[sksg] Initial stroke wrapper support

TBR=

Change-Id: I33e2fe076334de34c4427e7bfe6b6aaa724130b2
Reviewed-on: https://skia-review.googlesource.com/89641
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>

BUILD.gn

@@ -1372,6 +1372,7 @@ if (skia_enable_tools) {
       "experimental/sksg/geometry/SkSGPath.cpp",
       "experimental/sksg/geometry/SkSGRect.cpp",
       "experimental/sksg/paint/SkSGColor.cpp",
+      "experimental/sksg/paint/SkSGStroke.cpp",
     ]
     deps = [
       ":skia",

experimental/sksg/SkSGNode.h

@@ -51,6 +51,7 @@ private:
     friend class Draw;
     friend class EffectNode;
     friend class Group;
+    friend class Stroke;
 
     template <typename Func>
     void forEachInvalReceiver(Func&&) const;

experimental/sksg/paint/SkSGStroke.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkSGStroke.h"
+
+namespace sksg {
+
+Stroke::Stroke(sk_sp<PaintNode> paint)
+    : fPaint(std::move(paint)) {
+    fPaint->addInvalReceiver(this);
+}
+
+Stroke::~Stroke() {
+    fPaint->removeInvalReceiver(this);
+}
+
+void Stroke::onRevalidate(InvalidationController* ic, const SkMatrix& ctm) {
+    fPaint->revalidate(ic, ctm);
+    INHERITED::onRevalidate(ic, ctm);
+}
+
+SkPaint Stroke::onMakePaint() const {
+    SkPaint paint = fPaint->makePaint();
+
+    paint.setStyle(SkPaint::kStroke_Style);
+    paint.setStrokeWidth(fStrokeWidth);
+    paint.setStrokeMiter(fStrokeMiter);
+    paint.setStrokeJoin(fStrokeJoin);
+    paint.setStrokeCap(fStrokeCap);
+
+    return paint;
+}
+
+} // namespace sksg

experimental/sksg/paint/SkSGStroke.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkSGStroke_DEFINED
+#define SkSGStroke_DEFINED
+
+#include "SkSGPaintNode.h"
+
+#include "SkScalar.h"
+
+namespace sksg {
+
+/**
+ * Concrete Paint node wrapper, applying a stroke effect to an existing paint.
+ */
+class Stroke final : public PaintNode {
+public:
+    static sk_sp<Stroke> Make(sk_sp<PaintNode> paint) {
+        return paint ? sk_sp<Stroke>(new Stroke(std::move(paint))) : nullptr;
+    }
+
+    SG_ATTRIBUTE(StrokeWidth, SkScalar     , fStrokeWidth)
+    SG_ATTRIBUTE(StrokeMiter, SkScalar     , fStrokeMiter)
+    SG_ATTRIBUTE(StrokeJoin , SkPaint::Join, fStrokeJoin )
+    SG_ATTRIBUTE(StrokeCap  , SkPaint::Cap , fStrokeCap  )
+
+protected:
+    void onRevalidate(InvalidationController*, const SkMatrix&) override;
+
+    SkPaint onMakePaint() const override;
+
+private:
+    explicit Stroke(sk_sp<PaintNode>);
+    ~Stroke() override;
+
+    sk_sp<PaintNode> fPaint;
+    SkScalar         fStrokeWidth = 1,
+                     fStrokeMiter = 4;
+    SkPaint::Join    fStrokeJoin  = SkPaint::kMiter_Join;
+    SkPaint::Cap     fStrokeCap   = SkPaint::kButt_Cap;
+
+    typedef PaintNode INHERITED;
+};
+
+} // namespace sksg
+
+#endif // SkSGStroke_DEFINED