Initial work on generating markers.js from signposts

Details:
 * A queue object is passed to all renderers, allowing each process to
   avoid using shared memory when recording signpost data.
 * New overviewer.dat file that stores persistent data between runs.
   Currently used to store information on signs.  markers.js is
   generated by merging the stored POI list with the newly generated POI
   list.
 * POIs are tagged with their type (e.g. "spawn" or "sign").  This
   should be useful if different types of POIs needs to be
   handled/displayed differently

Known bugs:
 * If you delete the last sign in a chunk, it won't be removed from
   markers.js

world.py

@@ -19,6 +19,7 @@ import os.path
 import multiprocessing
 import sys
 import logging
+import cPickle
 
 import numpy
 
@@ -105,6 +106,20 @@ class WorldRenderer(object):
         #  a list of dictionaries, see below for an example
         self.POI = []
 
+        # if it exists, open overviewer.dat, and read in the data structure
+        # info self.persistentData.  This dictionary can hold any information
+        # that may be needed between runs.
+        # Currently only holds into about POIs (more more details, see quadtree)
+        self.pickleFile = os.path.join(self.cachedir,"overviewer.dat")
+        if os.path.exists(self.pickleFile):
+            with open(self.pickleFile,"rb") as p:
+                self.persistentData = cPickle.load(p)
+        else:
+            # some defaults
+            self.persistentData = dict(POI=[])
+
+
+
     def _get_chunk_renderset(self):
         """Returns a set of (col, row) chunks that should be rendered. Returns
         None if all chunks should be rendered"""
@@ -180,7 +195,8 @@ class WorldRenderer(object):
             spawnY += 1
 
 
-        self.POI.append( dict(x=spawnX, y=spawnY, z=spawnZ, msg="Spawn"))
+        self.POI.append( dict(x=spawnX, y=spawnY, z=spawnZ, 
+                msg="Spawn", type="spawn", chunk=(inChunkX,inChunkZ)))
 
     def go(self, procs):
         """Starts the render. This returns when it is finished"""
@@ -242,6 +258,9 @@ class WorldRenderer(object):
         inclusion_set = self._get_chunk_renderset()
 
         results = {}
+        manager = multiprocessing.Manager()
+        q = manager.Queue()
+
         if processes == 1:
             # Skip the multiprocessing stuff
             logging.debug("Rendering chunks synchronously since you requested 1 process")
@@ -254,9 +273,15 @@ class WorldRenderer(object):
                         results[(col, row)] = imgpath
                         continue
 
-                result = chunk.render_and_save(chunkfile, self.cachedir, self, cave=self.caves)
+                result = chunk.render_and_save(chunkfile, self.cachedir, self, cave=self.caves, queue=q)
                 results[(col, row)] = result
                 if i > 0:
+                    try:
+                        item = q.get(block=False)
+                        if item[0] == "newpoi":
+                            self.POI.append(item[1])
+                    except:
+                        pass
                     if 1000 % i == 0 or i % 1000 == 0:
                         logging.info("{0}/{1} chunks rendered".format(i, len(chunks)))
         else:
@@ -274,13 +299,20 @@ class WorldRenderer(object):
 
                 result = pool.apply_async(chunk.render_and_save,
                         args=(chunkfile,self.cachedir,self),
-                        kwds=dict(cave=self.caves))
+                        kwds=dict(cave=self.caves, queue=q))
                 asyncresults.append((col, row, result))
 
             pool.close()
 
             for i, (col, row, result) in enumerate(asyncresults):
                 results[(col, row)] = result.get()
+                try:
+                    item = q.get(block=False)
+                    if item[0] == "newpoi":
+                        self.POI.append(item[1])
+
+                except:
+                    pass
                 if i > 0:
                     if 1000 % i == 0 or i % 1000 == 0:
                         logging.info("{0}/{1} chunks rendered".format(i, len(asyncresults)))