Place the out of flow positioned blocks

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc

Index: third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
index 039ca524b65373f21255750a959c87ea33b288f2..c3eb0c6681bdbd3c37c1186f3c005df73f214d69 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
@@ -12,6 +12,7 @@
 #include "core/layout/ng/ng_fragment.h"
 #include "core/layout/ng/ng_layout_opportunity_iterator.h"
 #include "core/layout/ng/ng_length_utils.h"
+#include "core/layout/ng/ng_out_of_flow_layout_part.h"
 #include "core/layout/ng/ng_units.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/LengthFunctions.h"
@@ -243,23 +244,36 @@ NGLayoutStatus NGBlockLayoutAlgorithm::Layout(
     }
     case kStatePrepareForChildLayout: {
       if (current_child_) {
-        // TODO(atotic): uncomment this code when implementing oof layout.
-        // This code cannot be turned on because it prevents layout of
-        // oof children, and non-layedout objects trigger  a DCHECK.
-        // EPosition position = current_child_->Style()->position();
-        // if ((position == AbsolutePosition || position == FixedPosition)) {
-        //   builder_->AddOutOfFlowCandidateChild(current_child_,
-        //   GetChildSpaceOffset());
-        // }
-        // else
-        space_for_current_child_ = CreateConstraintSpaceForCurrentChild();
-        *algorithm_out = NGLayoutInputNode::AlgorithmForInputNode(
-            current_child_, space_for_current_child_);
-        state_ = kStateChildLayout;
-        return kChildAlgorithmRequired;
+        EPosition position = current_child_->Style()->position();
+        if ((position == AbsolutePosition || position == FixedPosition)) {
+          builder_->AddOutOfFlowChildCandidate(current_child_,
+                                               GetChildSpaceOffset());
+          current_child_ = current_child_->NextSibling();
+          return kNotFinished;
+        } else {

[cbiesinger, 2016/12/21 21:38:50]

No need for an "else" after a return.

[atotic, 2016/12/28 19:36:46]

done

+          space_for_current_child_ = CreateConstraintSpaceForCurrentChild();
+          *algorithm_out = NGLayoutInputNode::AlgorithmForInputNode(
+              current_child_, space_for_current_child_);
+          state_ = kStateChildLayout;
+          return kChildAlgorithmRequired;
+        }
       }
 
-      state_ = kStateFinalize;
+      // Prepare for kStateOutOfFlowLayout
+      content_size_ += border_and_padding_.block_end;
+
+      // Recompute the block-axis size now that we know our content size.
+      LayoutUnit block_size = ComputeBlockSizeForFragment(
+          ConstraintSpace(), Style(), content_size_);
+      builder_->SetBlockSize(block_size);
+
+      // Out of flow setup.
+      out_of_flow_layout_ = new NGOutOfFlowLayoutPart(style_, builder_->Size());
+      builder_->GetAndClearOutOfFlowDescendantCandidates(
+          &out_of_flow_candidates_, &out_of_flow_candidate_positions_);
+      out_of_flow_candidate_positions_index_ = 0;
+      current_child_ = nullptr;
+      state_ = kStateOutOfFlowLayout;
       return kNotFinished;
     }
     case kStateChildLayout: {
@@ -277,9 +291,11 @@ NGLayoutStatus NGBlockLayoutAlgorithm::Layout(
       state_ = kStatePrepareForChildLayout;
       return kNotFinished;
     }
+    case kStateOutOfFlowLayout:
+      if (LayoutOutOfFlowChild())
+        state_ = kStateFinalize;
+      return kNotFinished;
     case kStateFinalize: {
-      content_size_ += border_and_padding_.block_end;
-
       // Recompute the block-axis size now that we know our content size.
       LayoutUnit block_size = ComputeBlockSizeForFragment(

[cbiesinger, 2016/12/21 21:38:50]

You don't need this anymore since you're now calling it above, right?

[atotic, 2016/12/28 19:36:45]

done. Thanks, nice catch, I blame this on persistent merge conflicts.

           ConstraintSpace(), Style(), content_size_);
@@ -314,6 +330,34 @@ void NGBlockLayoutAlgorithm::FinishCurrentChildLayout(
   builder_->AddChild(fragment, fragment_offset);
 }
 
+bool NGBlockLayoutAlgorithm::LayoutOutOfFlowChild() {

[cbiesinger, 2016/12/21 21:38:50]

Maybe use NGLayoutStatus as the return type so it's not necessary to remember
whether true means finished or more work.
(Of course, kChildAlgorithmRequired would not be used here)

[atotic, 2016/12/28 19:36:45]

Unsure about this. 
Pros: not necessary to remember what true means
Cons: introducing state machine knowledge into this routine. Currently, all it
knows is how to layout oof children. Only routine that knows about layout_state_
is Layout().

What do you think about just adding documentation for the return value?

[cbiesinger, 2017/01/04 00:13:16]

Just documentation is fine with me, though it seems that this function will
implicitly know about state machines via NGOutOfFlowLayoutPart::Layout.

+  if (!current_child_) {
+    if (out_of_flow_candidates_.isEmpty()) {
+      out_of_flow_layout_ = nullptr;
+      out_of_flow_candidate_positions_.clear();
+      return true;
+    }
+    current_child_ = out_of_flow_candidates_.first();
+    out_of_flow_candidates_.removeFirst();
+    NGStaticPosition position = out_of_flow_candidate_positions_
+        [out_of_flow_candidate_positions_index_++];
+
+    if (!out_of_flow_layout_->StartLayout(current_child_, position)) {
+      builder_->AddOutOfFlowDescendant(current_child_, position);
+      current_child_ = nullptr;
+      return false;
+    }
+  }
+  NGFragmentBase* fragment;
+  NGLogicalOffset offset;
+  if (out_of_flow_layout_->Layout(&fragment, &offset)) {
+    // TODO(atotic) Do we need to adjust builder content size here?

[cbiesinger, 2016/12/21 21:38:50]

abspos does not change the width/height of the containing block, but it does
affect the overflow rect:
http://plexode.com/eval3/#s=aekVQXANJVQMbAx1yAXgePQOCGwESERFRWRwBfJ1CVlVQpIud...

But, that can be done later.

[atotic, 2016/12/28 19:36:46]

done. Added a comment.

+    builder_->AddChild(fragment, offset);
+    current_child_ = nullptr;
+  }
+  return false;
+}
+
 NGBoxStrut NGBlockLayoutAlgorithm::CollapseMargins(
     const NGBoxStrut& margins,
     const NGFragment& fragment) {
@@ -466,6 +510,8 @@ DEFINE_TRACE(NGBlockLayoutAlgorithm) {
   visitor->trace(space_builder_);
   visitor->trace(space_for_current_child_);
   visitor->trace(current_child_);
+  visitor->trace(out_of_flow_layout_);
+  visitor->trace(out_of_flow_candidates_);
 }
 
 }  // namespace blink