Force values to 0.0f in QuadUVMatrix::set

src/gpu/GrPathUtils.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrPathUtils.h"
 
 #include "GrTypes.h"
@@ skipping 249 matching lines @@
         } else {
             // It's a point. It should cover zero area. Just set the matrix such
             // that (u, v) will always be far away from the quad.
             fM[0] = 0; fM[1] = 0; fM[2] = 100.f;
             fM[3] = 0; fM[4] = 0; fM[5] = 100.f;
         }
     } else {
         double scale = 1.0/det;
 
         // compute adjugate matrix
-        double a0, a1, a2, a3, a4, a5, a6, a7, a8;
-        a0 = y1-y2;
-        a1 = x2-x1;
+        double a2, a3, a4, a5, a6, a7, a8;
         a2 = x1*y2-x2*y1;
 
         a3 = y2-y0;
         a4 = x0-x2;
         a5 = x2*y0-x0*y2;
 
         a6 = y0-y1;
         a7 = x1-x0;
         a8 = x0*y1-x1*y0;
 
         // this performs the uv_pts*adjugate(control_pts) multiply,
         // then does the scale by 1/det afterwards to improve precision
         m[SkMatrix::kMScaleX] = (float)((0.5*a3 + a6)*scale);
         m[SkMatrix::kMSkewX]  = (float)((0.5*a4 + a7)*scale);
         m[SkMatrix::kMTransX] = (float)((0.5*a5 + a8)*scale);
 
         m[SkMatrix::kMSkewY]  = (float)(a6*scale);
         m[SkMatrix::kMScaleY] = (float)(a7*scale);
         m[SkMatrix::kMTransY] = (float)(a8*scale);
 
-        m[SkMatrix::kMPersp0] = (float)((a0 + a3 + a6)*scale);
-        m[SkMatrix::kMPersp1] = (float)((a1 + a4 + a7)*scale);
+        // kMPersp0 & kMPersp1 should algebraically be zero
+        m[SkMatrix::kMPersp0] = 0.0f;
+        m[SkMatrix::kMPersp1] = 0.0f;
         m[SkMatrix::kMPersp2] = (float)((a2 + a5 + a8)*scale);
 
-        // The matrix should not have perspective.
-        SkDEBUGCODE(static const SkScalar gTOL = 1.f / 100.f);
-        SkASSERT(SkScalarAbs(m.get(SkMatrix::kMPersp0)) < gTOL);
-        SkASSERT(SkScalarAbs(m.get(SkMatrix::kMPersp1)) < gTOL);
-
         // It may not be normalized to have 1.0 in the bottom right
         float m33 = m.get(SkMatrix::kMPersp2);
         if (1.f != m33) {
             m33 = 1.f / m33;
             fM[0] = m33 * m.get(SkMatrix::kMScaleX);
             fM[1] = m33 * m.get(SkMatrix::kMSkewX);
             fM[2] = m33 * m.get(SkMatrix::kMTransX);
             fM[3] = m33 * m.get(SkMatrix::kMSkewY);
             fM[4] = m33 * m.get(SkMatrix::kMScaleY);
             fM[5] = m33 * m.get(SkMatrix::kMTransY);
@@ skipping 507 matching lines @@
         set_loop_klm(d, controlK, controlL, controlM);
     } else if (kCusp_SkCubicType == cType) {
         SkASSERT(0.f == d[0]);
         set_cusp_klm(d, controlK, controlL, controlM);
     } else if (kQuadratic_SkCubicType == cType) {
         set_quadratic_klm(d, controlK, controlL, controlM);
     }
 
     calc_cubic_klm(p, controlK, controlL, controlM, klm, &klm[3], &klm[6]);
 }