Bug 1201327 - Let DLBI detect background-position changes. r=mattwoodrow

--HG--
extra : commitid : CDTUZNG0PYF
extra : rebase_source : 0f5db6e4a5cde5fe8faeb77e15f95d12f6753fac

layout/base/nsDisplayList.cpp

@@ -2141,6 +2141,25 @@ nsDisplayBackgroundImage::nsDisplayBackgroundImage(nsDisplayListBuilder* aBuilde
   MOZ_COUNT_CTOR(nsDisplayBackgroundImage);
 
   mBounds = GetBoundsInternal(aBuilder);
+  mDestArea = GetDestAreaInternal(aBuilder);
+}
+
+nsRect
+nsDisplayBackgroundImage::GetDestAreaInternal(nsDisplayListBuilder* aBuilder)
+{
+  if (!mBackgroundStyle) {
+    return nsRect();
+  }
+
+  nsPresContext* presContext = mFrame->PresContext();
+  uint32_t flags = aBuilder->GetBackgroundPaintFlags();
+  nsRect borderArea = nsRect(ToReferenceFrame(), mFrame->GetSize());
+  const nsStyleBackground::Layer &layer = mBackgroundStyle->mLayers[mLayer];
+
+  nsBackgroundLayerState state =
+    nsCSSRendering::PrepareBackgroundLayer(presContext, mFrame, flags,
+                                           borderArea, borderArea, layer);
+  return state.mDestArea;
 }
 
 nsDisplayBackgroundImage::~nsDisplayBackgroundImage()
@@ -2791,6 +2810,13 @@ void nsDisplayBackgroundImage::ComputeInvalidationRegion(nsDisplayListBuilder* a
     }
     return;
   }
+  if (!mDestArea.IsEqualInterior(geometry->mDestArea)) {
+    // Dest area changed in a way that could cause everything to change,
+    // so invalidate everything (both old and new painting areas).
+    aInvalidRegion->Or(bounds, geometry->mBounds);
+    NotifyRenderingChanged();
+    return;
+  }
   if (aBuilder->ShouldSyncDecodeImages()) {
     const nsStyleImage& image = mBackgroundStyle->mLayers[mLayer].mImage;
     if (image.GetType() == eStyleImageType_Image &&

layout/base/nsDisplayList.h

@@ -2575,6 +2575,11 @@ public:
    */
   nsRect GetPositioningArea();
 
+  /**
+   * Return the destination area of one instance of the image.
+   */
+  nsRect GetDestArea() const { return mDestArea; }
+
   /**
    * Returns true if existing rendered pixels of this display item may need
    * to be redrawn if the positioning area size changes but its position does
@@ -2615,6 +2620,7 @@ protected:
                                   gfxRect* aDestRect);
   bool IsNonEmptyFixedImage() const;
   nsRect GetBoundsInternal(nsDisplayListBuilder* aBuilder);
+  nsRect GetDestAreaInternal(nsDisplayListBuilder* aBuilder);
 
   void PaintInternal(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx,
                      const nsRect& aBounds, nsRect* aClipRect);
@@ -2637,6 +2643,7 @@ protected:
   LayoutDeviceRect mImageLayerDestRect;
   /* Bounds of this display item */
   nsRect mBounds;
+  nsRect mDestArea;
   uint32_t mLayer;
 };
 

layout/base/nsDisplayListInvalidation.cpp

@@ -63,6 +63,7 @@ nsDisplayBackgroundGeometry::nsDisplayBackgroundGeometry(nsDisplayBackgroundImag
   : nsDisplayItemGeometry(aItem, aBuilder)
   , nsImageGeometryMixin(aItem, aBuilder)
   , mPositioningArea(aItem->GetPositioningArea())
+  , mDestArea(aItem->GetDestArea())
 {}
 
 void
@@ -70,6 +71,7 @@ nsDisplayBackgroundGeometry::MoveBy(const nsPoint& aOffset)
 {
   nsDisplayItemGeometry::MoveBy(aOffset);
   mPositioningArea.MoveBy(aOffset);
+  mDestArea.MoveBy(aOffset);
 }
 
 nsDisplayThemedBackgroundGeometry::nsDisplayThemedBackgroundGeometry(nsDisplayThemedBackground* aItem,

layout/base/nsDisplayListInvalidation.h

@@ -194,6 +194,7 @@ public:
   virtual void MoveBy(const nsPoint& aOffset) override;
 
   nsRect mPositioningArea;
+  nsRect mDestArea;
 };
 
 class nsDisplayThemedBackgroundGeometry : public nsDisplayItemGeometry

layout/reftests/image-rect/reftest.list

@@ -3,7 +3,7 @@ skip-if(B2G||Mulet) == background-common-usage-floating-point.html background-co
 == background-common-usage-pixel.html background-common-usage-ref.html
 == background-draw-nothing-empty-rect.html background-draw-nothing-ref.html
 == background-draw-nothing-invalid-syntax.html background-draw-nothing-ref.html
-asserts(0-4) == background-draw-nothing-malformed-images.html background-draw-nothing-ref.html # Bug 576419
+asserts(0-6) == background-draw-nothing-malformed-images.html background-draw-nothing-ref.html # Bug 576419
 == background-monster-rect.html background-monster-rect-ref.html
 == background-over-size-rect.html background-over-size-rect-ref.html
 == background-test-parser.html background-test-parser-ref.html