Index: src/core/SkGeometry.cpp |
diff --git a/src/core/SkGeometry.cpp b/src/core/SkGeometry.cpp |
index a3ebfb38a892740aed025a08e31653f9a5585e5c..027b65f0f1962e82e0bbfc38afb77184a23fdc12 100644 |
--- a/src/core/SkGeometry.cpp |
+++ b/src/core/SkGeometry.cpp |
@@ -1153,6 +1153,12 @@ int SkConic::computeQuadPOW2(SkScalar tol) const { |
return pow2; |
} |
+// This was originally developed and tested for pathops: see SkOpTypes.h |
+// returns true if (a <= b <= c) || (a >= b >= c) |
+static bool between(SkScalar a, SkScalar b, SkScalar c) { |
+ return (a - b) * (c - b) <= 0; |
+} |
+ |
static SkPoint* subdivide(const SkConic& src, SkPoint pts[], int level) { |
SkASSERT(level >= 0); |
@@ -1162,6 +1168,32 @@ static SkPoint* subdivide(const SkConic& src, SkPoint pts[], int level) { |
} else { |
SkConic dst[2]; |
src.chop(dst); |
+ const SkScalar startY = src.fPts[0].fY; |
+ const SkScalar endY = src.fPts[2].fY; |
+ if (between(startY, src.fPts[1].fY, endY)) { |
+ // If the input is monotonic and the output is not, the scan converter hangs. |
+ // Ensure that the chopped conics maintain their y-order. |
+ SkScalar midY = dst[0].fPts[2].fY; |
+ if (!between(startY, midY, endY)) { |
+ // If the computed midpoint is outside the ends, move it to the closer one. |
+ SkScalar closerY = SkTAbs(midY - startY) < SkTAbs(midY - endY) ? startY : endY; |
+ dst[0].fPts[2].fY = dst[1].fPts[0].fY = closerY; |
+ } |
+ if (!between(startY, dst[0].fPts[1].fY, dst[0].fPts[2].fY)) { |
+ // If the 1st control is not between the start and end, put it at the start. |
+ // This also reduces the quad to a line. |
+ dst[0].fPts[1].fY = startY; |
+ } |
+ if (!between(dst[1].fPts[0].fY, dst[1].fPts[1].fY, endY)) { |
+ // If the 2nd control is not between the start and end, put it at the end. |
+ // This also reduces the quad to a line. |
+ dst[1].fPts[1].fY = endY; |
+ } |
+ // Verify that all five points are in order. |
+ SkASSERT(between(startY, dst[0].fPts[1].fY, dst[0].fPts[2].fY)); |
+ SkASSERT(between(dst[0].fPts[1].fY, dst[0].fPts[2].fY, dst[1].fPts[1].fY)); |
+ SkASSERT(between(dst[0].fPts[2].fY, dst[1].fPts[1].fY, endY)); |
+ } |
--level; |
pts = subdivide(dst[0], pts, level); |
return subdivide(dst[1], pts, level); |