Clipping and fragmentation code cleanup.

1. Remove an unused method from PaintLayerClipper.
2. Don't conditionally set cache slots which are ignored anyway for PaintLayerClipper
use-cases that use GeometryMapper.
3. Remove unnecessary pagination_clip parameter in PaintLayerFragment.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I6cd7b8646ac68873a245c76813ec3723d48858c9
Reviewed-on: https://chromium-review.googlesource.com/595109
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Walter Korman <wkorman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491162}

third_party/WebKit/Source/core/paint/ClipRectsCache.h

@@ -24,7 +24,7 @@ enum ClipRectsCacheSlot {
   // Relative to the LayoutView's layer. Used for compositing overlap testing.
   kAbsoluteClipRects,
 
-  // Relative to painting ancestor. Used for painting.
+  // Relative to painting ancestor. Used for SPv1 compositing.
   kPaintingClipRects,
   kPaintingClipRectsIgnoringOverflowClip,
 

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

@@ -1745,7 +1745,7 @@ void PaintLayer::CollectFragments(
   for (; !iterator.AtEnd(); iterator.Advance()) {
     PaintLayerFragment fragment;
     fragment.pagination_offset = ToLayoutPoint(iterator.PaginationOffset());
-    fragment.pagination_clip = iterator.ClipRectInFlowThread();
+    LayoutRect pagination_clip = iterator.ClipRectInFlowThread();
 
     // Set our four rects with all clipping applied that was internal to the
     // flow thread.
@@ -1755,9 +1755,11 @@ void PaintLayer::CollectFragments(
 
     // Shift to the root-relative physical position used when painting the flow
     // thread in this fragment.
-    fragment.MoveBy(fragment.pagination_offset +
-                    offset_of_pagination_layer_from_root +
-                    sub_pixel_accumulation_if_needed);
+    LayoutPoint offset = fragment.pagination_offset +
+                         offset_of_pagination_layer_from_root +
+                         sub_pixel_accumulation_if_needed;
+    fragment.MoveBy(offset);
+    pagination_clip.MoveBy(offset);
 
     // Intersect the fragment with our ancestor's background clip so that e.g.,
     // columns in an overflow:hidden block are properly clipped by the overflow.
@@ -1766,7 +1768,7 @@ void PaintLayer::CollectFragments(
     // Now intersect with our pagination clip. This will typically mean we're
     // just intersecting the dirty rect with the column clip, so the column clip
     // ends up being all we apply.
-    fragment.Intersect(fragment.pagination_clip);
+    fragment.Intersect(pagination_clip);
 
     // TODO(mstensho): Don't add empty fragments. We've always done that in some
     // cases, but there should be no reason to do so. Either filter them out
@@ -2199,8 +2201,8 @@ bool PaintLayer::HitTestContentsForFragments(
          !fragment.foreground_rect.Intersects(hit_test_location)))
       continue;
     inside_clip_rect = true;
-    if (HitTestContents(result, fragment.layer_bounds, hit_test_location,
-                        hit_test_filter))
+    if (HitTestContents(result, fragment.layer_bounds.Location(),
+                        hit_test_location, hit_test_filter))
       return true;
   }
 
@@ -2308,14 +2310,14 @@ PaintLayer* PaintLayer::HitTestLayerByApplyingTransform(
 }
 
 bool PaintLayer::HitTestContents(HitTestResult& result,
-                                 const LayoutRect& layer_bounds,
+                                 const LayoutPoint& fragment_offset,
                                  const HitTestLocation& hit_test_location,
                                  HitTestFilter hit_test_filter) const {
   DCHECK(IsSelfPaintingLayer() || HasSelfPaintingLayerDescendant());
 
   if (!GetLayoutObject().HitTest(
           result, hit_test_location,
-          ToLayoutPoint(layer_bounds.Location() - LayoutBoxLocation()),
+          ToLayoutPoint(fragment_offset - LayoutBoxLocation()),
           hit_test_filter)) {
     // It's wrong to set innerNode, but then claim that you didn't hit anything,
     // unless it is a rect-based test.

third_party/WebKit/Source/core/paint/PaintLayer.h

@@ -1078,7 +1078,7 @@ class CORE_EXPORT PaintLayer : public DisplayItemClient {
       const LayoutPoint& translation_offset = LayoutPoint()) const;
 
   bool HitTestContents(HitTestResult&,
-                       const LayoutRect& layer_bounds,
+                       const LayoutPoint& fragment_offset,
                        const HitTestLocation&,
                        HitTestFilter) const;
   bool HitTestContentsForFragments(const PaintLayerFragments&,

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

@@ -585,17 +585,4 @@ bool PaintLayerClipper::ShouldClipOverflow(
   return HasOverflowClip(layer_);
 }
 
-ClipRects& PaintLayerClipper::PaintingClipRects(
-    const PaintLayer* root_layer,
-    ShouldRespectOverflowClipType respect_overflow_clip,
-    const LayoutSize& subpixel_accumulation) const {
-  DCHECK(!use_geometry_mapper_);
-  ClipRectsContext context(root_layer, kPaintingClipRects,
-                           kIgnorePlatformOverlayScrollbarSize,
-                           subpixel_accumulation);
-  if (respect_overflow_clip == kIgnoreOverflowClip)
-    context.SetIgnoreOverflowClip();
-  return GetClipRects(context);
-}
-
 }  // namespace blink

third_party/WebKit/Source/core/paint/PaintLayerClipper.h

@@ -205,10 +205,6 @@ class CORE_EXPORT PaintLayerClipper {
                       ClipRect& foreground_rect,
                       const LayoutPoint* offset_from_root = 0) const;
 
-  ClipRects& PaintingClipRects(const PaintLayer* root_layer,
-                               ShouldRespectOverflowClipType,
-                               const LayoutSize& subpixel_accumulation) const;
-
  private:
   void ClearCache(ClipRectsCacheSlot);
   ClipRects& GetClipRects(const ClipRectsContext&) const;

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

@@ -271,7 +271,7 @@ TEST_F(PaintLayerClipperTest, ContainPaintClip) {
   EXPECT_EQ(background_rect.Rect(), foreground_rect.Rect());
   EXPECT_EQ(LayoutRect(0, 0, 200, 200), layer_bounds);
 
-  ClipRectsContext context_clip(layer, kPaintingClipRects);
+  ClipRectsContext context_clip(layer, kUncachedClipRects);
 
   layer->Clipper(PaintLayer::kUseGeometryMapper)
       .CalculateRects(context_clip, infinite_rect, layer_bounds,
@@ -304,7 +304,7 @@ TEST_F(PaintLayerClipperTest, NestedContainPaintClip) {
   EXPECT_EQ(LayoutRect(0, 0, 200, 400), foreground_rect.Rect());
   EXPECT_EQ(LayoutRect(0, 0, 200, 400), layer_bounds);
 
-  ClipRectsContext context_clip(layer->Parent(), kPaintingClipRects);
+  ClipRectsContext context_clip(layer->Parent(), kUncachedClipRects);
 
   layer->Clipper(PaintLayer::kUseGeometryMapper)
       .CalculateRects(context_clip, infinite_rect, layer_bounds,

third_party/WebKit/Source/core/paint/PaintLayerFragment.h

@@ -59,7 +59,6 @@ struct PaintLayerFragment {
     layer_bounds.MoveBy(offset);
     background_rect.MoveBy(offset);
     foreground_rect.MoveBy(offset);
-    pagination_clip.MoveBy(offset);
   }
 
   void Intersect(const LayoutRect& rect) {
@@ -108,15 +107,6 @@ struct PaintLayerFragment {
   // The physical translation to apply to shift the layer when
   // painting/hit-testing.
   LayoutPoint pagination_offset;
-
-  // Only set on paginated fragments.
-  //
-  // This is the additional clip from the fragmentainer (i.e. column or
-  // page) that applies to the layer. |backgroundRect| and |foregroundRect|
-  // are intersected with it (see collectFragments).
-  //
-  // It is in layer-local (physical) coordinates.
-  LayoutRect pagination_clip;
 };
 
 typedef Vector<PaintLayerFragment, 1> PaintLayerFragments;

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

@@ -409,9 +409,6 @@ PaintResult PaintLayerPainter::PaintLayerContents(
                               !is_painting_overlay_scrollbars;
 
   PaintLayerFragments layer_fragments;
-  ClipRectsCacheSlot cache_slot = (paint_flags & kPaintLayerUncachedClipRects)
-                                      ? kUncachedClipRects
-                                      : kPaintingClipRects;
 
   if (should_paint_content || should_paint_self_outline ||
       is_painting_overlay_scrollbars) {
@@ -445,7 +442,7 @@ PaintResult PaintLayerPainter::PaintLayerContents(
         RuntimeEnabledFeatures::SlimmingPaintV2Enabled()) {
       paint_layer_for_fragments->AppendSingleFragmentIgnoringPagination(
           layer_fragments, local_painting_info.root_layer,
-          local_painting_info.paint_dirty_rect, cache_slot,
+          local_painting_info.paint_dirty_rect, kUncachedClipRects,
           PaintLayer::kUseGeometryMapper, kIgnorePlatformOverlayScrollbarSize,
           respect_overflow_clip, &offset_from_root,
           local_painting_info.sub_pixel_accumulation);
@@ -453,7 +450,7 @@ PaintResult PaintLayerPainter::PaintLayerContents(
       PaintLayerFragments single_fragment;
       paint_layer_for_fragments->AppendSingleFragmentIgnoringPagination(
           single_fragment, local_painting_info.root_layer,
-          local_painting_info.paint_dirty_rect, cache_slot,
+          local_painting_info.paint_dirty_rect, kUncachedClipRects,
           PaintLayer::kUseGeometryMapper, kIgnorePlatformOverlayScrollbarSize,
           respect_overflow_clip, &offset_from_root,
           local_painting_info.sub_pixel_accumulation);
@@ -487,7 +484,7 @@ PaintResult PaintLayerPainter::PaintLayerContents(
     } else {
       paint_layer_for_fragments->CollectFragments(
           layer_fragments, local_painting_info.root_layer,
-          local_painting_info.paint_dirty_rect, cache_slot,
+          local_painting_info.paint_dirty_rect, kUncachedClipRects,
           PaintLayer::kUseGeometryMapper, kIgnorePlatformOverlayScrollbarSize,
           respect_overflow_clip, &offset_from_root,
           local_painting_info.sub_pixel_accumulation);
@@ -551,7 +548,7 @@ PaintResult PaintLayerPainter::PaintLayerContents(
       PaintLayerFragments filter_fragments;
       paint_layer_.AppendSingleFragmentIgnoringPagination(
           filter_fragments, local_painting_info.root_layer,
-          local_painting_info.paint_dirty_rect, cache_slot,
+          local_painting_info.paint_dirty_rect, kUncachedClipRects,
           PaintLayer::kUseGeometryMapper, kIgnorePlatformOverlayScrollbarSize,
           respect_overflow_clip, &offset_from_root,
           local_painting_info.sub_pixel_accumulation);
@@ -748,12 +745,6 @@ PaintResult PaintLayerPainter::PaintLayerWithTransform(
     else
       layer_fragments.push_back(fragment);
   } else {
-    // FIXME: This is a mess. Look closely at this code and the code in Layer
-    // and fix any issues in it & refactor to make it obvious from code
-    // structure what it does and that it's correct.
-    ClipRectsCacheSlot cache_slot = (paint_flags & kPaintLayerUncachedClipRects)
-                                        ? kUncachedClipRects
-                                        : kPaintingClipRects;
     ShouldRespectOverflowClipType respect_overflow_clip =
         ShouldRespectOverflowClip(paint_flags, paint_layer_.GetLayoutObject());
     // Calculate the transformed bounding box in the current coordinate space,
@@ -770,7 +761,7 @@ PaintResult PaintLayerPainter::PaintLayerWithTransform(
     // here.
     pagination_layer->CollectFragments(
         layer_fragments, painting_info.root_layer,
-        painting_info.paint_dirty_rect, cache_slot,
+        painting_info.paint_dirty_rect, kUncachedClipRects,
         PaintLayer::kUseGeometryMapper, kIgnorePlatformOverlayScrollbarSize,
         respect_overflow_clip, nullptr, painting_info.sub_pixel_accumulation,
         &transformed_extent);
@@ -799,12 +790,10 @@ PaintResult PaintLayerPainter::PaintLayerWithTransform(
       ancestor_background_clip_rect.SetRect(FloatClipRect());
     } else if (parent_layer) {
       // Calculate the clip rectangle that the ancestors establish.
-      ClipRectsContext clip_rects_context(
-          painting_info.root_layer,
-          (paint_flags & kPaintLayerUncachedClipRects) ? kUncachedClipRects
-                                                       : kPaintingClipRects,
-          kIgnorePlatformOverlayScrollbarSize,
-          painting_info.sub_pixel_accumulation);
+      ClipRectsContext clip_rects_context(painting_info.root_layer,
+                                          kUncachedClipRects,
+                                          kIgnorePlatformOverlayScrollbarSize,
+                                          painting_info.sub_pixel_accumulation);
       if (ShouldRespectOverflowClip(paint_flags,
                                     paint_layer_.GetLayoutObject()) ==
           kIgnoreOverflowClip)