Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2524 insertions, 0 deletions

diff --git a/gfx/src/nsRegion.h b/gfx/src/nsRegion.h
new file mode 100644
index 0000000000..9c0fd8ed00
--- /dev/null
+++ b/gfx/src/nsRegion.h
@@ -0,0 +1,2524 @@
+/* -*- 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 <ostream>  // for std::ostream
+#include <utility>  // for mozilla::Move
+
+#include "mozilla/ArrayView.h"      // for ArrayView
+#include "mozilla/gfx/MatrixFwd.h"  // for mozilla::gfx::Matrix4x4
+#include "nsCoord.h"                // for nscoord
+#include "nsMargin.h"               // for nsIntMargin
+#include "nsPoint.h"                // for nsIntPoint, nsPoint
+#include "nsRect.h"                 // for mozilla::gfx::IntRect, nsRect
+#include "nsRectAbsolute.h"
+#include "nsRegionFwd.h"  // for nsIntRegion
+#include "nsString.h"     // for nsCString
+#include "nsTArray.h"
+#include "pixman.h"
+
+// Uncomment this line to get additional integrity checking.
+//#define DEBUG_REGIONS
+#ifdef DEBUG_REGIONS
+#  include <sstream>
+#endif
+
+/* 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 };
+
+namespace regiondetails {
+struct Band;
+}
+
+template <>
+struct nsTArray_RelocationStrategy<regiondetails::Band> {
+  typedef nsTArray_RelocateUsingMoveConstructor<regiondetails::Band> Type;
+};
+
+namespace regiondetails {
+
+template <typename T, typename E>
+class UncheckedArray : public T {
+ public:
+  using T::Elements;
+  using T::Length;
+
+  UncheckedArray() = default;
+  MOZ_IMPLICIT UncheckedArray(T&& aSrc) : T(std::move(aSrc)) {}
+
+  E& operator[](size_t aIndex) { return Elements()[aIndex]; }
+  const E& operator[](size_t aIndex) const { return Elements()[aIndex]; }
+  E& LastElement() { return Elements()[Length() - 1]; }
+  const E& LastElement() const { return Elements()[Length() - 1]; }
+
+  using iterator = E*;
+  using const_iterator = const E*;
+
+  iterator begin() { return iterator(Elements()); }
+  const_iterator begin() const { return const_iterator(Elements()); }
+  const_iterator cbegin() const { return begin(); }
+  iterator end() { return iterator(Elements() + Length()); }
+  const_iterator end() const { return const_iterator(Elements() + Length()); }
+  const_iterator cend() const { return end(); }
+};
+
+struct Strip {
+  // Default constructor should never be called, but is required for
+  // vector::resize to compile.
+  Strip() { MOZ_CRASH(); }
+  Strip(int32_t aLeft, int32_t aRight) : left(aLeft), right(aRight) {}
+
+  bool operator!=(const Strip& aOther) const {
+    return left != aOther.left || right != aOther.right;
+  }
+
+  uint32_t Size() const { return right - left; }
+
+  int32_t left;
+  int32_t right;
+};
+
+struct Band {
+  using Strip = regiondetails::Strip;
+#ifndef DEBUG
+  using StripArray =
+      regiondetails::UncheckedArray<CopyableAutoTArray<Strip, 2>, Strip>;
+#else
+  using StripArray = CopyableAutoTArray<Strip, 2>;
+#endif
+
+  MOZ_IMPLICIT Band(const nsRectAbsolute& aRect)
+      : top(aRect.Y()), bottom(aRect.YMost()) {
+    mStrips.AppendElement(Strip{aRect.X(), aRect.XMost()});
+  }
+
+  Band(const Band& aOther) = default;
+  Band(Band&& aOther) = default;
+
+  void InsertStrip(const Strip& aStrip) {
+    for (size_t i = 0; i < mStrips.Length(); i++) {
+      Strip& strip = mStrips[i];
+      if (strip.left > aStrip.right) {
+        // Current strip is beyond aStrip, insert aStrip before.
+        mStrips.InsertElementAt(i, aStrip);
+        return;
+      }
+
+      if (strip.right < aStrip.left) {
+        // Current strip is before aStrip, try the next.
+        continue;
+      }
+
+      // Current strip intersects with aStrip, extend to the lext.
+      strip.left = std::min(strip.left, aStrip.left);
+
+      if (strip.right >= aStrip.right) {
+        // Current strip extends beyond aStrip, done.
+        return;
+      }
+
+      size_t next = i;
+      next++;
+      // Consume any subsequent strips intersecting with aStrip.
+      while (next < mStrips.Length() && mStrips[next].left <= aStrip.right) {
+        strip.right = mStrips[next].right;
+
+        mStrips.RemoveElementAt(next);
+      }
+
+      // Extend the strip in case the aStrip goes on beyond it.
+      strip.right = std::max(strip.right, aStrip.right);
+      return;
+    }
+    mStrips.AppendElement(aStrip);
+  }
+
+  void SubStrip(const Strip& aStrip) {
+    for (size_t i = 0; i < mStrips.Length(); i++) {
+      Strip& strip = mStrips[i];
+      if (strip.left > aStrip.right) {
+        // Strip is entirely to the right of aStrip. Done.
+        return;
+      }
+
+      if (strip.right < aStrip.left) {
+        // Strip is entirely to the left of aStrip. Move on.
+        continue;
+      }
+
+      if (strip.left < aStrip.left) {
+        if (strip.right <= aStrip.right) {
+          strip.right = aStrip.left;
+          // This strip lies to the left of the start of aStrip.
+          continue;
+        }
+
+        // aStrip is completely contained by this strip.
+        Strip newStrip(aStrip.right, strip.right);
+        strip.right = aStrip.left;
+        if (i < mStrips.Length()) {
+          i++;
+          mStrips.InsertElementAt(i, newStrip);
+        } else {
+          mStrips.AppendElement(newStrip);
+        }
+        return;
+      }
+
+      // This strip lies to the right of the start of aStrip.
+      if (strip.right <= aStrip.right) {
+        // aStrip completely contains this strip.
+        mStrips.RemoveElementAt(i);
+        // Make sure we evaluate the strip now at i. This loop will increment.
+        i--;
+        continue;
+      }
+      strip.left = aStrip.right;
+      return;
+    }
+  }
+
+  bool Intersects(const Strip& aStrip) const {
+    for (const Strip& strip : mStrips) {
+      if (strip.left >= aStrip.right) {
+        return false;
+      }
+
+      if (strip.right <= aStrip.left) {
+        continue;
+      }
+
+      return true;
+    }
+    return false;
+  }
+
+  bool IntersectStripBounds(Strip& aStrip) const {
+    bool intersected = false;
+
+    int32_t rightMost;
+    for (const Strip& strip : mStrips) {
+      if (strip.left > aStrip.right) {
+        break;
+      }
+
+      if (strip.right <= aStrip.left) {
+        continue;
+      }
+
+      if (!intersected) {
+        // First intersection, this is where the left side begins.
+        aStrip.left = std::max(aStrip.left, strip.left);
+      }
+
+      intersected = true;
+      // Expand to the right for each intersecting strip found.
+      rightMost = std::min(strip.right, aStrip.right);
+    }
+
+    if (intersected) {
+      aStrip.right = rightMost;
+    } else {
+      aStrip.right = aStrip.left = 0;
+    }
+    return intersected;
+  }
+
+  bool ContainsStrip(const Strip& aStrip) const {
+    for (const Strip& strip : mStrips) {
+      if (strip.left > aStrip.left) {
+        return false;
+      }
+
+      if (strip.right >= aStrip.right) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  bool EqualStrips(const Band& aBand) const {
+    if (mStrips.Length() != aBand.mStrips.Length()) {
+      return false;
+    }
+
+    for (auto iter1 = mStrips.begin(), iter2 = aBand.mStrips.begin();
+         iter1 != mStrips.end(); iter1++, iter2++) {
+      if (*iter1 != *iter2) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  void IntersectStrip(const Strip& aStrip) {
+    size_t i = 0;
+
+    while (i < mStrips.Length()) {
+      Strip& strip = mStrips[i];
+      if (strip.right <= aStrip.left) {
+        mStrips.RemoveElementAt(i);
+        continue;
+      }
+
+      if (strip.left >= aStrip.right) {
+        mStrips.TruncateLength(i);
+        return;
+      }
+
+      strip.left = std::max(aStrip.left, strip.left);
+      strip.right = std::min(aStrip.right, strip.right);
+      i++;
+    }
+  }
+
+  void IntersectStrips(const Band& aOther) {
+    auto iter = mStrips.begin();
+    auto iterOther = aOther.mStrips.begin();
+
+    StripArray newStrips;
+
+    // This function finds the intersection between two sets of strips.
+    while (true) {
+      while (true) {
+        while (iter != mStrips.end() && iter->right <= iterOther->left) {
+          // Increment our current strip until it ends beyond aOther's current
+          // strip.
+          iter++;
+        }
+
+        if (iter == mStrips.end()) {
+          // End of our strips. Done.
+          break;
+        }
+
+        while (iterOther != aOther.mStrips.end() &&
+               iterOther->right <= iter->left) {
+          // Increment aOther's current strip until it lies beyond our current
+          // strip.
+          iterOther++;
+        }
+
+        if (iterOther == aOther.mStrips.end()) {
+          // End of aOther's strips. Done.
+          break;
+        }
+
+        if (iterOther->left < iter->right) {
+          // Intersection!
+          break;
+        }
+      }
+
+      if (iter == mStrips.end() || iterOther == aOther.mStrips.end()) {
+        break;
+      }
+
+      newStrips.AppendElement(Strip(std::max(iter->left, iterOther->left),
+                                    std::min(iterOther->right, iter->right)));
+
+      if (iterOther->right < iter->right) {
+        iterOther++;
+        if (iterOther == aOther.mStrips.end()) {
+          break;
+        }
+      } else {
+        iter++;
+      }
+    }
+
+    mStrips = std::move(newStrips);
+  }
+
+  bool Intersects(const Band& aOther) const {
+    auto iter = mStrips.begin();
+    auto iterOther = aOther.mStrips.begin();
+
+    // This function finds the intersection between two sets of strips.
+    while (true) {
+      while (true) {
+        while (iter != mStrips.end() && iter->right <= iterOther->left) {
+          // Increment our current strip until it ends beyond aOther's current
+          // strip.
+          iter++;
+        }
+
+        if (iter == mStrips.end()) {
+          // End of our strips. Done.
+          break;
+        }
+
+        while (iterOther != aOther.mStrips.end() &&
+               iterOther->right <= iter->left) {
+          // Increment aOther's current strip until it lies beyond our current
+          // strip.
+          iterOther++;
+        }
+
+        if (iterOther == aOther.mStrips.end()) {
+          // End of aOther's strips. Done.
+          break;
+        }
+
+        if (iterOther->left < iter->right) {
+          // Intersection!
+          break;
+        }
+      }
+
+      if (iter == mStrips.end() || iterOther == aOther.mStrips.end()) {
+        break;
+      }
+
+      return true;
+    }
+    return false;
+  }
+
+  void SubStrips(const Band& aOther) {
+    size_t idx = 0;
+    auto iterOther = aOther.mStrips.begin();
+
+    // This function finds the intersection between two sets of strips.
+    while (true) {
+      while (true) {
+        while (idx < mStrips.Length() &&
+               mStrips[idx].right <= iterOther->left) {
+          // Increment our current strip until it ends beyond aOther's current
+          // strip.
+          idx++;
+        }
+
+        if (idx == mStrips.Length()) {
+          // End of our strips. Done.
+          break;
+        }
+
+        while (iterOther != aOther.mStrips.end() &&
+               iterOther->right <= mStrips[idx].left) {
+          // Increment aOther's current strip until it lies beyond our current
+          // strip.
+          iterOther++;
+        }
+
+        if (iterOther == aOther.mStrips.end()) {
+          // End of aOther's strips. Done.
+          break;
+        }
+
+        if (iterOther->left < mStrips[idx].right) {
+          // Intersection!
+          break;
+        }
+      }
+
+      if (idx == mStrips.Length() || iterOther == aOther.mStrips.end()) {
+        break;
+      }
+
+      if (mStrips[idx].left < iterOther->left) {
+        size_t oldIdx = idx;
+        // Our strip starts beyond other's
+        if (mStrips[idx].right > iterOther->right) {
+          // Our strip ends beyond other's as well.
+          Strip newStrip(mStrips[idx]);
+          newStrip.left = iterOther->right;
+          mStrips.InsertElementAt(idx + 1, newStrip);
+          idx++;
+        }
+        mStrips[oldIdx].right = iterOther->left;
+        // Either idx was just incremented, or the current index no longer
+        // intersects with iterOther.
+        continue;
+      } else if (mStrips[idx].right > iterOther->right) {
+        mStrips[idx].left = iterOther->right;
+        // Current strip no longer intersects, continue.
+        iterOther++;
+        if (iterOther == aOther.mStrips.end()) {
+          break;
+        }
+        continue;
+      }
+
+      // Our current strip is completely contained by the other strip.
+      mStrips.RemoveElementAt(idx);
+    }
+  }
+
+  int32_t top;
+  int32_t bottom;
+  StripArray mStrips;
+};
+}  // namespace regiondetails
+
+class nsRegion {
+ public:
+  using Band = regiondetails::Band;
+  using Strip = regiondetails::Strip;
+#ifndef DEBUG
+  using BandArray = regiondetails::UncheckedArray<nsTArray<Band>, Band>;
+  using StripArray = regiondetails::UncheckedArray<AutoTArray<Strip, 2>, Strip>;
+#else
+  using BandArray = nsTArray<Band>;
+  using StripArray = AutoTArray<Strip, 2>;
+#endif
+
+  typedef nsRect RectType;
+  typedef nsPoint PointType;
+  typedef nsMargin MarginType;
+
+  nsRegion() = default;
+  MOZ_IMPLICIT nsRegion(const nsRect& aRect) {
+    mBounds = nsRectAbsolute::FromRect(aRect);
+  }
+  MOZ_IMPLICIT nsRegion(const nsRectAbsolute& aRect) { mBounds = aRect; }
+  explicit nsRegion(mozilla::gfx::ArrayView<pixman_box32_t> aRects) {
+    for (uint32_t i = 0; i < aRects.Length(); i++) {
+      AddRect(BoxToRect(aRects[i]));
+    }
+  }
+
+  nsRegion(const nsRegion& aRegion) { Copy(aRegion); }
+  nsRegion(nsRegion&& aRegion)
+      : mBands(std::move(aRegion.mBands)), mBounds(aRegion.mBounds) {
+    aRegion.SetEmpty();
+  }
+  nsRegion& operator=(nsRegion&& aRegion) {
+    mBands = std::move(aRegion.mBands);
+    mBounds = aRegion.mBounds;
+    aRegion.SetEmpty();
+    return *this;
+  }
+  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 OutputToStream(std::string aObjName, std::ostream& stream) const;
+
+ private:
+#ifdef DEBUG_REGIONS
+  class OperationStringGenerator {
+   public:
+    virtual ~OperationStringGenerator() = default;
+
+    virtual void OutputOp() = 0;
+  };
+#endif
+ public:
+  void AssertStateInternal() const;
+  void AssertState() const {
+#ifdef DEBUG_REGIONS
+    AssertStateInternal();
+#endif
+  }
+
+ private:
+  void And(BandArray& aOut, const BandArray& aIn1, const BandArray& aIn2) {
+    size_t idx = 0;
+    size_t idxOther = 0;
+
+    // This algorithm essentially forms a new list of bands, by iterating over
+    // both regions' lists of band simultaneously, and building a new band
+    // wherever the two regions intersect.
+    while (true) {
+      while (true) {
+        while (idx != aIn1.Length() && aIn1[idx].bottom <= aIn2[idxOther].top) {
+          // Increment our current band until it ends beyond aOther's current
+          // band.
+          idx++;
+        }
+
+        if (idx == aIn1.Length()) {
+          // This region is out of bands, the other region's future bands are
+          // ignored.
+          break;
+        }
+
+        while (idxOther != aIn2.Length() &&
+               aIn2[idxOther].bottom <= aIn1[idx].top) {
+          // Increment aOther's current band until it ends beyond our current
+          // band.
+          idxOther++;
+        }
+
+        if (idxOther == aIn2.Length()) {
+          // The other region's bands are all processed, all our future bands
+          // are ignored.
+          break;
+        }
+
+        if (aIn2[idxOther].top < aIn1[idx].bottom) {
+          // We know the other band's bottom lies beyond our band's top because
+          // otherwise we would've incremented above. Intersecting bands found.
+          break;
+        }
+      }
+
+      if (idx == aIn1.Length() || idxOther == aIn2.Length()) {
+        // The above loop executed a break because we're done.
+        break;
+      }
+
+      Band newBand(aIn1[idx]);
+      // The new band is the intersection of the two current bands from both
+      // regions.
+      newBand.top = std::max(aIn1[idx].top, aIn2[idxOther].top);
+      newBand.bottom = std::min(aIn1[idx].bottom, aIn2[idxOther].bottom);
+      newBand.IntersectStrips(aIn2[idxOther]);
+
+      if (newBand.mStrips.Length()) {
+        // The intersecting area of the bands had overlapping strips, if it is
+        // identical to the band above it merge, otherwise append.
+        if (aOut.Length() && aOut.LastElement().bottom == newBand.top &&
+            aOut.LastElement().EqualStrips(newBand)) {
+          aOut.LastElement().bottom = newBand.bottom;
+        } else {
+          aOut.AppendElement(std::move(newBand));
+        }
+      }
+
+      if (aIn2[idxOther].bottom < aIn1[idx].bottom) {
+        idxOther++;
+        if (idxOther == aIn2.Length()) {
+          // Since we will access idxOther the next iteration, check if we're
+          // not done.
+          break;
+        }
+      } else {
+        // No need to check here since we do at the beginning of the next
+        // iteration.
+        idx++;
+      }
+    }
+  }
+
+ public:
+  nsRegion& AndWith(const nsRegion& aRegion) {
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorAndWith : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorAndWith(nsRegion& aRegion,
+                                      const nsRegion& aOtherRegion)
+          : mRegion(&aRegion),
+            mRegionCopy(aRegion),
+            mOtherRegion(aOtherRegion) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorAndWith() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegionCopy.OutputToStream("r1", stream);
+        mOtherRegion.OutputToStream("r2", stream);
+        stream << "r1.AndWith(r2);\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegionCopy;
+      nsRegion mOtherRegion;
+    };
+
+    OperationStringGeneratorAndWith opGenerator(*this, aRegion);
+#endif
+    if (mBounds.IsEmpty()) {
+      // Region is empty, stays empty.
+      return *this;
+    }
+
+    if (aRegion.IsEmpty()) {
+      SetEmpty();
+      return *this;
+    }
+
+    if (aRegion.mBands.IsEmpty()) {
+      // Other region is a rect.
+      return AndWith(aRegion.mBounds);
+    }
+
+    if (mBands.IsEmpty()) {
+      mBands.AppendElement(mBounds);
+    }
+
+    BandArray newBands;
+
+    And(newBands, mBands, aRegion.mBands);
+
+    mBands = std::move(newBands);
+    if (!mBands.Length()) {
+      mBounds = nsRectAbsolute();
+    } else {
+      mBounds = CalculateBounds();
+    }
+
+    EnsureSimplified();
+    AssertState();
+    return *this;
+  }
+
+  nsRegion& AndWith(const nsRectAbsolute& aRect) {
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorAndWith : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorAndWith(nsRegion& aRegion,
+                                      const nsRectAbsolute& aRect)
+          : mRegion(&aRegion), mRegionCopy(aRegion), mRect(aRect) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorAndWith() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegionCopy.OutputToStream("r", stream);
+        stream << "r.AndWith(nsRect(" << mRect.X() << ", " << mRect.Y() << ", "
+               << mRect.Width() << ", " << mRect.Height() << "));\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegionCopy;
+      nsRectAbsolute mRect;
+    };
+
+    OperationStringGeneratorAndWith opGenerator(*this, aRect);
+#endif
+    if (aRect.IsEmpty()) {
+      SetEmpty();
+      return *this;
+    }
+
+    if (mBands.IsEmpty()) {
+      mBounds = mBounds.Intersect(aRect);
+      return *this;
+    }
+
+    size_t idx = 0;
+
+    size_t removeStart = 0;
+
+    // This removes all bands that do not intersect with aRect, and intersects
+    // the remaining ones with aRect.
+
+    // Start by figuring out how much to remove from the start.
+    while (idx != mBands.Length() && mBands[idx].bottom <= aRect.Y()) {
+      idx++;
+    }
+
+    // We'll remove these later to avoid needless copying in the array.
+    removeStart = idx;
+
+    while (idx != mBands.Length()) {
+      if (mBands[idx].top >= aRect.YMost()) {
+        mBands.TruncateLength(idx);
+        break;
+      }
+
+      mBands[idx].top = std::max(mBands[idx].top, aRect.Y());
+      mBands[idx].bottom = std::min(mBands[idx].bottom, aRect.YMost());
+
+      mBands[idx].IntersectStrip(Strip(aRect.X(), aRect.XMost()));
+
+      if (!mBands[idx].mStrips.Length()) {
+        mBands.RemoveElementAt(idx);
+      } else {
+        if (idx > removeStart) {
+          CompressBefore(idx);
+        }
+        idx++;
+      }
+    }
+
+    if (removeStart) {
+      mBands.RemoveElementsAt(0, removeStart);
+    }
+
+    if (mBands.Length()) {
+      mBounds = CalculateBounds();
+    } else {
+      mBounds.SetEmpty();
+    }
+    EnsureSimplified();
+    AssertState();
+    return *this;
+  }
+  nsRegion& AndWith(const nsRect& aRect) {
+    return AndWith(nsRectAbsolute::FromRect(aRect));
+  }
+  nsRegion& And(const nsRegion& aRgn1, const nsRegion& aRgn2) {
+    if (&aRgn1 == this) {
+      return AndWith(aRgn2);
+    }
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorAnd : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorAnd(nsRegion& aRegion, const nsRegion& aRegion1,
+                                  const nsRegion& aRegion2)
+          : mRegion(&aRegion), mRegion1(aRegion1), mRegion2(aRegion2) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorAnd() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegion1.OutputToStream("r1", stream);
+        mRegion2.OutputToStream("r2", stream);
+        stream << "nsRegion r3;\nr3.And(r1, r2);\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegion1;
+      nsRegion mRegion2;
+    };
+
+    OperationStringGeneratorAnd opGenerator(*this, aRgn1, aRgn2);
+#endif
+    mBands.Clear();
+
+    if (aRgn1.IsEmpty() || aRgn2.IsEmpty()) {
+      mBounds.SetEmpty();
+      return *this;
+    }
+
+    if (aRgn1.mBands.IsEmpty() && aRgn2.mBands.IsEmpty()) {
+      mBounds = aRgn1.mBounds.Intersect(aRgn2.mBounds);
+      return *this;
+    } else if (aRgn1.mBands.IsEmpty()) {
+      return And(aRgn2, aRgn1.mBounds);
+    } else if (aRgn2.mBands.IsEmpty()) {
+      return And(aRgn1, aRgn2.mBounds);
+    }
+
+    And(mBands, aRgn1.mBands, aRgn2.mBands);
+
+    if (!mBands.Length()) {
+      mBounds = nsRectAbsolute();
+    } else {
+      mBounds = CalculateBounds();
+    }
+
+    EnsureSimplified();
+    AssertState();
+    return *this;
+  }
+  nsRegion& And(const nsRect& aRect, const nsRegion& aRegion) {
+    return And(aRegion, aRect);
+  }
+  nsRegion& And(const nsRegion& aRegion, const nsRectAbsolute& aRect) {
+    if (&aRegion == this) {
+      return AndWith(aRect);
+    }
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorAnd : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorAnd(nsRegion& aThisRegion,
+                                  const nsRegion& aRegion,
+                                  const nsRectAbsolute& aRect)
+          : mThisRegion(&aThisRegion), mRegion(aRegion), mRect(aRect) {
+        aThisRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorAnd() {
+        mThisRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegion.OutputToStream("r", stream);
+        stream << "nsRegion r2;\nr.And(r2, nsRect(" << mRect.X() << ", "
+               << mRect.Y() << ", " << mRect.Width() << ", " << mRect.Height()
+               << "));\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mThisRegion;
+      nsRegion mRegion;
+      nsRectAbsolute mRect;
+    };
+
+    OperationStringGeneratorAnd opGenerator(*this, aRegion, aRect);
+#endif
+    mBands.Clear();
+
+    if (aRect.IsEmpty()) {
+      mBounds.SetEmpty();
+      return *this;
+    }
+
+    if (aRegion.mBands.IsEmpty()) {
+      mBounds = aRegion.mBounds.Intersect(aRect);
+      return *this;
+    }
+
+    size_t idx = 0;
+    const BandArray& bands = aRegion.mBands;
+
+    mBands.SetCapacity(bands.Length() + 3);
+    while (idx != bands.Length()) {
+      // Ignore anything before.
+      if (bands[idx].bottom <= aRect.Y()) {
+        idx++;
+        continue;
+      }
+      // We're done once we've reached the bottom.
+      if (bands[idx].top >= aRect.YMost()) {
+        break;
+      }
+
+      // Now deal with bands actually intersecting the rectangle.
+      Band newBand(bands[idx]);
+      newBand.top = std::max(bands[idx].top, aRect.Y());
+      newBand.bottom = std::min(bands[idx].bottom, aRect.YMost());
+
+      newBand.IntersectStrip(Strip(aRect.X(), aRect.XMost()));
+
+      if (newBand.mStrips.Length()) {
+        if (!mBands.IsEmpty() && newBand.top == mBands.LastElement().bottom &&
+            newBand.EqualStrips(mBands.LastElement())) {
+          mBands.LastElement().bottom = newBand.bottom;
+        } else {
+          mBands.AppendElement(std::move(newBand));
+        }
+      }
+      idx++;
+    }
+
+    if (mBands.Length()) {
+      mBounds = CalculateBounds();
+    } else {
+      mBounds.SetEmpty();
+    }
+
+    EnsureSimplified();
+    AssertState();
+    return *this;
+  }
+  nsRegion& And(const nsRegion& aRegion, const nsRect& aRect) {
+    return And(aRegion, nsRectAbsolute::FromRect(aRect));
+  }
+  nsRegion& And(const nsRect& aRect1, const nsRect& aRect2) {
+    nsRect tmpRect;
+
+    tmpRect.IntersectRect(aRect1, aRect2);
+    return Copy(tmpRect);
+  }
+
+  nsRegion& OrWith(const nsRegion& aOther) {
+    for (RectIterator idx(aOther); !idx.Done(); idx.Next()) {
+      AddRect(idx.GetAbsolute());
+    }
+    return *this;
+  }
+  nsRegion& OrWith(const nsRect& aOther) {
+    AddRect(nsRectAbsolute::FromRect(aOther));
+    return *this;
+  }
+  nsRegion& Or(const nsRegion& aRgn1, const nsRegion& aRgn2) {
+    if (&aRgn1 != this) {
+      *this = aRgn1;
+    }
+    for (RectIterator idx(aRgn2); !idx.Done(); idx.Next()) {
+      AddRect(idx.GetAbsolute());
+    }
+    return *this;
+  }
+  nsRegion& Or(const nsRegion& aRegion, const nsRect& aRect) {
+    if (&aRegion != this) {
+      *this = aRegion;
+    }
+    AddRect(nsRectAbsolute::FromRect(aRect));
+    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& SubWith(const nsRegion& aOther) {
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorSubWith : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorSubWith(nsRegion& aRegion,
+                                      const nsRegion& aOtherRegion)
+          : mRegion(&aRegion),
+            mRegionCopy(aRegion),
+            mOtherRegion(aOtherRegion) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorSubWith() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegionCopy.OutputToStream("r1", stream);
+        mOtherRegion.OutputToStream("r2", stream);
+        stream << "r1.SubWith(r2);\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegionCopy;
+      nsRegion mOtherRegion;
+    };
+
+    OperationStringGeneratorSubWith opGenerator(*this, aOther);
+#endif
+
+    if (mBounds.IsEmpty()) {
+      return *this;
+    }
+
+    if (aOther.mBands.IsEmpty()) {
+      return SubWith(aOther.mBounds);
+    }
+
+    if (mBands.IsEmpty()) {
+      mBands.AppendElement(Band(mBounds));
+    }
+
+    size_t idx = 0;
+    size_t idxOther = 0;
+    while (idx < mBands.Length()) {
+      while (true) {
+        while (idx != mBands.Length() &&
+               mBands[idx].bottom <= aOther.mBands[idxOther].top) {
+          // Increment our current band until it ends beyond aOther's current
+          // band.
+          idx++;
+        }
+
+        if (idx == mBands.Length()) {
+          // This region is out of bands, the other region's future bands are
+          // ignored.
+          break;
+        }
+
+        while (idxOther != aOther.mBands.Length() &&
+               aOther.mBands[idxOther].bottom <= mBands[idx].top) {
+          // Increment aOther's current band until it ends beyond our current
+          // band.
+          idxOther++;
+        }
+
+        if (idxOther == aOther.mBands.Length()) {
+          // The other region's bands are all processed, all our future bands
+          // are ignored.
+          break;
+        }
+
+        if (aOther.mBands[idxOther].top < mBands[idx].bottom) {
+          // We know the other band's bottom lies beyond our band's top because
+          // otherwise we would've incremented above. Intersecting bands found.
+          break;
+        }
+      }
+
+      if (idx == mBands.Length() || idxOther == aOther.mBands.Length()) {
+        // The above loop executed a break because we're done.
+        break;
+      }
+
+      const Band& bandOther = aOther.mBands[idxOther];
+
+      if (!mBands[idx].Intersects(bandOther)) {
+        if (mBands[idx].bottom < bandOther.bottom) {
+          idx++;
+        } else {
+          idxOther++;
+          if (idxOther == aOther.mBands.Length()) {
+            break;
+          }
+        }
+        continue;
+      }
+
+      // These bands actually intersect.
+      if (mBands[idx].top < bandOther.top) {
+        mBands.InsertElementAt(idx + 1, Band(mBands[idx]));
+        mBands[idx].bottom = bandOther.top;
+        idx++;
+        mBands[idx].top = bandOther.top;
+      }
+
+      // mBands[idx].top >= bandOther.top;
+      if (mBands[idx].bottom <= bandOther.bottom) {
+        mBands[idx].SubStrips(bandOther);
+        if (mBands[idx].mStrips.IsEmpty()) {
+          mBands.RemoveElementAt(idx);
+        } else {
+          CompressBefore(idx);
+          idx++;
+          // The band before us just changed, it may be identical now.
+          CompressBefore(idx);
+        }
+        continue;
+      }
+
+      // mBands[idx].bottom > bandOther.bottom
+      Band newBand = mBands[idx];
+      newBand.SubStrips(bandOther);
+
+      if (!newBand.mStrips.IsEmpty()) {
+        mBands.InsertElementAt(idx, newBand);
+        mBands[idx].bottom = bandOther.bottom;
+        CompressBefore(idx);
+        idx++;
+      }
+
+      mBands[idx].top = bandOther.bottom;
+
+      idxOther++;
+      if (idxOther == aOther.mBands.Length()) {
+        break;
+      }
+    }
+
+    if (mBands.IsEmpty()) {
+      mBounds.SetEmpty();
+    } else {
+      mBounds = CalculateBounds();
+    }
+
+    AssertState();
+    EnsureSimplified();
+    return *this;
+  }
+  nsRegion& SubOut(const nsRegion& aOther) { return SubWith(aOther); }
+  nsRegion& SubOut(const nsRect& aOther) { return SubWith(aOther); }
+
+ private:
+  void AppendOrExtend(const Band& aNewBand) {
+    if (aNewBand.mStrips.IsEmpty()) {
+      return;
+    }
+    if (mBands.IsEmpty()) {
+      mBands.AppendElement(aNewBand);
+      return;
+    }
+
+    if (mBands.LastElement().bottom == aNewBand.top &&
+        mBands.LastElement().EqualStrips(aNewBand)) {
+      mBands.LastElement().bottom = aNewBand.bottom;
+    } else {
+      mBands.AppendElement(aNewBand);
+    }
+  }
+  void AppendOrExtend(const Band&& aNewBand) {
+    if (aNewBand.mStrips.IsEmpty()) {
+      return;
+    }
+    if (mBands.IsEmpty()) {
+      mBands.AppendElement(std::move(aNewBand));
+      return;
+    }
+
+    if (mBands.LastElement().bottom == aNewBand.top &&
+        mBands.LastElement().EqualStrips(aNewBand)) {
+      mBands.LastElement().bottom = aNewBand.bottom;
+    } else {
+      mBands.AppendElement(std::move(aNewBand));
+    }
+  }
+
+ public:
+  nsRegion& Sub(const nsRegion& aRgn1, const nsRegion& aRgn2) {
+    if (&aRgn1 == this) {
+      return SubWith(aRgn2);
+    }
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorSub : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorSub(nsRegion& aRegion, const nsRegion& aRgn1,
+                                  const nsRegion& aRgn2)
+          : mRegion(&aRegion), mRegion1(aRgn1), mRegion2(aRgn2) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorSub() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegion1.OutputToStream("r1", stream);
+        mRegion2.OutputToStream("r2", stream);
+        stream << "nsRegion r3;\nr3.Sub(r1, r2);\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegion1;
+      nsRegion mRegion2;
+    };
+
+    OperationStringGeneratorSub opGenerator(*this, aRgn1, aRgn2);
+#endif
+
+    mBands.Clear();
+
+    if (aRgn1.mBounds.IsEmpty()) {
+      mBounds.SetEmpty();
+      return *this;
+    }
+
+    if (aRgn2.mBounds.IsEmpty()) {
+      Copy(aRgn1);
+      return *this;
+    }
+
+    if (aRgn1.mBands.IsEmpty() && aRgn2.mBands.IsEmpty()) {
+      return Sub(aRgn1.mBounds, aRgn2.mBounds);
+    } else if (aRgn1.mBands.IsEmpty()) {
+      return Sub(aRgn1.mBounds, aRgn2);
+    } else if (aRgn2.mBands.IsEmpty()) {
+      return Sub(aRgn1, aRgn2.mBounds);
+    }
+
+    const BandArray& bands1 = aRgn1.mBands;
+    const BandArray& bands2 = aRgn2.mBands;
+
+    size_t idx = 0;
+    size_t idxOther = 0;
+
+    // We iterate the source region's bands, subtracting the other regions bands
+    // from them as we move them into ours.
+    while (idx < bands1.Length()) {
+      while (idxOther < bands2.Length() &&
+             bands2[idxOther].bottom <= bands1[idx].top) {
+        // These other bands are irrelevant as they don't intersect with the
+        // band we're currently processing.
+        idxOther++;
+      }
+      if (idxOther == bands2.Length()) {
+        break;
+      }
+
+      const Band& other = bands2[idxOther];
+
+      // bands2[idxOther].bottom >= bands1[idx].top
+      Band origBand(bands1[idx]);
+      if (other.top >= origBand.bottom) {
+        // No intersecting bands, append and continue.
+        AppendOrExtend(origBand);
+        idx++;
+        continue;
+      }
+
+      // Push a band for an uncovered region above our band.
+      if (origBand.top < other.top) {
+        Band newBand(origBand);
+        newBand.bottom = other.top;
+        AppendOrExtend(std::move(newBand));
+      }
+
+      int32_t lastBottom = std::max(other.top, origBand.top);
+      while (idxOther < bands2.Length() &&
+             bands2[idxOther].top < origBand.bottom) {
+        const Band& other = bands2[idxOther];
+        Band newBand(origBand);
+        newBand.top = std::max(origBand.top, other.top);
+        newBand.bottom = std::min(origBand.bottom, other.bottom);
+
+        // If there was a gap, we need to add the original band there.
+        if (newBand.top > lastBottom) {
+          Band betweenBand(newBand);
+          betweenBand.top = lastBottom;
+          betweenBand.bottom = newBand.top;
+          AppendOrExtend(std::move(betweenBand));
+        }
+
+        lastBottom = newBand.bottom;
+        newBand.SubStrips(other);
+        AppendOrExtend(std::move(newBand));
+        idxOther++;
+      }
+      // Decrement other here so we are back at the last band in region 2
+      // that intersected.
+      idxOther--;
+
+      if (bands2[idxOther].bottom < origBand.bottom) {
+        // The last band in region2 that intersected ended before this one,
+        // we can copy the rest.
+        Band newBand(origBand);
+        newBand.top = bands2[idxOther].bottom;
+        AppendOrExtend(std::move(newBand));
+        idxOther++;
+      }
+      idx++;
+    }
+
+    // Copy any remaining bands, the first one may have to be extended to fit
+    // the last one added before. The rest can be unconditionally appended.
+    if (idx < bands1.Length()) {
+      AppendOrExtend(bands1[idx]);
+      idx++;
+    }
+
+    while (idx < bands1.Length()) {
+      mBands.AppendElement(bands1[idx]);
+      idx++;
+    }
+
+    if (mBands.IsEmpty()) {
+      mBounds.SetEmpty();
+    } else {
+      mBounds = CalculateBounds();
+    }
+
+    AssertState();
+    EnsureSimplified();
+    return *this;
+  }
+
+ private:
+  // Internal helper for executing subtraction.
+  void RunSubtraction(const nsRectAbsolute& aRect) {
+    Strip rectStrip(aRect.X(), aRect.XMost());
+
+    size_t idx = 0;
+
+    while (idx < mBands.Length()) {
+      if (mBands[idx].top >= aRect.YMost()) {
+        return;
+      }
+
+      if (mBands[idx].bottom <= aRect.Y()) {
+        // This band is entirely before aRect, move on.
+        idx++;
+        continue;
+      }
+
+      if (!mBands[idx].Intersects(Strip(aRect.X(), aRect.XMost()))) {
+        // This band does not intersect aRect horizontally. Move on.
+        idx++;
+        continue;
+      }
+
+      // This band intersects with aRect.
+
+      if (mBands[idx].top < aRect.Y()) {
+        // This band starts above the start of aRect, split the band into two
+        // along the intersection, and continue to the next iteration to process
+        // the one that now intersects exactly.
+        auto above = mBands.InsertElementAt(idx, Band(mBands[idx]));
+        above->bottom = aRect.Y();
+        idx++;
+        mBands[idx].top = aRect.Y();
+        // Continue to run the loop for the next band.
+        continue;
+      }
+
+      if (mBands[idx].bottom <= aRect.YMost()) {
+        // This band ends before the end of aRect.
+        mBands[idx].SubStrip(rectStrip);
+        if (mBands[idx].mStrips.Length()) {
+          CompressAdjacentBands(idx);
+        } else {
+          mBands.RemoveElementAt(idx);
+        }
+        continue;
+      }
+
+      // This band extends beyond aRect.
+      Band newBand = mBands[idx];
+      newBand.SubStrip(rectStrip);
+      newBand.bottom = aRect.YMost();
+      mBands[idx].top = aRect.YMost();
+
+      if (newBand.mStrips.Length()) {
+        if (idx && mBands[idx - 1].bottom == newBand.top &&
+            newBand.EqualStrips(mBands[idx - 1])) {
+          mBands[idx - 1].bottom = aRect.YMost();
+        } else {
+          mBands.InsertElementAt(idx, std::move(newBand));
+        }
+      }
+
+      return;
+    }
+  }
+
+ public:
+  nsRegion& SubWith(const nsRectAbsolute& aRect) {
+    if (!mBounds.Intersects(aRect)) {
+      return *this;
+    }
+
+    if (aRect.Contains(mBounds)) {
+      SetEmpty();
+      return *this;
+    }
+
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorSubWith : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorSubWith(nsRegion& aRegion,
+                                      const nsRectAbsolute& aRect)
+          : mRegion(&aRegion), mRegionCopy(aRegion), mRect(aRect) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorSubWith() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegionCopy.OutputToStream("r", stream);
+        stream << "r.SubWith(nsRect(" << mRect.X() << ", " << mRect.Y() << ", "
+               << mRect.Width() << ", " << mRect.Height() << "));\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegionCopy;
+      nsRectAbsolute mRect;
+    };
+
+    OperationStringGeneratorSubWith opGenerator(*this, aRect);
+#endif
+
+    if (mBands.IsEmpty()) {
+      mBands.AppendElement(Band(mBounds));
+    }
+
+    RunSubtraction(aRect);
+
+    if (aRect.X() <= mBounds.X() || aRect.Y() <= mBounds.Y() ||
+        aRect.XMost() >= mBounds.XMost() || aRect.YMost() >= mBounds.YMost()) {
+      mBounds = CalculateBounds();
+    }
+    EnsureSimplified();
+    AssertState();
+    return *this;
+  }
+  nsRegion& Sub(const nsRegion& aRegion, const nsRectAbsolute& aRect) {
+    if (aRect.Contains(aRegion.mBounds)) {
+      SetEmpty();
+      return *this;
+    }
+    if (&aRegion == this) {
+      return SubWith(aRect);
+    }
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorSub : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorSub(nsRegion& aRegion,
+                                  const nsRegion& aRegionOther,
+                                  const nsRectAbsolute& aRect)
+          : mRegion(&aRegion), mRegionOther(aRegionOther), mRect(aRect) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorSub() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegionOther.OutputToStream("r1", stream);
+        stream << "nsRegion r2;\nr2.Sub(r1, nsRect(" << mRect.X() << ", "
+               << mRect.Y() << ", " << mRect.Width() << ", " << mRect.Height()
+               << "));\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegionOther;
+      nsRectAbsolute mRect;
+    };
+
+    OperationStringGeneratorSub opGenerator(*this, aRegion, aRect);
+#endif
+
+    mBands.Clear();
+
+    if (aRegion.mBounds.IsEmpty()) {
+      mBounds.SetEmpty();
+      return *this;
+    }
+
+    if (aRect.IsEmpty()) {
+      Copy(aRegion);
+      return *this;
+    }
+
+    if (aRegion.mBands.IsEmpty()) {
+      Copy(aRegion.mBounds);
+      return SubWith(aRect);
+    }
+
+    const BandArray& bands = aRegion.mBands;
+
+    size_t idx = 0;
+
+    Strip strip(aRect.X(), aRect.XMost());
+
+    mBands.SetCapacity(bands.Length() + 3);
+
+    // Process all bands that lie before aRect.
+    while (idx < bands.Length() && bands[idx].bottom <= aRect.Y()) {
+      mBands.AppendElement(bands[idx]);
+      idx++;
+    }
+
+    // This band's bottom lies beyond aRect.
+    if (idx < bands.Length() && bands[idx].top < aRect.Y()) {
+      Band newBand(bands[idx]);
+      if (bands[idx].Intersects(strip)) {
+        newBand.bottom = aRect.Y();
+      } else {
+        idx++;
+      }
+      mBands.AppendElement(std::move(newBand));
+    }
+
+    // This tracks whether the band when we -exit- the next loop intersected the
+    // rectangle.
+    bool didIntersect = false;
+
+    while (idx < bands.Length() && bands[idx].top < aRect.YMost()) {
+      // Process all bands intersecting with aRect.
+      if (!bands[idx].Intersects(strip)) {
+        AppendOrExtend(bands[idx]);
+        idx++;
+        didIntersect = false;
+        continue;
+      }
+
+      didIntersect = true;
+      Band newBand(bands[idx]);
+      newBand.top = std::max(newBand.top, aRect.Y());
+      newBand.bottom = std::min(newBand.bottom, aRect.YMost());
+      newBand.SubStrip(strip);
+      AppendOrExtend(std::move(newBand));
+      idx++;
+    }
+
+    if (didIntersect) {
+      if (aRect.YMost() < bands[idx - 1].bottom) {
+        // If this band does not intersect the loop above has already added the
+        // whole unmodified band.
+        Band newBand(bands[idx - 1]);
+        newBand.top = aRect.YMost();
+        AppendOrExtend(std::move(newBand));
+      }
+    }
+
+    // Now process all bands beyond aRect.
+    if (idx < bands.Length()) {
+      AppendOrExtend(bands[idx]);
+      idx++;
+    }
+
+    mBands.AppendElements(bands.Elements() + idx, bands.Length() - idx);
+
+    if (mBands.IsEmpty()) {
+      mBounds.SetEmpty();
+    } else {
+      mBounds = CalculateBounds();
+    }
+
+    AssertState();
+    EnsureSimplified();
+    return *this;
+  }
+  nsRegion& SubWith(const nsRect& aRect) {
+    return SubWith(nsRectAbsolute::FromRect(aRect));
+  }
+  nsRegion& Sub(const nsRect& aRect, const nsRegion& aRegion) {
+    Copy(aRect);
+    return SubWith(aRegion);
+  }
+  nsRegion& Sub(const nsRectAbsolute& aRect, const nsRegion& aRegion) {
+    Copy(aRect);
+    return SubWith(aRegion);
+  }
+  nsRegion& Sub(const nsRect& aRect1, const nsRect& aRect2) {
+    Copy(aRect1);
+    return SubWith(aRect2);
+  }
+  nsRegion& Sub(const nsRegion& aRegion, const nsRect& aRect) {
+    return Sub(aRegion, nsRectAbsolute::FromRect(aRect));
+  }
+  nsRegion& Sub(const nsRectAbsolute& aRect1, const nsRectAbsolute& aRect2) {
+    Copy(aRect1);
+    return SubWith(aRect2);
+  }
+
+  /**
+   * Returns true if 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 {
+    if (mBands.IsEmpty()) {
+      return mBounds.Contains(aX, aY);
+    }
+
+    auto iter = mBands.begin();
+
+    while (iter != mBands.end()) {
+      if (iter->bottom <= aY) {
+        iter++;
+        continue;
+      }
+
+      if (iter->top > aY) {
+        return false;
+      }
+
+      if (iter->ContainsStrip(Strip(aX, aX + 1))) {
+        return true;
+      }
+      return false;
+    }
+    return false;
+  }
+  bool Contains(const nsRectAbsolute& aRect) const {
+    if (aRect.IsEmpty()) {
+      return false;
+    }
+
+    if (mBands.IsEmpty()) {
+      return mBounds.Contains(aRect);
+    }
+
+    auto iter = mBands.begin();
+
+    while (iter != mBands.end()) {
+      if (iter->bottom <= aRect.Y()) {
+        iter++;
+        continue;
+      }
+
+      if (iter->top > aRect.Y()) {
+        return false;
+      }
+
+      // Now inside the rectangle.
+      if (!iter->ContainsStrip(Strip(aRect.X(), aRect.XMost()))) {
+        return false;
+      }
+
+      if (iter->bottom >= aRect.YMost()) {
+        return true;
+      }
+
+      int32_t lastY = iter->bottom;
+      iter++;
+      while (iter != mBands.end()) {
+        // Bands do not connect.
+        if (iter->top != lastY) {
+          return false;
+        }
+
+        if (!iter->ContainsStrip(Strip(aRect.X(), aRect.XMost()))) {
+          return false;
+        }
+
+        if (iter->bottom >= aRect.YMost()) {
+          return true;
+        }
+
+        lastY = iter->bottom;
+        iter++;
+      }
+    }
+    return false;
+  }
+  bool Contains(const nsRect& aRect) const {
+    return Contains(nsRectAbsolute::FromRect(aRect));
+  }
+
+  bool Contains(const nsRegion& aRgn) const;
+  bool Intersects(const nsRectAbsolute& aRect) const;
+  bool Intersects(const nsRect& aRect) const {
+    return Intersects(nsRectAbsolute::FromRect(aRect));
+  }
+
+  void MoveBy(int32_t aXOffset, int32_t aYOffset) {
+    MoveBy(nsPoint(aXOffset, aYOffset));
+  }
+  void MoveBy(nsPoint aPt) {
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorMoveBy : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorMoveBy(nsRegion& aRegion, const nsPoint& aPoint)
+          : mRegion(&aRegion), mRegionCopy(aRegion), mPoint(aPoint) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorMoveBy() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegionCopy.OutputToStream("r", stream);
+        stream << "r.MoveBy(nsPoint(" << mPoint.x << ", " << mPoint.y
+               << "));\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegionCopy;
+      nsPoint mPoint;
+    };
+
+    OperationStringGeneratorMoveBy opGenerator(*this, aPt);
+#endif
+
+    mBounds.MoveBy(aPt);
+    for (Band& band : mBands) {
+      band.top += aPt.Y();
+      band.bottom += aPt.Y();
+      for (Strip& strip : band.mStrips) {
+        strip.left += aPt.X();
+        strip.right += aPt.X();
+      }
+    }
+    AssertState();
+  }
+  void SetEmpty() {
+    mBands.Clear();
+    mBounds.SetEmpty();
+  }
+
+  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 mBounds.IsEmpty(); }
+  bool IsComplex() const { return GetNumRects() > 1; }
+  bool IsEqual(const nsRegion& aRegion) const {
+    if (!mBounds.IsEqualInterior(aRegion.mBounds)) {
+      return false;
+    }
+
+    if (mBands.Length() != aRegion.mBands.Length()) {
+      return false;
+    }
+
+    for (auto iter1 = mBands.begin(), iter2 = aRegion.mBands.begin();
+         iter1 != mBands.end(); iter1++, iter2++) {
+      if (iter1->top != iter2->top || iter1->bottom != iter2->bottom ||
+          !iter1->EqualStrips(*iter2)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  uint32_t GetNumRects() const {
+    if (mBands.IsEmpty()) {
+      return mBounds.IsEmpty() ? 0 : 1;
+    }
+
+    uint32_t rects = 0;
+
+    for (const Band& band : mBands) {
+      rects += band.mStrips.Length();
+    }
+
+    return rects;
+  }
+  const nsRect GetBounds() const { return mBounds.ToNSRect(); }
+  const nsRectAbsolute GetAbsoluteBounds() const { return mBounds; }
+  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
+   */
+  [[nodiscard]] nsRegion ScaleToOtherAppUnitsRoundOut(int32_t aFromAPP,
+                                                      int32_t aToAPP) const;
+  [[nodiscard]] 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) const;
+
+  nsCString ToString() const;
+
+  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;
+  }
+
+ private:
+  nsIntRegion ToPixels(nscoord aAppUnitsPerPixel, bool aOutsidePixels) const;
+
+  nsRegion& Copy(const nsRegion& aRegion) {
+    mBounds = aRegion.mBounds;
+    mBands = aRegion.mBands.Clone();
+    return *this;
+  }
+
+  nsRegion& Copy(const nsRect& aRect) {
+    mBands.Clear();
+    mBounds = nsRectAbsolute::FromRect(aRect);
+    return *this;
+  }
+
+  nsRegion& Copy(const nsRectAbsolute& aRect) {
+    mBands.Clear();
+    mBounds = aRect;
+    return *this;
+  }
+
+  void EnsureSimplified() {
+    if (mBands.Length() == 1 && mBands.begin()->mStrips.Length() == 1) {
+      mBands.Clear();
+    }
+  }
+
+  static inline nsRectAbsolute BoxToRect(const pixman_box32_t& aBox) {
+    return nsRectAbsolute(aBox.x1, aBox.y1, aBox.x2, aBox.y2);
+  }
+
+  void AddRect(const nsRectAbsolute& aRect) {
+#ifdef DEBUG_REGIONS
+    class OperationStringGeneratorAddRect : public OperationStringGenerator {
+     public:
+      OperationStringGeneratorAddRect(nsRegion& aRegion,
+                                      const nsRectAbsolute& aRect)
+          : mRegion(&aRegion), mRegionCopy(aRegion), mRect(aRect) {
+        aRegion.mCurrentOpGenerator = this;
+      }
+      virtual ~OperationStringGeneratorAddRect() {
+        mRegion->mCurrentOpGenerator = nullptr;
+      }
+
+      virtual void OutputOp() override {
+        std::stringstream stream;
+        mRegionCopy.OutputToStream("r", stream);
+        stream << "r.OrWith(nsRect(" << mRect.X() << ", " << mRect.Y() << ", "
+               << mRect.Width() << ", " << mRect.Height() << "));\n";
+        gfxCriticalError() << stream.str();
+      }
+
+     private:
+      nsRegion* mRegion;
+      nsRegion mRegionCopy;
+      nsRectAbsolute mRect;
+    };
+
+    OperationStringGeneratorAddRect opGenerator(*this, aRect);
+#endif
+    if (aRect.IsEmpty()) {
+      return;
+    }
+
+    if (mBands.IsEmpty()) {
+      if (mBounds.IsEmpty()) {
+        mBounds = aRect;
+        return;
+      } else if (mBounds.Contains(aRect)) {
+        return;
+      }
+
+      mBands.AppendElement(Band(mBounds));
+    }
+
+    mBounds = aRect.UnsafeUnion(mBounds);
+
+    size_t idx = 0;
+
+    Strip strip(aRect.X(), aRect.XMost());
+    Band remaining(aRect);
+
+    while (idx != mBands.Length()) {
+      if (mBands[idx].bottom <= remaining.top) {
+        // This band lies wholly above aRect.
+        idx++;
+        continue;
+      }
+
+      if (remaining.top >= remaining.bottom) {
+        AssertState();
+        EnsureSimplified();
+        return;
+      }
+
+      if (mBands[idx].top >= remaining.bottom) {
+        // This band lies wholly below aRect.
+        break;
+      }
+
+      if (mBands[idx].EqualStrips(remaining)) {
+        mBands[idx].top = std::min(mBands[idx].top, remaining.top);
+        // Nothing to do for this band. Just expand.
+        remaining.top = mBands[idx].bottom;
+        CompressBefore(idx);
+        idx++;
+        continue;
+      }
+
+      if (mBands[idx].top > remaining.top) {
+        auto before = mBands.InsertElementAt(idx, remaining);
+        before->bottom = mBands[idx + 1].top;
+        remaining.top = before->bottom;
+        CompressBefore(idx);
+        idx++;
+        CompressBefore(idx);
+        continue;
+      }
+
+      if (mBands[idx].ContainsStrip(strip)) {
+        remaining.top = mBands[idx].bottom;
+        idx++;
+        continue;
+      }
+
+      // mBands[idx].top <= remaining.top.
+
+      if (mBands[idx].top < remaining.top) {
+        auto before = mBands.InsertElementAt(idx, Band(mBands[idx]));
+        before->bottom = remaining.top;
+        idx++;
+        mBands[idx].top = remaining.top;
+        continue;
+      }
+
+      // mBands[idx].top == remaining.top
+      if (mBands[idx].bottom > remaining.bottom) {
+        auto below = mBands.InsertElementAt(idx + 1, Band(mBands[idx]));
+        below->top = remaining.bottom;
+        mBands[idx].bottom = remaining.bottom;
+      }
+
+      mBands[idx].InsertStrip(strip);
+      CompressBefore(idx);
+      remaining.top = mBands[idx].bottom;
+      idx++;
+      CompressBefore(idx);
+    }
+
+    if (remaining.top < remaining.bottom) {
+      // We didn't find any bands that overlapped aRect.
+      if (idx) {
+        if (mBands[idx - 1].bottom == remaining.top &&
+            mBands[idx - 1].EqualStrips(remaining)) {
+          mBands[idx - 1].bottom = remaining.bottom;
+          CompressBefore(idx);
+          AssertState();
+          EnsureSimplified();
+          return;
+        }
+      }
+      mBands.InsertElementAt(idx, remaining);
+      idx++;
+      CompressBefore(idx);
+    } else {
+      CompressBefore(idx);
+    }
+
+    AssertState();
+    EnsureSimplified();
+  }
+
+  // Most callers could probably do this on the fly, if this ever shows up
+  // in profiles we could optimize this.
+  nsRectAbsolute CalculateBounds() const {
+    if (mBands.IsEmpty()) {
+      return mBounds;
+    }
+
+    int32_t top = mBands.begin()->top;
+    int32_t bottom = mBands.LastElement().bottom;
+
+    int32_t leftMost = mBands.begin()->mStrips.begin()->left;
+    int32_t rightMost = mBands.begin()->mStrips.LastElement().right;
+    for (const Band& band : mBands) {
+      leftMost = std::min(leftMost, band.mStrips.begin()->left);
+      rightMost = std::max(rightMost, band.mStrips.LastElement().right);
+    }
+
+    return nsRectAbsolute(leftMost, top, rightMost, bottom);
+  }
+
+  static uint32_t ComputeMergedAreaIncrease(const Band& aTopBand,
+                                            const Band& aBottomBand);
+
+  // Returns true if idx is now referring to the 'next' band
+  bool CompressAdjacentBands(size_t& aIdx) {
+    if ((aIdx + 1) < mBands.Length()) {
+      if (mBands[aIdx + 1].top == mBands[aIdx].bottom &&
+          mBands[aIdx + 1].EqualStrips(mBands[aIdx])) {
+        mBands[aIdx].bottom = mBands[aIdx + 1].bottom;
+        mBands.RemoveElementAt(aIdx + 1);
+      }
+    }
+    if (aIdx) {
+      if (mBands[aIdx - 1].bottom == mBands[aIdx].top &&
+          mBands[aIdx].EqualStrips(mBands[aIdx - 1])) {
+        mBands[aIdx - 1].bottom = mBands[aIdx].bottom;
+        mBands.RemoveElementAt(aIdx);
+        return true;
+      }
+    }
+    return false;
+  }
+
+  void CompressBefore(size_t& aIdx) {
+    if (aIdx && aIdx < mBands.Length()) {
+      if (mBands[aIdx - 1].bottom == mBands[aIdx].top &&
+          mBands[aIdx - 1].EqualStrips(mBands[aIdx])) {
+        mBands[aIdx].top = mBands[aIdx - 1].top;
+        mBands.RemoveElementAt(aIdx - 1);
+        aIdx--;
+      }
+    }
+  }
+
+  BandArray mBands;
+  // Considering we only ever OR with nsRects, the bounds should fit in an
+  // nsRect as well.
+  nsRectAbsolute mBounds;
+#ifdef DEBUG_REGIONS
+  friend class OperationStringGenerator;
+  OperationStringGenerator* mCurrentOpGenerator;
+#endif
+
+ public:
+  class RectIterator {
+    const nsRegion& mRegion;
+    typename BandArray::const_iterator mCurrentBand;
+    typename StripArray::const_iterator mCurrentStrip;
+
+   public:
+    explicit RectIterator(const nsRegion& aRegion)
+        : mRegion(aRegion),
+          mCurrentBand(aRegion.mBands.begin())
+#ifndef DEBUG
+          ,
+          mCurrentStrip(nullptr)
+#endif
+    {
+      mIsDone = mRegion.mBounds.IsEmpty();
+      if (mCurrentBand != aRegion.mBands.end()) {
+        mCurrentStrip = mCurrentBand->mStrips.begin();
+      }
+    }
+
+    bool Done() const { return mIsDone; }
+
+    const nsRect Get() const {
+      if (mRegion.mBands.IsEmpty()) {
+        return mRegion.GetBounds();
+      }
+      return nsRect(mCurrentStrip->left, mCurrentBand->top,
+                    mCurrentStrip->right - mCurrentStrip->left,
+                    mCurrentBand->bottom - mCurrentBand->top);
+    }
+
+    const nsRectAbsolute GetAbsolute() const {
+      if (mRegion.mBands.IsEmpty()) {
+        return mRegion.mBounds;
+      }
+      return nsRectAbsolute(mCurrentStrip->left, mCurrentBand->top,
+                            mCurrentStrip->right, mCurrentBand->bottom);
+    }
+
+    void Next() {
+      if (mRegion.mBands.IsEmpty()) {
+        mIsDone = true;
+        return;
+      }
+
+      mCurrentStrip++;
+      if (mCurrentStrip == mCurrentBand->mStrips.end()) {
+        mCurrentBand++;
+        if (mCurrentBand != mRegion.mBands.end()) {
+          mCurrentStrip = mCurrentBand->mStrips.begin();
+        } else {
+          mIsDone = true;
+        }
+      }
+    }
+
+    bool mIsDone;
+  };
+
+  RectIterator RectIter() const { return RectIterator(*this); }
+};
+
+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() = default;
+  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(std::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 = std::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 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 = RectIterator(*this); !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) const {
+    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() = default;
+  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(std::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=(std::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