[layoutng] Support computing min-content and max-content

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

Index: third_party/WebKit/Source/core/layout/ng/ng_box.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_box.cc b/third_party/WebKit/Source/core/layout/ng/ng_box.cc
index 40062d95e97e529b9d4adec139b79c4ada13e61d..3be44c1d28f0390c273720b26e1fde178222c2b6 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_box.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_box.cc
@@ -7,6 +7,7 @@
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/ng/layout_ng_block_flow.h"
 #include "core/layout/ng/ng_block_layout_algorithm.h"
+#include "core/layout/ng/ng_constraint_space_builder.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_direction.h"
 #include "core/layout/ng/ng_fragment.h"
@@ -63,6 +64,54 @@ bool NGBox::Layout(const NGConstraintSpace* constraint_space,
   return true;
 }
 
+void NGBox::ComputeMinAndMaxContentSizes(NGFragment** min_content,
+                                         NGFragment** max_content) {
+  NGConstraintSpaceBuilder builder(
+      FromPlatformWritingMode(Style()->getWritingMode()));
+  builder.SetContainerSize(NGLogicalSize(LayoutUnit(), LayoutUnit()));

[Gleb Lanbin, 2016/10/31 19:52:47]

nit. you can chain SetContainerSize call to line above.

[cbiesinger, 2016/11/01 19:10:03]

I'd rather not chain something to the constructor like that

+  NGConstraintSpace* constraint_space = new NGConstraintSpace(
+      FromPlatformWritingMode(Style()->getWritingMode()),
+      FromPlatformDirection(Style()->direction()), builder.ToConstraintSpace());

[eae, 2016/10/31 19:30:25]

Presumably once Ian's work is done this will be
builder.ToConstraintSpace.ToLogicalConstraintSpace or something, right? Might
want to add a TODO.

[cbiesinger, 2016/11/01 19:10:03]

Ah, is that the plan? Added a TODO.

+
+  NGLayoutAlgorithm* algorithm =
+      new NGBlockLayoutAlgorithm(Style(), FirstChild(), constraint_space);
+  if (algorithm->ComputeMinAndMaxContentSizes(min_content, max_content) ==

[Gleb Lanbin, 2016/10/31 19:52:47]

IMO it's a bit confusing that we have 2 almost identical public functions with
the same name. If a person is not familiar with the code then they would
probably would be interested to know what's the difference between those 2
functions?

[cbiesinger, 2016/11/01 19:10:03]

Renamed this one to ComputeOrSynthesizeMinAndMaxContentSizes

+      NGLayoutAlgorithm::Success)
+    return;
+
+  // Have to synthesize this value.
+  NGPhysicalFragment* fragment;
+  while (!algorithm->Layout(&fragment))
+    continue;
+
+  HeapVector<Member<const NGPhysicalFragmentBase>> empty;

[Gleb Lanbin, 2016/10/31 19:52:47]

may be add an additional constructor to NGPhysicalFragment? otherwise it's not
clear why we pass an empty, unused? list of children here and below.

[cbiesinger, 2016/11/01 19:10:03]

Removed this entirely due to other changes.

+  fragment =
+      new NGPhysicalFragment(fragment->OverflowSize(), fragment->OverflowSize(),
+                             empty, NGMarginStrut());
+
+  *min_content =
+      new NGFragment(FromPlatformWritingMode(Style()->getWritingMode()),
+                     FromPlatformDirection(Style()->direction()), fragment);
+
+  // Now, redo with infinite space for max_content
+  builder.SetContainerSize(NGLogicalSize(LayoutUnit::max(), LayoutUnit()));
+  constraint_space = new NGConstraintSpace(
+      FromPlatformWritingMode(Style()->getWritingMode()),
+      FromPlatformDirection(Style()->direction()), builder.ToConstraintSpace());
+
+  algorithm =
+      new NGBlockLayoutAlgorithm(Style(), FirstChild(), constraint_space);
+  while (!algorithm->Layout(&fragment))
+    continue;
+
+  fragment =
+      new NGPhysicalFragment(fragment->OverflowSize(), fragment->OverflowSize(),
+                             empty, NGMarginStrut());
+  *max_content =
+      new NGFragment(FromPlatformWritingMode(Style()->getWritingMode()),
+                     FromPlatformDirection(Style()->direction()), fragment);
+}
+
 const ComputedStyle* NGBox::Style() const {
   if (style_)
     return style_.get();
@@ -97,6 +146,13 @@ void NGBox::SetFirstChild(NGBox* child) {
   first_child_ = child;
 }
 
+DEFINE_TRACE(NGBox) {
+  visitor->trace(algorithm_);
+  visitor->trace(fragment_);
+  visitor->trace(next_sibling_);
+  visitor->trace(first_child_);
+}
+
 void NGBox::PositionUpdated() {
   if (!layout_box_)
     return;