[SVGDom] Initial linear gradient support

Kind of a big change, to connect several new bits into something useful:

  * ID tracking & lookup
  * new asPaint() node virtual to support shader (and in the future filter) based paint servers
  * <defs>, <linearGradient> and <stop> element support
  * 'href', 'offset', 'stop-color', 'stop-opacity' attribute support
  * IRI/FuncIRI and rgb(...) parsing

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2327233003

Review-Url: https://codereview.chromium.org/2327233003

1 files changed, 35 insertions, 16 deletions

diff --git a/experimental/svg/model/SkSVGRenderContext.cpp b/experimental/svg/model/SkSVGRenderContext.cpp
index d8f762142f..46ed5a28c4 100644
--- a/experimental/svg/model/SkSVGRenderContext.cpp
+++ b/experimental/svg/model/SkSVGRenderContext.cpp
@@ -7,6 +7,7 @@
 
 #include "SkCanvas.h"
 #include "SkSVGAttribute.h"
+#include "SkSVGNode.h"
 #include "SkSVGRenderContext.h"
 #include "SkSVGTypes.h"
 
@@ -98,11 +99,18 @@ SkPaint::Join toSkJoin(const SkSVGLineJoin& join) {
     }
 }
 
-void applySvgPaint(const SkSVGPaint& svgPaint, SkPaint* p) {
+void applySvgPaint(const SkSVGRenderContext& ctx, const SkSVGPaint& svgPaint, SkPaint* p) {
     switch (svgPaint.type()) {
     case SkSVGPaint::Type::kColor:
         p->setColor(SkColorSetA(svgPaint.color(), p->getAlpha()));
         break;
+    case SkSVGPaint::Type::kIRI: {
+        const auto* node = ctx.findNodeById(svgPaint.iri());
+        if (!node || !node->asPaint(ctx, p)) {
+            p->setColor(SK_ColorTRANSPARENT);
+        }
+        break;
+    }
     case SkSVGPaint::Type::kCurrentColor:
         SkDebugf("unimplemented 'currentColor' paint type");
         // Fall through.
@@ -120,33 +128,33 @@ inline uint8_t opacity_to_alpha(SkScalar o) {
 // Commit the selected attribute to the paint cache.
 template <SkSVGAttribute>
 void commitToPaint(const SkSVGPresentationAttributes&,
-                   const SkSVGLengthContext&,
+                   const SkSVGRenderContext&,
                    SkSVGPresentationContext*);
 
 template <>
 void commitToPaint<SkSVGAttribute::kFill>(const SkSVGPresentationAttributes& attrs,
-                                          const SkSVGLengthContext&,
+                                          const SkSVGRenderContext& ctx,
                                           SkSVGPresentationContext* pctx) {
-    applySvgPaint(*attrs.fFill.get(), &pctx->fFillPaint);
+    applySvgPaint(ctx, *attrs.fFill.get(), &pctx->fFillPaint);
 }
 
 template <>
 void commitToPaint<SkSVGAttribute::kStroke>(const SkSVGPresentationAttributes& attrs,
-                                            const SkSVGLengthContext&,
+                                            const SkSVGRenderContext& ctx,
                                             SkSVGPresentationContext* pctx) {
-    applySvgPaint(*attrs.fStroke.get(), &pctx->fStrokePaint);
+    applySvgPaint(ctx, *attrs.fStroke.get(), &pctx->fStrokePaint);
 }
 
 template <>
 void commitToPaint<SkSVGAttribute::kFillOpacity>(const SkSVGPresentationAttributes& attrs,
-                                                 const SkSVGLengthContext&,
+                                                 const SkSVGRenderContext&,
                                                  SkSVGPresentationContext* pctx) {
     pctx->fFillPaint.setAlpha(opacity_to_alpha(*attrs.fFillOpacity.get()));
 }
 
 template <>
 void commitToPaint<SkSVGAttribute::kStrokeLineCap>(const SkSVGPresentationAttributes& attrs,
-                                                   const SkSVGLengthContext&,
+                                                   const SkSVGRenderContext&,
                                                    SkSVGPresentationContext* pctx) {
     const auto& cap = *attrs.fStrokeLineCap.get();
     if (cap.type() != SkSVGLineCap::Type::kInherit) {
@@ -156,7 +164,7 @@ void commitToPaint<SkSVGAttribute::kStrokeLineCap>(const SkSVGPresentationAttrib
 
 template <>
 void commitToPaint<SkSVGAttribute::kStrokeLineJoin>(const SkSVGPresentationAttributes& attrs,
-                                                    const SkSVGLengthContext&,
+                                                    const SkSVGRenderContext&,
                                                     SkSVGPresentationContext* pctx) {
     const auto& join = *attrs.fStrokeLineJoin.get();
     if (join.type() != SkSVGLineJoin::Type::kInherit) {
@@ -166,17 +174,17 @@ void commitToPaint<SkSVGAttribute::kStrokeLineJoin>(const SkSVGPresentationAttri
 
 template <>
 void commitToPaint<SkSVGAttribute::kStrokeOpacity>(const SkSVGPresentationAttributes& attrs,
-                                                   const SkSVGLengthContext&,
+                                                   const SkSVGRenderContext&,
                                                    SkSVGPresentationContext* pctx) {
     pctx->fStrokePaint.setAlpha(opacity_to_alpha(*attrs.fStrokeOpacity.get()));
 }
 
 template <>
 void commitToPaint<SkSVGAttribute::kStrokeWidth>(const SkSVGPresentationAttributes& attrs,
-                                                 const SkSVGLengthContext& lctx,
+                                                 const SkSVGRenderContext& ctx,
                                                  SkSVGPresentationContext* pctx) {
-    auto strokeWidth = lctx.resolve(*attrs.fStrokeWidth.get(),
-                                    SkSVGLengthContext::LengthType::kOther);
+    auto strokeWidth = ctx.lengthContext().resolve(*attrs.fStrokeWidth.get(),
+                                                   SkSVGLengthContext::LengthType::kOther);
     pctx->fStrokePaint.setStrokeWidth(strokeWidth);
 }
 
@@ -193,7 +201,10 @@ SkSVGPresentationContext::SkSVGPresentationContext()
     fStrokePaint.setAntiAlias(true);
 
     // Commit initial values to the paint cache.
-    SkSVGLengthContext dummy(SkSize::Make(0, 0));
+    SkCanvas dummyCanvas(0, 0);
+    SkSVGRenderContext dummy(&dummyCanvas, SkSVGIDMapper(), SkSVGLengthContext(SkSize::Make(0, 0)),
+                             *this);
+
     commitToPaint<SkSVGAttribute::kFill>(fInherited, dummy, this);
     commitToPaint<SkSVGAttribute::kFillOpacity>(fInherited, dummy, this);
     commitToPaint<SkSVGAttribute::kStroke>(fInherited, dummy, this);
@@ -204,15 +215,18 @@ SkSVGPresentationContext::SkSVGPresentationContext()
 }
 
 SkSVGRenderContext::SkSVGRenderContext(SkCanvas* canvas,
+                                       const SkSVGIDMapper& mapper,
                                        const SkSVGLengthContext& lctx,
                                        const SkSVGPresentationContext& pctx)
-    : fLengthContext(lctx)
+    : fIDMapper(mapper)
+    , fLengthContext(lctx)
     , fPresentationContext(pctx)
     , fCanvas(canvas)
     , fCanvasSaveCount(canvas->getSaveCount()) {}
 
 SkSVGRenderContext::SkSVGRenderContext(const SkSVGRenderContext& other)
     : SkSVGRenderContext(other.fCanvas,
+                         other.fIDMapper,
                          *other.fLengthContext,
                          *other.fPresentationContext) {}
 
@@ -220,6 +234,11 @@ SkSVGRenderContext::~SkSVGRenderContext() {
     fCanvas->restoreToCount(fCanvasSaveCount);
 }
 
+const SkSVGNode* SkSVGRenderContext::findNodeById(const SkString& id) const {
+    const auto* v = fIDMapper.find(id);
+    return v ? v->get() : nullptr;
+}
+
 void SkSVGRenderContext::applyPresentationAttributes(const SkSVGPresentationAttributes& attrs) {
 
 #define ApplyLazyInheritedAttribute(ATTR)                                               \
@@ -231,7 +250,7 @@ void SkSVGRenderContext::applyPresentationAttributes(const SkSVGPresentationAttr
             /* Update the local attribute value */                                      \
             fPresentationContext.writable()->fInherited.f ## ATTR.set(*value);          \
             /* Update the cached paints */                                              \
-            commitToPaint<SkSVGAttribute::k ## ATTR>(attrs, *fLengthContext,            \
+            commitToPaint<SkSVGAttribute::k ## ATTR>(attrs, *this,    \
                                                      fPresentationContext.writable());  \
         }                                                                               \
     } while (false)