diff -r 000000000000 -r 6474c204b198 gfx/thebes/gfxBlur.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/thebes/gfxBlur.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,151 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * 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 GFX_BLUR_H
+#define GFX_BLUR_H
+
+#include "gfxTypes.h"
+#include "nsSize.h"
+#include "nsAutoPtr.h"
+#include "gfxPoint.h"
+#include "mozilla/RefPtr.h"
+
+class gfxContext;
+struct gfxRect;
+struct gfxRGBA;
+class gfxCornerSizes;
+class gfxMatrix;
+
+namespace mozilla {
+  namespace gfx {
+    class AlphaBoxBlur;
+    class SourceSurface;
+    class DrawTarget;
+  }
+}
+
+/**
+ * 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.
+ *
+ * Creates an 8-bit alpha channel context for callers to draw in,
+ * spreads the contents of that context, blurs the contents, and applies
+ * it as an alpha mask on a different existing context.
+ * 
+ * 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.
+ * 
+ * A temporary surface is created in the Init function. The caller then draws
+ * any desired content onto the context acquired through GetContext, and lastly
+ * calls Paint to apply the blurred content as an alpha mask.
+ */
+class gfxAlphaBoxBlur
+{
+public:
+    gfxAlphaBoxBlur();
+
+    ~gfxAlphaBoxBlur();
+
+    /**
+     * Constructs a box blur and initializes the temporary surface.
+     * @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.
+     */
+    gfxContext* Init(const gfxRect& aRect,
+                     const gfxIntSize& aSpreadRadius,
+                     const gfxIntSize& aBlurRadius,
+                     const gfxRect* aDirtyRect,
+                     const gfxRect* aSkipRect);
+
+    /**
+     * Returns the context that should be drawn to supply the alpha mask to be
+     * blurred. If the returned surface is null, then there was an error in
+     * its creation.
+     */
+    gfxContext* GetContext()
+    {
+        return mContext;
+    }
+
+    /**
+     * Does the actual blurring/spreading and mask applying. Users of this
+     * object must have drawn whatever they want to be blurred onto the internal
+     * gfxContext returned by GetContext before calling this.
+     *
+     * @param aDestinationCtx The graphics context on which to apply the
+     *  blurred mask.
+     */
+    void Paint(gfxContext* aDestinationCtx);
+
+    /**
+     * 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 Init,
+     * above.
+     */
+    static gfxIntSize CalculateBlurRadius(const gfxPoint& aStandardDeviation);
+
+    /**
+     * Blurs a coloured rectangle onto aDestinationCtx. This is equivalent
+     * to calling Init(), drawing a rectangle onto the returned surface
+     * and then calling Paint, but may let us optimize better in the
+     * backend.
+     *
+     * @param aDestinationCtx      The destination to blur to.
+     * @param aRect                The rectangle to blur in device pixels.
+     * @param aCornerRadii         Corner radii for aRect, if it is a rounded
+     *                             rectangle.
+     * @param aBlurRadius          The standard deviation of the blur.
+     * @param aShadowColor         The color to draw the blurred shadow.
+     * @param aDirtyRect           An area in device pixels that is dirty and needs
+     *                             to be redrawn.
+     * @param aSkipRect            An area in device pixels to avoid blurring over,
+     *                             to prevent unnecessary work.
+     */
+    static void BlurRectangle(gfxContext *aDestinationCtx,
+                              const gfxRect& aRect,
+                              gfxCornerSizes* aCornerRadii,
+                              const gfxPoint& aBlurStdDev,
+                              const gfxRGBA& aShadowColor,
+                              const gfxRect& aDirtyRect,
+                              const gfxRect& aSkipRect);
+
+
+
+protected:
+    /**
+     * The context of the temporary alpha surface.
+     */
+    nsRefPtr<gfxContext> mContext;
+
+    /**
+     * The temporary alpha surface.
+     */
+    nsAutoArrayPtr<unsigned char> mData;
+
+     /**
+      * The object that actually does the blurring for us.
+      */
+    mozilla::gfx::AlphaBoxBlur *mBlur;
+};
+
+#endif /* GFX_BLUR_H */