Fix an infinite loop in agg's stroke_calc_arc().

third_party/agg23/agg_math_stroke.h

 
 //----------------------------------------------------------------------------
 // Anti-Grain Geometry - Version 2.3
 // Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
 //
 // Permission to copy, use, modify, sell and distribute this software
 // is granted provided this copyright notice appears in all copies.
 // This software is provided "as is" without express or implied
 // warranty, and with no claim as to its suitability for any purpose.
 //
@@ skipping 42 matching lines @@
     typedef typename VertexConsumer::value_type coord_type;
     FX_FLOAT a1 = FXSYS_atan2(dy1, dx1);
     FX_FLOAT a2 = FXSYS_atan2(dy2, dx2);
     FX_FLOAT da = a1 - a2;
     bool ccw = da > 0 && da < FX_PI;
     if(width < 0) {
         width = -width;
     }
     da = FXSYS_acos(width / (width + ((1.0f / 8) / approximation_scale))) * 2;
     out_vertices.add(coord_type(x + dx1, y + dy1));
-    if(!ccw) {
-        if(a1 > a2) {
-            a2 += 2 * FX_PI;
+    if (da > 0) {
+      if (!ccw) {
+        if (a1 > a2) {
+          a2 += 2 * FX_PI;
         }
         a2 -= da / 4;
         a1 += da;
-        while(a1 < a2) {
+        while (a1 < a2) {
           out_vertices.add(coord_type(x + (width * FXSYS_cos(a1)),
                                       y + (width * FXSYS_sin(a1))));
-            a1 += da;
+          a1 += da;
         }
-    } else {
-        if(a1 < a2) {
-            a2 -= 2 * FX_PI;
+      } else {
+        if (a1 < a2) {
+          a2 -= 2 * FX_PI;
         }
         a2 += da / 4;
         a1 -= da;
-        while(a1 > a2) {
+        while (a1 > a2) {
           out_vertices.add(coord_type(x + (width * FXSYS_cos(a1)),
                                       y + (width * FXSYS_sin(a1))));
-            a1 -= da;
+          a1 -= da;
         }
+      }
     }
     out_vertices.add(coord_type(x + dx2, y + dy2));
 }
 template<class VertexConsumer>
 void stroke_calc_miter(VertexConsumer& out_vertices,
                        const vertex_dist& v0,
                        const vertex_dist& v1,
                        const vertex_dist& v2,
                        FX_FLOAT dx1, FX_FLOAT dy1,
                        FX_FLOAT dx2, FX_FLOAT dy2,
@@ skipping 169 matching lines @@
                 break;
             default:
                 out_vertices.add(coord_type(v1.x + dx1, v1.y - dy1));
                 out_vertices.add(coord_type(v1.x + dx2, v1.y - dy2));
                 break;
         }
     }
 }
 }
 #endif