Use Path Ops to generate PDF clips

gm/circularclips.cpp

Index: gm/circularclips.cpp
diff --git a/gm/circularclips.cpp b/gm/circularclips.cpp
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+/*
+ * 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 "gm.h"
+#include "SkCanvas.h"
+#include "SkPath.h"
+
+namespace skiagm {
+
+class CircularClipsGM : public GM {
+public:
+    CircularClipsGM() {}
+
+protected:
+    virtual SkString onShortName() {
+        return SkString("circular-clips");
+    }
+
+    virtual SkISize onISize() {
+        return SkISize::Make(800, 600);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        SkRegion::Op ops[] = {
+            SkRegion::kDifference_Op,
+            SkRegion::kIntersect_Op,
+            SkRegion::kUnion_Op,
+            SkRegion::kXOR_Op,
+            SkRegion::kReverseDifference_Op,
+            SkRegion::kReplace_Op,
+        };
+
+        SkScalar x1 = 80, x2 = 120;
+        SkScalar y = 50;
+        SkScalar r = 40;
+
+        SkPath circle1, circle2;
+        circle1.addCircle(x1, y, r, SkPath::kCW_Direction);
+        circle2.addCircle(x2, y, r, SkPath::kCW_Direction);
+        SkRect rect = SkRect::MakeLTRB(x1 - r, y - r, x2 + r, y + r);
+
+        SkPaint fillPaint;
+
+        for (size_t i = 0; i < 4; i++) {
+            circle1.toggleInverseFillType();
+            if (i % 2 == 0) {
+                circle2.toggleInverseFillType();
+            }
+
+            canvas->save();
+            for (size_t op = 0; op < SK_ARRAY_COUNT(ops); op++) {
+                canvas->save();
+
+                canvas->clipPath(circle1, SkRegion::kReplace_Op);
+                canvas->clipPath(circle2, ops[op]);
+
+                canvas->drawRect(rect, fillPaint);
+
+                canvas->restore();
+                canvas->translate(0, 2 * y);
+            }
+            canvas->restore();
+            canvas->translate(x1 + x2, 0);
+        }
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM( return new CircularClipsGM; )
+}