Bug 1254134 - Use the full image size as the bounds for image layers during layer tree invalidation. r=mattwoodrow

MozReview-Commit-ID: DBF3H3I4rbS

--HG--
extra : rebase_source : 9fff4e9252027f354d6490d429085e11b0536212

gfx/layers/LayerTreeInvalidation.cpp

@@ -496,12 +496,42 @@ struct ImageLayerProperties : public LayerPropertiesBase
     , mLastFrameID(-1)
     , mIsMask(aIsMask)
   {
+    if (mContainer) {
+      mRect.SizeTo(mContainer->GetCurrentSize());
+    }
     if (mImageHost) {
+      mRect.SizeTo(mImageHost->GetImageSize());
       mLastProducerID = mImageHost->GetLastProducerID();
       mLastFrameID = mImageHost->GetLastFrameID();
     }
   }
 
+  // For image layers we want to use the image size rather than the
+  // visible region for two reasons:
+  // 1) If the image is mask layer, then the visible region is empty
+  // 2) If the image is partially outside the displayport then the visible
+  //    region is truncated, but the compositor is still drawing the full
+  //    image each time. Partial composition on the image can result in
+  //    the un-composited portion of the image becoming visibly stale in
+  //    a checkerboarding area.
+  IntRect NewTransformedBounds() override
+  {
+    IntRect rect;
+    ImageLayer* imageLayer = static_cast<ImageLayer*>(mLayer.get());
+    if (ImageContainer* container = imageLayer->GetContainer()) {
+      rect.SizeTo(container->GetCurrentSize());
+    }
+    if (ImageHost* host = GetImageHost(imageLayer)) {
+      rect.SizeTo(host->GetImageSize());
+    }
+    return TransformRect(rect, GetTransformForInvalidation(mLayer));
+  }
+
+  IntRect OldTransformedBounds() override
+  {
+    return TransformRect(mRect, mTransform);
+  }
+
   virtual nsIntRegion ComputeChangeInternal(const char* aPrefix,
                                             NotifySubDocInvalidationFunc aCallback,
                                             bool& aGeometryChanged)
@@ -527,20 +557,6 @@ struct ImageLayerProperties : public LayerPropertiesBase
         (host && host->GetFrameID() != mLastFrameID)) {
       aGeometryChanged = true;
 
-      if (mIsMask) {
-        // Mask layers have an empty visible region, so we have to
-        // use the image size instead.
-        IntSize size;
-        if (container) {
-          size = container->GetCurrentSize();
-        }
-        if (host) {
-          size = host->GetImageSize();
-        }
-        IntRect rect(0, 0, size.width, size.height);
-        LTI_DUMP(rect, "mask");
-        return TransformRect(rect, GetTransformForInvalidation(mLayer));
-      }
       LTI_DUMP(NewTransformedBounds(), "bounds");
       return NewTransformedBounds();
     }
@@ -553,6 +569,7 @@ struct ImageLayerProperties : public LayerPropertiesBase
   Filter mFilter;
   gfx::IntSize mScaleToSize;
   ScaleMode mScaleMode;
+  IntRect mRect;
   int32_t mLastProducerID;
   int32_t mLastFrameID;
   bool mIsMask;