Shrink SVG paint-order to take less bits

Source/core/style/SVGComputedStyle.cpp

Index: Source/core/style/SVGComputedStyle.cpp
diff --git a/Source/core/style/SVGComputedStyle.cpp b/Source/core/style/SVGComputedStyle.cpp
index 36b237672bf134d7b8ec97ba5448eca2edf3e5b1..8cf16fbb68a4c986399e967f5575c3b375214ab1 100644
--- a/Source/core/style/SVGComputedStyle.cpp
+++ b/Source/core/style/SVGComputedStyle.cpp
@@ -236,7 +236,7 @@ bool SVGComputedStyle::diffNeedsPaintInvalidation(const SVGComputedStyle* other)
         || 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)
@@ -248,11 +248,44 @@ bool SVGComputedStyle::diffNeedsPaintInvalidation(const SVGComputedStyle* other)
     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;
 }
 
 }