[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, 10 insertions, 4 deletions

diff --git a/experimental/svg/model/SkSVGNode.h b/experimental/svg/model/SkSVGNode.h
index 168b03c73b..38a17d8633 100644
--- a/experimental/svg/model/SkSVGNode.h
+++ b/experimental/svg/model/SkSVGNode.h
@@ -31,18 +31,24 @@ public:
 
     virtual void appendChild(sk_sp<SkSVGNode>) = 0;
 
-    void render(SkCanvas*, const SkSVGRenderContext&) const;
+    void render(const SkSVGRenderContext&) const;
 
     void setAttribute(SkSVGAttribute, const SkSVGValue&);
 
 protected:
     SkSVGNode(SkSVGTag);
 
-    virtual void onRender(SkCanvas*, const SkSVGRenderContext&) const = 0;
+    // Called before onRender(), to apply local attributes to the context.  Unlike onRender(),
+    // onPrepareToRender() bubbles up the inheritance chain: overriders should always call
+    // INHERITED::onPrepareToRender(), unless they intend to short-circuit rendering
+    // (return false).
+    // Implementations are expected to return true if rendering is to continue, or false if
+    // the node/subtree rendering is disabled.
+    virtual bool onPrepareToRender(SkSVGRenderContext*) const;
 
-    virtual void onSetAttribute(SkSVGAttribute, const SkSVGValue&);
+    virtual void onRender(const SkSVGRenderContext&) const = 0;
 
-    virtual const SkMatrix& onLocalMatrix() const;
+    virtual void onSetAttribute(SkSVGAttribute, const SkSVGValue&);
 
 private:
     SkSVGTag                    fTag;