Fix border radius on composited children.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index 93fc1fc50f8104c5db3e548ec07256bf3fd67305..d1230d559749ac8654ac950300551e1afe27aacc 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -9,6 +9,7 @@
 #include "core/paint/ClipPathClipper.h"
 #include "core/paint/FilterPainter.h"
 #include "core/paint/LayerClipRecorder.h"
+#include "core/paint/LayoutObjectDrawingRecorder.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintInfo.h"
 #include "core/paint/PaintLayer.h"
@@ -361,7 +362,8 @@ PaintResult PaintLayerPainter::paintLayerContents(
   // scrolling contents and scrollbars.
   if (m_paintLayer.layoutObject()->hasClipPath() &&
       (!m_paintLayer.needsCompositedScrolling() ||
-       (paintFlags & PaintLayerPaintingChildClippingMaskPhase))) {
+       (paintFlags & (PaintLayerPaintingChildClippingMaskPhase |
+                      PaintLayerPaintingAncestorClippingMaskPhase)))) {
     paintingInfo.ancestorHasClipPathClipping = true;
 
     LayoutRect referenceBox(m_paintLayer.boxForClipPath());
@@ -412,19 +414,35 @@ PaintResult PaintLayerPainter::paintLayerContents(
     ClipRectsCacheSlot cacheSlot = (paintFlags & PaintLayerUncachedClipRects)
                                        ? UncachedClipRects
                                        : PaintingClipRects;
+    LayoutPoint offsetToClipper;
+    PaintLayer* paintLayerForFragments = &m_paintLayer;
+    if (paintFlags & PaintLayerPaintingAncestorClippingMaskPhase) {
+      // Compute fragments and their clips with respect to the clipping
+      // container. The paint rect is in this layer's space, so convert it
+      // to the clipper's layer's space. The rootLayer is also changed to
+      // the clipper's layer to simplify coordinate system adjustments.
+      // The change to rootLayer must persist to correctly record the clips.
+      paintLayerForFragments =
+          m_paintLayer.clippingContainer()->enclosingLayer();
+      localPaintingInfo.rootLayer = paintLayerForFragments;
+      m_paintLayer.convertToLayerCoords(localPaintingInfo.rootLayer,
+                                        offsetToClipper);
+      localPaintingInfo.paintDirtyRect.moveBy(offsetToClipper);
+    }
+
     // TODO(trchen): We haven't decided how to handle visual fragmentation with
     // SPv2.  Related thread
     // https://groups.google.com/a/chromium.org/forum/#!topic/graphics-dev/81XuWFf-mxM
     if (fragmentPolicy == ForceSingleFragment ||
         RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
-      m_paintLayer.appendSingleFragmentIgnoringPagination(
+      paintLayerForFragments->appendSingleFragmentIgnoringPagination(
           layerFragments, localPaintingInfo.rootLayer,
           localPaintingInfo.paintDirtyRect, cacheSlot,
           IgnoreOverlayScrollbarSize, respectOverflowClip, &offsetFromRoot,
           localPaintingInfo.subPixelAccumulation);
     } else if (isFixedPositionObjectInPagedMedia()) {
       PaintLayerFragments singleFragment;
-      m_paintLayer.appendSingleFragmentIgnoringPagination(
+      paintLayerForFragments->appendSingleFragmentIgnoringPagination(
           singleFragment, localPaintingInfo.rootLayer,
           localPaintingInfo.paintDirtyRect, cacheSlot,
           IgnoreOverlayScrollbarSize, respectOverflowClip, &offsetFromRoot,
@@ -432,11 +450,23 @@ PaintResult PaintLayerPainter::paintLayerContents(
       repeatFixedPositionObjectInPages(singleFragment[0], paintingInfo,
                                        layerFragments);
     } else {
-      m_paintLayer.collectFragments(layerFragments, localPaintingInfo.rootLayer,
-                                    localPaintingInfo.paintDirtyRect, cacheSlot,
-                                    IgnoreOverlayScrollbarSize,
-                                    respectOverflowClip, &offsetFromRoot,
-                                    localPaintingInfo.subPixelAccumulation);
+      paintLayerForFragments->collectFragments(
+          layerFragments, localPaintingInfo.rootLayer,
+          localPaintingInfo.paintDirtyRect, cacheSlot,
+          IgnoreOverlayScrollbarSize, respectOverflowClip, &offsetFromRoot,
+          localPaintingInfo.subPixelAccumulation);
+    }
+
+    if (paintFlags & PaintLayerPaintingAncestorClippingMaskPhase) {
+      // Fragment offsets have been computed in the clipping container's
+      // layer's coordinate system, but for the rest of painting we need
+      // them in the layer coordinate. So move them and the foreground rect
+      // that is also in the clipper's space.
+      LayoutSize negativeOffset(-offsetToClipper.x(), -offsetToClipper.y());
+      for (auto& fragment : layerFragments) {
+        fragment.foregroundRect.move(negativeOffset);
+        fragment.paginationOffset.move(negativeOffset);
+      }
     }
 
     if (shouldPaintContent) {
@@ -537,7 +567,8 @@ PaintResult PaintLayerPainter::paintLayerContents(
       shouldPaintContent && m_paintLayer.layoutObject()->hasMask() &&
       !selectionOnly;
   bool shouldPaintClippingMask =
-      (paintFlags & PaintLayerPaintingChildClippingMaskPhase) &&
+      (paintFlags & (PaintLayerPaintingChildClippingMaskPhase |
+                     PaintLayerPaintingAncestorClippingMaskPhase)) &&
       shouldPaintContent && !selectionOnly;
 
   if (shouldPaintMask)
@@ -722,7 +753,7 @@ PaintResult PaintLayerPainter::paintLayerWithTransform(
       if (needsToClip(paintingInfo, clipRectForFragment)) {
         clipRecorder.emplace(context, *parentLayer->layoutObject(),
                              DisplayItem::kClipLayerParent, clipRectForFragment,
-                             &paintingInfo, fragment.paginationOffset,
+                             paintingInfo.rootLayer, fragment.paginationOffset,
                              paintFlags);
       }
     }
@@ -860,7 +891,7 @@ void PaintLayerPainter::paintOverflowControlsForFragments(
     if (needsToClip(localPaintingInfo, fragment.backgroundRect)) {
       clipRecorder.emplace(context, *m_paintLayer.layoutObject(),
                            DisplayItem::kClipLayerOverflowControls,
-                           fragment.backgroundRect, &localPaintingInfo,
+                           fragment.backgroundRect, localPaintingInfo.rootLayer,
                            fragment.paginationOffset, paintFlags);
     }
 
@@ -910,9 +941,21 @@ void PaintLayerPainter::paintFragmentWithPhase(
         break;
     }
 
+    // TODO(schenney): Nested border-radius clips are not applied to composited
+    // children, probably due to an incorrect clipRoot.
+    // https://bugs.chromium.org/p/chromium/issues/detail?id=672561
     clipRecorder.emplace(context, *m_paintLayer.layoutObject(), clipType,
-                         clipRect, &paintingInfo, fragment.paginationOffset,
-                         paintFlags, clippingRule);
+                         clipRect, paintingInfo.rootLayer,
+                         fragment.paginationOffset, paintFlags, clippingRule);
+  }
+
+  // If we are painting a mask for any reason and we have already processed the
+  // clips, there is no need to go through the remaining painting pipeline.
+  // We know that the mask just needs the area bounded by the clip rects to be
+  // filled with black.
+  if (clipRecorder && phase == PaintPhaseClippingMask) {
+    fillMaskingFragment(context, clipRect);

[Stephen Chennney, 2017/01/04 19:22:46]

This avoids all sorts of problems with coordinate systems and the necessary
paint area. We know we want a mask that allows anything inside the clip. If we
use the child's area we fail to render siblings that are also inside the clip.
If we try to use the clipper's area we have problems with border-related offsets
in computing the paint area, with no easy way to resolve them. Just filling all
of the clip is the fastest approach.

+    return;
   }
 
   LayoutRect newCullRect(clipRect.rect());
@@ -984,7 +1027,8 @@ void PaintLayerPainter::paintForegroundForFragments(
       needsToClip(localPaintingInfo, layerFragments[0].foregroundRect)) {
     clipRecorder.emplace(context, *m_paintLayer.layoutObject(),
                          DisplayItem::kClipLayerForeground,
-                         layerFragments[0].foregroundRect, &localPaintingInfo,
+                         layerFragments[0].foregroundRect,
+                         localPaintingInfo.rootLayer,
                          layerFragments[0].paginationOffset, paintFlags);
     clipState = HasClipped;
   }
@@ -1130,4 +1174,17 @@ void PaintLayerPainter::paintOverlayScrollbars(
   m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
+void PaintLayerPainter::fillMaskingFragment(GraphicsContext& context,
+                                            const ClipRect& clipRect) {
+  const LayoutBox* layoutBox = toLayoutBox(m_paintLayer.layoutObject());
+  if (LayoutObjectDrawingRecorder::useCachedDrawingIfPossible(
+          context, *layoutBox, PaintPhaseClippingMask))
+    return;
+
+  IntRect snappedClipRect = pixelSnappedIntRect(clipRect.rect());
+  LayoutObjectDrawingRecorder drawingRecorder(
+      context, *layoutBox, PaintPhaseClippingMask, snappedClipRect);
+  context.fillRect(snappedClipRect, Color::black);
+}
+
 }  // namespace blink