Stub for conic section max curvature

src/core/SkGeometry.cpp

Index: src/core/SkGeometry.cpp
diff --git a/src/core/SkGeometry.cpp b/src/core/SkGeometry.cpp
index 76d3a3f4f6ccbf2255aa1bff99ca89280c98cdde..da1f702acfb8d9e0e8ce99b1b78b2e10b2bf2818 100644
--- a/src/core/SkGeometry.cpp
+++ b/src/core/SkGeometry.cpp
@@ -1162,8 +1162,15 @@ int SkBuildQuadArc(const SkVector& uStart, const SkVector& uStop,
     return pointCount;
 }
 
-///////////////////////////////////////////////////////////////////////////////
 
+///////////////////////////////////////////////////////////////////////////////
+//
+// NURB representation for conics.  Helpful explanations at:
+//
+// http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.44.5740&rep=rep1&type=ps

[reed1, 2014/02/21 17:00:04]

nit: 80-col

[humper, 2014/02/21 17:07:21]

Done, and fixed a bunch of other 80 col issues in this file.

+// and
+// http://www.cs.mtu.edu/~shene/COURSES/cs3621/NOTES/spline/NURBS/RB-conics.html
+//
 // F = (A (1 - t)^2 + C t^2 + 2 B (1 - t) t w)
 //     ------------------------------------------
 //         ((1 - t)^2 + t^2 + 2 (1 - t) t w)
@@ -1173,12 +1180,6 @@ int SkBuildQuadArc(const SkVector& uStart, const SkVector& uStop,
 //             {t^2 (2 - 2 w), t (-2 + 2 w), 1}
 //
 
-// Take the parametric specification for the conic (either X or Y) and return
-// in coeff[] the coefficients for the simple quadratic polynomial
-//    coeff[0] for t^2
-//    coeff[1] for t
-//    coeff[2] for constant term
-//
 static SkScalar conic_eval_pos(const SkScalar src[], SkScalar w, SkScalar t) {
     SkASSERT(src);
     SkASSERT(t >= 0 && t <= SK_Scalar1);
@@ -1197,6 +1198,10 @@ static SkScalar conic_eval_pos(const SkScalar src[], SkScalar w, SkScalar t) {
     return SkScalarDiv(numer, denom);
 }
 
+
+// Take the parametric specification for the conic (either X or Y) and return

[reed1, 2014/02/21 17:00:04]

This comment does not go with deriv_coeff, but perhaps there is no longer a
helper function that just returns the poly coeff for the conic?

[humper, 2014/02/21 17:07:21]

Done.

+// in coeff[] the coefficients for the simple quadratic polynomial
+//
 // F' = 2 (C t (1 + t (-1 + w)) - A (-1 + t) (t (-1 + w) - w) + B (1 - 2 t) w)
 //
 //  t^2 : (2 P0 - 2 P2 - 2 P0 w + 2 P2 w)
@@ -1442,3 +1447,11 @@ void SkConic::computeTightBounds(SkRect* bounds) const {
 void SkConic::computeFastBounds(SkRect* bounds) const {
     bounds->set(fPts, 3);
 }
+
+// Find the parameter value where the conic takes on its maximum curvature.

[reed1, 2014/02/21 17:00:04]

Lets hoist this comment out to the header.

[humper, 2014/02/21 17:07:21]

Done.

+// Returns true if the max curvature is inside the 0..1 parameter range,
+// otherwise returns false and leaves its t parameter unchanged.
+bool SkConic::findMaxCurvature(SkScalar* t) const {
+    // TODO: Implement me
+    return false;
+}