Add GMs for Analytic Anti-Aliasing

gm/addarc.cpp

 /*
  * Copyright 2015 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 "SkAnimTimer.h"
 #include "SkCanvas.h"
@@ skipping 147 matching lines @@
 
 private:
     SkScalar fRotate;
 
     typedef skiagm::GM INHERITED;
 };
 DEF_GM( return new StrokeCircleGM; )
 
 //////////////////////
 
+// Fill circles and rotate them to test our Analytic Anti-Aliasing.
+// This test is based on StrokeCircleGM.
+class FillCircleGM : public skiagm::GM {
+public:
+    FillCircleGM() : fRotate(0) {}
+
+protected:
+    SkString onShortName() override { return SkString("fillcircle"); }
+
+    SkISize onISize() override { return SkISize::Make(520, 520); }
+
+    void onDraw(SkCanvas* canvas) override {
+        canvas->scale(20, 20);
+        canvas->translate(13, 13);
+
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setStyle(SkPaint::kStroke_Style);
+        paint.setStrokeWidth(SK_Scalar1 / 2);
+

[robertphillips, 2016/10/07 14:12:46]

Don't we just know strokeWidth is SK_Scalar1 / 2 (aka SK_ScalarHalf) ?

[liyuqian, 2016/10/07 14:15:50]

Yes, I was just copying from the StrokeCircleGM which does the same strange
thing...

+        const SkScalar strokeWidth = paint.getStrokeWidth();
+        const SkScalar delta = strokeWidth * 3 / 2;
+        SkRect r = SkRect::MakeXYWH(-12, -12, 24, 24);
+        SkRandom rand;
+
+        // Reset style to fill. We only need stroke stype for producing delta and strokeWidth
+        paint.setStyle(SkPaint::kFill_Style);
+
+        SkScalar sign = 1;
+        while (r.width() > strokeWidth * 2) {
+            SkAutoCanvasRestore acr(canvas, true);
+            canvas->rotate(fRotate * sign);
+            paint.setColor(sk_tool_utils::color_to_565(rand.nextU() | (0xFF << 24)));
+            canvas->drawOval(r, paint);
+            r.inset(delta, delta);
+            sign = -sign;
+        }
+    }
+
+    bool onAnimate(const SkAnimTimer& timer) override {
+        fRotate = timer.scaled(60, 360);
+        return true;
+    }
+
+private:
+    SkScalar fRotate;
+
+    typedef skiagm::GM INHERITED;
+};
+DEF_GM( return new FillCircleGM; )
+
+//////////////////////
+
 static void html_canvas_arc(SkPath* path, SkScalar x, SkScalar y, SkScalar r, SkScalar start,
                             SkScalar end, bool ccw) {
     SkRect bounds = { x - r, y - r, x + r, y + r };
     SkScalar sweep = ccw ? end - start : start - end;
     path->arcTo(bounds, start, sweep, false);
 }
 
 // Lifted from canvas-arc-circumference-fill-diffs.html
 class ManyArcsGM : public skiagm::GM {
 public:
@@ skipping 45 matching lines @@
             }
             canvas->restore();
             canvas->translate(0, 40);
         }
     }
 
 private:
     typedef skiagm::GM INHERITED;
 };
 DEF_GM( return new ManyArcsGM; )