[layoutng] Add methods to compute border and padding

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/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
+// - Take scrollbars into account
 
 LayoutUnit resolveInlineLength(const NGConstraintSpace& constraintSpace,
                                const Length& length,
                                LengthResolveType type) {
   // TODO(layout-ng): Handle min/max/fit-content
   DCHECK(!length.isMaxSizeNone());
   DCHECK_GE(constraintSpace.ContainerSize().inline_size, LayoutUnit());
 
   if (type == LengthResolveType::MinSize && length.isAuto())
     return LayoutUnit();
@@ skipping 97 matching lines @@
       constraintSpace, style.marginStart(), LengthResolveType::MarginSize);
   margins.inline_end = resolveInlineLength(constraintSpace, style.marginEnd(),
                                            LengthResolveType::MarginSize);
   margins.block_start = resolveInlineLength(
       constraintSpace, style.marginBefore(), LengthResolveType::MarginSize);
   margins.block_end = resolveInlineLength(constraintSpace, style.marginAfter(),
                                           LengthResolveType::MarginSize);
   return margins;
 }
 
+NGBoxStrut computeBorders(const ComputedStyle& style) {
+  NGBoxStrut borders;
+  borders.inline_start = LayoutUnit(style.borderStartWidth());
+  borders.inline_end = LayoutUnit(style.borderEndWidth());
+  borders.block_start = LayoutUnit(style.borderBeforeWidth());
+  borders.block_end = LayoutUnit(style.borderAfterWidth());
+  return borders;
+}
+
+NGBoxStrut computePadding(const NGConstraintSpace& constraintSpace,
+                          const ComputedStyle& style) {
+  // Padding always gets computed relative to the inline size:
+  // https://www.w3.org/TR/CSS2/box.html#value-def-padding-width
+  NGBoxStrut padding;
+  padding.inline_start = resolveInlineLength(
+      constraintSpace, style.paddingStart(), LengthResolveType::MarginSize);
+  padding.inline_end = resolveInlineLength(constraintSpace, style.paddingEnd(),
+                                           LengthResolveType::MarginSize);
+  padding.block_start = resolveInlineLength(
+      constraintSpace, style.paddingBefore(), LengthResolveType::MarginSize);

[ikilpatrick, 2016/08/30 20:30:44]

Is LengthResolveType::MarginSize better named something else now?

[cbiesinger, 2016/08/30 20:32:59]

Oh right. I guess I'll go with MarginBorderPaddingSize unless you have a better
idea.

+  padding.block_end = resolveInlineLength(constraintSpace, style.paddingAfter(),
+                                          LengthResolveType::MarginSize);
+  return padding;
+}
+
 }  // namespace blink