Place the out of flow positioned blocks

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

+// Copyright 2016 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/layout/ng/ng_out_of_flow_layout_part.h"
+
+#include "core/layout/ng/ng_absolute_utils.h"
+#include "core/layout/ng/ng_block_node.h"
+#include "core/layout/ng/ng_constraint_space_builder.h"
+#include "core/layout/ng/ng_fragment_base.h"
+#include "core/layout/ng/ng_length_utils.h"
+#include "core/style/ComputedStyle.h"
+
+namespace blink {
+
+NGOutOfFlowLayoutPart::NGOutOfFlowLayoutPart(
+    PassRefPtr<const ComputedStyle> container_style,
+    NGLogicalSize container_size) {
+  contains_fixed_ = container_style->canContainFixedPositionObjects();
+  contains_absolute_ =
+      container_style->canContainAbsolutePositionObjects() || contains_fixed_;
+  // Initialize ConstraintSpace
+  NGLogicalSize space_size = container_size;
+  NGBoxStrut borders = ComputeBorders(*container_style);
+  space_size.block_size -= borders.BlockSum();
+  space_size.inline_size -= borders.InlineSum();
+  parent_offset_ = NGLogicalOffset{borders.inline_start, borders.block_start};
+  parent_physical_offset_ = parent_offset_.ConvertToPhysical(
+      FromPlatformWritingMode(container_style->getWritingMode()),
+      container_style->direction(),
+      container_size.ConvertToPhysical(
+          FromPlatformWritingMode(container_style->getWritingMode())),
+      NGPhysicalSize());
+  NGConstraintSpaceBuilder space_builder(
+      FromPlatformWritingMode(container_style->getWritingMode()));
+  space_builder.SetAvailableSize(space_size);
+  space_builder.SetIsNewFormattingContext(true);
+  space_builder.SetTextDirection(container_style->direction());
+  parent_space_ = space_builder.ToConstraintSpace();
+}
+
+bool NGOutOfFlowLayoutPart::StartLayout(
+    NGBlockNode* node,
+    const NGStaticPosition& static_position) {
+  EPosition position = node->Style()->position();
+  if ((contains_absolute_ && position == AbsolutePosition) ||
+      (contains_fixed_ && position == FixedPosition)) {
+    node_ = node;
+    static_position_ = static_position;
+    // Adjust static_position origin. static_position coordinate origin is
+    //  border_box, absolute position coordinate origin is padding box.
+    static_position_.offset -= parent_physical_offset_;
+    node_fragment_ = nullptr;
+    node_position_ = NGAbsolutePhysicalPosition();
+    inline_estimate_.reset();
+    block_estimate_.reset();
+    state_ = kComputeInlineEstimate;
+    return true;
+  }
+  return false;
+}
+
+NGLayoutStatus NGOutOfFlowLayoutPart::Layout(NGFragmentBase** fragment,
+                                             NGLogicalOffset* offset) {
+  DCHECK(node_);
+  switch (state_) {
+    case kComputeInlineEstimate:
+      if (ComputeInlineSizeEstimate())
+        state_ = kPartialPosition;
+      break;
+    case kPartialPosition:
+      node_position_ = ComputePartialAbsoluteWithChildInlineSize(
+          *parent_space_, *node_->Style(), static_position_, inline_estimate_);
+      state_ = kComputeBlockEstimate;
+      break;
+    case kComputeBlockEstimate:
+      if (ComputeBlockSizeEstimate())
+        state_ = kFullPosition;
+      break;
+    case kFullPosition:
+      ComputeFullAbsoluteWithChildBlockSize(*parent_space_, *node_->Style(),
+                                            static_position_, block_estimate_,
+                                            &node_position_);
+      state_ = kGenerateFragment;
+      break;
+    case kGenerateFragment:
+      block_estimate_ =
+          node_position_.size.ConvertToLogical(parent_space_->WritingMode())
+              .block_size;
+      if (!ComputeNodeFragment())
+        return kNotFinished;
+      state_ = kDone;
+      break;
+    case kDone:
+      *fragment = node_fragment_;
+      // Compute offset
+      NGBoxStrut inset = node_position_.inset.ConvertToLogical(
+          parent_space_->WritingMode(), parent_space_->Direction());
+      offset->inline_offset = inset.inline_start + parent_offset_.inline_offset;
+      offset->block_offset = inset.block_start + parent_offset_.block_offset;
+      return kNewFragment;
+  }
+  return kNotFinished;
+}
+
+bool NGOutOfFlowLayoutPart::ComputeInlineSizeEstimate() {
+  if (AbsoluteNeedsChildInlineSize(*node_->Style())) {
+    MinAndMaxContentSizes size;
+    if (node_->ComputeMinAndMaxContentSizes(&size)) {
+      inline_estimate_ =
+          size.ShrinkToFit(parent_space_->AvailableSize().inline_size);
+      return true;
+    }
+    return false;
+  }
+  return true;
+}
+
+bool NGOutOfFlowLayoutPart::ComputeBlockSizeEstimate() {
+  if (AbsoluteNeedsChildBlockSize(*node_->Style())) {
+    if (ComputeNodeFragment()) {
+      block_estimate_ = node_fragment_->BlockSize();
+      return true;
+    }
+    return false;
+  }
+  return true;
+}
+
+bool NGOutOfFlowLayoutPart::ComputeNodeFragment() {
+  if (node_fragment_)
+    return true;
+  if (!node_space_) {
+    NGConstraintSpaceBuilder builder(parent_space_->WritingMode());
+    LayoutUnit inline_width =
+        node_position_.size.ConvertToLogical(parent_space_->WritingMode())
+            .inline_size;
+    // Node fragment is computed in one of these two scenarios:
+    // 1. To estimate block size
+    //    In this case, available block_size is parent's size.
+    // 2. To compute final block fragment, when block size is known.
+
+    NGLogicalSize available_size =
+        NGLogicalSize(inline_width, parent_space_->AvailableSize().block_size);
+    if (block_estimate_)

[atotic, 2016/12/28 20:35:16]

I was wrong. block_estimate is needed here because size computed by abspos
algorithm needs to be applied to constraint space used to layout oof block.

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

I misread the code, I think. We set block_estimate_ in kGenerateFragment even if
we did not previously call ComputeNodeFragment.

[atotic, 2017/01/04 01:34:35]

ack.

+      available_size.block_size = *block_estimate_;
+    builder.SetAvailableSize(available_size);
+    builder.SetPercentageResolutionSize(available_size);
+    if (block_estimate_)
+      builder.SetIsFixedSizeBlock(true);
+    builder.SetIsFixedSizeInline(true);
+    builder.SetIsNewFormattingContext(true);
+    node_space_ = builder.ToConstraintSpace();
+  }
+  NGFragmentBase* fragment;
+  if (node_->Layout(node_space_, &fragment)) {
+    node_fragment_ = fragment;
+    return true;
+  }
+  return false;
+}
+
+DEFINE_TRACE(NGOutOfFlowLayoutPart) {
+  visitor->trace(node_);
+  visitor->trace(parent_space_);
+  visitor->trace(node_fragment_);
+  visitor->trace(node_space_);
+}
+}