Add string art GM and sample.

samplecode/SampleStringArt.cpp

+/*
+ * Copyright 2013 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"
+
+// Reproduces https://code.google.com/p/chromium/issues/detail?id=279014
+
+// Renders a string art shape.
+// The particular shape rendered can be controlled by clicking horizontally, thereby
+// generating an angle from 0 to 1.
+
+class StringArtView : public SampleView {
+public:
+    StringArtView() : fAngle(0.305f) {}
+
+protected:
+    // overrides from SkEventSink
+    virtual bool onQuery(SkEvent* evt) SK_OVERRIDE {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "StringArt");
+            return true;
+        }
+        return this->INHERITED::onQuery(evt);
+    }
+
+    virtual void onDrawContent(SkCanvas* canvas) SK_OVERRIDE {
+        SkScalar angle = fAngle*SK_ScalarPI + SkScalarHalf(SK_ScalarPI);
+
+        SkPoint center = SkPoint::Make(SkScalarHalf(this->width()), SkScalarHalf(this->height()));
+        SkScalar length = 5;
+        SkScalar step = angle;
+
+        SkPath path;
+        path.moveTo(center);
+
+        while (length < (SkScalarHalf(SkMin32(this->width(), this->height())) - 10.f))
+        {
+            SkPoint rp = SkPoint::Make(length*SkScalarCos(step) + center.fX,
+                                       length*SkScalarSin(step) + center.fY);
+            path.lineTo(rp);
+            length += SkScalarDiv(angle, SkScalarHalf(SK_ScalarPI));
+            step += angle;
+        }
+        path.close();
+
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setStyle(SkPaint::kStroke_Style);
+        paint.setColor(0xFF007700);
+
+        canvas->drawPath(path, paint);
+    }
+
+    virtual SkView::Click* onFindClickHandler(SkScalar x, SkScalar y, unsigned) SK_OVERRIDE {
+        fAngle = x/width();
+        this->inval(NULL);
+        return NULL;
+    }
+private:
+
+    SkScalar fAngle;
+    typedef SampleView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new StringArtView; }
+static SkViewRegister reg(MyFactory);