fix for chrome bug with sub pixel hairlines

gm/hairlines.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 "gm.h"
 #include "SkCanvas.h"
 #include "SkTArray.h"
 
 namespace skiagm {
 
 class HairlinesGM : public GM {
 protected:
     virtual uint32_t onGetFlags() const SK_OVERRIDE {
         return kSkipTiled_Flag;
     }
 
 
     virtual SkString onShortName() SK_OVERRIDE {
         return SkString("hairlines");
     }
 
-    virtual SkISize onISize() { return SkISize::Make(800, 600); }
+    virtual SkISize onISize() { return SkISize::Make(1250, 1250); }
 
     virtual void onOnceBeforeDraw() SK_OVERRIDE {
         {
             SkPath* lineAnglesPath = &fPaths.push_back();
             enum {
                 kNumAngles = 15,
                 kRadius = 40,
             };
             for (int i = 0; i < kNumAngles; ++i) {
                 SkScalar angle = SK_ScalarPI * SkIntToScalar(i) / kNumAngles;
@@ skipping 123 matching lines @@
 
             SkPoint p1 = SkPoint::Make(kRad * cosV, kRad * sinV);
 
             bug->moveTo(p0);
             bug->lineTo(p1);
         }
     }
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         static const SkAlpha kAlphaValue[] = { 0xFF, 0x40 };
+        static const SkScalar kWidths[] = { 0, 0.5f, 1.5f };
 
         enum {
             kMargin = 5,
         };
         int wrapX = canvas->getDeviceSize().fWidth - kMargin;
 
         SkScalar maxH = 0;
         canvas->translate(SkIntToScalar(kMargin), SkIntToScalar(kMargin));
         canvas->save();
 
         SkScalar x = SkIntToScalar(kMargin);
         for (int p = 0; p < fPaths.count(); ++p) {
             for (size_t a = 0; a < SK_ARRAY_COUNT(kAlphaValue); ++a) {
                 for (int aa = 0; aa < 2; ++aa) {
-                    const SkRect& bounds = fPaths[p].getBounds();
+                    for (size_t w = 0; w < SK_ARRAY_COUNT(kWidths); w++) {
+                        const SkRect& bounds = fPaths[p].getBounds();
 
-                    if (x + bounds.width() > wrapX) {
+                        if (x + bounds.width() > wrapX) {
+                            canvas->restore();
+                            canvas->translate(0, maxH + SkIntToScalar(kMargin));
+                            canvas->save();
+                            maxH = 0;
+                            x = SkIntToScalar(kMargin);
+                        }
+
+                        SkPaint paint;
+                        paint.setARGB(kAlphaValue[a], 0, 0, 0);
+                        paint.setAntiAlias(SkToBool(aa));
+                        paint.setStyle(SkPaint::kStroke_Style);
+                        paint.setStrokeWidth(kWidths[w]);
+
+                        canvas->save();
+                        canvas->translate(-bounds.fLeft, -bounds.fTop);
+                        canvas->drawPath(fPaths[p], paint);
                         canvas->restore();
-                        canvas->translate(0, maxH + SkIntToScalar(kMargin));
-                        canvas->save();
-                        maxH = 0;
-                        x = SkIntToScalar(kMargin);
+
+                        maxH = SkMaxScalar(maxH, bounds.height());
+
+                        SkScalar dx = bounds.width() + SkIntToScalar(kMargin);
+                        x += dx;
+                        canvas->translate(dx, 0);
                     }
-
-                    SkPaint paint;
-                    paint.setARGB(kAlphaValue[a], 0, 0, 0);
-                    paint.setAntiAlias(SkToBool(aa));
-                    paint.setStyle(SkPaint::kStroke_Style);
-                    paint.setStrokeWidth(0);
-
-                    canvas->save();
-                    canvas->translate(-bounds.fLeft, -bounds.fTop);
-                    canvas->drawPath(fPaths[p], paint);
-                    canvas->restore();
-
-                    maxH = SkMaxScalar(maxH, bounds.height());
-
-                    SkScalar dx = bounds.width() + SkIntToScalar(kMargin);
-                    x += dx;
-                    canvas->translate(dx, 0);
                 }
             }
         }
         canvas->restore();
     }
 
 private:
     SkTArray<SkPath> fPaths;
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new HairlinesGM; }
 static GMRegistry reg(MyFactory);
 
 }