Add grid/flex layout support for <fieldset>

third_party/WebKit/Source/core/layout/LayoutFieldset.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2006, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef LayoutFieldset_h
 #define LayoutFieldset_h
 
-#include "core/layout/LayoutBlockFlow.h"
+#include "core/layout/LayoutFlexibleBox.h"
 
 namespace blink {
 
-class LayoutFieldset final : public LayoutBlockFlow {
+class LayoutFieldset final : public LayoutFlexibleBox {

[Manuel Rego, 2016/07/20 06:00:23]

Are we sure we want to do this change?
Inheriting from Flexbox might be a bad idea thinking on the long term.
What's the main reason to do this?

We've been getting rid of this kind of inheritance as they cause issues
when you're developing things on Flexbox.
Some changes on Flexbox might affect the classes inheriting for him,
so you might be broken things or you might need to tweak things in many places.
IMHO, we should try to avoid this kind of things as the code becomes
very complex.

For example, we're using Flexbox for full-screen and we want to avoid it,
and this was causing issues when implementing some alignment stuff.

[Gleb Lanbin, 2016/07/21 18:25:31]

please see the reply from cbiesenger@ on a similar question below.

 public:
     explicit LayoutFieldset(Element*);
 
     LayoutBox* findInFlowLegend() const;
 
     const char* name() const override { return "LayoutFieldset"; }
 
 private:
-    bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectFieldset || LayoutBlockFlow::isOfType(type); }
-
-    LayoutObject* layoutSpecialExcludedChild(bool relayoutChildren, SubtreeLayoutScope&) override;
-
-    void computePreferredLogicalWidths() override;
+    void addChild(LayoutObject* newChild, LayoutObject* beforeChild = nullptr) override;
     bool avoidsFloats() const override { return true; }
 
+    // Let the baseline to be the bottom of our margin box.
+    int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode) const override;
+    int inlineBlockBaseline(LineDirectionMode) const override { return -1; }
+
+    void computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const override;
+    bool createsAnonymousWrapper() const override { return true; }
+    bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectFieldset || LayoutFlexibleBox::isOfType(type); }
+    LayoutObject* layoutSpecialExcludedChild(bool relayoutChildren, SubtreeLayoutScope&) override;
     void paintBoxDecorationBackground(const PaintInfo&, const LayoutPoint&) const override;
     void paintMask(const PaintInfo&, const LayoutPoint&) const override;
+    void styleDidChange(StyleDifference, const ComputedStyle* oldStyle) override;
+    void updateLogicalWidth() override;
+
+    void adjustInnerStyle();
+    void createInnerBlock();
+    void setLogicalLeftForChild(LayoutBox& child, LayoutUnit logicalLeft);
+    void setLogicalTopForChild(LayoutBox& child, LayoutUnit logicalTop);
+    void removeChild(LayoutObject*) override;
+
+    LayoutBlock* m_innerBlock;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutFieldset, isFieldset());
 
 } // namespace blink
 
 #endif // LayoutFieldset_h