Scaling and offset fix for FELighting (software and skia paths)

Source/platform/graphics/filters/FELighting.cpp

Index: Source/platform/graphics/filters/FELighting.cpp
diff --git a/Source/platform/graphics/filters/FELighting.cpp b/Source/platform/graphics/filters/FELighting.cpp
index 4214ba9f4520448aaef9d6208b17cc1db0133189..f14f271db60122fd3202449da5ff6c59cbc8d167 100644
--- a/Source/platform/graphics/filters/FELighting.cpp
+++ b/Source/platform/graphics/filters/FELighting.cpp
@@ -187,7 +187,9 @@ inline void FELighting::LightingData::bottomRight(int offset, IntPoint& normalVe
 inline void FELighting::inlineSetPixel(int offset, LightingData& data, LightSource::PaintingData& paintingData,
                                        int lightX, int lightY, float factorX, float factorY, IntPoint& normal2DVector)
 {
-    m_lightSource->updatePaintingData(paintingData, lightX, lightY, static_cast<float>(data.pixels->item(offset + cAlphaChannelOffset)) * data.surfaceScale);
+    float transformedLightX = (static_cast<float>(lightX) + data.originOffset.width()) / data.worldScale.x();
+    float transformedLightY = (static_cast<float>(lightY) + data.originOffset.height()) / data.worldScale.y();
+    m_lightSource->updatePaintingData(paintingData, transformedLightX, transformedLightY, static_cast<float>(data.pixels->item(offset + cAlphaChannelOffset)) * data.surfaceScale * data.worldScale.z());
 
     float lightStrength;
     if (!normal2DVector.x() && !normal2DVector.y()) {
@@ -302,6 +304,20 @@ inline void FELighting::platformApply(LightingData& data, LightSource::PaintingD
 #endif
 }
 
+void FELighting::getTransform(FloatSize* offset, FloatPoint3D* scale) const
+{
+    FloatRect initialEffectRect = effectBoundaries();
+    FloatRect absoluteEffectRect = filter()->mapLocalRectToAbsoluteRect(initialEffectRect);
+    FloatPoint absoluteLocation(absolutePaintRect().location());
+    FloatSize positionOffset(absoluteLocation - absoluteEffectRect.location());
+    offset->setWidth(positionOffset.width());
+    offset->setHeight(positionOffset.height());
+    scale->setX(initialEffectRect.width() > 0.0f && initialEffectRect.width() > 0.0f ? absoluteEffectRect.width() / initialEffectRect.width() : 1.0f);
+    scale->setY(initialEffectRect.height() > 0.0f && initialEffectRect.height() > 0.0f ? absoluteEffectRect.height() / initialEffectRect.height() : 1.0f);
+    // X and Y scale should be the same, but, if not, do a best effort by averaging the 2 for Z scale
+    scale->setZ(0.5f * (scale->x() + scale->y()));
+}
+
 bool FELighting::drawLighting(Uint8ClampedArray* pixels, int width, int height)
 {
     LightSource::PaintingData paintingData;
@@ -320,6 +336,7 @@ bool FELighting::drawLighting(Uint8ClampedArray* pixels, int width, int height)
     data.widthMultipliedByPixelSize = width * cPixelSize;
     data.widthDecreasedByOne = width - 1;
     data.heightDecreasedByOne = height - 1;
+    getTransform(&data.originOffset, &data.worldScale);
     Color lightColor = adaptColorToOperatingColorSpace(m_lightingColor);
     paintingData.colorVector = FloatPoint3D(lightColor.red(), lightColor.green(), lightColor.blue());
     m_lightSource->initPaintingData(paintingData);
@@ -439,15 +456,21 @@ PassRefPtr<SkImageFilter> FELighting::createImageFilter(SkiaImageFilterBuilder*
     case LS_POINT: {
         PointLightSource* pointLightSource = static_cast<PointLightSource*>(m_lightSource.get());
         FloatPoint3D position = pointLightSource->position();
-        SkPoint3 skPosition(position.x(), position.y(), position.z());
+        FloatSize offset;
+        FloatPoint3D scale;
+        getTransform(&offset, &scale);
+        SkPoint3 skPosition(position.x() * scale.x() - offset.width(), position.y() * scale.y() - offset.height(), position.z() * scale.z());

[Stephen White, 2014/03/03 17:55:09]

I don't think we should do this. I think we should leave the createImageFilter()
path alone for now, and fix reference filters later by moving all scaling to the
CTM, and fixing Skia lighting filters to simulate Z scale, as you've done in
getTransform() above.

In fact, I think this change may break the SVG-on-SVG path already, since it
applies all scaling and offsets via the CTM.

[sugoi1, 2014/03/03 20:29:30]

Done.

         if (m_specularConstant > 0)
             return adoptRef(SkLightingImageFilter::CreatePointLitSpecular(skPosition, lightColor.rgb(), m_surfaceScale, m_specularConstant, m_specularExponent, input.get(), &rect));
         return adoptRef(SkLightingImageFilter::CreatePointLitDiffuse(skPosition, lightColor.rgb(), m_surfaceScale, m_diffuseConstant, input.get(), &rect));
     }
     case LS_SPOT: {
         SpotLightSource* spotLightSource = static_cast<SpotLightSource*>(m_lightSource.get());
-        SkPoint3 location(spotLightSource->position().x(), spotLightSource->position().y(), spotLightSource->position().z());
-        SkPoint3 target(spotLightSource->direction().x(), spotLightSource->direction().y(), spotLightSource->direction().z());
+        FloatSize offset;
+        FloatPoint3D scale;
+        getTransform(&offset, &scale);
+        SkPoint3 location(spotLightSource->position().x() * scale.x() - offset.width(), spotLightSource->position().y() * scale.y() - offset.height(), spotLightSource->position().z() * scale.z());
+        SkPoint3 target(spotLightSource->direction().x() * scale.x() - offset.width(), spotLightSource->direction().y() * scale.y() - offset.height(), spotLightSource->direction().z() * scale.z());

[Stephen White, 2014/03/03 17:55:09]

Same here.

[sugoi1, 2014/03/03 20:29:30]

Done.

         float specularExponent = spotLightSource->specularExponent();
         float limitingConeAngle = spotLightSource->limitingConeAngle();
         if (!limitingConeAngle || limitingConeAngle > 90 || limitingConeAngle < -90)