[LayoutNG] Correct inline size for children of multicol containers.

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 86e5fd7aa84d50ea9963c7ad820533e0d239dfdc..e4e9d23747bcb76e763db8d129e6bc65d66c4676 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
@@ -228,6 +228,53 @@ LayoutUnit ComputeBlockSizeForFragment(const NGConstraintSpace& constraintSpace,
   return extent;
 }
 
+int ResolveUsedColumnCount(int computed_count,

[ikilpatrick, 2016/11/28 17:12:46]

would it be better to split multicol utils out into another file?
(ng_multilcol_utils.cc)

up to you.

(slight preference if we'll adding more).

[mstensho (USE GERRIT), 2016/11/28 19:30:29]

Not planning on adding more. I think I'll keep it here for now, if that's fine.

+                           LayoutUnit computed_size,
+                           LayoutUnit used_gap,
+                           LayoutUnit available_size) {
+  if (computed_size == NGSizeIndefinite) {
+    DCHECK(computed_count);
+    return computed_count;
+  }
+  DCHECK(computed_size > LayoutUnit());
+  int count_from_width =
+      ((available_size + used_gap) / (computed_size + used_gap)).toInt();
+  count_from_width = std::max(1, count_from_width);
+  if (!computed_count)
+    return count_from_width;
+  return std::max(1, std::min(computed_count, count_from_width));
+}
+
+LayoutUnit ResolveUsedColumnInlineSize(int computed_count,
+                                       LayoutUnit computed_size,
+                                       LayoutUnit used_gap,
+                                       LayoutUnit available_size) {
+  int used_count = ResolveUsedColumnCount(computed_count, computed_size,
+                                          used_gap, available_size);
+  return ((available_size + used_gap) / used_count) - used_gap;
+}
+
+LayoutUnit ResolveUsedColumnInlineSize(LayoutUnit available_size,
+                                       const ComputedStyle& style) {
+  // Should only attempt to resolve this if columns != auto.
+  DCHECK(!style.hasAutoColumnCount() || !style.hasAutoColumnWidth());
+
+  LayoutUnit computed_size =
+      style.hasAutoColumnWidth()
+          ? NGSizeIndefinite
+          : std::max(LayoutUnit(1), LayoutUnit(style.columnWidth()));
+  int computed_count = style.hasAutoColumnCount() ? 0 : style.columnCount();
+  LayoutUnit used_gap = ResolveUsedColumnGap(style);
+  return ResolveUsedColumnInlineSize(computed_count, computed_size, used_gap,
+                                     available_size);
+}
+
+LayoutUnit ResolveUsedColumnGap(const ComputedStyle& style) {
+  if (style.hasNormalColumnGap())
+    return LayoutUnit(style.getFontDescription().computedPixelSize());
+  return LayoutUnit(style.columnGap());
+}
+
 NGBoxStrut ComputeMargins(const NGConstraintSpace& constraintSpace,
                           const ComputedStyle& style,
                           const NGWritingMode writing_mode,