add gm for path-arcs, and catch degenerate arc in conic-case

gm/addarc.cpp

Index: gm/addarc.cpp
diff --git a/gm/addarc.cpp b/gm/addarc.cpp
index 67d752aeb1f32224122b9fe05774b56b5205a8b9..fea15bacb727bae6b1a15402b47b2353c428c22a 100644
--- a/gm/addarc.cpp
+++ b/gm/addarc.cpp
@@ -162,3 +162,71 @@ private:
     typedef skiagm::GM INHERITED;
 };
 DEF_GM( return new StrokeCircleGM; )
+
+//////////////////////
+
+static void 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);
+}
+

[robertphillips, 2015/02/17 17:33:45]

Which one?

[reed2, 2015/02/17 18:35:36]

Done.

+// Lifted from layouttest
+class ManyArcsGM : public skiagm::GM {
+public:
+    ManyArcsGM() {}
+    
+protected:
+    SkString onShortName() SK_OVERRIDE { return SkString("manyarcs"); }
+    
+    SkISize onISize() SK_OVERRIDE { return SkISize::Make(620, 330); }
+    
+    void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setStyle(SkPaint::kStroke_Style);
+
+        canvas->translate(10, 10);
+
+        // 20 angles.
+        SkScalar sweepAngles[] = {
+                           -123.7, -2.3, -2, -1, -0.3, -0.000001, 0, 0.000001, 0.3, 0.7,
+                           1, 1.3, 1.5, 1.7, 1.99999, 2, 2.00001, 2.3, 4.3, 3934723942837.3
+        };
+        for (size_t i = 0; i < SK_ARRAY_COUNT(sweepAngles); ++i) {
+            sweepAngles[i] *= 180;
+        }
+        
+        SkScalar startAngles[] = { -1, -0.5, 0, 0.5 };
+        for (size_t i = 0; i < SK_ARRAY_COUNT(startAngles); ++i) {
+            startAngles[i] *= 180;
+        }
+        
+        bool anticlockwise = false;
+        SkScalar sign = 1;
+        for (size_t i = 0; i < SK_ARRAY_COUNT(startAngles) * 2; ++i) {
+            if (i == SK_ARRAY_COUNT(startAngles)) {
+                anticlockwise = true;
+                sign = -1;
+            }
+            SkScalar startAngle = startAngles[i % SK_ARRAY_COUNT(startAngles)] * sign;
+            canvas->save();
+            for (size_t j = 0; j < SK_ARRAY_COUNT(sweepAngles); ++j) {
+                SkPath path;
+                path.moveTo(0, 2);

[robertphillips, 2015/02/17 17:33:45]

overlength ?

[reed2, 2015/02/17 18:35:36]

Not sure what you mean.

[reed2, 2015/02/17 18:55:20]

Done.

+                arc(&path, 18, 15, 10, startAngle, startAngle + (sweepAngles[j] * sign), anticlockwise);
+                path.lineTo(0, 28);
+                canvas->drawPath(path, paint);
+                canvas->translate(30, 0);
+            }
+            canvas->restore();
+            canvas->translate(0, 40);
+        }
+    }
+    
+private:
+    typedef skiagm::GM INHERITED;
+};
+DEF_GM( return new ManyArcsGM; )
+