Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

1 files changed, 1224 insertions, 0 deletions

diff --git a/gfx/thebes/gfxBlur.cpp b/gfx/thebes/gfxBlur.cpp
new file mode 100644
index 0000000000..605bd5567c
--- /dev/null
+++ b/gfx/thebes/gfxBlur.cpp
@@ -0,0 +1,1224 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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/. */
+
+#include "gfxBlur.h"
+
+#include "gfx2DGlue.h"
+#include "gfxContext.h"
+#include "gfxPlatform.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Blur.h"
+#include "mozilla/gfx/PathHelpers.h"
+#include "mozilla/Maybe.h"
+#include "nsExpirationTracker.h"
+#include "nsClassHashtable.h"
+#include "gfxUtils.h"
+#include <limits>
+#include <cmath>
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+
+gfxAlphaBoxBlur::~gfxAlphaBoxBlur() = default;
+
+UniquePtr<gfxContext> gfxAlphaBoxBlur::Init(gfxContext* aDestinationCtx,
+                                            const gfxRect& aRect,
+                                            const IntSize& aSpreadRadius,
+                                            const IntSize& aBlurRadius,
+                                            const gfxRect* aDirtyRect,
+                                            const gfxRect* aSkipRect,
+                                            bool aUseHardwareAccel) {
+  DrawTarget* refDT = aDestinationCtx->GetDrawTarget();
+  Maybe<Rect> dirtyRect = aDirtyRect ? Some(ToRect(*aDirtyRect)) : Nothing();
+  Maybe<Rect> skipRect = aSkipRect ? Some(ToRect(*aSkipRect)) : Nothing();
+  RefPtr<DrawTarget> dt = InitDrawTarget(
+      refDT, ToRect(aRect), aSpreadRadius, aBlurRadius,
+      dirtyRect.ptrOr(nullptr), skipRect.ptrOr(nullptr), aUseHardwareAccel);
+  if (!dt || !dt->IsValid()) {
+    return nullptr;
+  }
+
+  auto context = MakeUnique<gfxContext>(dt);
+  context->SetMatrix(Matrix::Translation(-mBlur.GetRect().TopLeft()));
+  return context;
+}
+
+already_AddRefed<DrawTarget> gfxAlphaBoxBlur::InitDrawTarget(
+    const DrawTarget* aReferenceDT, const Rect& aRect,
+    const IntSize& aSpreadRadius, const IntSize& aBlurRadius,
+    const Rect* aDirtyRect, const Rect* aSkipRect, bool aUseHardwareAccel) {
+  mBlur.Init(aRect, aSpreadRadius, aBlurRadius, aDirtyRect, aSkipRect);
+  size_t blurDataSize = mBlur.GetSurfaceAllocationSize();
+  if (blurDataSize == 0) {
+    return nullptr;
+  }
+
+  BackendType backend = aReferenceDT->GetBackendType();
+
+  // Check if the backend has an accelerated DrawSurfaceWithShadow.
+  // Currently, only D2D1.1 supports this.
+  // Otherwise, DrawSurfaceWithShadow only supports square blurs without spread.
+  // When blurring small draw targets such as short spans text, the cost of
+  // creating and flushing an accelerated draw target may exceed the speedup
+  // gained from the faster blur. It's up to the users of this blur
+  // to determine whether they want to use hardware acceleration.
+  if (aBlurRadius.IsSquare() && aSpreadRadius.IsEmpty() && aUseHardwareAccel &&
+      backend == BackendType::DIRECT2D1_1) {
+    mAccelerated = true;
+  }
+
+  if (mAccelerated) {
+    // Note: CreateShadowDrawTarget is only implemented for Cairo.
+    mDrawTarget = aReferenceDT->CreateShadowDrawTarget(
+        mBlur.GetSize(), SurfaceFormat::A8,
+        AlphaBoxBlur::CalculateBlurSigma(aBlurRadius.width));
+    if (mDrawTarget) {
+      // See Bug 1526045 - this is to force DT initialization.
+      mDrawTarget->ClearRect(gfx::Rect());
+    }
+  } else {
+    // Make an alpha-only surface to draw on. We will play with the data after
+    // everything is drawn to create a blur effect.
+    // This will be freed when the DrawTarget dies
+    mData = static_cast<uint8_t*>(calloc(1, blurDataSize));
+    if (!mData) {
+      return nullptr;
+    }
+    mDrawTarget =
+        Factory::DoesBackendSupportDataDrawtarget(backend)
+            ? Factory::CreateDrawTargetForData(backend, mData, mBlur.GetSize(),
+                                               mBlur.GetStride(),
+                                               SurfaceFormat::A8)
+            : gfxPlatform::CreateDrawTargetForData(
+                  mData, mBlur.GetSize(), mBlur.GetStride(), SurfaceFormat::A8);
+  }
+
+  if (!mDrawTarget || !mDrawTarget->IsValid()) {
+    if (mData) {
+      free(mData);
+    }
+
+    return nullptr;
+  }
+
+  if (mData) {
+    mDrawTarget->AddUserData(reinterpret_cast<UserDataKey*>(mDrawTarget.get()),
+                             mData, free);
+  }
+
+  mDrawTarget->SetTransform(Matrix::Translation(-mBlur.GetRect().TopLeft()));
+  return do_AddRef(mDrawTarget);
+}
+
+already_AddRefed<SourceSurface> gfxAlphaBoxBlur::DoBlur(
+    const sRGBColor* aShadowColor, IntPoint* aOutTopLeft) {
+  if (aOutTopLeft) {
+    *aOutTopLeft = mBlur.GetRect().TopLeft();
+  }
+
+  RefPtr<SourceSurface> blurMask;
+  if (mData) {
+    mBlur.Blur(mData);
+    blurMask = mDrawTarget->Snapshot();
+  } else if (mAccelerated) {
+    blurMask = mDrawTarget->Snapshot();
+    RefPtr<DrawTarget> blurDT = mDrawTarget->CreateSimilarDrawTarget(
+        blurMask->GetSize(), SurfaceFormat::A8);
+    if (!blurDT) {
+      return nullptr;
+    }
+    blurDT->DrawSurfaceWithShadow(
+        blurMask, Point(0, 0),
+        ShadowOptions(
+            DeviceColor::MaskOpaqueWhite(), Point(0, 0),
+            AlphaBoxBlur::CalculateBlurSigma(mBlur.GetBlurRadius().width)),
+        CompositionOp::OP_OVER);
+    blurMask = blurDT->Snapshot();
+  }
+
+  if (!aShadowColor) {
+    return blurMask.forget();
+  }
+
+  RefPtr<DrawTarget> shadowDT = mDrawTarget->CreateSimilarDrawTarget(
+      blurMask->GetSize(), SurfaceFormat::B8G8R8A8);
+  if (!shadowDT) {
+    return nullptr;
+  }
+  ColorPattern shadowColor(ToDeviceColor(*aShadowColor));
+  shadowDT->MaskSurface(shadowColor, blurMask, Point(0, 0));
+
+  return shadowDT->Snapshot();
+}
+
+void gfxAlphaBoxBlur::Paint(gfxContext* aDestinationCtx) {
+  if (mDrawTarget && !mAccelerated && !mData) {
+    return;
+  }
+
+  DrawTarget* dest = aDestinationCtx->GetDrawTarget();
+  if (!dest) {
+    NS_WARNING("Blurring not supported for Thebes contexts!");
+    return;
+  }
+
+  RefPtr<gfxPattern> thebesPat = aDestinationCtx->GetPattern();
+  Pattern* pat = thebesPat->GetPattern(dest, nullptr);
+  if (!pat) {
+    NS_WARNING("Failed to get pattern for blur!");
+    return;
+  }
+
+  IntPoint topLeft;
+  RefPtr<SourceSurface> mask = DoBlur(nullptr, &topLeft);
+  if (!mask) {
+    NS_ERROR("Failed to create mask!");
+    return;
+  }
+
+  // Avoid a semi-expensive clip operation if we can, otherwise
+  // clip to the dirty rect
+  Rect* dirtyRect = mBlur.GetDirtyRect();
+  if (dirtyRect) {
+    dest->PushClipRect(*dirtyRect);
+  }
+
+  Matrix oldTransform = dest->GetTransform();
+  Matrix newTransform = oldTransform;
+  newTransform.PreTranslate(topLeft);
+  dest->SetTransform(newTransform);
+
+  dest->MaskSurface(*pat, mask, Point(0, 0));
+
+  dest->SetTransform(oldTransform);
+
+  if (dirtyRect) {
+    dest->PopClip();
+  }
+}
+
+IntSize gfxAlphaBoxBlur::CalculateBlurRadius(const gfxPoint& aStd) {
+  mozilla::gfx::Point std(Float(aStd.x), Float(aStd.y));
+  IntSize size = AlphaBoxBlur::CalculateBlurRadius(std);
+  return IntSize(size.width, size.height);
+}
+
+struct BlurCacheKey : public PLDHashEntryHdr {
+  typedef const BlurCacheKey& KeyType;
+  typedef const BlurCacheKey* KeyTypePointer;
+  enum { ALLOW_MEMMOVE = true };
+
+  IntSize mMinSize;
+  IntSize mBlurRadius;
+  sRGBColor mShadowColor;
+  BackendType mBackend;
+  RectCornerRadii mCornerRadii;
+  bool mIsInset;
+
+  // Only used for inset blurs
+  IntSize mInnerMinSize;
+
+  BlurCacheKey(const IntSize& aMinSize, const IntSize& aBlurRadius,
+               const RectCornerRadii* aCornerRadii,
+               const sRGBColor& aShadowColor, BackendType aBackendType)
+      : BlurCacheKey(aMinSize, IntSize(0, 0), aBlurRadius, aCornerRadii,
+                     aShadowColor, false, aBackendType) {}
+
+  explicit BlurCacheKey(const BlurCacheKey* aOther)
+      : mMinSize(aOther->mMinSize),
+        mBlurRadius(aOther->mBlurRadius),
+        mShadowColor(aOther->mShadowColor),
+        mBackend(aOther->mBackend),
+        mCornerRadii(aOther->mCornerRadii),
+        mIsInset(aOther->mIsInset),
+        mInnerMinSize(aOther->mInnerMinSize) {}
+
+  explicit BlurCacheKey(const IntSize& aOuterMinSize,
+                        const IntSize& aInnerMinSize,
+                        const IntSize& aBlurRadius,
+                        const RectCornerRadii* aCornerRadii,
+                        const sRGBColor& aShadowColor, bool aIsInset,
+                        BackendType aBackendType)
+      : mMinSize(aOuterMinSize),
+        mBlurRadius(aBlurRadius),
+        mShadowColor(aShadowColor),
+        mBackend(aBackendType),
+        mCornerRadii(aCornerRadii ? *aCornerRadii : RectCornerRadii()),
+        mIsInset(aIsInset),
+        mInnerMinSize(aInnerMinSize) {}
+
+  BlurCacheKey(BlurCacheKey&&) = default;
+
+  static PLDHashNumber HashKey(const KeyTypePointer aKey) {
+    PLDHashNumber hash = 0;
+    hash = AddToHash(hash, aKey->mMinSize.width, aKey->mMinSize.height);
+    hash = AddToHash(hash, aKey->mBlurRadius.width, aKey->mBlurRadius.height);
+
+    hash = AddToHash(
+        hash, HashBytes(&aKey->mShadowColor.r, sizeof(aKey->mShadowColor.r)));
+    hash = AddToHash(
+        hash, HashBytes(&aKey->mShadowColor.g, sizeof(aKey->mShadowColor.g)));
+    hash = AddToHash(
+        hash, HashBytes(&aKey->mShadowColor.b, sizeof(aKey->mShadowColor.b)));
+    hash = AddToHash(
+        hash, HashBytes(&aKey->mShadowColor.a, sizeof(aKey->mShadowColor.a)));
+
+    for (int i = 0; i < 4; i++) {
+      hash = AddToHash(hash, aKey->mCornerRadii[i].width,
+                       aKey->mCornerRadii[i].height);
+    }
+
+    hash = AddToHash(hash, (uint32_t)aKey->mBackend);
+
+    if (aKey->mIsInset) {
+      hash = AddToHash(hash, aKey->mInnerMinSize.width,
+                       aKey->mInnerMinSize.height);
+    }
+    return hash;
+  }
+
+  bool KeyEquals(KeyTypePointer aKey) const {
+    if (aKey->mMinSize == mMinSize && aKey->mBlurRadius == mBlurRadius &&
+        aKey->mCornerRadii == mCornerRadii &&
+        aKey->mShadowColor == mShadowColor && aKey->mBackend == mBackend) {
+      if (mIsInset) {
+        return (mInnerMinSize == aKey->mInnerMinSize);
+      }
+
+      return true;
+    }
+
+    return false;
+  }
+
+  static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
+};
+
+/**
+ * This class is what is cached. It need to be allocated in an object separated
+ * to the cache entry to be able to be tracked by the nsExpirationTracker.
+ * */
+struct BlurCacheData {
+  BlurCacheData(SourceSurface* aBlur, const IntMargin& aBlurMargin,
+                BlurCacheKey&& aKey)
+      : mBlur(aBlur), mBlurMargin(aBlurMargin), mKey(std::move(aKey)) {}
+
+  BlurCacheData(BlurCacheData&& aOther) = default;
+
+  nsExpirationState* GetExpirationState() { return &mExpirationState; }
+
+  nsExpirationState mExpirationState;
+  RefPtr<SourceSurface> mBlur;
+  IntMargin mBlurMargin;
+  BlurCacheKey mKey;
+};
+
+/**
+ * This class implements a cache with no maximum size, that retains the
+ * SourceSurfaces used to draw the blurs.
+ *
+ * An entry stays in the cache as long as it is used often.
+ */
+class BlurCache final : public nsExpirationTracker<BlurCacheData, 4> {
+ public:
+  BlurCache()
+      : nsExpirationTracker<BlurCacheData, 4>(GENERATION_MS, "BlurCache") {}
+
+  virtual void NotifyExpired(BlurCacheData* aObject) override {
+    RemoveObject(aObject);
+    mHashEntries.Remove(aObject->mKey);
+  }
+
+  BlurCacheData* Lookup(const IntSize& aMinSize, const IntSize& aBlurRadius,
+                        const RectCornerRadii* aCornerRadii,
+                        const sRGBColor& aShadowColor,
+                        BackendType aBackendType) {
+    BlurCacheData* blur = mHashEntries.Get(BlurCacheKey(
+        aMinSize, aBlurRadius, aCornerRadii, aShadowColor, aBackendType));
+    if (blur) {
+      MarkUsed(blur);
+    }
+
+    return blur;
+  }
+
+  BlurCacheData* LookupInsetBoxShadow(const IntSize& aOuterMinSize,
+                                      const IntSize& aInnerMinSize,
+                                      const IntSize& aBlurRadius,
+                                      const RectCornerRadii* aCornerRadii,
+                                      const sRGBColor& aShadowColor,
+                                      BackendType aBackendType) {
+    bool insetBoxShadow = true;
+    BlurCacheKey key(aOuterMinSize, aInnerMinSize, aBlurRadius, aCornerRadii,
+                     aShadowColor, insetBoxShadow, aBackendType);
+    BlurCacheData* blur = mHashEntries.Get(key);
+    if (blur) {
+      MarkUsed(blur);
+    }
+
+    return blur;
+  }
+
+  void RegisterEntry(UniquePtr<BlurCacheData> aValue) {
+    nsresult rv = AddObject(aValue.get());
+    if (NS_FAILED(rv)) {
+      // We are OOM, and we cannot track this object. We don't want stall
+      // entries in the hash table (since the expiration tracker is responsible
+      // for removing the cache entries), so we avoid putting that entry in the
+      // table, which is a good thing considering we are short on memory
+      // anyway, we probably don't want to retain things.
+      return;
+    }
+    mHashEntries.InsertOrUpdate(aValue->mKey, std::move(aValue));
+  }
+
+ protected:
+  static const uint32_t GENERATION_MS = 1000;
+  /**
+   * FIXME use nsTHashtable to avoid duplicating the BlurCacheKey.
+   * https://bugzilla.mozilla.org/show_bug.cgi?id=761393#c47
+   */
+  nsClassHashtable<BlurCacheKey, BlurCacheData> mHashEntries;
+};
+
+static BlurCache* gBlurCache = nullptr;
+
+static IntSize ComputeMinSizeForShadowShape(const RectCornerRadii* aCornerRadii,
+                                            const IntSize& aBlurRadius,
+                                            IntMargin& aOutSlice,
+                                            const IntSize& aRectSize) {
+  Size cornerSize(0, 0);
+  if (aCornerRadii) {
+    const RectCornerRadii& corners = *aCornerRadii;
+    for (const auto i : mozilla::AllPhysicalCorners()) {
+      cornerSize.width = std::max(cornerSize.width, corners[i].width);
+      cornerSize.height = std::max(cornerSize.height, corners[i].height);
+    }
+  }
+
+  IntSize margin = IntSize::Ceil(cornerSize) + aBlurRadius;
+  aOutSlice =
+      IntMargin(margin.height, margin.width, margin.height, margin.width);
+
+  IntSize minSize(aOutSlice.LeftRight() + 1, aOutSlice.TopBottom() + 1);
+
+  // If aRectSize is smaller than minSize, the border-image approach won't
+  // work; there's no way to squeeze parts of the min box-shadow source
+  // image such that the result looks correct. So we need to adjust minSize
+  // in such a way that we can later draw it without stretching in the affected
+  // dimension. We also need to adjust "slice" to ensure that we're not trying
+  // to slice away more than we have.
+  if (aRectSize.width < minSize.width) {
+    minSize.width = aRectSize.width;
+    aOutSlice.left = 0;
+    aOutSlice.right = 0;
+  }
+  if (aRectSize.height < minSize.height) {
+    minSize.height = aRectSize.height;
+    aOutSlice.top = 0;
+    aOutSlice.bottom = 0;
+  }
+
+  MOZ_ASSERT(aOutSlice.LeftRight() <= minSize.width);
+  MOZ_ASSERT(aOutSlice.TopBottom() <= minSize.height);
+  return minSize;
+}
+
+static void CacheBlur(DrawTarget* aDT, const IntSize& aMinSize,
+                      const IntSize& aBlurRadius,
+                      const RectCornerRadii* aCornerRadii,
+                      const sRGBColor& aShadowColor,
+                      const IntMargin& aBlurMargin, SourceSurface* aBoxShadow) {
+  gBlurCache->RegisterEntry(MakeUnique<BlurCacheData>(
+      aBoxShadow, aBlurMargin,
+      BlurCacheKey(aMinSize, aBlurRadius, aCornerRadii, aShadowColor,
+                   aDT->GetBackendType())));
+}
+
+// Blurs a small surface and creates the colored box shadow.
+static already_AddRefed<SourceSurface> CreateBoxShadow(
+    DrawTarget* aDestDrawTarget, const IntSize& aMinSize,
+    const RectCornerRadii* aCornerRadii, const IntSize& aBlurRadius,
+    const sRGBColor& aShadowColor, bool aMirrorCorners,
+    IntMargin& aOutBlurMargin) {
+  gfxAlphaBoxBlur blur;
+  Rect minRect(Point(0, 0), Size(aMinSize));
+  Rect blurRect(minRect);
+  // If mirroring corners, we only need to draw the top-left quadrant.
+  // Use ceil to preserve the remaining 1x1 middle area for minimized box
+  // shadows.
+  if (aMirrorCorners) {
+    blurRect.SizeTo(ceil(blurRect.Width() * 0.5f),
+                    ceil(blurRect.Height() * 0.5f));
+  }
+  IntSize zeroSpread(0, 0);
+  RefPtr<DrawTarget> blurDT =
+      blur.InitDrawTarget(aDestDrawTarget, blurRect, zeroSpread, aBlurRadius);
+  if (!blurDT) {
+    return nullptr;
+  }
+
+  ColorPattern black(DeviceColor::MaskOpaqueBlack());
+
+  if (aCornerRadii) {
+    RefPtr<Path> roundedRect =
+        MakePathForRoundedRect(*blurDT, minRect, *aCornerRadii);
+    blurDT->Fill(roundedRect, black);
+  } else {
+    blurDT->FillRect(minRect, black);
+  }
+
+  IntPoint topLeft;
+  RefPtr<SourceSurface> result = blur.DoBlur(&aShadowColor, &topLeft);
+  if (!result) {
+    return nullptr;
+  }
+
+  // Since blurRect is at (0, 0), we can find the inflated margin by
+  // negating the new rect origin, which would have been negative if
+  // the rect was inflated.
+  aOutBlurMargin = IntMargin(-topLeft.y, -topLeft.x, -topLeft.y, -topLeft.x);
+
+  return result.forget();
+}
+
+static already_AddRefed<SourceSurface> GetBlur(
+    gfxContext* aDestinationCtx, const IntSize& aRectSize,
+    const IntSize& aBlurRadius, const RectCornerRadii* aCornerRadii,
+    const sRGBColor& aShadowColor, bool aMirrorCorners,
+    IntMargin& aOutBlurMargin, IntMargin& aOutSlice, IntSize& aOutMinSize) {
+  if (!gBlurCache) {
+    gBlurCache = new BlurCache();
+  }
+
+  IntSize minSize = ComputeMinSizeForShadowShape(aCornerRadii, aBlurRadius,
+                                                 aOutSlice, aRectSize);
+
+  // We can get seams using the min size rect when drawing to the destination
+  // rect if we have a non-pixel aligned destination transformation. In those
+  // cases, fallback to just rendering the destination rect. During printing, we
+  // record all the Moz 2d commands and replay them on the parent side with
+  // Cairo. Cairo printing uses StretchDIBits to stretch the surface. However,
+  // since our source image is only 1px for some parts, we make thousands of
+  // calls. Instead just render the blur ourself here as one image and send it
+  // over for printing.
+  // TODO: May need to change this with the blob renderer in WR since it also
+  // records.
+  Matrix destMatrix = aDestinationCtx->CurrentMatrix();
+  bool useDestRect = !destMatrix.IsRectilinear() ||
+                     destMatrix.HasNonIntegerTranslation() ||
+                     aDestinationCtx->GetDrawTarget()->IsRecording();
+  if (useDestRect) {
+    minSize = aRectSize;
+  }
+
+  int32_t maxTextureSize = gfxPlatform::MaxTextureSize();
+  if (minSize.width > maxTextureSize || minSize.height > maxTextureSize) {
+    return nullptr;
+  }
+
+  aOutMinSize = minSize;
+
+  DrawTarget* destDT = aDestinationCtx->GetDrawTarget();
+
+  if (!useDestRect) {
+    BlurCacheData* cached =
+        gBlurCache->Lookup(minSize, aBlurRadius, aCornerRadii, aShadowColor,
+                           destDT->GetBackendType());
+    if (cached) {
+      // See CreateBoxShadow() for these values
+      aOutBlurMargin = cached->mBlurMargin;
+      RefPtr<SourceSurface> blur = cached->mBlur;
+      return blur.forget();
+    }
+  }
+
+  RefPtr<SourceSurface> boxShadow =
+      CreateBoxShadow(destDT, minSize, aCornerRadii, aBlurRadius, aShadowColor,
+                      aMirrorCorners, aOutBlurMargin);
+  if (!boxShadow) {
+    return nullptr;
+  }
+
+  if (RefPtr<SourceSurface> opt = destDT->OptimizeSourceSurface(boxShadow)) {
+    boxShadow = opt;
+  }
+
+  if (!useDestRect) {
+    CacheBlur(destDT, minSize, aBlurRadius, aCornerRadii, aShadowColor,
+              aOutBlurMargin, boxShadow);
+  }
+  return boxShadow.forget();
+}
+
+void gfxAlphaBoxBlur::ShutdownBlurCache() {
+  delete gBlurCache;
+  gBlurCache = nullptr;
+}
+
+static Rect RectWithEdgesTRBL(Float aTop, Float aRight, Float aBottom,
+                              Float aLeft) {
+  return Rect(aLeft, aTop, aRight - aLeft, aBottom - aTop);
+}
+
+static bool ShouldStretchSurface(DrawTarget* aDT, SourceSurface* aSurface) {
+  // Use stretching if possible, since it leads to less seams when the
+  // destination is transformed. However, don't do this if we're using cairo,
+  // because if cairo is using pixman it won't render anything for large
+  // stretch factors because pixman's internal fixed point precision is not
+  // high enough to handle those scale factors.
+  return aDT->GetBackendType() != BackendType::CAIRO;
+}
+
+static void RepeatOrStretchSurface(DrawTarget* aDT, SourceSurface* aSurface,
+                                   const Rect& aDest, const Rect& aSrc,
+                                   const Rect& aSkipRect) {
+  if (aSkipRect.Contains(aDest)) {
+    return;
+  }
+
+  if (ShouldStretchSurface(aDT, aSurface)) {
+    aDT->DrawSurface(aSurface, aDest, aSrc);
+    return;
+  }
+
+  SurfacePattern pattern(aSurface, ExtendMode::REPEAT,
+                         Matrix::Translation(aDest.TopLeft() - aSrc.TopLeft()),
+                         SamplingFilter::GOOD, RoundedToInt(aSrc));
+  aDT->FillRect(aDest, pattern);
+}
+
+static void DrawCorner(DrawTarget* aDT, SourceSurface* aSurface,
+                       const Rect& aDest, const Rect& aSrc,
+                       const Rect& aSkipRect) {
+  if (aSkipRect.Contains(aDest)) {
+    return;
+  }
+
+  aDT->DrawSurface(aSurface, aDest, aSrc);
+}
+
+static void DrawMinBoxShadow(DrawTarget* aDestDrawTarget,
+                             SourceSurface* aSourceBlur, const Rect& aDstOuter,
+                             const Rect& aDstInner, const Rect& aSrcOuter,
+                             const Rect& aSrcInner, const Rect& aSkipRect,
+                             bool aMiddle = false) {
+  // Corners: top left, top right, bottom left, bottom right
+  DrawCorner(aDestDrawTarget, aSourceBlur,
+             RectWithEdgesTRBL(aDstOuter.Y(), aDstInner.X(), aDstInner.Y(),
+                               aDstOuter.X()),
+             RectWithEdgesTRBL(aSrcOuter.Y(), aSrcInner.X(), aSrcInner.Y(),
+                               aSrcOuter.X()),
+             aSkipRect);
+
+  DrawCorner(aDestDrawTarget, aSourceBlur,
+             RectWithEdgesTRBL(aDstOuter.Y(), aDstOuter.XMost(), aDstInner.Y(),
+                               aDstInner.XMost()),
+             RectWithEdgesTRBL(aSrcOuter.Y(), aSrcOuter.XMost(), aSrcInner.Y(),
+                               aSrcInner.XMost()),
+             aSkipRect);
+
+  DrawCorner(aDestDrawTarget, aSourceBlur,
+             RectWithEdgesTRBL(aDstInner.YMost(), aDstInner.X(),
+                               aDstOuter.YMost(), aDstOuter.X()),
+             RectWithEdgesTRBL(aSrcInner.YMost(), aSrcInner.X(),
+                               aSrcOuter.YMost(), aSrcOuter.X()),
+             aSkipRect);
+
+  DrawCorner(aDestDrawTarget, aSourceBlur,
+             RectWithEdgesTRBL(aDstInner.YMost(), aDstOuter.XMost(),
+                               aDstOuter.YMost(), aDstInner.XMost()),
+             RectWithEdgesTRBL(aSrcInner.YMost(), aSrcOuter.XMost(),
+                               aSrcOuter.YMost(), aSrcInner.XMost()),
+             aSkipRect);
+
+  // Edges: top, left, right, bottom
+  RepeatOrStretchSurface(aDestDrawTarget, aSourceBlur,
+                         RectWithEdgesTRBL(aDstOuter.Y(), aDstInner.XMost(),
+                                           aDstInner.Y(), aDstInner.X()),
+                         RectWithEdgesTRBL(aSrcOuter.Y(), aSrcInner.XMost(),
+                                           aSrcInner.Y(), aSrcInner.X()),
+                         aSkipRect);
+  RepeatOrStretchSurface(aDestDrawTarget, aSourceBlur,
+                         RectWithEdgesTRBL(aDstInner.Y(), aDstInner.X(),
+                                           aDstInner.YMost(), aDstOuter.X()),
+                         RectWithEdgesTRBL(aSrcInner.Y(), aSrcInner.X(),
+                                           aSrcInner.YMost(), aSrcOuter.X()),
+                         aSkipRect);
+
+  RepeatOrStretchSurface(
+      aDestDrawTarget, aSourceBlur,
+      RectWithEdgesTRBL(aDstInner.Y(), aDstOuter.XMost(), aDstInner.YMost(),
+                        aDstInner.XMost()),
+      RectWithEdgesTRBL(aSrcInner.Y(), aSrcOuter.XMost(), aSrcInner.YMost(),
+                        aSrcInner.XMost()),
+      aSkipRect);
+  RepeatOrStretchSurface(aDestDrawTarget, aSourceBlur,
+                         RectWithEdgesTRBL(aDstInner.YMost(), aDstInner.XMost(),
+                                           aDstOuter.YMost(), aDstInner.X()),
+                         RectWithEdgesTRBL(aSrcInner.YMost(), aSrcInner.XMost(),
+                                           aSrcOuter.YMost(), aSrcInner.X()),
+                         aSkipRect);
+
+  // Middle part
+  if (aMiddle) {
+    RepeatOrStretchSurface(aDestDrawTarget, aSourceBlur,
+                           RectWithEdgesTRBL(aDstInner.Y(), aDstInner.XMost(),
+                                             aDstInner.YMost(), aDstInner.X()),
+                           RectWithEdgesTRBL(aSrcInner.Y(), aSrcInner.XMost(),
+                                             aSrcInner.YMost(), aSrcInner.X()),
+                           aSkipRect);
+  }
+}
+
+static void DrawMirroredRect(DrawTarget* aDT, SourceSurface* aSurface,
+                             const Rect& aDest, const Point& aSrc,
+                             Float aScaleX, Float aScaleY) {
+  SurfacePattern pattern(
+      aSurface, ExtendMode::CLAMP,
+      Matrix::Scaling(aScaleX, aScaleY)
+          .PreTranslate(-aSrc)
+          .PostTranslate(aScaleX < 0 ? aDest.XMost() : aDest.X(),
+                         aScaleY < 0 ? aDest.YMost() : aDest.Y()));
+  aDT->FillRect(aDest, pattern);
+}
+
+static void DrawMirroredBoxShadow(DrawTarget* aDT, SourceSurface* aSurface,
+                                  const Rect& aDestRect) {
+  Point center(ceil(aDestRect.X() + aDestRect.Width() / 2),
+               ceil(aDestRect.Y() + aDestRect.Height() / 2));
+  Rect topLeft(aDestRect.X(), aDestRect.Y(), center.x - aDestRect.X(),
+               center.y - aDestRect.Y());
+  Rect bottomRight(topLeft.BottomRight(), aDestRect.Size() - topLeft.Size());
+  Rect topRight(bottomRight.X(), topLeft.Y(), bottomRight.Width(),
+                topLeft.Height());
+  Rect bottomLeft(topLeft.X(), bottomRight.Y(), topLeft.Width(),
+                  bottomRight.Height());
+  DrawMirroredRect(aDT, aSurface, topLeft, Point(), 1, 1);
+  DrawMirroredRect(aDT, aSurface, topRight, Point(), -1, 1);
+  DrawMirroredRect(aDT, aSurface, bottomLeft, Point(), 1, -1);
+  DrawMirroredRect(aDT, aSurface, bottomRight, Point(), -1, -1);
+}
+
+static void DrawMirroredCorner(DrawTarget* aDT, SourceSurface* aSurface,
+                               const Rect& aDest, const Point& aSrc,
+                               const Rect& aSkipRect, Float aScaleX,
+                               Float aScaleY) {
+  if (aSkipRect.Contains(aDest)) {
+    return;
+  }
+
+  DrawMirroredRect(aDT, aSurface, aDest, aSrc, aScaleX, aScaleY);
+}
+
+static void RepeatOrStretchMirroredSurface(DrawTarget* aDT,
+                                           SourceSurface* aSurface,
+                                           const Rect& aDest, const Rect& aSrc,
+                                           const Rect& aSkipRect, Float aScaleX,
+                                           Float aScaleY) {
+  if (aSkipRect.Contains(aDest)) {
+    return;
+  }
+
+  if (ShouldStretchSurface(aDT, aSurface)) {
+    aScaleX *= aDest.Width() / aSrc.Width();
+    aScaleY *= aDest.Height() / aSrc.Height();
+    DrawMirroredRect(aDT, aSurface, aDest, aSrc.TopLeft(), aScaleX, aScaleY);
+    return;
+  }
+
+  SurfacePattern pattern(
+      aSurface, ExtendMode::REPEAT,
+      Matrix::Scaling(aScaleX, aScaleY)
+          .PreTranslate(-aSrc.TopLeft())
+          .PostTranslate(aScaleX < 0 ? aDest.XMost() : aDest.X(),
+                         aScaleY < 0 ? aDest.YMost() : aDest.Y()),
+      SamplingFilter::GOOD, RoundedToInt(aSrc));
+  aDT->FillRect(aDest, pattern);
+}
+
+static void DrawMirroredMinBoxShadow(
+    DrawTarget* aDestDrawTarget, SourceSurface* aSourceBlur,
+    const Rect& aDstOuter, const Rect& aDstInner, const Rect& aSrcOuter,
+    const Rect& aSrcInner, const Rect& aSkipRect, bool aMiddle = false) {
+  // Corners: top left, top right, bottom left, bottom right
+  // Compute quadrant bounds and then clip them to corners along
+  // dimensions where we need to stretch from min size.
+  Point center(ceil(aDstOuter.X() + aDstOuter.Width() / 2),
+               ceil(aDstOuter.Y() + aDstOuter.Height() / 2));
+  Rect topLeft(aDstOuter.X(), aDstOuter.Y(), center.x - aDstOuter.X(),
+               center.y - aDstOuter.Y());
+  Rect bottomRight(topLeft.BottomRight(), aDstOuter.Size() - topLeft.Size());
+  Rect topRight(bottomRight.X(), topLeft.Y(), bottomRight.Width(),
+                topLeft.Height());
+  Rect bottomLeft(topLeft.X(), bottomRight.Y(), topLeft.Width(),
+                  bottomRight.Height());
+
+  // Check if the middle part has been minimized along each dimension.
+  // If so, those will be strecthed/drawn separately and need to be clipped out.
+  if (aSrcInner.Width() == 1) {
+    topLeft.SetRightEdge(aDstInner.X());
+    topRight.SetLeftEdge(aDstInner.XMost());
+    bottomLeft.SetRightEdge(aDstInner.X());
+    bottomRight.SetLeftEdge(aDstInner.XMost());
+  }
+  if (aSrcInner.Height() == 1) {
+    topLeft.SetBottomEdge(aDstInner.Y());
+    topRight.SetBottomEdge(aDstInner.Y());
+    bottomLeft.SetTopEdge(aDstInner.YMost());
+    bottomRight.SetTopEdge(aDstInner.YMost());
+  }
+
+  DrawMirroredCorner(aDestDrawTarget, aSourceBlur, topLeft, aSrcOuter.TopLeft(),
+                     aSkipRect, 1, 1);
+  DrawMirroredCorner(aDestDrawTarget, aSourceBlur, topRight,
+                     aSrcOuter.TopLeft(), aSkipRect, -1, 1);
+  DrawMirroredCorner(aDestDrawTarget, aSourceBlur, bottomLeft,
+                     aSrcOuter.TopLeft(), aSkipRect, 1, -1);
+  DrawMirroredCorner(aDestDrawTarget, aSourceBlur, bottomRight,
+                     aSrcOuter.TopLeft(), aSkipRect, -1, -1);
+
+  // Edges: top, bottom, left, right
+  // Draw middle edges where they need to be stretched. The top and left
+  // sections that are part of the top-left quadrant will be mirrored to
+  // the bottom and right sections, respectively.
+  if (aSrcInner.Width() == 1) {
+    Rect dstTop = RectWithEdgesTRBL(aDstOuter.Y(), aDstInner.XMost(),
+                                    aDstInner.Y(), aDstInner.X());
+    Rect srcTop = RectWithEdgesTRBL(aSrcOuter.Y(), aSrcInner.XMost(),
+                                    aSrcInner.Y(), aSrcInner.X());
+    Rect dstBottom = RectWithEdgesTRBL(aDstInner.YMost(), aDstInner.XMost(),
+                                       aDstOuter.YMost(), aDstInner.X());
+    Rect srcBottom = RectWithEdgesTRBL(aSrcOuter.Y(), aSrcInner.XMost(),
+                                       aSrcInner.Y(), aSrcInner.X());
+    // If we only need to stretch along the X axis and we're drawing
+    // the middle section, just sample all the way to the center of the
+    // source on the Y axis to avoid extra draw calls.
+    if (aMiddle && aSrcInner.Height() != 1) {
+      dstTop.SetBottomEdge(center.y);
+      srcTop.SetHeight(dstTop.Height());
+      dstBottom.SetTopEdge(dstTop.YMost());
+      srcBottom.SetHeight(dstBottom.Height());
+    }
+    RepeatOrStretchMirroredSurface(aDestDrawTarget, aSourceBlur, dstTop, srcTop,
+                                   aSkipRect, 1, 1);
+    RepeatOrStretchMirroredSurface(aDestDrawTarget, aSourceBlur, dstBottom,
+                                   srcBottom, aSkipRect, 1, -1);
+  }
+
+  if (aSrcInner.Height() == 1) {
+    Rect dstLeft = RectWithEdgesTRBL(aDstInner.Y(), aDstInner.X(),
+                                     aDstInner.YMost(), aDstOuter.X());
+    Rect srcLeft = RectWithEdgesTRBL(aSrcInner.Y(), aSrcInner.X(),
+                                     aSrcInner.YMost(), aSrcOuter.X());
+    Rect dstRight = RectWithEdgesTRBL(aDstInner.Y(), aDstOuter.XMost(),
+                                      aDstInner.YMost(), aDstInner.XMost());
+    Rect srcRight = RectWithEdgesTRBL(aSrcInner.Y(), aSrcInner.X(),
+                                      aSrcInner.YMost(), aSrcOuter.X());
+    // Only stretching on Y axis, so sample source to the center of the X axis.
+    if (aMiddle && aSrcInner.Width() != 1) {
+      dstLeft.SetRightEdge(center.x);
+      srcLeft.SetWidth(dstLeft.Width());
+      dstRight.SetLeftEdge(dstLeft.XMost());
+      srcRight.SetWidth(dstRight.Width());
+    }
+    RepeatOrStretchMirroredSurface(aDestDrawTarget, aSourceBlur, dstLeft,
+                                   srcLeft, aSkipRect, 1, 1);
+    RepeatOrStretchMirroredSurface(aDestDrawTarget, aSourceBlur, dstRight,
+                                   srcRight, aSkipRect, -1, 1);
+  }
+
+  // If we need to stretch along both dimensions, then the middle part
+  // must be drawn separately.
+  if (aMiddle && aSrcInner.Width() == 1 && aSrcInner.Height() == 1) {
+    RepeatOrStretchSurface(aDestDrawTarget, aSourceBlur,
+                           RectWithEdgesTRBL(aDstInner.Y(), aDstInner.XMost(),
+                                             aDstInner.YMost(), aDstInner.X()),
+                           RectWithEdgesTRBL(aSrcInner.Y(), aSrcInner.XMost(),
+                                             aSrcInner.YMost(), aSrcInner.X()),
+                           aSkipRect);
+  }
+}
+
+/***
+ * We draw a blurred a rectangle by only blurring a smaller rectangle and
+ * splitting the rectangle into 9 parts.
+ * First, a small minimum source rect is calculated and used to create a blur
+ * mask since the actual blurring itself is expensive. Next, we use the mask
+ * with the given shadow color to create a minimally-sized box shadow of the
+ * right color. Finally, we cut out the 9 parts from the box-shadow source and
+ * paint each part in the right place, stretching the non-corner parts to fill
+ * the space between the corners.
+ */
+
+/* static */
+void gfxAlphaBoxBlur::BlurRectangle(gfxContext* aDestinationCtx,
+                                    const gfxRect& aRect,
+                                    const RectCornerRadii* aCornerRadii,
+                                    const gfxPoint& aBlurStdDev,
+                                    const sRGBColor& aShadowColor,
+                                    const gfxRect& aDirtyRect,
+                                    const gfxRect& aSkipRect) {
+  if (!RectIsInt32Safe(ToRect(aRect))) {
+    return;
+  }
+
+  IntSize blurRadius = CalculateBlurRadius(aBlurStdDev);
+  bool mirrorCorners = !aCornerRadii || aCornerRadii->AreRadiiSame();
+
+  IntRect rect = RoundedToInt(ToRect(aRect));
+  IntMargin blurMargin;
+  IntMargin slice;
+  IntSize minSize;
+  RefPtr<SourceSurface> boxShadow =
+      GetBlur(aDestinationCtx, rect.Size(), blurRadius, aCornerRadii,
+              aShadowColor, mirrorCorners, blurMargin, slice, minSize);
+  if (!boxShadow) {
+    return;
+  }
+
+  DrawTarget* destDrawTarget = aDestinationCtx->GetDrawTarget();
+  destDrawTarget->PushClipRect(ToRect(aDirtyRect));
+
+  // Copy the right parts from boxShadow into destDrawTarget. The middle parts
+  // will be stretched, border-image style.
+
+  Rect srcOuter(Point(blurMargin.left, blurMargin.top), Size(minSize));
+  Rect srcInner(srcOuter);
+  srcOuter.Inflate(Margin(blurMargin));
+  srcInner.Deflate(Margin(slice));
+
+  Rect dstOuter(rect);
+  Rect dstInner(rect);
+  dstOuter.Inflate(Margin(blurMargin));
+  dstInner.Deflate(Margin(slice));
+
+  Rect skipRect = ToRect(aSkipRect);
+
+  if (minSize == rect.Size()) {
+    // The target rect is smaller than the minimal size so just draw the surface
+    if (mirrorCorners) {
+      DrawMirroredBoxShadow(destDrawTarget, boxShadow, dstOuter);
+    } else {
+      destDrawTarget->DrawSurface(boxShadow, dstOuter, srcOuter);
+    }
+  } else {
+    if (mirrorCorners) {
+      DrawMirroredMinBoxShadow(destDrawTarget, boxShadow, dstOuter, dstInner,
+                               srcOuter, srcInner, skipRect, true);
+    } else {
+      DrawMinBoxShadow(destDrawTarget, boxShadow, dstOuter, dstInner, srcOuter,
+                       srcInner, skipRect, true);
+    }
+  }
+
+  // A note about anti-aliasing and seems between adjacent parts:
+  // We don't explicitly disable anti-aliasing in the DrawSurface calls above,
+  // so if there's a transform on destDrawTarget that is not pixel-aligned,
+  // there will be seams between adjacent parts of the box-shadow. It's hard to
+  // avoid those without the use of an intermediate surface.
+  // You might think that we could avoid those by just turning off AA, but there
+  // is a problem with that: Box-shadow rendering needs to clip out the
+  // element's border box, and we'd like that clip to have anti-aliasing -
+  // especially if the element has rounded corners! So we can't do that unless
+  // we have a way to say "Please anti-alias the clip, but don't antialias the
+  // destination rect of the DrawSurface call".
+
+  destDrawTarget->PopClip();
+}
+
+static already_AddRefed<Path> GetBoxShadowInsetPath(
+    DrawTarget* aDrawTarget, const Rect aOuterRect, const Rect aInnerRect,
+    const RectCornerRadii* aInnerClipRadii) {
+  /***
+   * We create an inset path by having two rects.
+   *
+   *  -----------------------
+   *  |  ________________   |
+   *  | |                |  |
+   *  | |                |  |
+   *  | ------------------  |
+   *  |_____________________|
+   *
+   * The outer rect and the inside rect. The path
+   * creates a frame around the content where we draw the inset shadow.
+   */
+  RefPtr<PathBuilder> builder =
+      aDrawTarget->CreatePathBuilder(FillRule::FILL_EVEN_ODD);
+  AppendRectToPath(builder, aOuterRect, true);
+
+  if (aInnerClipRadii) {
+    AppendRoundedRectToPath(builder, aInnerRect, *aInnerClipRadii, false);
+  } else {
+    AppendRectToPath(builder, aInnerRect, false);
+  }
+  return builder->Finish();
+}
+
+static void FillDestinationPath(
+    gfxContext* aDestinationCtx, const Rect& aDestinationRect,
+    const Rect& aShadowClipRect, const sRGBColor& aShadowColor,
+    const RectCornerRadii* aInnerClipRadii = nullptr) {
+  // When there is no blur radius, fill the path onto the destination
+  // surface.
+  aDestinationCtx->SetColor(aShadowColor);
+  DrawTarget* destDrawTarget = aDestinationCtx->GetDrawTarget();
+  RefPtr<Path> shadowPath = GetBoxShadowInsetPath(
+      destDrawTarget, aDestinationRect, aShadowClipRect, aInnerClipRadii);
+
+  aDestinationCtx->SetPath(shadowPath);
+  aDestinationCtx->Fill();
+}
+
+static void CacheInsetBlur(const IntSize& aMinOuterSize,
+                           const IntSize& aMinInnerSize,
+                           const IntSize& aBlurRadius,
+                           const RectCornerRadii* aCornerRadii,
+                           const sRGBColor& aShadowColor,
+                           BackendType aBackendType,
+                           SourceSurface* aBoxShadow) {
+  bool isInsetBlur = true;
+  BlurCacheKey key(aMinOuterSize, aMinInnerSize, aBlurRadius, aCornerRadii,
+                   aShadowColor, isInsetBlur, aBackendType);
+  IntMargin blurMargin(0, 0, 0, 0);
+
+  gBlurCache->RegisterEntry(
+      MakeUnique<BlurCacheData>(aBoxShadow, blurMargin, std::move(key)));
+}
+
+already_AddRefed<SourceSurface> gfxAlphaBoxBlur::GetInsetBlur(
+    const Rect& aOuterRect, const Rect& aWhitespaceRect, bool aIsDestRect,
+    const sRGBColor& aShadowColor, const IntSize& aBlurRadius,
+    const RectCornerRadii* aInnerClipRadii, DrawTarget* aDestDrawTarget,
+    bool aMirrorCorners) {
+  if (!gBlurCache) {
+    gBlurCache = new BlurCache();
+  }
+
+  IntSize outerSize = IntSize::Truncate(aOuterRect.Size());
+  IntSize whitespaceSize = IntSize::Truncate(aWhitespaceRect.Size());
+  if (!aIsDestRect) {
+    BlurCacheData* cached = gBlurCache->LookupInsetBoxShadow(
+        outerSize, whitespaceSize, aBlurRadius, aInnerClipRadii, aShadowColor,
+        aDestDrawTarget->GetBackendType());
+    if (cached) {
+      // So we don't forget the actual cached blur
+      RefPtr<SourceSurface> cachedBlur = cached->mBlur;
+      return cachedBlur.forget();
+    }
+  }
+
+  // If we can do a min rect, the whitespace rect will be expanded in Init to
+  // aOuterRect.
+  Rect blurRect = aIsDestRect ? aOuterRect : aWhitespaceRect;
+  // If mirroring corners, we only need to draw the top-left quadrant.
+  // Use ceil to preserve the remaining 1x1 middle area for minimized box
+  // shadows.
+  if (aMirrorCorners) {
+    blurRect.SizeTo(ceil(blurRect.Width() * 0.5f),
+                    ceil(blurRect.Height() * 0.5f));
+  }
+  IntSize zeroSpread(0, 0);
+  RefPtr<DrawTarget> minDrawTarget =
+      InitDrawTarget(aDestDrawTarget, blurRect, zeroSpread, aBlurRadius);
+  if (!minDrawTarget) {
+    return nullptr;
+  }
+
+  // This is really annoying. When we create the AlphaBoxBlur, the DrawTarget
+  // has a translation applied to it that is the topLeft point. This is actually
+  // the rect we gave it plus the blur radius. The rects we give this for the
+  // outer and whitespace rects are based at (0, 0). We could either translate
+  // those rects when we don't have a destination rect or ignore the translation
+  // when using the dest rect. The dest rects layout gives us expect this
+  // translation.
+  if (!aIsDestRect) {
+    minDrawTarget->SetTransform(Matrix());
+  }
+
+  // Fill in the path between the inside white space / outer rects
+  // NOT the inner frame
+  RefPtr<Path> maskPath = GetBoxShadowInsetPath(
+      minDrawTarget, aOuterRect, aWhitespaceRect, aInnerClipRadii);
+
+  ColorPattern black(DeviceColor::MaskOpaqueBlack());
+  minDrawTarget->Fill(maskPath, black);
+
+  // Blur and fill in with the color we actually wanted
+  RefPtr<SourceSurface> minInsetBlur = DoBlur(&aShadowColor);
+  if (!minInsetBlur) {
+    return nullptr;
+  }
+
+  if (RefPtr<SourceSurface> opt =
+          aDestDrawTarget->OptimizeSourceSurface(minInsetBlur)) {
+    minInsetBlur = opt;
+  }
+
+  if (!aIsDestRect) {
+    CacheInsetBlur(outerSize, whitespaceSize, aBlurRadius, aInnerClipRadii,
+                   aShadowColor, aDestDrawTarget->GetBackendType(),
+                   minInsetBlur);
+  }
+
+  return minInsetBlur.forget();
+}
+
+/***
+ * We create our minimal rect with 2 rects.
+ * The first is the inside whitespace rect, that is "cut out"
+ * from the box. This is (1). This must be the size
+ * of the blur radius + corner radius so we can have a big enough
+ * inside cut.
+ *
+ * The second (2) is one blur radius surrounding the inner
+ * frame of (1). This is the amount of blur space required
+ * to get a proper blend.
+ *
+ * B = one blur size
+ * W = one blur + corner radii - known as inner margin
+ * ___________________________________
+ * |                                |
+ * |          |             |       |
+ * |      (2) |    (1)      |  (2)  |
+ * |       B  |     W       |   B   |
+ * |          |             |       |
+ * |          |             |       |
+ * |          |                     |
+ * |________________________________|
+ */
+static void GetBlurMargins(const RectCornerRadii* aInnerClipRadii,
+                           const IntSize& aBlurRadius, Margin& aOutBlurMargin,
+                           Margin& aOutInnerMargin) {
+  Size cornerSize(0, 0);
+  if (aInnerClipRadii) {
+    const RectCornerRadii& corners = *aInnerClipRadii;
+    for (const auto i : mozilla::AllPhysicalCorners()) {
+      cornerSize.width = std::max(cornerSize.width, corners[i].width);
+      cornerSize.height = std::max(cornerSize.height, corners[i].height);
+    }
+  }
+
+  // Only the inside whitespace size cares about the border radius size.
+  // Outer sizes only care about blur.
+  IntSize margin = IntSize::Ceil(cornerSize) + aBlurRadius;
+
+  aOutInnerMargin.SizeTo(margin.height, margin.width, margin.height,
+                         margin.width);
+  aOutBlurMargin.SizeTo(aBlurRadius.height, aBlurRadius.width,
+                        aBlurRadius.height, aBlurRadius.width);
+}
+
+static bool GetInsetBoxShadowRects(const Margin& aBlurMargin,
+                                   const Margin& aInnerMargin,
+                                   const Rect& aShadowClipRect,
+                                   const Rect& aDestinationRect,
+                                   Rect& aOutWhitespaceRect,
+                                   Rect& aOutOuterRect) {
+  // We always copy (2 * blur radius) + corner radius worth of data to the
+  // destination rect This covers the blend of the path + the actual blur Need
+  // +1 so that we copy the edges correctly as we'll copy over the min box
+  // shadow corners then the +1 for the edges between Note, the (x,y)
+  // coordinates are from the blur margin since the frame outside the whitespace
+  // rect is 1 blur radius extra space.
+  Rect insideWhiteSpace(aBlurMargin.left, aBlurMargin.top,
+                        aInnerMargin.LeftRight() + 1,
+                        aInnerMargin.TopBottom() + 1);
+
+  // If the inner white space rect is larger than the shadow clip rect
+  // our approach does not work as we'll just copy one corner
+  // and cover the destination. In those cases, fallback to the destination rect
+  bool useDestRect = (aShadowClipRect.Width() <= aInnerMargin.LeftRight()) ||
+                     (aShadowClipRect.Height() <= aInnerMargin.TopBottom());
+
+  if (useDestRect) {
+    aOutWhitespaceRect = aShadowClipRect;
+    aOutOuterRect = aDestinationRect;
+  } else {
+    aOutWhitespaceRect = insideWhiteSpace;
+    aOutOuterRect = aOutWhitespaceRect;
+    aOutOuterRect.Inflate(aBlurMargin);
+  }
+
+  return useDestRect;
+}
+
+void gfxAlphaBoxBlur::BlurInsetBox(
+    gfxContext* aDestinationCtx, const Rect& aDestinationRect,
+    const Rect& aShadowClipRect, const IntSize& aBlurRadius,
+    const sRGBColor& aShadowColor, const RectCornerRadii* aInnerClipRadii,
+    const Rect& aSkipRect, const Point& aShadowOffset) {
+  if ((aBlurRadius.width == 0 && aBlurRadius.height == 0) ||
+      aShadowClipRect.IsEmpty()) {
+    FillDestinationPath(aDestinationCtx, aDestinationRect, aShadowClipRect,
+                        aShadowColor, aInnerClipRadii);
+    return;
+  }
+
+  DrawTarget* destDrawTarget = aDestinationCtx->GetDrawTarget();
+
+  Margin innerMargin;
+  Margin blurMargin;
+  GetBlurMargins(aInnerClipRadii, aBlurRadius, blurMargin, innerMargin);
+
+  Rect whitespaceRect;
+  Rect outerRect;
+  bool useDestRect =
+      GetInsetBoxShadowRects(blurMargin, innerMargin, aShadowClipRect,
+                             aDestinationRect, whitespaceRect, outerRect);
+
+  // Check that the inset margin between the outer and whitespace rects is
+  // symmetric, and that all corner radii are the same, in which case the blur
+  // can be mirrored.
+  Margin checkMargin = outerRect - whitespaceRect;
+  bool mirrorCorners = checkMargin.left == checkMargin.right &&
+                       checkMargin.top == checkMargin.bottom &&
+                       (!aInnerClipRadii || aInnerClipRadii->AreRadiiSame());
+  RefPtr<SourceSurface> minBlur =
+      GetInsetBlur(outerRect, whitespaceRect, useDestRect, aShadowColor,
+                   aBlurRadius, aInnerClipRadii, destDrawTarget, mirrorCorners);
+  if (!minBlur) {
+    return;
+  }
+
+  if (useDestRect) {
+    Rect destBlur = aDestinationRect;
+    destBlur.Inflate(blurMargin);
+    if (mirrorCorners) {
+      DrawMirroredBoxShadow(destDrawTarget, minBlur.get(), destBlur);
+    } else {
+      Rect srcBlur(Point(0, 0), Size(minBlur->GetSize()));
+      MOZ_ASSERT(RoundedOut(srcBlur).Size() == RoundedOut(destBlur).Size());
+      destDrawTarget->DrawSurface(minBlur, destBlur, srcBlur);
+    }
+  } else {
+    Rect srcOuter(outerRect);
+    Rect srcInner(srcOuter);
+    srcInner.Deflate(blurMargin);   // The outer color fill
+    srcInner.Deflate(innerMargin);  // The inner whitespace
+
+    // The shadow clip rect already takes into account the spread radius
+    Rect outerFillRect(aShadowClipRect);
+    outerFillRect.Inflate(blurMargin);
+    FillDestinationPath(aDestinationCtx, aDestinationRect, outerFillRect,
+                        aShadowColor);
+
+    // Inflate once for the frame around the whitespace
+    Rect destRect(aShadowClipRect);
+    destRect.Inflate(blurMargin);
+
+    // Deflate for the blurred in white space
+    Rect destInnerRect(aShadowClipRect);
+    destInnerRect.Deflate(innerMargin);
+
+    if (mirrorCorners) {
+      DrawMirroredMinBoxShadow(destDrawTarget, minBlur, destRect, destInnerRect,
+                               srcOuter, srcInner, aSkipRect);
+    } else {
+      DrawMinBoxShadow(destDrawTarget, minBlur, destRect, destInnerRect,
+                       srcOuter, srcInner, aSkipRect);
+    }
+  }
+}