Extract subpixel offsets from composited layer transforms when possible.

third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintLayerPainter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/layout/ClipPathOperation.h"
 #include "core/layout/LayoutBlock.h"
@@ skipping 78 matching lines @@
         return FullyPainted;
 
     if (m_paintLayer.paintsWithTransparency(paintingInfo.getGlobalPaintFlags()))
         paintFlags |= PaintLayerHaveTransparency;
 
     // Transforms will be applied by property nodes directly for SPv2.
     // PaintLayerAppliedTransform is used in LayoutReplica, to avoid applying the transform twice.
     if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() && m_paintLayer.paintsWithTransform(paintingInfo.getGlobalPaintFlags()) && !(paintFlags & PaintLayerAppliedTransform))
         return paintLayerWithTransform(context, paintingInfo, paintFlags);
 
+
+
     return paintLayerContentsAndReflection(context, paintingInfo, paintFlags);
 }
 
 PaintLayerPainter::PaintResult PaintLayerPainter::paintLayerContentsAndReflection(GraphicsContext& context, const PaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
 {
     ASSERT(m_paintLayer.isSelfPaintingLayer() || m_paintLayer.hasSelfPaintingLayerDescendant());
 
     PaintLayerFlags localPaintFlags = paintFlags & ~(PaintLayerAppliedTransform);
 
     PaintResult result = FullyPainted;
@@ skipping 406 matching lines @@
     ASSERT(!RuntimeEnabledFeatures::slimmingPaintV2Enabled());
 
     // This involves subtracting out the position of the layer in our current coordinate space, but preserving
     // the accumulated error for sub-pixel layout.
     LayoutPoint delta;
     m_paintLayer.convertToLayerCoords(paintingInfo.rootLayer, delta);
     delta.moveBy(fragmentTranslation);
     TransformationMatrix transform(m_paintLayer.renderableTransform(paintingInfo.getGlobalPaintFlags()));
     IntPoint roundedDelta = roundedIntPoint(delta);
     transform.translateRight(roundedDelta.x(), roundedDelta.y());
+    LOG(ERROR) << "PaintLayerPainter::paintFragmentByApplyingTransform: delta x=" << roundedDelta.x() << ", y=" << roundedDelta.y();
     LayoutSize adjustedSubPixelAccumulation = paintingInfo.subPixelAccumulation + (delta - roundedDelta);
 
     // TODO(jbroman): Put the real transform origin here, instead of using a
     // matrix with the origin baked in.
     FloatPoint3D transformOrigin;
     Transform3DRecorder transform3DRecorder(context, *m_paintLayer.layoutObject(), DisplayItem::Transform3DElementTransform, transform, transformOrigin);
 
     // Now do a paint with the root layer shifted to be us.
     PaintLayerPaintingInfo transformedPaintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(transform.inverse().mapRect(paintingInfo.paintDirtyRect))), paintingInfo.getGlobalPaintFlags(),
         adjustedSubPixelAccumulation);
@@ skipping 239 matching lines @@
     if (!m_paintLayer.containsDirtyOverlayScrollbars())
         return;
 
     PaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), paintFlags, LayoutSize());
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink