[layoutng] Add methods to compute border and padding

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

Index: third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc b/third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc
index 97c79543d977b06764c0c0f78739f925d2f6eee4..05e419cfbb8134110351dc542dea8f2c617bb8b3 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc
@@ -14,6 +14,7 @@ namespace blink {
 // - 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,
@@ -131,4 +132,29 @@ NGBoxStrut computeMargins(const NGConstraintSpace& constraintSpace,
   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