[SVG] Implement currentColor for fill and stroke

The 'color' presentation attribute when set determines the value of the
special color value 'currentColor'. See the color-prop-01-b test for an
example.

Not handled in this CL:
- The color type needs to be changed to be inheritable.
- currentColor should also be usable for stop-color for gradients. See
  <https://www.w3.org/TR/SVG11/color.html#ColorProperty> for a full list
  of attributes that can use currentColor.

Change-Id: Icf81b5313cda688d1b6e20809b9b339f517b9ada
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/282638
Commit-Queue: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

experimental/svg/model/SkSVGAttribute.cpp

@@ -26,5 +26,7 @@ SkSVGPresentationAttributes SkSVGPresentationAttributes::MakeInitial() {
 
     result.fVisibility.set(SkSVGVisibility(SkSVGVisibility::Type::kVisible));
 
+    result.fColor.set(SkSVGColorType(SK_ColorBLACK));
+
     return result;
 }

experimental/svg/model/SkSVGAttribute.h

@@ -16,6 +16,7 @@ class SkSVGRenderContext;
 enum class SkSVGAttribute {
     kClipPath,
     kClipRule,
+    kColor,
     kCx, // <circle>, <ellipse>, <radialGradient>: center x position
     kCy, // <circle>, <ellipse>, <radialGradient>: center y position
     kD,
@@ -84,6 +85,8 @@ struct SkSVGPresentationAttributes {
 
     SkTLazy<SkSVGVisibility> fVisibility;
 
+    SkTLazy<SkSVGColorType>  fColor;
+
     // uninherited
     SkTLazy<SkSVGNumberType> fOpacity;
     SkTLazy<SkSVGClip>       fClipPath;

experimental/svg/model/SkSVGDOM.cpp

@@ -316,6 +316,7 @@ struct AttrParseInfo {
 SortedDictionaryEntry<AttrParseInfo> gAttributeParseInfo[] = {
     { "clip-path"        , { SkSVGAttribute::kClipPath         , SetClipPathAttribute     }},
     { "clip-rule"        , { SkSVGAttribute::kClipRule         , SetFillRuleAttribute     }},
+    { "color"            , { SkSVGAttribute::kColor            , SetColorAttribute        }},
     { "cx"               , { SkSVGAttribute::kCx               , SetLengthAttribute       }},
     { "cy"               , { SkSVGAttribute::kCy               , SetLengthAttribute       }},
     { "d"                , { SkSVGAttribute::kD                , SetPathDataAttribute     }},

experimental/svg/model/SkSVGNode.cpp

@@ -79,6 +79,11 @@ void SkSVGNode::setClipRule(const SkSVGFillRule& clipRule) {
     SetInheritedByDefault(fPresentationAttributes.fClipRule, clipRule);
 }
 
+void SkSVGNode::setColor(const SkSVGColorType& color) {
+    // TODO: Color should be inherited by default
+    fPresentationAttributes.fColor.set(color);
+}
+
 void SkSVGNode::setFill(const SkSVGPaint& svgPaint) {
     SetInheritedByDefault(fPresentationAttributes.fFill, svgPaint);
 }
@@ -146,6 +151,11 @@ void SkSVGNode::onSetAttribute(SkSVGAttribute attr, const SkSVGValue& v) {
             this->setClipRule(*clipRule);
         }
         break;
+    case SkSVGAttribute::kColor:
+        if (const SkSVGColorValue* color = v.as<SkSVGColorValue>()) {
+            this->setColor(*color);
+        }
+        break;
     case SkSVGAttribute::kFill:
         if (const SkSVGPaintValue* paint = v.as<SkSVGPaintValue>()) {
             this->setFill(*paint);

experimental/svg/model/SkSVGNode.h

@@ -54,6 +54,7 @@ public:
 
     void setClipPath(const SkSVGClip&);
     void setClipRule(const SkSVGFillRule&);
+    void setColor(const SkSVGColorType&);
     void setFill(const SkSVGPaint&);
     void setFillOpacity(const SkSVGNumberType&);
     void setFillRule(const SkSVGFillRule&);

experimental/svg/model/SkSVGRenderContext.cpp

@@ -116,8 +116,8 @@ void applySvgPaint(const SkSVGRenderContext& ctx, const SkSVGPaint& svgPaint, Sk
         break;
     }
     case SkSVGPaint::Type::kCurrentColor:
-        SkDebugf("unimplemented 'currentColor' paint type");
-        // Fall through.
+        p->setColor(*ctx.presentationContext().fInherited.fColor);
+        break;
     case SkSVGPaint::Type::kNone:
         // Fall through.
     case SkSVGPaint::Type::kInherit:
@@ -267,6 +267,13 @@ void commitToPaint<SkSVGAttribute::kVisibility>(const SkSVGPresentationAttribute
     // Not part of the SkPaint state; queried to veto rendering.
 }
 
+template <>
+void commitToPaint<SkSVGAttribute::kColor>(const SkSVGPresentationAttributes&,
+                                           const SkSVGRenderContext&,
+                                           SkSVGPresentationContext*) {
+    // Not part of the SkPaint state; applied via 'currentColor' color value
+}
+
 } // anonymous ns
 
 SkSVGPresentationContext::SkSVGPresentationContext()
@@ -354,6 +361,7 @@ void SkSVGRenderContext::applyPresentationAttributes(const SkSVGPresentationAttr
     ApplyLazyInheritedAttribute(StrokeOpacity);
     ApplyLazyInheritedAttribute(StrokeWidth);
     ApplyLazyInheritedAttribute(Visibility);
+    ApplyLazyInheritedAttribute(Color);
 
 #undef ApplyLazyInheritedAttribute