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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef StyleDifference_h
      6 #define StyleDifference_h
      7 
      8 #include "wtf/Assertions.h"
      9 
     10 namespace blink {
     11 
     12 class StyleDifference {
     13 public:
     14     enum PropertyDifference {
     15         TransformChanged = 1 << 0,
     16         OpacityChanged = 1 << 1,
     17         ZIndexChanged = 1 << 2,
     18         FilterChanged = 1 << 3,
     19         // The object needs to issue paint invalidations if it contains text or properties dependent on color (e.g., border or outline).
     20         TextOrColorChanged = 1 << 4,
     21     };
     22 
     23     StyleDifference()
     24         : m_paintInvalidationType(NoPaintInvalidation)
     25         , m_layoutType(NoLayout)
     26         , m_propertySpecificDifferences(0)
     27     { }
     28 
     29     bool hasDifference() const { return m_paintInvalidationType || m_layoutType || m_propertySpecificDifferences; }
     30 
     31     bool hasAtMostPropertySpecificDifferences(unsigned propertyDifferences) const
     32     {
     33         return !m_paintInvalidationType && !m_layoutType && !(m_propertySpecificDifferences & ~propertyDifferences);
     34     }
     35 
     36     bool needsPaintInvalidation() const { return m_paintInvalidationType != NoPaintInvalidation; }
     37     void clearNeedsPaintInvalidation() { m_paintInvalidationType = NoPaintInvalidation; }
     38 
     39     // The object just needs to issue paint invalidations.
     40     bool needsPaintInvalidationObject() const { return m_paintInvalidationType == PaintInvalidationObject; }
     41     void setNeedsPaintInvalidationObject()
     42     {
     43         ASSERT(!needsPaintInvalidationLayer());
     44         m_paintInvalidationType = PaintInvalidationObject;
     45     }
     46 
     47     // The layer and its descendant layers need to issue paint invalidations.
     48     bool needsPaintInvalidationLayer() const { return m_paintInvalidationType == PaintInvalidationLayer; }
     49     void setNeedsPaintInvalidationLayer() { m_paintInvalidationType = PaintInvalidationLayer; }
     50 
     51     bool needsLayout() const { return m_layoutType != NoLayout; }
     52     void clearNeedsLayout() { m_layoutType = NoLayout; }
     53 
     54     // The offset of this positioned object has been updated.
     55     bool needsPositionedMovementLayout() const { return m_layoutType == PositionedMovement; }
     56     void setNeedsPositionedMovementLayout()
     57     {
     58         ASSERT(!needsFullLayout());
     59         m_layoutType = PositionedMovement;
     60     }
     61 
     62     bool needsFullLayout() const { return m_layoutType == FullLayout; }
     63     void setNeedsFullLayout() { m_layoutType = FullLayout; }
     64 
     65     bool transformChanged() const { return m_propertySpecificDifferences & TransformChanged; }
     66     void setTransformChanged() { m_propertySpecificDifferences |= TransformChanged; }
     67 
     68     bool opacityChanged() const { return m_propertySpecificDifferences & OpacityChanged; }
     69     void setOpacityChanged() { m_propertySpecificDifferences |= OpacityChanged; }
     70 
     71     bool zIndexChanged() const { return m_propertySpecificDifferences & ZIndexChanged; }
     72     void setZIndexChanged() { m_propertySpecificDifferences |= ZIndexChanged; }
     73 
     74     bool filterChanged() const { return m_propertySpecificDifferences & FilterChanged; }
     75     void setFilterChanged() { m_propertySpecificDifferences |= FilterChanged; }
     76 
     77     bool textOrColorChanged() const { return m_propertySpecificDifferences & TextOrColorChanged; }
     78     void setTextOrColorChanged() { m_propertySpecificDifferences |= TextOrColorChanged; }
     79 
     80 private:
     81     enum PaintInvalidationType {
     82         NoPaintInvalidation = 0,
     83         PaintInvalidationObject,
     84         PaintInvalidationLayer
     85     };
     86     unsigned m_paintInvalidationType : 2;
     87 
     88     enum LayoutType {
     89         NoLayout = 0,
     90         PositionedMovement,
     91         FullLayout
     92     };
     93     unsigned m_layoutType : 2;
     94 
     95     unsigned m_propertySpecificDifferences : 5;
     96 };
     97 
     98 } // namespace blink
     99 
    100 #endif // StyleDifference_h
    101