Consider subpixel accumulation when invalidating paint

Source/core/rendering/RenderLayerRepainter.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 59 matching lines @@
 }
 
 // Since we're only painting non-composited layers, we know that they all share the same repaintContainer.
 void RenderLayerRepainter::repaintIncludingNonCompositingDescendants()
 {
     repaintIncludingNonCompositingDescendantsInternal(m_renderer.containerForPaintInvalidation());
 }
 
 void RenderLayerRepainter::repaintIncludingNonCompositingDescendantsInternal(const RenderLayerModelObject* repaintContainer)
 {
-    m_renderer.invalidatePaintUsingContainer(repaintContainer, pixelSnappedIntRect(m_renderer.boundsRectForPaintInvalidation(repaintContainer)), InvalidationLayer);
+    m_renderer.invalidatePaintUsingContainer(repaintContainer, m_renderer.boundsRectForPaintInvalidation(repaintContainer), InvalidationLayer);
 
     // FIXME: Repaints can be issued during style recalc at present, via RenderLayerModelObject::styleWillChange. This happens in scenarios when
     // repaint is needed but not layout.
     DisableCompositingQueryAsserts disabler;
 
     for (RenderLayer* curr = m_renderer.layer()->firstChild(); curr; curr = curr->nextSibling()) {
         if (curr->compositingState() != PaintsIntoOwnBacking && curr->compositingState() != PaintsIntoGroupedBacking)
             curr->repainter().repaintIncludingNonCompositingDescendantsInternal(repaintContainer);
     }
 }
@@ skipping 26 matching lines @@
         absRect.moveBy(delta);
 
         if (absRect.isEmpty())
             return;
 
         RenderView* view = m_renderer.view();
         if (view)
             view->repaintViewRectangle(absRect);
         return;
     }
-    IntRect repaintRect = pixelSnappedIntRect(r);
     // FIXME: generalize accessors to backing GraphicsLayers so that this code is squasphing-agnostic.
     if (m_renderer.layer()->groupedMapping()) {
+        // FIXME: how about subpixel accumulation?

[chrishtr, 2014/07/02 04:39:58]

Instead of a non-squashing specific fix, please change this CL to do the
following before line 128:

r.move(renderer()->subpixelAccumulation());


Then you can remove the FIXME and the subpixelAccumulation part of
CompositedLayerMapping.cpp:1928.

[Xianzhu, 2014/07/02 16:19:10]

Thanks for the solution! Done.

         if (GraphicsLayer* squashingLayer = m_renderer.layer()->groupedMapping()->squashingLayer())
-            squashingLayer->setNeedsDisplayInRect(repaintRect);
+            squashingLayer->setNeedsDisplayInRect(pixelSnappedIntRect(r));
     } else {
-        m_renderer.layer()->compositedLayerMapping()->setContentsNeedDisplayInRect(repaintRect);
+        m_renderer.layer()->compositedLayerMapping()->setContentsNeedDisplayInRect(r);
     }
 }
 
 void RenderLayerRepainter::setFilterBackendNeedsRepaintingInRect(const LayoutRect& rect)
 {
     if (rect.isEmpty())
         return;
     LayoutRect rectForRepaint = rect;
     m_renderer.style()->filterOutsets().expandRect(rectForRepaint);
 
@@ skipping 31 matching lines @@
 RenderLayer* RenderLayerRepainter::enclosingFilterRepaintLayer() const
 {
     for (const RenderLayer* curr = m_renderer.layer(); curr; curr = curr->parent()) {
         if ((curr != m_renderer.layer() && curr->requiresFullLayerImageForFilters()) || curr->compositingState() == PaintsIntoOwnBacking || curr->isRootLayer())
             return const_cast<RenderLayer*>(curr);
     }
     return 0;
 }
 
 } // Namespace WebCore