Initial scene graph (SkSG)

Sketching a thin (as in close-to-skia-semantics) scene graph API, focused on
external animation, inval tracking and minimal repaint.

Only a few concrete classes/features so far:

* Rect/Color/Transform/Group
* basic inval tracking
* a trivial animated sample with inval visualization

Pretty much everything (especially naming) is volatile, so treat accordingly.

The interesting bits to review are likely in Node.{h,cpp} for inval and
SampleSGInval.cpp for usage.

Initial class hierarchy:

  * Node: invalidation/ancestors tracking
  |
   -- * RenderNode: onRender(SkCanvas)
  |   |
  |    -- * Draw (concrete): rendering a [geometry, paint] tuple
  |   |
  |    -- * Group (concrete): grouping multiple RenderNodes
  |   |
  |    -- * EffectNode: single-descendant effect wrapper
  |       |
  |        -- * Transform (concrete): transform effect
  |
   -- * PaintNode: onMakePaint()
  |   |
  |    -- * Color (concrete): SkColor paint wrapper
  |
   -- * GeometryNode: onComputeBounds(), onDraw(SkCanvas, SkPaint)
      |
       -- * Rect (concrete): SkRect wrapper

TBR=

Change-Id: Iacf9b773c181a7582ecd31ee968562f179d1aa1b
Reviewed-on: https://skia-review.googlesource.com/85502
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/experimental/sksg/SkSGGroup.h b/experimental/sksg/SkSGGroup.h
new file mode 100644
index 0000000000..2ed9d0ecb5
--- /dev/null
+++ b/experimental/sksg/SkSGGroup.h
@@ -0,0 +1,44 @@
+/*
+ * 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 SkSGGroup_DEFINED
+#define SkSGGroup_DEFINED
+
+#include "SkSGRenderNode.h"
+
+#include "SkTArray.h"
+
+namespace sksg {
+
+/**
+ * Concrete node, grouping together multiple descendants.
+ */
+class Group : public RenderNode {
+public:
+    static sk_sp<Group> Make() {
+        return sk_sp<Group>(new Group());
+    }
+
+    void addChild(sk_sp<RenderNode>);
+    void removeChild(const sk_sp<RenderNode>&);
+
+protected:
+    Group();
+    ~Group() override;
+
+    void onRender(SkCanvas*) const override;
+    void onRevalidate(InvalidationController*, const SkMatrix&) override;
+
+private:
+    SkTArray<sk_sp<RenderNode>, true> fChildren;
+
+    typedef RenderNode INHERITED;
+};
+
+} // namespace sksg
+
+#endif // SkSGGroup_DEFINED