Bug 781731 - Fix shadow surface extents so they aren't double padded. r=joe

gfx/2d/Blur.cpp

@@ -330,7 +330,8 @@ AlphaBoxBlur::AlphaBoxBlur(const Rect& aRect,
                            const Rect* aSkipRect)
  : mSpreadRadius(aSpreadRadius),
    mBlurRadius(aBlurRadius),
-   mData(nullptr)
+   mData(nullptr),
+   mFreeData(true)
 {
   Rect rect(aRect);
   rect.Inflate(Size(aBlurRadius + aSpreadRadius));
@@ -384,9 +385,25 @@ AlphaBoxBlur::AlphaBoxBlur(const Rect& aRect,
   }
 }
 
+AlphaBoxBlur::AlphaBoxBlur(uint8_t* aData,
+                           const Rect& aRect,
+                           int32_t aStride,
+                           float aSigma)
+  : mSpreadRadius(),
+    mBlurRadius(CalculateBlurRadius(Point(aSigma, aSigma))),
+    mData(aData),
+    mFreeData(false),
+    mStride(aStride),
+    mRect(aRect.x, aRect.y, aRect.width, aRect.height)
+{
+}
+
+
 AlphaBoxBlur::~AlphaBoxBlur()
 {
-  free(mData);
+  if (mFreeData) {
+    delete mData;
+  }
 }
 
 unsigned char*

gfx/2d/Blur.h

@@ -57,6 +57,11 @@ public:
                const Rect* aDirtyRect,
                const Rect* aSkipRect);
 
+  AlphaBoxBlur(uint8_t* aData,
+               const Rect& aRect,
+               int32_t aStride,
+               float aSigma);
+
   ~AlphaBoxBlur();
 
   /**
@@ -135,7 +140,12 @@ private:
   /**
    * A pointer to the backing 8-bit alpha surface.
    */
-  unsigned char* mData;
+  uint8_t* mData;
+
+  /**
+   * True if we need to dispose the data.
+   */
+  bool mFreeData;
 
   /**
    * The stride of the data contained in mData.

gfx/2d/DrawTargetCairo.cpp

@@ -387,43 +387,33 @@ DrawTargetCairo::DrawSurfaceWithShadow(SourceSurface *aSurface,
     return;
   }
 
-  WillChange();
-
   Float width = aSurface->GetSize().width;
   Float height = aSurface->GetSize().height;
-  Rect extents(0, 0, width, height);
-
-  AlphaBoxBlur blur(extents, IntSize(0, 0),
-                    AlphaBoxBlur::CalculateBlurRadius(Point(aSigma, aSigma)),
-                    nullptr, nullptr);
-  if (!blur.GetData()) {
-    return;
-  }
-
-  IntSize blursize = blur.GetSize();
-  cairo_surface_t* blursurf = cairo_image_surface_create_for_data(blur.GetData(),
-                                                                  CAIRO_FORMAT_A8,
-                                                                  blursize.width,
-                                                                  blursize.height,
-                                                                  blur.GetStride());
-
-  ClearSurfaceForUnboundedSource(aOperator);
-  
-  // Draw the source surface into the surface we're going to blur.
+ 
   SourceSurfaceCairo* source = static_cast<SourceSurfaceCairo*>(aSurface);
   cairo_surface_t* surf = source->GetSurface();
+ 
+  cairo_surface_t* blursurf = cairo_image_surface_create(CAIRO_FORMAT_A8,
+                                                         width,
+                                                         height);
 
   cairo_t* ctx = cairo_create(blursurf);
   cairo_set_source_surface(ctx, surf, 0, 0);
-  IntRect blurrect = blur.GetRect();
   cairo_new_path(ctx);
-  cairo_rectangle(ctx, blurrect.x, blurrect.y, blurrect.width, blurrect.height);
+  cairo_rectangle(ctx, 0, 0, width, height);
   cairo_fill(ctx);
   cairo_destroy(ctx);
-
-  // Blur the result, then use that blurred result as a mask to draw the shadow
-  // colour to the surface.
+ 
+  Rect extents(0, 0, width, height);
+  AlphaBoxBlur blur(cairo_image_surface_get_data(blursurf),
+                    extents,
+                    cairo_image_surface_get_stride(blursurf),
+                    aSigma);
   blur.Blur();
+
+  WillChange();
+  ClearSurfaceForUnboundedSource(aOperator);
+  
   cairo_save(mContext);
   cairo_set_operator(mContext, GfxOpToCairoOp(aOperator));
   cairo_identity_matrix(mContext);