[SVGDom] Add viewBox support

The main feature is <svg> viewBox and proper viewport support, but the CL
touches a few other things:

* refactor SkSVGRenderContext to auto-restore canvas state, and split the
  presentation bits into a separate CoW SkSVGPresentationContext

* introduce SkSVGNode::onPrepareToRender(), as a way for nodes to push their
  custom state before the actual onRender() call (instead of relying on
  non-virtual SkSVGNode to know about all possible state bits)

* add a "Type" suffix to SVG types, to disambiguate (e.g. SkSVGRectType vs.
  SkSVGRect)

R=robertphillips@google.com,stephana@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2222793002

Review-Url: https://codereview.chromium.org/2222793002

1 files changed, 9 insertions, 14 deletions

diff --git a/experimental/svg/model/SkSVGNode.cpp b/experimental/svg/model/SkSVGNode.cpp
index eb82834f38..34c6e17d61 100644
--- a/experimental/svg/model/SkSVGNode.cpp
+++ b/experimental/svg/model/SkSVGNode.cpp
@@ -16,18 +16,17 @@ SkSVGNode::SkSVGNode(SkSVGTag t) : fTag(t) { }
 
 SkSVGNode::~SkSVGNode() { }
 
-void SkSVGNode::render(SkCanvas* canvas, const SkSVGRenderContext& ctx) const {
-    SkTCopyOnFirstWrite<SkSVGRenderContext> localContext(ctx);
-    fPresentationAttributes.applyTo(localContext);
-
-    SkAutoCanvasRestore acr(canvas, false);
-    const SkMatrix& m = this->onLocalMatrix();
-    if (!m.isIdentity()) {
-        canvas->save();
-        canvas->concat(m);
+void SkSVGNode::render(const SkSVGRenderContext& ctx) const {
+    SkSVGRenderContext localContext(ctx);
+
+    if (this->onPrepareToRender(&localContext)) {
+        this->onRender(localContext);
     }
+}
 
-    this->onRender(canvas, *localContext);
+bool SkSVGNode::onPrepareToRender(SkSVGRenderContext* ctx) const {
+    fPresentationAttributes.applyTo(ctx);
+    return true;
 }
 
 void SkSVGNode::setAttribute(SkSVGAttribute attr, const SkSVGValue& v) {
@@ -51,7 +50,3 @@ void SkSVGNode::onSetAttribute(SkSVGAttribute attr, const SkSVGValue& v) {
         break;
     }
 }
-
-const SkMatrix& SkSVGNode::onLocalMatrix() const {
-    return SkMatrix::I();
-}