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diff --git a/gfx/2d/Blur.h b/gfx/2d/Blur.h
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+/* -*- 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 MOZILLA_GFX_BLUR_H_
+#define MOZILLA_GFX_BLUR_H_
+
+#include "mozilla/gfx/Rect.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/CheckedInt.h"
+
+namespace mozilla {
+namespace gfx {
+
+#ifdef _MSC_VER
+#  pragma warning(disable : 4251)
+#endif
+
+/**
+ * Implementation of a triple box blur approximation of a Gaussian blur.
+ *
+ * A Gaussian blur is good for blurring because, when done independently
+ * in the horizontal and vertical directions, it matches the result that
+ * would be obtained using a different (rotated) set of axes.  A triple
+ * box blur is a very close approximation of a Gaussian.
+ *
+ * This is a "service" class; the constructors set up all the information
+ * based on the values and compute the minimum size for an 8-bit alpha
+ * channel context.
+ * The callers are responsible for creating and managing the backing surface
+ * and passing the pointer to the data to the Blur() method.  This class does
+ * not retain the pointer to the data outside of the Blur() call.
+ *
+ * A spread N makes each output pixel the maximum value of all source
+ * pixels within a square of side length 2N+1 centered on the output pixel.
+ */
+class GFX2D_API AlphaBoxBlur final {
+ public:
+  /** Constructs a box blur and computes the backing surface size.
+   *
+   * @param aRect The coordinates of the surface to create in device units.
+   *
+   * @param aBlurRadius The blur radius in pixels.  This is the radius of the
+   *   entire (triple) kernel function.  Each individual box blur has radius
+   *   approximately 1/3 this value, or diameter approximately 2/3 this value.
+   *   This parameter should nearly always be computed using
+   * CalculateBlurRadius, below.
+   *
+   * @param aDirtyRect A pointer to a dirty rect, measured in device units, if
+   *   available.  This will be used for optimizing the blur operation. It is
+   *   safe to pass nullptr here.
+   *
+   * @param aSkipRect A pointer to a rect, measured in device units, that
+   *   represents an area where blurring is unnecessary and shouldn't be done
+   * for speed reasons. It is safe to pass nullptr here.
+   */
+  AlphaBoxBlur(const Rect& aRect, const IntSize& aSpreadRadius,
+               const IntSize& aBlurRadius, const Rect* aDirtyRect,
+               const Rect* aSkipRect);
+
+  AlphaBoxBlur(const Rect& aRect, int32_t aStride, float aSigmaX,
+               float aSigmaY);
+
+  AlphaBoxBlur();
+
+  void Init(const Rect& aRect, const IntSize& aSpreadRadius,
+            const IntSize& aBlurRadius, const Rect* aDirtyRect,
+            const Rect* aSkipRect);
+
+  ~AlphaBoxBlur();
+
+  /**
+   * Return the size, in pixels, of the 8-bit alpha surface we'd use.
+   */
+  IntSize GetSize() const;
+
+  /**
+   * Return the stride, in bytes, of the 8-bit alpha surface we'd use.
+   */
+  int32_t GetStride() const;
+
+  /**
+   * Returns the device-space rectangle the 8-bit alpha surface covers.
+   */
+  IntRect GetRect() const;
+
+  /**
+   * Return a pointer to a dirty rect, as passed in to the constructor, or
+   * nullptr if none was passed in.
+   */
+  Rect* GetDirtyRect();
+
+  /**
+   * Return the spread radius, in pixels.
+   */
+  IntSize GetSpreadRadius() const { return mSpreadRadius; }
+
+  /**
+   * Return the blur radius, in pixels.
+   */
+  IntSize GetBlurRadius() const { return mBlurRadius; }
+
+  /**
+   * Return the minimum buffer size that should be given to Blur() method.  If
+   * zero, the class is not properly setup for blurring.  Note that this
+   * includes the extra three bytes on top of the stride*width, where something
+   * like gfxImageSurface::GetDataSize() would report without it, even if it
+   * happens to have the extra bytes.
+   */
+  size_t GetSurfaceAllocationSize() const;
+
+  /**
+   * Perform the blur in-place on the surface backed by specified 8-bit
+   * alpha surface data. The size must be at least that returned by
+   * GetSurfaceAllocationSize() or bad things will happen.
+   */
+  void Blur(uint8_t* aData) const;
+
+  /**
+   * Calculates a blur radius that, when used with box blur, approximates a
+   * Gaussian blur with the given standard deviation.  The result of this
+   * function should be used as the aBlurRadius parameter to AlphaBoxBlur's
+   * constructor, above.
+   */
+  static IntSize CalculateBlurRadius(const Point& aStandardDeviation);
+  static Float CalculateBlurSigma(int32_t aBlurRadius);
+
+ private:
+  void BoxBlur_C(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
+                 int32_t aTopLobe, int32_t aBottomLobe,
+                 uint32_t* aIntegralImage, size_t aIntegralImageStride) const;
+  void BoxBlur_SSE2(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
+                    int32_t aTopLobe, int32_t aBottomLobe,
+                    uint32_t* aIntegralImage,
+                    size_t aIntegralImageStride) const;
+  void BoxBlur_NEON(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
+                    int32_t aTopLobe, int32_t aBottomLobe,
+                    uint32_t* aIntegralImage,
+                    size_t aIntegralImageStride) const;
+#ifdef _MIPS_ARCH_LOONGSON3A
+  void BoxBlur_LS3(uint8_t* aData, int32_t aLeftLobe, int32_t aRightLobe,
+                   int32_t aTopLobe, int32_t aBottomLobe,
+                   uint32_t* aIntegralImage, size_t aIntegralImageStride) const;
+#endif
+
+  static CheckedInt<int32_t> RoundUpToMultipleOf4(int32_t aVal);
+
+  /**
+   * A rect indicating the area where blurring is unnecessary, and the blur
+   * algorithm should skip over it.
+   *
+   * This is guaranteed to be 4-pixel aligned in the x axis.
+   */
+  IntRect mSkipRect;
+
+  /**
+   * The device-space rectangle the the backing 8-bit alpha surface covers.
+   */
+  IntRect mRect;
+
+  /**
+   * A copy of the dirty rect passed to the constructor. This will only be valid
+   * if mHasDirtyRect is true.
+   */
+  Rect mDirtyRect;
+
+  /**
+   * The spread radius, in pixels.
+   */
+  IntSize mSpreadRadius;
+
+  /**
+   * The blur radius, in pixels.
+   */
+  IntSize mBlurRadius;
+
+  /**
+   * The stride of the data passed to Blur()
+   */
+  int32_t mStride;
+
+  /**
+   * The minimum size of the buffer needed for the Blur() operation.
+   */
+  size_t mSurfaceAllocationSize;
+
+  /**
+   * Whether mDirtyRect contains valid data.
+   */
+  bool mHasDirtyRect;
+};
+
+}  // namespace gfx
+}  // namespace mozilla
+
+#endif /* MOZILLA_GFX_BLUR_H_ */