Patch against Agg-2.4 so overly-complex paths can be handled gracefully by matplotlib

gistfile1.txt

--- agg-2.4/include/agg_rasterizer_cells_aa.h	2006-06-23 16:35:22.000000000 -0400
+++ matplotlib/agg24/include/agg_rasterizer_cells_aa.h	2012-11-19 14:02:54.755434558 -0500
@@ -29,15 +29,14 @@
 #ifndef AGG_RASTERIZER_CELLS_AA_INCLUDED
 #define AGG_RASTERIZER_CELLS_AA_INCLUDED
 
+#include <stdexcept>
 #include <string.h>
 #include <math.h>
 #include "agg_math.h"
 #include "agg_array.h"
 
-
 namespace agg
 {
-
     //-----------------------------------------------------rasterizer_cells_aa
     // An internal class that implements the main rasterization algorithm.
     // Used in the rasterizer. Should not be used direcly.
@@ -49,7 +48,7 @@
             cell_block_size  = 1 << cell_block_shift,
             cell_block_mask  = cell_block_size - 1,
             cell_block_pool  = 256,
-            cell_block_limit = 1024
+            cell_block_limit = 4096
         };
 
         struct sorted_y
@@ -183,7 +182,10 @@
         {
             if((m_num_cells & cell_block_mask) == 0)
             {
-                if(m_num_blocks >= cell_block_limit) return;
+                if (m_num_blocks >= cell_block_limit)
+                {
+                    throw std::overflow_error("Allocated too many blocks");
+                }
                 allocate_block();
             }
             *m_curr_cell_ptr++ = m_curr_cell;
@@ -667,13 +669,15 @@
             }
         }
 
-        cell_ptr = *block_ptr++;
         i = m_num_cells & cell_block_mask;
+        if (i) {
+          cell_ptr = *block_ptr++;
         while(i--) 
         {
             m_sorted_y[cell_ptr->y - m_min_y].start++;
             ++cell_ptr;
         }
+        }
 
         // Convert the Y-histogram into the array of starting indexes
         unsigned start = 0;
@@ -700,8 +704,9 @@
             }
         }
         
-        cell_ptr = *block_ptr++;
         i = m_num_cells & cell_block_mask;
+        if (i) {
+          cell_ptr = *block_ptr++;
         while(i--) 
         {
             sorted_y& curr_y = m_sorted_y[cell_ptr->y - m_min_y];
@@ -709,6 +714,7 @@
             ++curr_y.num;
             ++cell_ptr;
         }
+        }
 
         // Finally arrange the X-arrays
         for(i = 0; i < m_sorted_y.size(); i++)