Fix SkPath::arcTo when sweepAngle is tiny and radius is big
In this function, it first check whether this arc is a lone point
or not. If not, it converts angles to unit vectors. The problem
here is that when the radius is huge and the sweepAngle is small,
the function angles_to_unit_vectors() could return a startV ==stopV.
When that happens, it will draw a dot at the point that corresponding
to the startAngle. This CL adds a special branch for this case, and
draw a connecting line between the points at startAngle and endAngle.
BUG=640031, skia:5807
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2388833002
Review-Url: https://codereview.chromium.org/2388833002
diff --git a/src/core/SkPath.cpp b/src/core/SkPath.cpp
index 3cbc76a..4c49e6b 100644
--- a/src/core/SkPath.cpp
+++ b/src/core/SkPath.cpp
@@ -1290,6 +1290,25 @@
angles_to_unit_vectors(startAngle, sweepAngle, &startV, &stopV, &dir);
SkPoint singlePt;
+
+ // At this point, we know that the arc is not a lone point, but startV == stopV
+ // indicates that the sweepAngle is too small such that angles_to_unit_vectors
+ // cannot handle it.
+ if (startV == stopV) {
+ SkScalar endAngle = SkDegreesToRadians(startAngle + sweepAngle);
+ SkScalar radiusX = oval.width() / 2;
+ SkScalar radiusY = oval.height() / 2;
+ // We cannot use SkScalarSinCos function in the next line because
+ // SkScalarSinCos has a threshold *SkScalarNearlyZero*. When sin(startAngle)
+ // is 0 and sweepAngle is very small and radius is huge, the expected
+ // behavior here is to draw a line. But calling SkScalarSinCos will
+ // make sin(endAngle) to be 0 which will then draw a dot.
+ singlePt.set(oval.centerX() + radiusX * sk_float_cos(endAngle),
+ oval.centerY() + radiusY * sk_float_sin(endAngle));
+ forceMoveTo ? this->moveTo(singlePt) : this->lineTo(singlePt);
+ return;
+ }
+
SkConic conics[SkConic::kMaxConicsForArc];
int count = build_arc_conics(oval, startV, stopV, dir, conics, &singlePt);
if (count) {