[css-grid] Implement fit-content track size

third_party/WebKit/Source/core/style/GridTrackSize.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 20 matching lines @@
 #ifndef GridTrackSize_h
 #define GridTrackSize_h
 
 #include "core/style/GridLength.h"
 #include "wtf/Allocator.h"
 
 namespace blink {
 
 enum GridTrackSizeType {
     LengthTrackSizing,
-    MinMaxTrackSizing
+    MinMaxTrackSizing,
+    FitContentTrackSizing
 };
 
+// This class represents a <track-size> from the spec. Althought there are 3 different types of
+// <track-size> there is always an equivalent minmax() representation that could represent any of
+// them. The only special case is fit-content(argument) which is similar to minmax(auto,max-content)

[Manuel Rego, 2016/08/31 07:24:29]

Nit: Missing space after "auto,".

[svillar, 2016/08/31 09:50:04]

Acknowledged.

+// except that the track size is clamped at argument if it is greater than the auto minimum. At the
+// GridTrackSize level we don't need to worry about clamping so we treat that case exactly as
+// minmax(auto, max-content) althought we store the argument for later use in m_maxTrackBreadth.
 class GridTrackSize {
     DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
 public:
-    GridTrackSize(const GridLength& length)
-        : m_type(LengthTrackSizing)
-        , m_minTrackBreadth(length)
+    GridTrackSize(const GridLength& length, GridTrackSizeType trackSizeType = LengthTrackSizing)
+        : m_type(trackSizeType)
+        , m_minTrackBreadth(trackSizeType == FitContentTrackSizing ? Length(Auto) : length)
         , m_maxTrackBreadth(length)
-        , m_minTrackBreadthIsMaxContent(false)
-        , m_maxTrackBreadthIsMaxContent(false)
     {
+        DCHECK(trackSizeType == LengthTrackSizing || trackSizeType == FitContentTrackSizing);
         cacheMinMaxTrackBreadthTypes();
     }
 
     GridTrackSize(const GridLength& minTrackBreadth, const GridLength& maxTrackBreadth)
         : m_type(MinMaxTrackSizing)
         , m_minTrackBreadth(minTrackBreadth)
         , m_maxTrackBreadth(maxTrackBreadth)
-        , m_minTrackBreadthIsMaxContent(false)
-        , m_maxTrackBreadthIsMaxContent(false)
     {
         cacheMinMaxTrackBreadthTypes();
     }
 
-    const GridLength& length() const
+    GridLength length() const
     {
-        ASSERT(m_type == LengthTrackSizing);
-        ASSERT(m_minTrackBreadth == m_maxTrackBreadth);
-        const GridLength& minTrackBreadth = m_minTrackBreadth;
-        return minTrackBreadth;
+        DCHECK(m_type == LengthTrackSizing || m_type == FitContentTrackSizing);
+        DCHECK(m_minTrackBreadth == m_maxTrackBreadth || m_type == FitContentTrackSizing);
+        return m_maxTrackBreadth;
     }
 
-    const GridLength& minTrackBreadth() const { return m_minTrackBreadth; }
-
-    const GridLength& maxTrackBreadth() const { return m_maxTrackBreadth; }
+    GridLength minTrackBreadth() const { return m_minTrackBreadth; }
+    GridLength maxTrackBreadth() const { return !isFitContent() ? m_maxTrackBreadth : GridLength(Length(MaxContent)); }

[cbiesinger, 2016/08/29 20:07:07]

please don't use negation like that, it's harder to read -- just to
isFitContent() ? GridLength(...) : m_MaxTrackBreadth

 
     GridTrackSizeType type() const { return m_type; }
 
     bool isContentSized() const { return m_minTrackBreadth.isContentSized() || m_maxTrackBreadth.isContentSized(); }
+    bool isFitContent() const { return m_type == FitContentTrackSizing; }
 
     bool operator==(const GridTrackSize& other) const
     {
         return m_type == other.m_type && m_minTrackBreadth == other.m_minTrackBreadth && m_maxTrackBreadth == other.m_maxTrackBreadth;
     }
 
     void cacheMinMaxTrackBreadthTypes()
     {
         m_minTrackBreadthIsAuto = minTrackBreadth().isLength() && minTrackBreadth().length().isAuto();
         m_minTrackBreadthIsMinContent = minTrackBreadth().isLength() && minTrackBreadth().length().isMinContent();
@@ skipping 12 matching lines @@
     bool hasMinOrMaxContentMaxTrackBreadth() const { return m_maxTrackBreadthIsMaxContent || m_maxTrackBreadthIsMinContent; }
     bool hasMaxContentMaxTrackBreadth() const { return m_maxTrackBreadthIsMaxContent; }
     bool hasMaxContentOrAutoMaxTrackBreadth() const { return m_maxTrackBreadthIsMaxContent || m_maxTrackBreadthIsAuto; }
     bool hasMinContentMaxTrackBreadth() const { return m_maxTrackBreadthIsMinContent; }
     bool hasMaxContentMinTrackBreadthAndMaxContentMaxTrackBreadth() const { return m_minTrackBreadthIsMaxContent && m_maxTrackBreadthIsMaxContent; }
     bool hasAutoOrMinContentMinTrackBreadthAndIntrinsicMaxTrackBreadth() const { return (m_minTrackBreadthIsMinContent || m_minTrackBreadthIsAuto) && (m_maxTrackBreadthIsMaxContent || m_maxTrackBreadthIsMinContent || m_maxTrackBreadthIsAuto); }
 
 private:
     GridTrackSizeType m_type;
     GridLength m_minTrackBreadth;
     GridLength m_maxTrackBreadth;

[Manuel Rego, 2016/08/31 07:24:29]

Probably it's good adding a comment to explain that this field
is used sometimes as m_maxTrackBreadth and other times
as m_fitContentCap.
I know it's already explained above but I think it doesn't harm.

Another option would be avoid to reuse m_maxTrackBreadth
for this and add a new attribute to this class, bur probably
it's not worth.

[svillar, 2016/08/31 09:50:04]

As you know it's in the policy of the project not to add comments unless
strictly needed because they usually became obsolete and misleading as nobody
updates them. As you mentioned is already explained above.

[cbiesinger, 2016/08/31 15:18:44]

FWIW, I really don't think that's the policy in blink, unlike webkit.

     bool m_minTrackBreadthIsAuto;
     bool m_minTrackBreadthIsMaxContent;
     bool m_minTrackBreadthIsMinContent;
     bool m_maxTrackBreadthIsAuto;
     bool m_maxTrackBreadthIsMaxContent;
     bool m_maxTrackBreadthIsMinContent;
 };
 
 } // namespace blink
 
 #endif // GridTrackSize_h