[Alignment] Single class for holding the alignment data.

Source/core/style/StyleAlignmentData.h

+// Copyright (c) 2015 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.
+
+#ifndef StyleAlignmentData_h
+#define StyleAlignmentData_h
+
+#include "core/style/ComputedStyleConstants.h"
+
+namespace blink {
+
+class StyleAlignmentData {
+public:
+    // Style data for Self-Aligment and Default-Alignment properties: align-{self, items}, justify-{self, items}.
+    // [ <self-position> && <overflow-position>? ] | [ legacy && [ left | right | center ] ]
+    StyleAlignmentData(ItemPosition, OverflowAlignment = OverflowAlignmentDefault, ItemPositionType = NonLegacyPosition);
+    // Style data for Content-Distribution properties: align-content, justify-content.
+    // <content-distribution> || [ <overflow-position>? && <content-position> ]
+    StyleAlignmentData(ContentPosition, ContentDistributionType, OverflowAlignment = OverflowAlignmentDefault);
+
+    bool operator==(const StyleAlignmentData& o) const
+    {
+        return m_itemPosition == o.m_itemPosition && m_contentPosition == o.m_contentPosition && m_distribution == o.m_distribution && m_positionType == o.m_positionType && m_overflow == o.m_overflow;
+    }
+
+    bool operator==(ItemPosition position) const

[Timothy Loh, 2015/04/13 00:56:43]

These overloads seem a bit weird to me, why do we need them?

[Julien - ping for review, 2015/04/13 14:46:20]

They are used above when we do e.g. justifyItems() == LegacyPosition. I do agree
that this is weird and it's an easy foot-gun.

[jfernandez, 2015/04/14 00:18:43]

Done.

[esprehn, 2015/04/14 00:48:55]

I'd like to avoid an operator== overload to a totally different type.

[jfernandez, 2015/04/14 22:56:21]

Acknowledged.

+    {
+        return m_itemPosition == position;
+    }
+
+    bool operator==(ContentPosition position) const
+    {
+        return m_contentPosition == position;
+    }
+
+    bool operator==(ContentDistributionType distribution) const
+    {
+        return m_distribution == distribution;
+    }
+
+    bool operator==(ItemPositionType positionType) const

[esprehn, 2015/04/14 00:48:55]

Can we remove these and instead be explicit.

[jfernandez, 2015/04/14 22:56:21]

Yes, it'd be a good idea. However, I finally removed them and I just called
specific getter methods to perform the different value comparisons across the
code base.  I was experimenting with functions like "isEqualTo(ItemPosition)"
instead of the operator overloading, but I don't think an advantage from just
using the getter approach.

+    {
+        return m_positionType == positionType;
+    }
+
+    bool operator!=(const StyleAlignmentData& o) const
+    {
+        return !(*this == o);
+    }
+
+    unsigned m_itemPosition : 4; // ItemPosition

[esprehn, 2015/04/14 00:48:55]

Remove the m_ prefix if these are going to be public (or add getters).

[jfernandez, 2015/04/14 22:56:20]

I finally made private the class fields, so they still have the m_prefix.

+    unsigned m_contentPosition : 4; // ContentPosition
+    unsigned m_distribution : 3; // ContentDistributionType
+    unsigned m_positionType: 1; // Whether or not alignment uses the 'legacy' keyword.
+    unsigned m_overflow : 2; // OverflowAlignment
+};
+
+} // namespace blink
+
+#endif // StyleAlignmentData_h