1 files changed, 42 insertions, 0 deletions
diff --git a/modules/sksg/src/SkSGOpacityEffect.cpp b/modules/sksg/src/SkSGOpacityEffect.cpp
new file mode 100644
index 0000000000..b1ff10d217
--- /dev/null
+++ b/modules/sksg/src/SkSGOpacityEffect.cpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkSGOpacityEffect.h"
+
+#include "SkCanvas.h"
+
+#include <math.h>
+
+namespace sksg {
+
+OpacityEffect::OpacityEffect(sk_sp<RenderNode> child, float opacity)
+    : INHERITED(std::move(child))
+    , fOpacity(opacity) {}
+
+void OpacityEffect::onRender(SkCanvas* canvas) const {
+    // opacity <= 0 disables rendering
+    if (fOpacity <= 0)
+        return;
+
+    // TODO: we could avoid savelayer if there is no more than one drawing primitive
+    //       in the sub-DAG.
+    SkAutoCanvasRestore acr(canvas, false);
+    if (fOpacity < 1) {
+        canvas->saveLayerAlpha(&this->bounds(), roundf(fOpacity * 255));
+    }
+
+    this->INHERITED::onRender(canvas);
+}
+
+SkRect OpacityEffect::onRevalidate(InvalidationController* ic, const SkMatrix& ctm) {
+    SkASSERT(this->hasInval());
+
+    // opacity <= 0 disables rendering AND revalidation for the sub-DAG
+    return fOpacity > 0 ? this->INHERITED::onRevalidate(ic, ctm) : SkRect::MakeEmpty();
+}
+
+} // namespace sksg