {
    pixman_region32_clear(&mImpl);
  }

  nsRegion MovedBy(int32_t aXOffset, int32_t aYOffset) const
  {
    return MovedBy(nsPoint(aXOffset, aYOffset));
  }
  nsRegion MovedBy(const nsPoint& aPt) const
  {
    nsRegion copy(*this);
    copy.MoveBy(aPt);
    return copy;
  }

  nsRegion Intersect(const nsRegion& aOther) const
  {
    nsRegion intersection;
    intersection.And(*this, aOther);
    return intersection;
  }

  void Inflate(const nsMargin& aMargin);

  nsRegion Inflated(const nsMargin& aMargin) const
  {
    nsRegion copy(*this);
    copy.Inflate(aMargin);
    return copy;
  }

  bool IsEmpty () const { return !pixman_region32_not_empty(Impl()); }
  bool IsComplex () const { return GetNumRects() > 1; }
  bool IsEqual (const nsRegion& aRegion) const
  {
    return pixman_region32_equal(Impl(), aRegion.Impl());
  }
  uint32_t GetNumRects () const
  {
    // Work around pixman bug. Sometimes pixman creates regions with 1 rect
    // that's empty.
    uint32_t result = pixman_region32_n_rects(Impl());
    return (result == 1 && GetBounds().IsEmpty()) ? 0 : result;
  }
  const nsRect GetBounds () const { return BoxToRect(mImpl.extents); }
  uint64_t Area () const;

  /**
   * Return this region scaled to a different appunits per pixel (APP) ratio.
   * This applies nsRect::ScaleToOtherAppUnitsRoundOut/In to each rect of the region.
   * @param aFromAPP the APP to scale from
   * @param aToAPP the APP to scale to
   * @note this can turn an empty region into a non-empty region
   */
  MOZ_MUST_USE nsRegion
    ScaleToOtherAppUnitsRoundOut (int32_t aFromAPP, int32_t aToAPP) const;
  MOZ_MUST_USE nsRegion
    ScaleToOtherAppUnitsRoundIn (int32_t aFromAPP, int32_t aToAPP) const;
  nsRegion& ScaleRoundOut(float aXScale, float aYScale);
  nsRegion& ScaleInverseRoundOut(float aXScale, float aYScale);
  nsRegion& Transform (const mozilla::gfx::Matrix4x4 &aTransform);
  nsIntRegion ScaleToOutsidePixels (float aXScale, float aYScale, nscoord aAppUnitsPerPixel) const;
  nsIntRegion ScaleToInsidePixels (float aXScale, float aYScale, nscoord aAppUnitsPerPixel) const;
  nsIntRegion ScaleToNearestPixels (float aXScale, float aYScale, nscoord aAppUnitsPerPixel) const;
  nsIntRegion ToOutsidePixels (nscoord aAppUnitsPerPixel) const;
  nsIntRegion ToNearestPixels (nscoord aAppUnitsPerPixel) const;

  /**
   * Gets the largest rectangle contained in the region.
   * @param aContainingRect if non-empty, we choose a rectangle that
   * maximizes the area intersecting with aContainingRect (and break ties by
   * then choosing the largest rectangle overall)
   */
  nsRect GetLargestRectangle (const nsRect& aContainingRect = nsRect()) const;

  /**
   * Make sure the region has at most aMaxRects by adding area to it
   * if necessary. The simplified region will be a superset of the
   * original region. The simplified region's bounding box will be
   * the same as for the current region.
   */
  void SimplifyOutward (uint32_t aMaxRects);
  /**
   * Simplify the region by adding at most aThreshold area between spans of
   * rects.  The simplified region will be a superset of the original region.
   * The simplified region's bounding box will be the same as for the current
   * region.
   */
  void SimplifyOutwardByArea(uint32_t aThreshold);
  /**
   * Make sure the region has at most aMaxRects by removing area from
   * it if necessary. The simplified region will be a subset of the
   * original region.
   */
  void SimplifyInward (uint32_t aMaxRects);

  /**
   * VisitEdges is a weird kind of function that we use for padding
   * out surfaces to prevent texture filtering artifacts.
   * It calls the visitFn callback for each of the exterior edges of
   * the regions. The top and bottom edges will be expanded 1 pixel
   * to the left and right if there's an outside corner. The order
   * the edges are visited is not guaranteed.
   *
   * visitFn has a side parameter that can be TOP,BOTTOM,LEFT,RIGHT
   * and specifies which kind of edge is being visited. x1, y1, x2, y2
   * are the coordinates of the line. (x1 == x2) || (y1 == y2)
   */
  typedef void (*visitFn)(void *closure, VisitSide side, int x1, int y1, int x2, int y2);
  void VisitEdges(visitFn, void *closure);

  nsCString ToString() const;

  class RectIterator
  {
    int mCurrent;               // Index of the current entry
    int mLimit;                 // Index one past the final entry.
    mutable nsRect mTmp;        // The most recently gotten rectangle.
    pixman_box32_t *mBoxes;

  public:
    explicit RectIterator(const nsRegion& aRegion)
    {
      mCurrent = 0;
      mBoxes = pixman_region32_rectangles(aRegion.Impl(), &mLimit);
      // Work around pixman bug. Sometimes pixman creates regions with 1 rect
      // that's empty.
      if (mLimit == 1 && nsRegion::BoxToRect(mBoxes[0]).IsEmpty()) {
        mLimit = 0;
      }
    }

    bool Done() const { return mCurrent == mLimit; }

    const nsRect& Get() const
    {
      MOZ_ASSERT(!Done());
      mTmp = nsRegion::BoxToRect(mBoxes[mCurrent]);
      NS_ASSERTION(!mTmp.IsEmpty(), "Shouldn't return empty rect");
      return mTmp;
    }

    void Next()
    {
      MOZ_ASSERT(!Done());
      mCurrent++;
    }
  };

  RectIterator RectIter() const { return RectIterator(*this); }

private:
  pixman_region32_t mImpl;

#ifndef MOZ_TREE_PIXMAN
  // For compatibility with pixman versions older than 0.25.2.
  static inline void
  pixman_region32_clear(pixman_region32_t *region)
  {
    pixman_region32_fini(region);
    pixman_region32_init(region);
  }
#endif

  nsIntRegion ToPixels(nscoord aAppUnitsPerPixel, bool aOutsidePixels) const;

  nsRegion& Copy (const nsRegion& aRegion)
  {
    pixman_region32_copy(&mImpl, aRegion.Impl());
    return *this;
  }

  nsRegion& Copy (const nsRect& aRect)
  {
    // pixman needs to distinguish between an empty region and a region
    // with one rect so that it can return a different number of rectangles.
    // Empty rect: data = empty_box
    //     1 rect: data = null
    //    >1 rect: data = rects
    if (aRect.IsEmpty()) {
      pixman_region32_clear(&mImpl);
    } else {
      pixman_box32_t box = RectToBox(aRect);
      pixman_region32_reset(&mImpl, &box);
    }
    return *this;
  }

  static inline pixman_box32_t RectToBox(const nsRect &aRect)
  {
    pixman_box32_t box = { aRect.x, aRect.y, aRect.XMost(), aRect.YMost() };
    return box;
  }

  static inline pixman_box32_t RectToBox(const mozilla::gfx::IntRect &aRect)
  {
    pixman_box32_t box = { aRect.x, aRect.y, aRect.XMost(), aRect.YMost() };
    return box;
  }


  static inline nsRect BoxToRect(const pixman_box32_t &aBox)
  {
    return nsRect(aBox.x1, aBox.y1,
                  aBox.x2 - aBox.x1,
                  aBox.y2 - aBox.y1);
  }

  pixman_region32_t* Impl() const
  {
    return const_cast<pixman_region32_t*>(&mImpl);
  }
};

namespace mozilla {
namespace gfx {

/**
 * BaseIntRegions use int32_t coordinates.
 */
template <typename Derived, typename Rect, typename Point, typename Margin>
class BaseIntRegion
{
  friend class ::nsRegion;

  // Give access to all specializations of IntRegionTyped, not just ones that
  // derive from this specialization of BaseIntRegion.
  template <typename units>
  friend class IntRegionTyped;

public:
  typedef Rect RectType;
  typedef Point PointType;
  typedef Margin MarginType;

  BaseIntRegion () {}
  MOZ_IMPLICIT BaseIntRegion (const Rect& aRect) : mImpl (ToRect(aRect)) {}
  explicit BaseIntRegion (mozilla::gfx::ArrayView<pixman_box32_t> aRects) : mImpl (aRects) {}
  BaseIntRegion (const BaseIntRegion& aRegion) : mImpl (aRegion.mImpl) {}
  BaseIntRegion (BaseIntRegion&& aRegion) : mImpl (mozilla::Move(aRegion.mImpl)) {}
  Derived& operator = (const Rect& aRect) { mImpl = ToRect (aRect); return This(); }
  Derived& operator = (const Derived& aRegion) { mImpl = aRegion.mImpl; return This(); }
  Derived& operator = (Derived&& aRegion) { mImpl = mozilla::Move(aRegion.mImpl); return This(); }

  bool operator==(const Derived& aRgn) const
  {
    return IsEqual(aRgn);
  }
  bool operator!=(const Derived& aRgn) const
  {
    return !(*this == aRgn);
  }

  friend std::ostream& operator<<(std::ostream& stream, const Derived& m) {
    return stream << m.mImpl;
  }

  void Swap(Derived* aOther)
  {
    mImpl.Swap(&aOther->mImpl);
  }

  void AndWith(const Derived& aOther)
  {
    And(This(), aOther);
  }
  void AndWith(const Rect& aOther)
  {
    And(This(), aOther);
  }
  Derived& And  (const Derived& aRgn1,   const Derived& aRgn2)
  {
    mImpl.And (aRgn1.mImpl, aRgn2.mImpl);
    return This();
  }
  Derived& And  (const Derived& aRegion, const Rect& aRect)
  {
    mImpl.And (aRegion.mImpl, ToRect (aRect));
    return This();
  }
  Derived& And  (const Rect& aRect, const Derived& aRegion)
  {
    return  And  (aRegion, aRect);
  }
  Derived& And  (const Rect& aRect1, const Rect& aRect2)
  {
    Rect TmpRect;

    TmpRect.IntersectRect (aRect1, aRect2);
    mImpl = ToRect (TmpRect);
    return This();
  }

  Derived& OrWith(const Derived& aOther)
  {
    return Or(This(), aOther);
  }
  Derived& OrWith(const Rect& aOther)
  {
    return Or(This(), aOther);
  }
  Derived& Or   (const Derived& aRgn1,   const Derived& aRgn2)
  {
    mImpl.Or (aRgn1.mImpl, aRgn2.mImpl);
    return This();
  }
  Derived& Or   (const Derived& aRegion, const Rect& aRect)
  {
    mImpl.Or (aRegion.mImpl, ToRect (aRect));
    return This();
  }
  Derived& Or   (const Rect& aRect, const Derived& aRegion)
  {
    return  Or   (aRegion, aRect);
  }
  Derived& Or   (const Rect& aRect1, const Rect& aRect2)
  {
    mImpl = ToRect (aRect1);
    return Or (This(), aRect2);
  }

  Derived& XorWith(const Derived& aOther)
  {
    return Xor(This(), aOther);
  }
  Derived& XorWith(const Rect& aOther)
  {
    return Xor(This(), aOther);
  }
  Derived& Xor  (const Derived& aRgn1,   const Derived& aRgn2)
  {
    mImpl.Xor (aRgn1.mImpl, aRgn2.mImpl);
    return This();
  }
  Derived& Xor  (const Derived& aRegion, const Rect& aRect)
  {
    mImpl.Xor (aRegion.mImpl, ToRect (aRect));
    return This();
  }
  Derived& Xor  (const Rect& aRect, const Derived& aRegion)
  {
    return  Xor  (aRegion, aRect);
  }
  Derived& Xor  (const Rect& aRect1, const Rect& aRect2)
  {
    mImpl = ToRect (aRect1);
    return Xor (This(), aRect2);
  }

  Derived& SubOut(const Derived& aOther)
  {
    return Sub(This(), aOther);
  }
  Derived& SubOut(const Rect& aOther)
  {
    return Sub(This(), aOther);
  }
  Derived& Sub  (const Derived& aRgn1,   const Derived& aRgn2)
  {
    mImpl.Sub (aRgn1.mImpl, aRgn2.mImpl);
    return This();
  }
  Derived& Sub  (const Derived& aRegion, const Rect& aRect)
  {
    mImpl.Sub (aRegion.mImpl, ToRect (aRect));
    return This();
  }
  Derived& Sub  (const Rect& aRect, const Derived& aRegion)
  {
    return Sub (Derived (aRect), aRegion);
  }
  Derived& Sub  (const Rect& aRect1, const Rect& aRect2)
  {
    mImpl = ToRect (aRect1);
    return Sub (This(), aRect2);
  }

  /**
   * Returns true iff the given point is inside the region. A region
   * created from a rect (x=0, y=0, w=100, h=100) will NOT contain
   * the point x=100, y=100.
   */
  bool Contains (int aX, int aY) const
  {
    return mImpl.Contains(aX, aY);
  }
  bool Contains (const Rect& aRect) const
  {
    return mImpl.Contains (ToRect (aRect));
  }
  bool Contains (const Derived& aRgn) const
  {
    return mImpl.Contains (aRgn.mImpl);
  }
  bool Intersects (const Rect& aRect) const
  {
    return mImpl.Intersects (ToRect (aRect));
  }

  void MoveBy (int32_t aXOffset, int32_t aYOffset)
  {
    MoveBy (Point (aXOffset, aYOffset));
  }
  void MoveBy (Point aPt)
  {
    mImpl.MoveBy (aPt.x, aPt.y);
  }
  Derived MovedBy(int32_t aXOffset, int32_t aYOffset) const
  {
    return MovedBy(Point(aXOffset, aYOffset));
  }
  Derived MovedBy(const Point& aPt) const
  {
    Derived copy(This());
    copy.MoveBy(aPt);
    return copy;
  }

  Derived Intersect(const Derived& aOther) const
  {
    Derived intersection;
    intersection.And(This(), aOther);
    return intersection;
  }

  void Inflate(const Margin& aMargin)
  {
    mImpl.Inflate(nsMargin(aMargin.top, aMargin.right, aMargin.bottom, aMargin.left));
  }
  Derived Inflated(const Margin& aMargin) const
  {
    Derived copy(This());
    copy.Inflate(aMargin);
    return copy;
  }

  void SetEmpty ()
  {
    mImpl.SetEmpty  ();
  }

  bool IsEmpty () const { return mImpl.IsEmpty (); }
  bool IsComplex () const { return mImpl.IsComplex (); }
  bool IsEqual (const Derived& aRegion) const
  {
    return mImpl.IsEqual (aRegion.mImpl);
  }
  uint32_t GetNumRects () const { return mImpl.GetNumRects (); }
  Rect GetBounds () const { return FromRect (mImpl.GetBounds ()); }
  uint64_t Area () const { return mImpl.Area(); }
  nsRegion ToAppUnits (nscoord aAppUnitsPerPixel) const
  {
    nsRegion result;
    for (auto iter = RectIter(); !iter.Done(); iter.Next()) {
      nsRect appRect = ::ToAppUnits(iter.Get(), aAppUnitsPerPixel);
      result.Or(result, appRect);
    }
    return result;
  }
  Rect GetLargestRectangle (const Rect& aContainingRect = Rect()) const
  {
    return FromRect (mImpl.GetLargestRectangle( ToRect(aContainingRect) ));
  }

  Derived& ScaleRoundOut (float aXScale, float aYScale)
  {
    mImpl.ScaleRoundOut(aXScale, aYScale);
    return This();
  }

  Derived& ScaleInverseRoundOut (float aXScale, float aYScale)
  {
    mImpl.ScaleInverseRoundOut(aXScale, aYScale);
    return This();
  }

  // Prefer using TransformBy(matrix, region) from UnitTransforms.h,
  // as applying the transform should typically change the unit system.
  // TODO(botond): Move this to IntRegionTyped and disable it for
  //               unit != UnknownUnits.
  Derived& Transform (const mozilla::gfx::Matrix4x4 &aTransform)
  {
    mImpl.Transform(aTransform);
    return This();
  }

  /**
   * Make sure the region has at most aMaxRects by adding area to it
   * if necessary. The simplified region will be a superset of the
   * original region. The simplified region's bounding box will be
   * the same as for the current region.
   */
  void SimplifyOutward (uint32_t aMaxRects)
  {
    mImpl.SimplifyOutward (aMaxRects);
  }
  void SimplifyOutwardByArea (uint32_t aThreshold)
  {
    mImpl.SimplifyOutwardByArea (aThreshold);
  }
  /**
   * Make sure the region has at most aMaxRects by removing area from
   * it if necessary. The simplified region will be a subset of the
   * original region.
   */
  void SimplifyInward (uint32_t aMaxRects)
  {
    mImpl.SimplifyInward (aMaxRects);
  }

  typedef void (*visitFn)(void *closure, VisitSide side, int x1, int y1, int x2, int y2);
  void VisitEdges (visitFn visit, void *closure)
  {
    mImpl.VisitEdges (visit, closure);
  }

  nsCString ToString() const { return mImpl.ToString(); }

  class RectIterator
  {
    nsRegion::RectIterator mImpl; // The underlying iterator.
    mutable Rect mTmp;            // The most recently gotten rectangle.

  public:
    explicit RectIterator(const BaseIntRegion& aRegion)
      : mImpl(aRegion.mImpl)
    {}

    bool Done() const { return mImpl.Done(); }

    const Rect& Get() const
    {
      mTmp = FromRect(mImpl.Get());
      return mTmp;
    }

    void Next() { mImpl.Next(); }
  };

  RectIterator RectIter() const { return RectIterator(*this); }

protected:
  // Expose enough to derived classes from them to define conversions
  // between different types of BaseIntRegions.
  explicit BaseIntRegion(const nsRegion& aImpl) : mImpl(aImpl) {}
  const nsRegion& Impl() const { return mImpl; }
private:
  nsRegion mImpl;

  static nsRect ToRect(const Rect& aRect)
  {
    return nsRect (aRect.x, aRect.y, aRect.Width(), aRect.Height());
  }
  static Rect FromRect(const nsRect& aRect)
  {
    return Rect (aRect.x, aRect.y, aRect.Width(), aRect.Height());
  }

  Derived& This()
  {
    return *static_cast<Derived*>(this);
  }
  const Derived& This() const
  {
    return *static_cast<const Derived*>(this);
  }
};

template <class units>
class IntRegionTyped :
    public BaseIntRegion<IntRegionTyped<units>, IntRectTyped<units>, IntPointTyped<units>, IntMarginTyped<units>>
{
  typedef BaseIntRegion<IntRegionTyped<units>, IntRectTyped<units>, IntPointTyped<units>, IntMarginTyped<units>> Super;

  // Make other specializations of IntRegionTyped friends.
  template <typename OtherUnits>
  friend class IntRegionTyped;

  static_assert(IsPixel<units>::value, "'units' must be a coordinate system tag");

public:
  typedef IntRectTyped<units> RectType;
  typedef IntPointTyped<units> PointType;
  typedef IntMarginTyped<units> MarginType;

  // Forward constructors.
  IntRegionTyped() {}
  MOZ_IMPLICIT IntRegionTyped(const IntRectTyped<units>& aRect) : Super(aRect) {}
  IntRegionTyped(const IntRegionTyped& aRegion) : Super(aRegion) {}
  explicit IntRegionTyped(mozilla::gfx::ArrayView<pixman_box32_t> aRects) : Super(aRects) {}
  IntRegionTyped(IntRegionTyped&& aRegion) : Super(mozilla::Move(aRegion)) {}

  // Assignment operators need to be forwarded as well, otherwise the compiler
  // will declare deleted ones.
  IntRegionTyped& operator=(const IntRegionTyped& aRegion)
  {
    return Super::operator=(aRegion);
  }
  IntRegionTyped& operator=(IntRegionTyped&& aRegion)
  {
    return Super::operator=(mozilla::Move(aRegion));
  }

  static IntRegionTyped FromUnknownRegion(const IntRegion& aRegion)
  {
    return IntRegionTyped(aRegion.Impl());
  }
  IntRegion ToUnknownRegion() const
  {
    // Need |this->| because Impl() is defined in a dependent base class.
    return IntRegion(this->Impl());
  }
private:
  // This is deliberately private, so calling code uses FromUnknownRegion().
  explicit IntRegionTyped(const nsRegion& aRegion) : Super(aRegion) {}
};

} // namespace gfx
} // namespace mozilla

typedef mozilla::gfx::IntRegion nsIntRegion;

#endif