Bug 1285320 - (Part 1) Add struct "CachedBorderImageData" to keep cached data for border in nsStyleImage. r=dholbert

--HG--
extra : rebase_source : 5c654bd0dab03864ed1e1bf2883525bccea73d8a

layout/style/nsStyleStruct.cpp

@@ -1909,6 +1909,30 @@ nsStyleGradient::HasCalc()
          mRadiusX.IsCalcUnit() || mRadiusY.IsCalcUnit();
 }
 
+// --------------------
+// CachedBorderImageData
+//
+void
+CachedBorderImageData::PurgeCachedImages()
+{
+  mSubImages.Clear();
+}
+
+void
+CachedBorderImageData::SetSubImage(uint8_t aIndex, imgIContainer* aSubImage)
+{
+  mSubImages.ReplaceObjectAt(aSubImage, aIndex);
+}
+
+imgIContainer*
+CachedBorderImageData::GetSubImage(uint8_t aIndex)
+{
+  imgIContainer* subImage = nullptr;
+  if (aIndex < mSubImages.Count())
+    subImage = mSubImages[aIndex];
+  return subImage;
+}
+
 // --------------------
 // nsStyleImage
 //
@@ -2004,7 +2028,9 @@ nsStyleImage::SetImageData(imgRequestProxy* aImage)
     mImage = aImage;
     mType = eStyleImageType_Image;
   }
-  mSubImages.Clear();
+  if (mCachedBIData) {
+    mCachedBIData->PurgeCachedImages();
+  }
 }
 
 void

layout/style/nsStyleStruct.h

@@ -18,6 +18,7 @@
 #include "mozilla/SheetType.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/StyleStructContext.h"
+#include "mozilla/UniquePtr.h"
 #include "nsAutoPtr.h"
 #include "nsColor.h"
 #include "nsCoord.h"
@@ -246,6 +247,16 @@ enum nsStyleImageType {
   eStyleImageType_Element
 };
 
+struct CachedBorderImageData
+{
+  void PurgeCachedImages();
+  void SetSubImage(uint8_t aIndex, imgIContainer* aSubImage);
+  imgIContainer* GetSubImage(uint8_t aIndex);
+
+private:
+  nsCOMArray<imgIContainer> mSubImages;
+};
+
 /**
  * Represents a paintable image of one of the following types.
  * (1) A real image loaded from an external source.
@@ -361,9 +372,11 @@ struct nsStyleImage
 
 private:
   void DoCopy(const nsStyleImage& aOther);
+  void EnsureCachedBIData() const;
 
-  // Cache for border-image painting.
-  nsCOMArray<imgIContainer> mSubImages;
+  // This variable keeps some cache data for border image and is lazily
+  // allocated since it is only used in border image case.
+  mozilla::UniquePtr<CachedBorderImageData> mCachedBIData;
 
   nsStyleImageType mType;
   union {

layout/style/nsStyleStructInlines.h

@@ -16,19 +16,26 @@
 #include "nsIContent.h" // for GetParent()
 #include "nsTextFrame.h" // for nsTextFrame::ShouldSuppressLineBreak
 
+inline void
+nsStyleImage::EnsureCachedBIData() const
+{
+  if (!mCachedBIData) {
+    const_cast<nsStyleImage*>(this)->mCachedBIData =
+      mozilla::MakeUnique<CachedBorderImageData>();
+  }
+}
+
 inline void
 nsStyleImage::SetSubImage(uint8_t aIndex, imgIContainer* aSubImage) const
 {
-  const_cast<nsStyleImage*>(this)->mSubImages.ReplaceObjectAt(aSubImage, aIndex);
+  EnsureCachedBIData();
+  mCachedBIData->SetSubImage(aIndex, aSubImage);
 }
 
 inline imgIContainer*
 nsStyleImage::GetSubImage(uint8_t aIndex) const
 {
-  imgIContainer* subImage = nullptr;
-  if (aIndex < mSubImages.Count())
-    subImage = mSubImages[aIndex];
-  return subImage;
+  return (mCachedBIData) ? mCachedBIData->GetSubImage(aIndex) : nullptr;
 }
 
 bool