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, 90 insertions, 0 deletions

diff --git a/samplecode/SampleSGInval.cpp b/samplecode/SampleSGInval.cpp
new file mode 100644
index 0000000000..08bfd64377
--- /dev/null
+++ b/samplecode/SampleSGInval.cpp
@@ -0,0 +1,90 @@
+/*
+ * 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 "SampleCode.h"
+#include "SkCanvas.h"
+#include "SkSGColor.h"
+#include "SkSGDraw.h"
+#include "SkSGGroup.h"
+#include "SkSGInvalidationController.h"
+#include "SkSGRect.h"
+#include "SkSGTransform.h"
+#include "SkAnimTimer.h"
+
+#include <cmath>
+
+class SGInvalView final : public SampleView {
+public:
+    SGInvalView() {}
+
+protected:
+    void onOnceBeforeDraw() override {
+        fRect1 = sksg::Rect::Make(SkRect::MakeLTRB(100, 100, 100, 100));
+        fRect2 = sksg::Rect::Make(SkRect::MakeLTRB(300, 200, 300, 200));
+        fColor1 = sksg::Color::Make(0);
+        fColor2 = sksg::Color::Make(0);
+
+        fRoot = sksg::Group::Make();
+        fRoot->addChild(sksg::Draw::Make(fRect1, fColor1));
+        fRoot->addChild(sksg::Transform::Make(sksg::Draw::Make(fRect2, fColor2),
+                                              SkMatrix::MakeScale(1.5f, 1.5f)));
+    }
+
+    bool onQuery(SkEvent* evt) override {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "SGInval");
+            return true;
+        }
+
+        return this->INHERITED::onQuery(evt);
+    }
+
+    void onDrawContent(SkCanvas* canvas) override {
+        sksg::InvalidationController ic;
+        fRoot->revalidate(&ic, SkMatrix::I());
+
+        // TODO: clip/cull
+        fRoot->render(canvas);
+
+        SkPaint p;
+        p.setColor(0xffff0000);
+        p.setStyle(SkPaint::kStroke_Style);
+        p.setAntiAlias(true);
+        p.setStrokeWidth(0);
+
+        for (const auto& r : ic) {
+            canvas->drawRect(r, p);
+        }
+    }
+
+    bool onAnimate(const SkAnimTimer& timer) override {
+        static constexpr SkScalar kSize = 50;
+        static constexpr SkScalar kRate = 1.0f / 500;
+        const auto t = timer.msec() * kRate;
+
+        fRect1->setR(fRect1->getL() + kSize * (1 + std::sin(t)));
+        fRect1->setB(fRect1->getT() + kSize * (1 + std::cos(t)));
+        fRect2->setR(fRect2->getL() + kSize * (1 + std::cos(SK_ScalarPI / 2 + t)));
+        fRect2->setB(fRect2->getT() + kSize * (1 + std::sin(SK_ScalarPI / 2 + t)));
+
+        fColor1->setColor(SkColorSetARGB(128 * (1 + std::sin(t)), 0, 0x80, 0));
+        fColor2->setColor(SkColorSetARGB(128 * (1 + std::cos(t)), 0, 0, 0x80));
+        return true;
+    }
+
+private:
+    typedef SampleView INHERITED;
+
+    sk_sp<sksg::Rect>  fRect1,
+                       fRect2;
+    sk_sp<sksg::Color> fColor1,
+                       fColor2;
+    sk_sp<sksg::Group> fRoot;
+};
+
+static SkView* SGInvalFactory() { return new SGInvalView; }
+static SkViewRegister reg(SGInvalFactory);