Rework BoxBorderPainter's mitre clipping logic

Source/core/paint/BoxBorderPainter.h

 // Copyright 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 BoxBorderPainter_h
 #define BoxBorderPainter_h
 
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/style/BorderEdge.h"
 #include "platform/geometry/FloatRoundedRect.h"
@@ skipping 10 matching lines @@
 class BoxBorderPainter {
     STACK_ALLOCATED();
 public:
     BoxBorderPainter(const LayoutRect& borderRect, const ComputedStyle&, const IntRect& clipRect,
         BackgroundBleedAvoidance, bool includeLogicalLeftEdge, bool includeLogicalRightEdge);
 
     void paintBorder(const PaintInfo&, const LayoutRect& borderRect) const;
 
 private:
     struct ComplexBorderInfo;
+    enum MitreType {

[fs, 2015/06/08 21:06:31]

Maybe MiterType (etc.) so them Americans understand too ;-)

+        NoMitre,
+        SoftMitre, // Anti-aliased
+        HardMitre, // Not anti-aliased
+    };
 
     BorderEdgeFlags paintOpacityGroup(GraphicsContext*, const ComplexBorderInfo&, unsigned index,
         float accumulatedOpacity) const;
     void paintSide(GraphicsContext*, const ComplexBorderInfo&, BoxSide, unsigned alpha, BorderEdgeFlags) const;
     void paintOneBorderSide(GraphicsContext*, const FloatRect& sideRect, BoxSide, BoxSide adjacentSide1,
         BoxSide adjacentSide2, const Path*, bool antialias, Color, BorderEdgeFlags) const;
     bool paintBorderFastPath(GraphicsContext*, const LayoutRect& borderRect) const;
     void drawDoubleBorder(GraphicsContext*, const LayoutRect& borderRect) const;
 
     void drawBoxSideFromPath(GraphicsContext*, const LayoutRect&, const Path&, float thickness,
         float drawThickness, BoxSide, Color, EBorderStyle) const;
-    void clipBorderSidePolygon(GraphicsContext*, BoxSide, bool firstEdgeMatches,
-        bool secondEdgeMatches) const;
+    void clipBorderSidePolygon(GraphicsContext*, BoxSide, MitreType mitre1, MitreType mitre2) const;
     void clipBorderSideForComplexInnerPath(GraphicsContext*, BoxSide) const;
 
+    MitreType computeMitre(BoxSide, BoxSide adjacentSide, BorderEdgeFlags, bool antialias) const;
+    static bool mitresRequireClipping(MitreType mitre1, MitreType mitre2, EBorderStyle, bool antialias);
+
     const BorderEdge& firstEdge() const
     {
         ASSERT(m_visibleEdgeSet);
         return m_edges[m_firstVisibleEdge];
     }
 
     // const inputs
     const ComputedStyle& m_style;
     const BackgroundBleedAvoidance m_bleedAvoidance;
     const bool m_includeLogicalLeftEdge;
@@ skipping 11 matching lines @@
     bool m_isUniformStyle;
     bool m_isUniformWidth;
     bool m_isUniformColor;
     bool m_isRounded;
     bool m_hasAlpha;
 };
 
 } // namespace blink
 
 #endif