1 files changed, 61 insertions, 0 deletions
diff --git a/experimental/sksg/geometry/SkSGTrimEffect.cpp b/experimental/sksg/geometry/SkSGTrimEffect.cpp
new file mode 100644
index 0000000000..4c30389877
--- /dev/null
+++ b/experimental/sksg/geometry/SkSGTrimEffect.cpp
@@ -0,0 +1,61 @@
+/*
+ * 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 "SkSGTrimEffect.h"
+
+#include "SkCanvas.h"
+#include "SkDashPathEffect.h"
+#include "SkPathMeasure.h"
+
+namespace sksg {
+
+TrimEffect::TrimEffect(sk_sp<GeometryNode> child)
+    : fChild(std::move(child)) {
+    fChild->addInvalReceiver(this);
+}
+
+TrimEffect::~TrimEffect() {
+    fChild->removeInvalReceiver(this);
+}
+
+// TODO
+//   This is a quick hack to get something on the screen.  What we really want here is to apply
+//   the geometry transformation and cache the result on revalidation. Or an SkTrimPathEffect.
+void TrimEffect::onDraw(SkCanvas* canvas, const SkPaint& paint) const {
+    SkASSERT(!this->hasInval());
+
+    SkASSERT(!paint.getPathEffect());
+
+    const auto path = fChild->asPath();
+    SkScalar pathLen = 0;
+    SkPathMeasure measure(path, false);
+    do {
+        pathLen += measure.getLength();
+    } while (measure.nextContour());
+
+    const auto start  = SkScalarPin(fStart , 0, 1) * pathLen,
+               end    = SkScalarPin(fEnd   , 0, 1) * pathLen,
+               offset = SkScalarPin(fOffset, 0, 1) * pathLen,
+               len    = SkTMax<SkScalar>(end - start, 0);
+
+    const SkScalar dashes[4] = { 0, start, len, pathLen - end };
+    SkPaint dashedPaint(paint);
+    dashedPaint.setPathEffect(SkDashPathEffect::Make(dashes, 4, -offset));
+
+    canvas->drawPath(path, dashedPaint);
+}
+
+SkPath TrimEffect::onAsPath() const {
+    return fChild->asPath();
+}
+
+SkRect TrimEffect::onRevalidate(InvalidationController* ic, const SkMatrix& ctm) {
+    SkASSERT(this->hasInval());
+    return fChild->revalidate(ic, ctm);
+}
+
+} // namespace sksg