Support radial-gradients with relative offsets

Source/core/css/CSSGradientValue.cpp

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/css/CSSGradientValue.h"
 
 #include "core/CSSValueKeywords.h"
 #include "core/css/CSSCalculationValue.h"
 #include "core/css/CSSToLengthConversionData.h"
+#include "core/css/Pair.h"
 #include "core/dom/NodeRenderStyle.h"
 #include "core/dom/TextLinkColors.h"
 #include "core/rendering/RenderObject.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/Gradient.h"
 #include "platform/graphics/GradientGeneratedImage.h"
 #include "platform/graphics/Image.h"
 #include "wtf/text/StringBuilder.h"
 #include "wtf/text/WTFString.h"
 
@@ skipping 340 matching lines @@
             gradient->setEndRadius(gradient->endRadius() * scale);
         }
     }
 
     for (unsigned i = 0; i < numStops; i++)
         gradient->addColorStop(stops[i].offset, stops[i].color);
 }
 
 static float positionFromValue(CSSPrimitiveValue* value, const CSSToLengthConversionData& conversionData, const IntSize& size, bool isHorizontal)
 {
+    int origin = 0;
+    int sign = 1;
+    int edgeDistance = isHorizontal ? size.width() : size.height();
+
+    // In this case the center of the gradient is given relative to an edge in the form of:
+    // [ top | bottom | right | left ] [ <percentage> | <length> ].
+    if (Pair* pair = value->getPairValue()) {
+        CSSValueID originID = pair->first()->getValueID();
+        value = pair->second();
+
+        if (originID == CSSValueRight || originID == CSSValueBottom) {
+            // For right/bottom, the offset is relative to the far edge.
+            origin = edgeDistance;
+            sign = -1;
+        }
+    }
+
     if (value->isNumber())
-        return value->getFloatValue() * conversionData.zoom();
+        return origin + sign * value->getFloatValue() * conversionData.zoom();
 
-    int edgeDistance = isHorizontal ? size.width() : size.height();
     if (value->isPercentage())
-        return value->getFloatValue() / 100.f * edgeDistance;
+        return origin + sign * value->getFloatValue() / 100.f * edgeDistance;
 
     if (value->isCalculatedPercentageWithLength())
-        return value->cssCalcValue()->toCalcValue(conversionData)->evaluate(edgeDistance);
+        return origin + sign * value->cssCalcValue()->toCalcValue(conversionData)->evaluate(edgeDistance);
 
     switch (value->getValueID()) {
     case CSSValueTop:
         ASSERT(!isHorizontal);
         return 0;
     case CSSValueLeft:
         ASSERT(isHorizontal);
         return 0;
     case CSSValueBottom:
         ASSERT(!isHorizontal);
         return size.height();
     case CSSValueRight:
         ASSERT(isHorizontal);
         return size.width();
     default:
         break;
     }
 
-    return value->computeLength<float>(conversionData);
+    return origin + sign * value->computeLength<float>(conversionData);
 }
 
 FloatPoint CSSGradientValue::computeEndPoint(CSSPrimitiveValue* horizontal, CSSPrimitiveValue* vertical, const CSSToLengthConversionData& conversionData, const IntSize& size)
 {
     FloatPoint result;
 
     if (horizontal)
         result.setX(positionFromValue(horizontal, conversionData, size, true));
 
     if (vertical)
@@ skipping 751 matching lines @@
     visitor->trace(m_firstRadius);
     visitor->trace(m_secondRadius);
     visitor->trace(m_shape);
     visitor->trace(m_sizingBehavior);
     visitor->trace(m_endHorizontalSize);
     visitor->trace(m_endVerticalSize);
     CSSGradientValue::traceAfterDispatch(visitor);
 }
 
 } // namespace WebCore