now defaults to the map's current north direction unless otherwise specified

README.rst

@@ -198,6 +198,9 @@ Options
 --north-direction=NORTH_DIRECTION
     Specifies which corner of the screen north will point to.
     Valid options are: lower-left, upper-left, upper-right, lower-right.
+    If you do not specify this option, it will default to whatever direction
+    the existing map uses. For new maps, it defaults to lower-left for
+    historical reasons.
 
 --settings=PATH
     Use this option to load settings from a file. The format of this file is

overviewer.py

@@ -96,7 +96,7 @@ def main():
         cpus = 1
     
     avail_rendermodes = c_overviewer.get_render_modes()
-    avail_north_dirs = ['lower-left', 'upper-left', 'upper-right', 'lower-right']
+    avail_north_dirs = ['lower-left', 'upper-left', 'upper-right', 'lower-right', 'auto']
     
     parser = ConfigOptionParser(usage=helptext, config="settings.py")
     parser.add_option("-V", "--version", dest="version", helptext="Displays version information and then exits", action="store_true")
@@ -117,7 +117,7 @@ def main():
     parser.add_option("-v", "--verbose", dest="verbose", action="count", default=0, helptext="Print more output. You can specify this option multiple times.")
     parser.add_option("--skip-js", dest="skipjs", action="store_true", helptext="Don't output marker.js or regions.js")
     parser.add_option("--no-signs", dest="nosigns", action="store_true", helptext="Don't output signs to markers.js")
-    parser.add_option("--north-direction", dest="north_direction", action="store", helptext="Specifies which corner of the screen north will point to. Valid options are: " + ", ".join(avail_north_dirs) + ".", type="choice", default=avail_north_dirs[0], choices=avail_north_dirs)
+    parser.add_option("--north-direction", dest="north_direction", action="store", helptext="Specifies which corner of the screen north will point to. Defaults to whatever the current map uses, or lower-left for new maps. Valid options are: " + ", ".join(avail_north_dirs) + ".", type="choice", default="auto", choices=avail_north_dirs)
     parser.add_option("--display-config", dest="display_config", action="store_true", helptext="Display the configuration parameters, but don't render the map.  Requires all required options to be specified", commandLineOnly=True)
     #parser.add_option("--write-config", dest="write_config", action="store_true", helptext="Writes out a sample config file", commandLineOnly=True)
 
@@ -225,7 +225,7 @@ def main():
     if options.north_direction:
         north_direction = options.north_direction
     else:
-        north_direction = 'lower-left'
+        north_direction = 'auto'
     
     logging.getLogger().setLevel(
         logging.getLogger().level + 10*options.quiet)
@@ -241,7 +241,10 @@ def main():
     
     # First do world-level preprocessing
     w = world.World(worlddir, destdir, useBiomeData=useBiomeData, regionlist=regionlist, north_direction=north_direction)
-    if not (w.persistentData['north_direction'] == north_direction) and not options.forcerender:
+    if north_direction == 'auto':
+        north_direction = w.persistentData['north_direction']
+        options.north_direction = north_direction
+    elif w.persistentData['north_direction'] != north_direction and not options.forcerender:
         logging.error("Conflicting north-direction setting!")
         logging.error("Overviewer.dat gives previous north-direction as "+w.persistentData['north_direction'])
         logging.error("Requested north-direction was "+north_direction)

overviewer_core/world.py

@@ -69,33 +69,11 @@ class World(object):
 
     mincol = maxcol = minrow = maxrow = 0
     
-    def __init__(self, worlddir, outputdir, useBiomeData=False, regionlist=None, north_direction="lower-left"):
+    def __init__(self, worlddir, outputdir, useBiomeData=False, regionlist=None, north_direction="auto"):
         self.worlddir = worlddir
         self.outputdir = outputdir
         self.useBiomeData = useBiomeData
         self.north_direction = north_direction
-                
-        #find region files, or load the region list
-        #this also caches all the region file header info
-        logging.info("Scanning regions")
-        regionfiles = {}
-        self.regions = {}
-        if regionlist:
-            self.regionlist = map(os.path.abspath, regionlist) # a list of paths
-        else:
-            self.regionlist = None
-        for x, y, regionfile in self._iterate_regionfiles(regionlist):
-            mcr = self.reload_region(regionfile) 
-            mcr.get_chunk_info()
-            regionfiles[(x,y)]	= (x,y,regionfile,mcr)
-        self.regionfiles = regionfiles	
-        # set the number of region file handles we will permit open at any time before we start closing them
-#        self.regionlimit = 1000
-        # the max number of chunks we will keep before removing them (includes emptry chunks)
-        self.chunklimit = 1024 
-        self.chunkcount = 0
-        self.empty_chunk = [None,None]
-        logging.debug("Done scanning regions")
         
         # figure out chunk format is in use
         # if not mcregion, error out early
@@ -136,10 +114,38 @@ class World(object):
             with open(self.pickleFile,"rb") as p:
                 self.persistentData = cPickle.load(p)
                 if not self.persistentData.get('north_direction', False):
-                    self.persistentData['north_direction']=='lower-left'
+                    # this is a pre-configurable-north map, so add the north_direction key
+                    self.persistentData['north_direction'] = 'lower-left'
         else:
-            # some defaults
+            # some defaults, presumably a new map
-            self.persistentData = dict(POI=[], north_direction=self.north_direction)
+            self.persistentData = dict(POI=[], north_direction='lower-left')
+        
+        # handle 'auto' north
+        if self.north_direction == 'auto':
+            self.north_direction = self.persistentData['north_direction']
+            north_direction = self.north_direction
+        
+        #find region files, or load the region list
+        #this also caches all the region file header info
+        logging.info("Scanning regions")
+        regionfiles = {}
+        self.regions = {}
+        if regionlist:
+            self.regionlist = map(os.path.abspath, regionlist) # a list of paths
+        else:
+            self.regionlist = None
+        for x, y, regionfile in self._iterate_regionfiles(regionlist):
+            mcr = self.reload_region(regionfile) 
+            mcr.get_chunk_info()
+            regionfiles[(x,y)]	= (x,y,regionfile,mcr)
+        self.regionfiles = regionfiles	
+        # set the number of region file handles we will permit open at any time before we start closing them
+#        self.regionlimit = 1000
+        # the max number of chunks we will keep before removing them (includes emptry chunks)
+        self.chunklimit = 1024 
+        self.chunkcount = 0
+        self.empty_chunk = [None,None]
+        logging.debug("Done scanning regions")
         
  
     def get_region_path(self, chunkX, chunkY):