[layoutng] Margin support, part 1

third_party/WebKit/Source/core/layout/ng/ng_length_utils.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_length_utils.h"
 
 #include "core/layout/ng/ng_constraint_space.h"
+#include "core/layout/ng/ng_margin_strut.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/LayoutUnit.h"
 #include "platform/Length.h"
 
 namespace blink {
 // TODO(layout-ng):
 // - Handle border-box correctly
 // - positioned and/or replaced calculations
 // - Handle margins for fill-available and width: auto
 
 LayoutUnit resolveInlineLength(const NGConstraintSpace& constraintSpace,
                                const Length& length,
                                LengthResolveType type) {
   // TODO(layout-ng): Handle min/max/fit-content
   DCHECK(!length.isMaxSizeNone());
 
   if (type == LengthResolveType::MinSize && length.isAuto())
     return LayoutUnit();
 
+  if (type == LengthResolveType::MarginSize && length.isAuto())
+    return LayoutUnit();
+
   return valueForLength(length, constraintSpace.ContainerSize().inlineSize);
 }
 
 LayoutUnit resolveBlockLength(const NGConstraintSpace& constraintSpace,
                               const Length& length,
                               LayoutUnit contentSize,
                               LengthResolveType type) {
   DCHECK(!length.isMaxSizeNone());
+  DCHECK(type != LengthResolveType::MarginSize);
 
   if (type == LengthResolveType::MinSize && length.isAuto())
     return LayoutUnit();
 
   if (length.isAuto())
     return contentSize;
 
   if (length.isMinContent() || length.isMaxContent() || length.isFitContent())
     return contentSize;
 
@@ skipping 48 matching lines @@
                                       contentSize, LengthResolveType::MinSize);
   extent = std::max(extent, min);
 
   if (style.boxSizing() == BoxSizingContentBox) {
     // TODO(layout-ng): Compute border/padding size and add it
   }
 
   return extent;
 }
 
+NGBoxMargins computeMargins(const NGConstraintSpace& constraintSpace,
+                            const ComputedStyle& style) {
+  // Margins always get computed relative to the inline size:
+  // https://www.w3.org/TR/CSS2/box.html#value-def-margin-width
+  NGBoxMargins margins;
+  margins.inlineStart = resolveInlineLength(
+      constraintSpace, style.marginStart(), LengthResolveType::MarginSize);
+  margins.inlineEnd = resolveInlineLength(constraintSpace, style.marginEnd(),
+                                          LengthResolveType::MarginSize);
+  margins.blockStart = resolveInlineLength(
+      constraintSpace, style.marginBefore(), LengthResolveType::MarginSize);
+  margins.blockEnd = resolveInlineLength(constraintSpace, style.marginAfter(),
+                                         LengthResolveType::MarginSize);
+  return margins;
+}
+
 }  // namespace blink