[SVGDom] Initial <use> support

https://www.w3.org/TR/SVG/struct.html#UseElement

Change-Id: Id85c2648255dcd4763bf11c7bdb8b1490286f1e4
Reviewed-on: https://skia-review.googlesource.com/58260
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Robert Phillips <robertphillips@google.com>

BUILD.gn

@@ -1185,6 +1185,7 @@ if (skia_enable_tools) {
       "experimental/svg/model/SkSVGShape.cpp",
       "experimental/svg/model/SkSVGStop.cpp",
       "experimental/svg/model/SkSVGTransformableNode.cpp",
+      "experimental/svg/model/SkSVGUse.cpp",
       "experimental/svg/model/SkSVGValue.cpp",
     ]
     deps = [

experimental/svg/model/SkSVGContainer.h

@@ -33,4 +33,4 @@ private:
     typedef SkSVGTransformableNode INHERITED;
 };
 
-#endif // SkSVGSVG_DEFINED
+#endif // SkSVGContainer_DEFINED

experimental/svg/model/SkSVGDOM.cpp

@@ -27,6 +27,7 @@
 #include "SkSVGStop.h"
 #include "SkSVGSVG.h"
 #include "SkSVGTypes.h"
+#include "SkSVGUse.h"
 #include "SkSVGValue.h"
 #include "SkTSearch.h"
 
@@ -335,6 +336,7 @@ SortedDictionaryEntry<sk_sp<SkSVGNode>(*)()> gTagFactories[] = {
     { "rect"          , []() -> sk_sp<SkSVGNode> { return SkSVGRect::Make();           }},
     { "stop"          , []() -> sk_sp<SkSVGNode> { return SkSVGStop::Make();           }},
     { "svg"           , []() -> sk_sp<SkSVGNode> { return SkSVGSVG::Make();            }},
+    { "use"           , []() -> sk_sp<SkSVGNode> { return SkSVGUse::Make();            }},
 };
 
 struct ConstructionContext {

experimental/svg/model/SkSVGNode.h

@@ -32,7 +32,8 @@ enum class SkSVGTag {
     kRadialGradient,
     kRect,
     kStop,
-    kSvg
+    kSvg,
+    kUse
 };
 
 class SkSVGNode : public SkRefCnt {

experimental/svg/model/SkSVGUse.cpp

@@ -0,0 +1,86 @@
+/*
+ * 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 "SkSVGUse.h"
+
+#include "SkCanvas.h"
+#include "SkSVGRenderContext.h"
+#include "SkSVGValue.h"
+
+SkSVGUse::SkSVGUse() : INHERITED(SkSVGTag::kUse) {}
+
+void SkSVGUse::appendChild(sk_sp<SkSVGNode>) {
+    SkDebugf("cannot append child nodes to this element.\n");
+}
+
+void SkSVGUse::setHref(const SkSVGStringType& href) {
+    fHref = href;
+}
+
+void SkSVGUse::setX(const SkSVGLength& x) {
+    fX = x;
+}
+
+void SkSVGUse::setY(const SkSVGLength& y) {
+    fY = y;
+}
+
+void SkSVGUse::onSetAttribute(SkSVGAttribute attr, const SkSVGValue& v) {
+    switch (attr) {
+    case SkSVGAttribute::kHref:
+        if (const auto* href = v.as<SkSVGStringValue>()) {
+            this->setHref(*href);
+        }
+        break;
+    case SkSVGAttribute::kX:
+        if (const auto* x = v.as<SkSVGLengthValue>()) {
+            this->setX(*x);
+        }
+        break;
+    case SkSVGAttribute::kY:
+        if (const auto* y = v.as<SkSVGLengthValue>()) {
+            this->setY(*y);
+        }
+        break;
+    default:
+        this->INHERITED::onSetAttribute(attr, v);
+    }
+}
+
+bool SkSVGUse::onPrepareToRender(SkSVGRenderContext* ctx) const {
+    if (fHref.value().isEmpty() || !INHERITED::onPrepareToRender(ctx)) {
+        return false;
+    }
+
+    if (fX.value() || fY.value()) {
+        // Restored when the local SkSVGRenderContext leaves scope.
+        ctx->canvas()->save();
+        ctx->canvas()->translate(fX.value(), fY.value());
+    }
+
+    // TODO: width/height override for <svg> targets.
+
+    return true;
+}
+
+void SkSVGUse::onRender(const SkSVGRenderContext& ctx) const {
+    const auto* ref = ctx.findNodeById(fHref);
+    if (!ref) {
+        return;
+    }
+
+    ref->render(ctx);
+}
+
+SkPath SkSVGUse::onAsPath(const SkSVGRenderContext& ctx) const {
+    const auto* ref = ctx.findNodeById(fHref);
+    if (!ref) {
+        return SkPath();
+    }
+
+    return ref->asPath(ctx);
+}

experimental/svg/model/SkSVGUse.h

@@ -0,0 +1,47 @@
+/*
+ * 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 SkSVGUse_DEFINED
+#define SkSVGUse_DEFINED
+
+#include "SkSVGTransformableNode.h"
+#include "SkSVGTypes.h"
+
+/**
+ * Implements support for <use> (reference) elements.
+ * (https://www.w3.org/TR/SVG/struct.html#UseElement)
+ */
+class SkSVGUse final : public SkSVGTransformableNode {
+public:
+    ~SkSVGUse() override = default;
+
+    static sk_sp<SkSVGUse> Make() { return sk_sp<SkSVGUse>(new SkSVGUse()); }
+
+    void appendChild(sk_sp<SkSVGNode>) override;
+
+    void setHref(const SkSVGStringType&);
+    void setX(const SkSVGLength&);
+    void setY(const SkSVGLength&);
+
+protected:
+    void onSetAttribute(SkSVGAttribute, const SkSVGValue&) override;
+
+    bool onPrepareToRender(SkSVGRenderContext*) const override;
+    void onRender(const SkSVGRenderContext&) const override;
+    SkPath onAsPath(const SkSVGRenderContext&) const override;
+
+private:
+    SkSVGUse();
+
+    SkSVGStringType    fHref;
+    SkSVGLength        fX = SkSVGLength(0);
+    SkSVGLength        fY = SkSVGLength(0);
+
+    typedef SkSVGTransformableNode INHERITED;
+};
+
+#endif // SkSVGUse_DEFINED