From 4c1b0ad4f8687150c56172a13a0279686cf7d1b8 Mon Sep 17 00:00:00 2001
From: Lee Salzman <lsalzman@mozilla.com>
Date: Fri, 25 Mar 2016 22:14:50 -0400
Subject: [PATCH] Bug 1259621 - use AlphaBoxBlur in
 DrawTargetSkia::DrawSurfaceWithShadow. r=mchang

---
 gfx/2d/DrawTargetSkia.cpp | 36 +++++++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/gfx/2d/DrawTargetSkia.cpp b/gfx/2d/DrawTargetSkia.cpp
index 3232dde9c3c5..b44a4c8fba13 100644
--- a/gfx/2d/DrawTargetSkia.cpp
+++ b/gfx/2d/DrawTargetSkia.cpp
@@ -17,6 +17,7 @@
 #include "skia/include/core/SkColorFilter.h"
 #include "skia/include/effects/SkBlurImageFilter.h"
 #include "skia/include/effects/SkLayerRasterizer.h"
+#include "Blur.h"
 #include "Logging.h"
 #include "Tools.h"
 #include "DataSurfaceHelpers.h"
@@ -432,16 +433,37 @@ DrawTargetSkia::DrawSurfaceWithShadow(SourceSurface *aSurface,
   // to blur the image ourselves.
 
   SkPaint shadowPaint;
-  SkAutoTUnref<SkImageFilter> blurFilter(SkBlurImageFilter::Create(aSigma, aSigma));
-  SkAutoTUnref<SkColorFilter> colorFilter(
-    SkColorFilter::CreateModeFilter(ColorToSkColor(aColor, 1.0), SkXfermode::kSrcIn_Mode));
-
   shadowPaint.setXfermode(paint.getXfermode());
-  shadowPaint.setImageFilter(blurFilter.get());
-  shadowPaint.setColorFilter(colorFilter.get());
 
   IntPoint shadowDest = RoundedToInt(aDest + aOffset);
-  mCanvas->drawBitmap(bitmap, shadowDest.x, shadowDest.y, &shadowPaint);
+
+  SkBitmap blurMask;
+  if (!UsingSkiaGPU() &&
+      bitmap.extractAlpha(&blurMask)) {
+    // Prefer using our own box blur instead of Skia's when we're
+    // not using the GPU. It currently performs much better than
+    // SkBlurImageFilter or SkBlurMaskFilter on the CPU.
+    AlphaBoxBlur blur(Rect(0, 0, blurMask.width(), blurMask.height()),
+                      int32_t(blurMask.rowBytes()),
+                      aSigma, aSigma);
+    blurMask.lockPixels();
+    blur.Blur(reinterpret_cast<uint8_t*>(blurMask.getPixels()));
+    blurMask.unlockPixels();
+    blurMask.notifyPixelsChanged();
+
+    shadowPaint.setColor(ColorToSkColor(aColor, 1.0f));
+
+    mCanvas->drawBitmap(blurMask, shadowDest.x, shadowDest.y, &shadowPaint);
+  } else {
+    SkAutoTUnref<SkImageFilter> blurFilter(SkBlurImageFilter::Create(aSigma, aSigma));
+    SkAutoTUnref<SkColorFilter> colorFilter(
+      SkColorFilter::CreateModeFilter(ColorToSkColor(aColor, 1.0f), SkXfermode::kSrcIn_Mode));
+
+    shadowPaint.setImageFilter(blurFilter.get());
+    shadowPaint.setColorFilter(colorFilter.get());
+
+    mCanvas->drawBitmap(bitmap, shadowDest.x, shadowDest.y, &shadowPaint);
+  }
 
   // Composite the original image after the shadow
   IntPoint dest = RoundedToInt(aDest);