[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>

1 files changed, 86 insertions, 0 deletions

diff --git a/experimental/svg/model/SkSVGUse.cpp b/experimental/svg/model/SkSVGUse.cpp
new file mode 100644
index 0000000000..b98909f8b4
--- /dev/null
+++ b/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);
+}