Shrink SVG paint-order to take less bits

Source/core/style/SVGComputedStyle.cpp

 /*
     Copyright (C) 2004, 2005, 2007 Nikolas Zimmermann <zimmermann@kde.org>
                   2004, 2005, 2010 Rob Buis <buis@kde.org>
     Copyright (C) Research In Motion Limited 2010. All rights reserved.
 
     Based on khtml code by:
     Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
     Copyright (C) 1999-2003 Lars Knoll (knoll@kde.org)
     Copyright (C) 2002-2003 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Apple Computer, Inc.
@@ skipping 218 matching lines @@
     if (stops != other->stops)
         return true;
 
     // Changes of these flags only cause paint invalidations.
     if (svg_inherited_flags._colorRendering != other->svg_inherited_flags._colorRendering
         || svg_inherited_flags._shapeRendering != other->svg_inherited_flags._shapeRendering
         || svg_inherited_flags._clipRule != other->svg_inherited_flags._clipRule
         || svg_inherited_flags._fillRule != other->svg_inherited_flags._fillRule
         || svg_inherited_flags._colorInterpolation != other->svg_inherited_flags._colorInterpolation
         || svg_inherited_flags._colorInterpolationFilters != other->svg_inherited_flags._colorInterpolationFilters
-        || svg_inherited_flags._paintOrder != other->svg_inherited_flags._paintOrder)
+        || svg_inherited_flags.paintOrder != other->svg_inherited_flags.paintOrder)
         return true;
 
     if (svg_noninherited_flags.f.bufferedRendering != other->svg_noninherited_flags.f.bufferedRendering)
         return true;
 
     if (svg_noninherited_flags.f.maskType != other->svg_noninherited_flags.f.maskType)
         return true;
 
     return false;
 }
 
-EPaintOrderType SVGComputedStyle::paintOrderType(unsigned index) const
+Vector<EPaintOrderType, 3> SVGComputedStyle::paintTypesForPaintOrder() const

[pdr., 2015/07/29 05:20:50]

Returning a Vector seems a bit heavy for this code since painting is quite
performance sensitive. The WebKit code was very careful to use move semantics to
avoid copies but we can't yet use them in blink. I think it may be best to keep
using bit twiddling tricks here. This won't be too hard and I think we can even
make the code a little cleaner.

My recommendation would be to try to re-use the existing (unsigned pt =
(paintOrder() >> (kPaintOrderBitwidth*index)) & ((1u << kPaintOrderBitwidth) -
1)) code here.

It's also very possible that I'm optimizing too early here. If you think so,
could you run the svg perf tests with and without your change to see what the
difference is?

[Shanmuga Pandi, 2015/07/29 06:55:04]

Ok. I will try to change the code as you suggested.

 {
-    ASSERT(index < ((1 << kPaintOrderBitwidth)-1));
-    unsigned pt = (paintOrder() >> (kPaintOrderBitwidth*index)) & ((1u << kPaintOrderBitwidth) - 1);
-    return (EPaintOrderType)pt;
+    Vector<EPaintOrderType, 3> paintOrder;
+    switch (this->paintOrder()) {
+    case PaintOrderNormal:
+    case PaintOrderFill:
+        paintOrder.append(PT_FILL);
+        paintOrder.append(PT_STROKE);
+        paintOrder.append(PT_MARKERS);
+        break;
+    case PaintOrderFillMarkers:
+        paintOrder.append(PT_FILL);
+        paintOrder.append(PT_MARKERS);
+        paintOrder.append(PT_STROKE);
+        break;
+    case PaintOrderStroke:
+        paintOrder.append(PT_STROKE);
+        paintOrder.append(PT_FILL);
+        paintOrder.append(PT_MARKERS);
+        break;
+    case PaintOrderStrokeMarkers:
+        paintOrder.append(PT_STROKE);
+        paintOrder.append(PT_MARKERS);
+        paintOrder.append(PT_FILL);
+        break;
+    case PaintOrderMarkers:
+        paintOrder.append(PT_MARKERS);
+        paintOrder.append(PT_FILL);
+        paintOrder.append(PT_STROKE);
+        break;
+    case PaintOrderMarkersStroke:
+        paintOrder.append(PT_MARKERS);
+        paintOrder.append(PT_STROKE);
+        paintOrder.append(PT_FILL);
+        break;
+    }
+
+    return paintOrder;
 }
 
 }