[skotty,sksg] Initial gradient support

TBR=
Change-Id: I61e4d46ac14660f4c9ea757be2278e4098131a6b
Reviewed-on: https://skia-review.googlesource.com/94121
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>

6 files changed, 359 insertions, 29 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 16e6819abd..c27af9468f 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1392,6 +1392,7 @@ if (skia_enable_tools) {
       "experimental/sksg/geometry/SkSGRect.cpp",
       "experimental/sksg/geometry/SkSGTrimEffect.cpp",
       "experimental/sksg/paint/SkSGColor.cpp",
+      "experimental/sksg/paint/SkSGGradient.cpp",
     ]
     deps = [
       ":skia",
diff --git a/experimental/skotty/Skotty.cpp b/experimental/skotty/Skotty.cpp
index 284b37704a..ce2644ea51 100644
--- a/experimental/skotty/Skotty.cpp
+++ b/experimental/skotty/Skotty.cpp
@@ -21,6 +21,7 @@
 #include "SkPoint.h"
 #include "SkSGColor.h"
 #include "SkSGDraw.h"
+#include "SkSGGradient.h"
 #include "SkSGGroup.h"
 #include "SkSGImage.h"
 #include "SkSGInvalidationController.h"
@@ -293,13 +294,11 @@ sk_sp<sksg::GeometryNode> AttachPolystarGeometry(const Json::Value& jstar, Attac
     return path_node;
 }
 
-sk_sp<sksg::Color> AttachColorPaint(const Json::Value& obj, AttachContext* ctx) {
+sk_sp<sksg::Color> AttachColor(const Json::Value& obj, AttachContext* ctx) {
     SkASSERT(obj.isObject());
 
     auto color_node = sksg::Color::Make(SK_ColorBLACK);
-    color_node->setAntiAlias(true);
-
-    auto composite = sk_make_sp<CompositeColor>(color_node);
+    auto composite  = sk_make_sp<CompositeColor>(color_node);
     auto color_attached = BindProperty<VectorValue>(obj["c"], ctx, composite,
         [](CompositeColor* node, const VectorValue& c) {
             node->setColor(ValueTraits<VectorValue>::As<SkColor>(c));
@@ -312,29 +311,70 @@ sk_sp<sksg::Color> AttachColorPaint(const Json::Value& obj, AttachContext* ctx)
     return (color_attached || opacity_attached) ? color_node : nullptr;
 }
 
-sk_sp<sksg::PaintNode> AttachFillPaint(const Json::Value& jfill, AttachContext* ctx) {
-    SkASSERT(jfill.isObject());
+sk_sp<sksg::Gradient> AttachGradient(const Json::Value& obj, AttachContext* ctx) {
+    SkASSERT(obj.isObject());
+
+    const auto& stops = obj["g"];
+    if (!stops.isObject())
+        return nullptr;
+
+    const auto stopCount = ParseInt(stops["p"], -1);
+    if (stopCount < 0)
+        return nullptr;
+
+    sk_sp<sksg::Gradient> gradient_node;
+    sk_sp<CompositeGradient> composite;
+
+    if (ParseInt(obj["t"], 1) == 1) {
+        auto linear_node = sksg::LinearGradient::Make();
+        composite = sk_make_sp<CompositeLinearGradient>(linear_node, stopCount);
+        gradient_node = std::move(linear_node);
+    } else {
+        auto radial_node = sksg::RadialGradient::Make();
+        composite = sk_make_sp<CompositeRadialGradient>(radial_node, stopCount);
 
-    auto color = AttachColorPaint(jfill, ctx);
-    if (color) {
-        LOG("** Attached color fill: 0x%x\n", color->getColor());
+        // TODO: highlight, angle
+        gradient_node = std::move(radial_node);
     }
-    return color;
+
+    BindProperty<VectorValue>(stops["k"], ctx, composite,
+        [](CompositeGradient* node, const VectorValue& stops) {
+            node->setColorStops(stops);
+        });
+    BindProperty<VectorValue>(obj["s"], ctx, composite,
+        [](CompositeGradient* node, const VectorValue& s) {
+            node->setStartPoint(ValueTraits<VectorValue>::As<SkPoint>(s));
+        });
+    BindProperty<VectorValue>(obj["e"], ctx, composite,
+        [](CompositeGradient* node, const VectorValue& e) {
+            node->setEndPoint(ValueTraits<VectorValue>::As<SkPoint>(e));
+        });
+
+    return gradient_node;
 }
 
-sk_sp<sksg::PaintNode> AttachStrokePaint(const Json::Value& jstroke, AttachContext* ctx) {
+sk_sp<sksg::PaintNode> AttachPaint(const Json::Value& jfill, AttachContext* ctx,
+                                   sk_sp<sksg::PaintNode> paint_node) {
+    if (paint_node) {
+        paint_node->setAntiAlias(true);
+
+        // TODO: refactor opacity
+    }
+
+    return paint_node;
+}
+
+sk_sp<sksg::PaintNode> AttachStroke(const Json::Value& jstroke, AttachContext* ctx,
+                                    sk_sp<sksg::PaintNode> stroke_node) {
     SkASSERT(jstroke.isObject());
 
-    auto stroke_node = AttachColorPaint(jstroke, ctx);
     if (!stroke_node)
         return nullptr;
 
-    LOG("** Attached color stroke: 0x%x\n", stroke_node->getColor());
-
     stroke_node->setStyle(SkPaint::kStroke_Style);
 
     auto width_attached = BindProperty<ScalarValue>(jstroke["w"], ctx, stroke_node,
-        [](sksg::Color* node, const ScalarValue& w) {
+        [](sksg::PaintNode* node, const ScalarValue& w) {
             node->setStrokeWidth(w);
         });
     if (!width_attached)
@@ -361,6 +401,30 @@ sk_sp<sksg::PaintNode> AttachStrokePaint(const Json::Value& jstroke, AttachConte
     return stroke_node;
 }
 
+sk_sp<sksg::PaintNode> AttachColorFill(const Json::Value& jfill, AttachContext* ctx) {
+    SkASSERT(jfill.isObject());
+
+    return AttachPaint(jfill, ctx, AttachColor(jfill, ctx));
+}
+
+sk_sp<sksg::PaintNode> AttachGradientFill(const Json::Value& jfill, AttachContext* ctx) {
+    SkASSERT(jfill.isObject());
+
+    return AttachPaint(jfill, ctx, AttachGradient(jfill, ctx));
+}
+
+sk_sp<sksg::PaintNode> AttachColorStroke(const Json::Value& jstroke, AttachContext* ctx) {
+    SkASSERT(jstroke.isObject());
+
+    return AttachStroke(jstroke, ctx, AttachPaint(jstroke, ctx, AttachColor(jstroke, ctx)));
+}
+
+sk_sp<sksg::PaintNode> AttachGradientStroke(const Json::Value& jstroke, AttachContext* ctx) {
+    SkASSERT(jstroke.isObject());
+
+    return AttachStroke(jstroke, ctx, AttachPaint(jstroke, ctx, AttachGradient(jstroke, ctx)));
+}
+
 std::vector<sk_sp<sksg::GeometryNode>> AttachMergeGeometryEffect(
     const Json::Value& jmerge, AttachContext* ctx, std::vector<sk_sp<sksg::GeometryNode>>&& geos) {
     std::vector<sk_sp<sksg::GeometryNode>> merged;
@@ -433,8 +497,10 @@ static constexpr GeometryAttacherT gGeometryAttachers[] = {
 
 using PaintAttacherT = sk_sp<sksg::PaintNode> (*)(const Json::Value&, AttachContext*);
 static constexpr PaintAttacherT gPaintAttachers[] = {
-    AttachFillPaint,
-    AttachStrokePaint,
+    AttachColorFill,
+    AttachColorStroke,
+    AttachGradientFill,
+    AttachGradientStroke,
 };
 
 using GroupAttacherT = sk_sp<sksg::RenderNode> (*)(const Json::Value&, AttachContext*);
@@ -468,13 +534,15 @@ struct ShapeInfo {
 const ShapeInfo* FindShapeInfo(const Json::Value& shape) {
     static constexpr ShapeInfo gShapeInfo[] = {
         { "el", ShapeType::kGeometry      , 2 }, // ellipse   -> AttachEllipseGeometry
-        { "fl", ShapeType::kPaint         , 0 }, // fill      -> AttachFillPaint
+        { "fl", ShapeType::kPaint         , 0 }, // fill      -> AttachColorFill
+        { "gf", ShapeType::kPaint         , 2 }, // gfill     -> AttachGradientFill
         { "gr", ShapeType::kGroup         , 0 }, // group     -> AttachShapeGroup
+        { "gs", ShapeType::kPaint         , 3 }, // gstroke   -> AttachGradientStroke
         { "mm", ShapeType::kGeometryEffect, 0 }, // merge     -> AttachMergeGeometryEffect
         { "rc", ShapeType::kGeometry      , 1 }, // rrect     -> AttachRRectGeometry
         { "sh", ShapeType::kGeometry      , 0 }, // shape     -> AttachPathGeometry
         { "sr", ShapeType::kGeometry      , 3 }, // polystar  -> AttachPolyStarGeometry
-        { "st", ShapeType::kPaint         , 1 }, // stroke    -> AttachStrokePaint
+        { "st", ShapeType::kPaint         , 1 }, // stroke    -> AttachColorStroke
         { "tm", ShapeType::kGeometryEffect, 1 }, // trim      -> AttachTrimGeometryEffect
         { "tr", ShapeType::kTransform     , 0 }, // transform -> In-place handler
     };
diff --git a/experimental/skotty/SkottyProperties.cpp b/experimental/skotty/SkottyProperties.cpp
index 579823b24c..e962a7d538 100644
--- a/experimental/skotty/SkottyProperties.cpp
+++ b/experimental/skotty/SkottyProperties.cpp
@@ -11,6 +11,7 @@
 #include "SkottyPriv.h"
 #include "SkPath.h"
 #include "SkSGColor.h"
+#include "SkSGGradient.h"
 #include "SkSGPath.h"
 #include "SkSGRect.h"
 #include "SkSGTransform.h"
@@ -41,6 +42,19 @@ bool ParsePoints(const Json::Value& v, PointArray* pts) {
     return true;
 }
 
+SkColor VecToColor(const float* v, size_t size) {
+    // best effort to turn this into a color
+    const auto r = size > 0 ? v[0] : 0,
+               g = size > 1 ? v[1] : 0,
+               b = size > 2 ? v[2] : 0,
+               a = size > 3 ? v[3] : 1;
+
+    return SkColorSetARGB(SkTPin<SkScalar>(a, 0, 1) * 255,
+                          SkTPin<SkScalar>(r, 0, 1) * 255,
+                          SkTPin<SkScalar>(g, 0, 1) * 255,
+                          SkTPin<SkScalar>(b, 0, 1) * 255);
+}
+
 } // namespace
 
 template <>
@@ -94,16 +108,7 @@ size_t ValueTraits<VectorValue>::Cardinality(const VectorValue& vec) {
 template <>
 template <>
 SkColor ValueTraits<VectorValue>::As<SkColor>(const VectorValue& vec) {
-    // best effort to turn this into a color
-    const auto r = vec.size() > 0 ? vec[0] : 0,
-               g = vec.size() > 1 ? vec[1] : 0,
-               b = vec.size() > 2 ? vec[2] : 0,
-               a = vec.size() > 3 ? vec[3] : 1;
-
-    return SkColorSetARGB(SkTPin<SkScalar>(a, 0, 1) * 255,
-                          SkTPin<SkScalar>(r, 0, 1) * 255,
-                          SkTPin<SkScalar>(g, 0, 1) * 255,
-                          SkTPin<SkScalar>(b, 0, 1) * 255);
+    return VecToColor(vec.data(), vec.size());
 }
 
 template <>
@@ -251,4 +256,49 @@ void CompositePolyStar::apply() {
     fPathNode->setPath(poly);
 }
 
+CompositeGradient::CompositeGradient(sk_sp<sksg::Gradient> grad, size_t stopCount)
+    : fGradient(std::move(grad))
+    , fStopCount(stopCount) {}
+
+void CompositeGradient::apply() {
+    this->onApply();
+
+    // |fColorStops| holds |fStopCount| x [ pos, r, g, g ] + ? x [ pos, alpha ]
+
+    if (fColorStops.size() < fStopCount * 4 || ((fColorStops.size() - fStopCount * 4) % 2)) {
+        LOG("!! Invalid gradient stop array size: %zu", fColorStops.size());
+        return;
+    }
+
+    std::vector<sksg::Gradient::ColorStop> stops;
+
+    // TODO: merge/lerp opacity stops
+    const auto csEnd = fColorStops.cbegin() + fStopCount * 4;
+    for (auto cs = fColorStops.cbegin(); cs != csEnd; cs += 4) {
+        stops.push_back({ *cs, VecToColor(&*(cs + 1), 3) });
+    }
+
+    fGradient->setColorStops(std::move(stops));
+}
+
+CompositeLinearGradient::CompositeLinearGradient(sk_sp<sksg::LinearGradient> grad, size_t stopCount)
+    : INHERITED(std::move(grad), stopCount) {}
+
+void CompositeLinearGradient::onApply() {
+    auto* grad = static_cast<sksg::LinearGradient*>(fGradient.get());
+    grad->setStartPoint(this->startPoint());
+    grad->setEndPoint(this->endPoint());
+}
+
+CompositeRadialGradient::CompositeRadialGradient(sk_sp<sksg::RadialGradient> grad, size_t stopCount)
+    : INHERITED(std::move(grad), stopCount) {}
+
+void CompositeRadialGradient::onApply() {
+    auto* grad = static_cast<sksg::RadialGradient*>(fGradient.get());
+    grad->setStartCenter(this->startPoint());
+    grad->setEndCenter(this->startPoint());
+    grad->setStartRadius(0);
+    grad->setEndRadius(SkPoint::Distance(this->startPoint(), this->endPoint()));
+}
+
 } // namespace skotty
diff --git a/experimental/skotty/SkottyProperties.h b/experimental/skotty/SkottyProperties.h
index cb64ed748b..cd22810c2e 100644
--- a/experimental/skotty/SkottyProperties.h
+++ b/experimental/skotty/SkottyProperties.h
@@ -22,8 +22,11 @@
 
 namespace sksg {
 class Color;
+class Gradient;
+class LinearGradient;
 class Matrix;
 class Path;
+class RadialGradient;
 class RRect;
 class RenderNode;;
 }
@@ -130,6 +133,49 @@ private:
     using INHERITED = SkRefCnt;
 };
 
+class CompositeGradient : public SkRefCnt {
+public:
+    COMPOSITE_PROPERTY(StartPoint, SkPoint              , SkPoint::Make(0, 0)    )
+    COMPOSITE_PROPERTY(EndPoint  , SkPoint              , SkPoint::Make(0, 0)    )
+    COMPOSITE_PROPERTY(ColorStops, std::vector<SkScalar>, std::vector<SkScalar>())
+
+protected:
+    CompositeGradient(sk_sp<sksg::Gradient>, size_t stopCount);
+
+    const SkPoint& startPoint() const { return fStartPoint; }
+    const SkPoint& endPoint()   const { return fEndPoint;   }
+
+    sk_sp<sksg::Gradient> fGradient;
+    size_t                fStopCount;
+
+    virtual void onApply() = 0;
+
+private:
+    void apply();
+
+    using INHERITED = SkRefCnt;
+};
+
+class CompositeLinearGradient final : public CompositeGradient {
+public:
+    CompositeLinearGradient(sk_sp<sksg::LinearGradient>, size_t stopCount);
+
+private:
+    void onApply() override;
+
+    using INHERITED = CompositeGradient;
+};
+
+class CompositeRadialGradient final : public CompositeGradient {
+public:
+    CompositeRadialGradient(sk_sp<sksg::RadialGradient>, size_t stopCount);
+
+private:
+    void onApply() override;
+
+    using INHERITED = CompositeGradient;
+};
+
 #undef COMPOSITE_PROPERTY
 
 } // namespace skotty
diff --git a/experimental/sksg/paint/SkSGGradient.cpp b/experimental/sksg/paint/SkSGGradient.cpp
new file mode 100644
index 0000000000..98e7f395f8
--- /dev/null
+++ b/experimental/sksg/paint/SkSGGradient.cpp
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkSGGradient.h"
+
+#include "SkGradientShader.h"
+#include "SkPaint.h"
+
+namespace sksg {
+
+void Gradient::onApplyToPaint(SkPaint* paint) const {
+    if (fColorStops.empty()) {
+        paint->setShader(nullptr);
+        return;
+    }
+
+    std::vector<SkColor>  colors;
+    std::vector<SkScalar> positions;
+    colors.reserve(fColorStops.size());
+    positions.reserve(fColorStops.size());
+
+    SkScalar position = 0;
+    for (const auto& stop : fColorStops) {
+        colors.push_back(stop.fColor);
+        position = SkTPin(stop.fPosition, position, 1.0f);
+        positions.push_back(position);
+    }
+
+    // TODO: detect even stop distributions, pass null for positions.
+    paint->setShader(this->onMakeShader(colors, positions));
+}
+
+sk_sp<SkShader> LinearGradient::onMakeShader(const std::vector<SkColor>& colors,
+                                             const std::vector<SkScalar>& positions) const {
+    SkASSERT(colors.size() == positions.size());
+
+    const SkPoint pts[] = { fStartPoint, fEndPoint };
+    return SkGradientShader::MakeLinear(pts, colors.data(), positions.data(), colors.size(),
+                                        this->getTileMode());
+}
+
+sk_sp<SkShader> RadialGradient::onMakeShader(const std::vector<SkColor>& colors,
+                                             const std::vector<SkScalar>& positions) const {
+    SkASSERT(colors.size() == positions.size());
+
+    return (fStartRadius <= 0 && fStartCenter == fEndCenter)
+        ? SkGradientShader::MakeRadial(fEndCenter, fEndRadius,
+                                       colors.data(), positions.data(), colors.size(),
+                                       this->getTileMode())
+        : SkGradientShader::MakeTwoPointConical(fStartCenter, fStartRadius,
+                                                fEndCenter, fEndRadius,
+                                                colors.data(), positions.data(), colors.size(),
+                                                this->getTileMode());
+}
+
+} //namespace sksg
diff --git a/experimental/sksg/paint/SkSGGradient.h b/experimental/sksg/paint/SkSGGradient.h
new file mode 100644
index 0000000000..d69cb1495c
--- /dev/null
+++ b/experimental/sksg/paint/SkSGGradient.h
@@ -0,0 +1,105 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkSGGradient_DEFINED
+#define SkSGGradient_DEFINED
+
+#include "SkSGPaintNode.h"
+
+#include "SkColor.h"
+#include "SkPoint.h"
+#include "SkScalar.h"
+#include "SkShader.h"
+
+#include <vector>
+
+namespace sksg {
+
+/**
+ * Gradient base class.
+ */
+class Gradient : public PaintNode {
+public:
+    struct ColorStop {
+        SkScalar fPosition;
+        SkColor  fColor;
+
+        bool operator==(const ColorStop& other) const {
+            return fPosition == other.fPosition && fColor == other.fColor;
+        }
+    };
+
+    SG_ATTRIBUTE(ColorStops, std::vector<ColorStop>, fColorStops)
+    SG_ATTRIBUTE(TileMode  , SkShader::TileMode    , fTileMode  )
+
+protected:
+    void onApplyToPaint(SkPaint*) const final;
+
+    virtual sk_sp<SkShader> onMakeShader(const std::vector<SkColor>& colors,
+                                         const std::vector<SkScalar>& positions) const = 0;
+
+protected:
+    Gradient() = default;
+
+private:
+    std::vector<ColorStop> fColorStops;
+    SkShader::TileMode     fTileMode = SkShader::kClamp_TileMode;
+
+    using INHERITED = PaintNode;
+};
+
+class LinearGradient final : public Gradient {
+public:
+    static sk_sp<LinearGradient> Make() {
+        return sk_sp<LinearGradient>(new LinearGradient());
+    }
+
+    SG_ATTRIBUTE(StartPoint, SkPoint, fStartPoint)
+    SG_ATTRIBUTE(EndPoint  , SkPoint, fEndPoint  )
+
+protected:
+    sk_sp<SkShader> onMakeShader(const std::vector<SkColor>& colors,
+                                 const std::vector<SkScalar>& positions) const override;
+
+private:
+    LinearGradient() = default;
+
+    SkPoint fStartPoint = SkPoint::Make(0, 0),
+            fEndPoint   = SkPoint::Make(0, 0);
+
+    using INHERITED = Gradient;
+};
+
+class RadialGradient final : public Gradient {
+public:
+    static sk_sp<RadialGradient> Make() {
+        return sk_sp<RadialGradient>(new RadialGradient());
+    }
+
+    SG_ATTRIBUTE(StartCenter, SkPoint , fStartCenter)
+    SG_ATTRIBUTE(EndCenter  , SkPoint , fEndCenter  )
+    SG_ATTRIBUTE(StartRadius, SkScalar, fStartRadius)
+    SG_ATTRIBUTE(EndRadius  , SkScalar, fEndRadius  )
+
+protected:
+    sk_sp<SkShader> onMakeShader(const std::vector<SkColor>& colors,
+                                 const std::vector<SkScalar>& positions) const override;
+
+private:
+    RadialGradient() = default;
+
+    SkPoint  fStartCenter = SkPoint::Make(0, 0),
+             fEndCenter   = SkPoint::Make(0, 0);
+    SkScalar fStartRadius = 0,
+             fEndRadius   = 0;
+
+    using INHERITED = Gradient;
+};
+
+} // namespace sksg
+
+#endif // SkSGGradient_DEFINED