fix circular dashing

Path measure cannot use the same code approach for quadratics
and cubics. Subdividing cubics repeatedly does not result in
subdivided t values, e.g. a quarter circle cubic divided in
half twice does not have a t value equivalent to 1/4.

Instead, always compute the cubic segment from a pair of
t values.

When finding the length of the cubic through recursive measures,
it is enough to carry the point at a given t to the next
subdivision.

(Chrome suppression has landed already.)

R=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1602153002

Review URL: https://codereview.chromium.org/1602153002

1 files changed, 6 insertions, 0 deletions

diff --git a/include/core/SkPathMeasure.h b/include/core/SkPathMeasure.h
index 7528736ba8..415ee2709c 100644
--- a/include/core/SkPathMeasure.h
+++ b/include/core/SkPathMeasure.h
@@ -107,7 +107,13 @@ private:
     void     buildSegments();
     SkScalar compute_quad_segs(const SkPoint pts[3], SkScalar distance,
                                 int mint, int maxt, int ptIndex);
+#ifdef SK_SUPPORT_LEGACY_CONIC_MEASURE
     SkScalar compute_conic_segs(const SkConic&, SkScalar distance, int mint, int maxt, int ptIndex);
+#else
+    SkScalar compute_conic_segs(const SkConic&, SkScalar distance,
+                                int mint, const SkPoint& minPt,
+                                int maxt, const SkPoint& maxPt, int ptIndex);
+#endif
     SkScalar compute_cubic_segs(const SkPoint pts[3], SkScalar distance,
                                 int mint, int maxt, int ptIndex);
     const Segment* distanceToSegment(SkScalar distance, SkScalar* t);