Don't add duplicate points when clipping

cc/base/math_util.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/base/math_util.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #ifdef __SSE__
@@ skipping 140 matching lines @@
                                               const gfx::PointF& p) {
   *xmin = std::min(p.x(), *xmin);
   *xmax = std::max(p.x(), *xmax);
   *ymin = std::min(p.y(), *ymin);
   *ymax = std::max(p.y(), *ymax);
 }
 
 static inline void AddVertexToClippedQuad(const gfx::PointF& new_vertex,
                                           gfx::PointF clipped_quad[8],
                                           int* num_vertices_in_clipped_quad) {
+  if (*num_vertices_in_clipped_quad > 0) {
+    if (clipped_quad[*num_vertices_in_clipped_quad - 1] == new_vertex)

[Peter Mayo, 2016/12/08 19:37:39]

These are floating point values, and should use an approximately equal to,
rather than absolute equality.

[flackr, 2016/12/08 20:24:01]

If the problem case is clipping to the same infinity do they not end up exactly
equal?

[Peter Mayo, 2016/12/08 20:29:09]

Inifinity is a single value in the non-parametric code, but becomes a vaguer
region in the parametric case - in order to stay planar in the 3d case.

+      return;
+    if (clipped_quad[0] == new_vertex)
+      return;
+  }
   clipped_quad[*num_vertices_in_clipped_quad] = new_vertex;
   (*num_vertices_in_clipped_quad)++;
 }
 
 static inline void AddVertexToClippedQuad3d(const gfx::Point3F& new_vertex,
                                             gfx::Point3F clipped_quad[8],
                                             int* num_vertices_in_clipped_quad) {
+  if (*num_vertices_in_clipped_quad > 0) {
+    if (clipped_quad[*num_vertices_in_clipped_quad - 1] == new_vertex)
+      return;
+    if (clipped_quad[0] == new_vertex)
+      return;
+  }
   clipped_quad[*num_vertices_in_clipped_quad] = new_vertex;
   (*num_vertices_in_clipped_quad)++;
 }
 
 gfx::Rect MathUtil::MapEnclosingClippedRect(const gfx::Transform& transform,
                                             const gfx::Rect& src_rect) {
   if (transform.IsIdentityOrIntegerTranslation()) {
     gfx::Vector2d offset(static_cast<int>(transform.matrix().getFloat(0, 3)),
                          static_cast<int>(transform.matrix().getFloat(1, 3)));
     return src_rect + offset;
@@ skipping 751 matching lines @@
 #endif
 }
 
 ScopedSubnormalFloatDisabler::~ScopedSubnormalFloatDisabler() {
 #ifdef __SSE__
   _mm_setcsr(orig_state_);
 #endif
 }
 
 }  // namespace cc