Add implicit hairline conic rendering to GPU

src/core/SkGeometry.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkGeometry.h"
@@ skipping 364 matching lines @@
         // if we get here, we need to force dst to be monotonic, even though
         // we couldn't compute a unit_divide value (probably underflow).
         b = SkScalarAbs(a - b) < SkScalarAbs(b - c) ? a : c;
     }
     dst[0].set(a, src[0].fY);
     dst[1].set(b, src[1].fY);
     dst[2].set(c, src[2].fY);
     return 0;
 }
 
-//  F(t)    = a (1 - t) ^ 2 + 2 b t (1 - t) + c t ^ 2
-//  F'(t)   = 2 (b - a) + 2 (a - 2b + c) t
-//  F''(t)  = 2 (a - 2b + c)
-//
-//  A = 2 (b - a)
-//  B = 2 (a - 2b + c)
-//
-//  Maximum curvature for a quadratic means solving
-//  Fx' Fx'' + Fy' Fy'' = 0
-//
-//  t = - (Ax Bx + Ay By) / (Bx ^ 2 + By ^ 2)
-//
-int SkChopQuadAtMaxCurvature(const SkPoint src[3], SkPoint dst[5])
-{
+float SkGetTQuadAtMaxCurvature(const SkPoint src[3]) {
+
     SkScalar    Ax = src[1].fX - src[0].fX;
     SkScalar    Ay = src[1].fY - src[0].fY;
     SkScalar    Bx = src[0].fX - src[1].fX - src[1].fX + src[2].fX;
     SkScalar    By = src[0].fY - src[1].fY - src[1].fY + src[2].fY;
     SkScalar    t = 0;  // 0 means don't chop
 
 #ifdef SK_SCALAR_IS_FLOAT
     (void)valid_unit_divide(-(Ax * Bx + Ay * By), Bx * Bx + By * By, &t);
 #else
     // !!! should I use SkFloat here? seems like it
@@ skipping 11 matching lines @@
         SkASSERT(!denom.isNeg());
         if (numer < denom)
         {
             t = numer.getFixedDiv(denom);
             SkASSERT(t >= 0 && t <= SK_Fixed1);     // assert that we're numerically stable (ha!)
             if ((unsigned)t >= SK_Fixed1)           // runtime check for numerical stability
                 t = 0;  // ignore the chop
         }
     }
 #endif
+    return t;
+}
 
+//  F(t)    = a (1 - t) ^ 2 + 2 b t (1 - t) + c t ^ 2

[bsalomon, 2013/07/10 15:14:36]

Maybe these comments belong with the new function that does all the work?

+//  F'(t)   = 2 (b - a) + 2 (a - 2b + c) t
+//  F''(t)  = 2 (a - 2b + c)
+//
+//  A = 2 (b - a)
+//  B = 2 (a - 2b + c)
+//
+//  Maximum curvature for a quadratic means solving
+//  Fx' Fx'' + Fy' Fy'' = 0
+//
+//  t = - (Ax Bx + Ay By) / (Bx ^ 2 + By ^ 2)
+//
+int SkChopQuadAtMaxCurvature(const SkPoint src[3], SkPoint dst[5])
+{
+    SkScalar t = SkGetTQuadAtMaxCurvature(src);
     if (t == 0)
     {
         memcpy(dst, src, 3 * sizeof(SkPoint));
         return 1;
     }
     else
     {
         SkChopQuadAt(src, dst, t);
         return 2;
     }
@@ skipping 1217 matching lines @@
     }
     if (this->findYExtrema(&t)) {
         this->evalAt(t, &pts[count++]);
     }
     bounds->set(pts, count);
 }
 
 void SkConic::computeFastBounds(SkRect* bounds) const {
     bounds->set(fPts, 3);
 }